Tesis Doctorals - Departament - Biologia Evolutiva, Ecologia i Ciències Ambientals

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Research and development of a new biocontrol agent against the foliar diseases downy and powdery mildews in cucurbit crops
(Universitat de Barcelona, 2025-02-21) Barceló Genestar, Maria; Trillas Gay, M. Isabel; Segarra Braunstein, Guillem; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[eng] This doctoral thesis explores the initial phases of the development of a new phytosanitary product aimed at combating fungal diseases mildew (Pseudoperonospora cubensis) and powdery mildew (Podosphaera fusca) in cucurbit crops. The study began with the isolation and pre-selection of microbial species from different places and types of plants affected by one of these two diseases. This phase concluded with 724 microbial isolates (491 bacteria and 233 fungi). The selected strains were subjected to molecular screening for taxonomic classification by sequencing the 16S rRNA gene in bacteria and the ITS region in fungi. This process led to the identification of 128 bacterial strains of the desired group and 11 strains of the fungal species of interest. Efficacy trials against both pathogens, carried out under controlled conditions in cucumbers, showed that several isolates significantly reduced the severity of the disease. The most effective strains against one disease also showed high efficacy against the other. Among these, some strains of bacteria obtained the best preventive efficacy in both pathosystems and were selected for subsequent studies. In contrast, yeasts proved to be more effective as curative treatments for powdery mildew. The safety assessments of the five most effective strains were carried out based on the bioinformatics study of genome sequencing in accordance with EU regulatory requirements. Finally, only two bacterial strains were selected for further analysis as the most promising candidates. Their safety profiles were confirmed based on their taxonomic classification, the absence of plasmids or genetic motility elements associated with antimicrobial resistance, the lack of toxin genes or virulence factors, and the absence of dangerous metabolites. In addition, genes involved in the synthesis of beneficial secondary metabolites, such as surfactin and phengicin, were found in their genomes, which are very important for the efficacy of biocontrol. The production of these lipopeptides, along with other secondary metabolites, was subsequently validated by LC-QTOF-MS/MS analysis. In addition, in the evaluation of biofilm formation and leaf permanence, one of the two strains showed a superior biofilm formation capacity and environmental adaptability, especially in outdoor conditions, suggesting a greater potential for application in the field. Scanning electron microscopy also confirmed that this same strain formed more homogeneous biofilms with a mucous texture than the other previously selected strain. In summary, this work underlines the potential of biocontrol agents in sustainable agriculture, presenting the strain finally selected, based on a collection of 724 isolates, as a leading candidate for biocontrol products intended for the management of downy mildew and powdery mildew in cucurbits and possibly in other crops.
Mecanismos de aclimatación a la sequía extrema en especies tolerantes al estrés
(2025-02-14) Villadangos Redondo, Sabina; Munné Bosch, Sergi; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[spa] La sequía ejerce un estrés abiótico en las plantas, causando un déficit hídrico que, de ser severo y/o prolongado, puede comprometer su estado fisiológico. Por lo tanto, la aclimatación a la sequía es esencial para sobrevivir y dependerá de la capacidad de respuesta de la especie. En este estudio se exploraron mecanismos de aclimatación a la sequía extrema, en dos especies tolerantes al estrés: la especie clonal subalpina Sempervivum tectorum L., y la especie de gran interés agronómico Olea europaea L. Por un lado, S. tectorum activó respuestas a nivel de hoja que podían ser simultáneamente mediatas por el ácido abscísico y la forma bioactiva de jasmonados, la jasmonoil-isoleucina, modulando la composición y contenido de antioxidantes, como los tocoferoles (vitamina E). Asimismo, esta especie contaba con estrategias que operan a nivel de planta entera y que permiten una gran tolerancia y resiliencia al estrés, estableciendo una senescencia foliar gradual a través de la roseta o estrategias similares a la quiescencia que mantienen niveles oxidativos bajos en hojas durante periodos prolongados de estrés, garantizando así restaurar rápidamente el crecimiento durante la recuperación. Al profundizar en la respuesta de aclimatación de S. tectorum a su hábitat natural encontró que esta especie ajustó la producción de nuevos rametes clonales y activó una respuesta hormonal compleja para sobrevivir a un episodio de sequía extrema. Abordando la reproducción clonal como posible estrategia de escapar del estrés, en esta tesis revelamos una priorización de la descendencia clonal bajo estrés, donde los ramillos no arraigados presentaban una mayor viabilidad que sus rosetas parentales ante un estrés moderado, y que ante un estrés severo estos ramillos permanecían aún vivos unidos a la roseta parental. Este comportamiento fue explorado también en su hábitat natural, donde encontramos que esta especie mantuvo los nuevos rayos unidos hasta que encontraran la oportunidad de arraigar sin comprometer la supervivencia de la roseta parental. Por otro lado, escogimos el olivo como modelo para evaluar si las oxilipinas estaban implicadas en el proceso de abscisión foliar inducida por sequía. Mediante un muestreo espacial basipétalo de hojas, encontramos que el estrés foto-oxidativo produjo una acumulación de jasmonoil-isoleucina en el pecíolo de hojas estresadas, sugiriendo un acondicionamiento previo de la zona de abscisión a través de oxilipinas. Se concluye que las plantas tolerantes al estrés tienen mecanismos de aclimatación que les permite afrontar sequías extremas como (i) respuesta fotoprotectora en hojas modulada por el ácido abscísico y la jasmonoil-isoleucina; (ii) estrategia de tipo quiescente para evitar la carga de estrés oxidativo durante la reproducción clonal para prolongar la supervivencia al estrés de todo el jinete; (iii) senescencia foliar gradual para proteger los meristemas apicales; (iv) abscisión foliar inducida por sequía condicionada por oxilipinas.
Movimientos y variabilidad geográfica en la codorniz común (Coturnix coturnix) en su área de distribución occidental
(Universitat de Barcelona, 2025-01-10) Jiménez Blasco, Irene; Rodríguez Teijeiro, José Domingo; Puigcerver Oliván, Manuel; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[spa] El desplazamiento en las aves está asociado a la variación espacio- temporal en los recursos. La variación estacional predecible se relaciona con la migración, un desplazamiento regular anual que puede ser de larga distancia, entre un lugar de reproducción y otro de descanso, y que se asocia a unos rasgos morfológicos, fisiológicos y comportamentales característicos. La variación irregular e impredecible se relaciona con el nomadismo y la dispersión, desplazamientos sin una dirección determinada. Existe un insuficiente conocimiento de la ecología de movimiento de muchas especies nomádicas debido a la dificultad en su seguimiento; por ejemplo, la codorniz común (Coturnix coturnix) es un ave cinegética que exhibe un complejo patrón de movimientos migratorios, nomádicos y dispersivos aún poco conocidos. Las poblaciones del Paleártico occidental son principalmente migratorias transaharianas, pero albergan también individuos migratorios de corta distancia y residentes. Estos últimos serían más abundantes en áreas más meridionales del sur del mediterráneo o en las islas atlánticas y mediterráneas. Además de la migración, la codorniz se desplaza durante la época reproductora en latitud y altitud siguiendo la dinámica del hábitat y, en el caso de los machos, entre zonas de reproducción en búsqueda de nuevas parejas. La distancia y dirección de estos movimientos es poco conocida y no se entiende bien el mantenimiento de diferentes estrategias migratorias en una misma población. Además, los jóvenes se incorporan a la población reproductora a los pocos meses y pueden desplazarse y potencialmente reproducirse en zonas distantes el mismo año de su nacimiento. Esta tesis pretende profundizar en el conocimiento de las estrategias de movimiento en la codorniz común en la península ibérica, sureste de Francia y archipiélago balear y en cómo se relacionan con la diferenciación poblacional. Concretamente, se comparan rasgos morfológicos asociados a la migración entre los machos adultos de la península ibérica para diferenciar fracciones de la población con diferentes estrategias migratorias; se cuantifican los jóvenes presentes en una zona de reproducción en la que no pueden haber nacido (foráneos) y se analiza cómo varía su proporción con la latitud y altitud desde el sur de la península ibérica hasta el sur de Francia; por último, se describe la dinámica temporal de la densidad de jóvenes y adultos durante la época reproductora en dos poblaciones del noreste de la península ibérica y una insular de Mallorca. Hemos diferenciado dos morfotipos en la península ibérica que seguirían estrategias migratorias distintas según sus rasgos del aparato de vuelo. En el este y norte peninsular predomina un morfotipo migratorio de larga distancia y en la mitad occidental, principalmente en el suroeste, un morfotipo migratorio de corta distancia o sedentario. En el este son más pequeños y de coloración más clara que en el oeste, sugiriendo una diferenciación de la población de la península en un eje occidental – oriental. Por otro lado, la proporción de jóvenes foráneos aumenta exponencialmente con la latitud y altitud de las zonas de reproducción, llegando en determinados años a constituir más de la mitad de la población reproductora en las zonas más altas. Este resultado indica la interdependencia demográfica de las poblaciones a gran escala geográfica. Finalmente, la densidad de machos jóvenes y adultos varía durante la época reproductora, probablemente por los continuos desplazamientos y por la reproducción local. A pesar de la elevada movilidad, las poblaciones insulares parecen más aisladas, como la de Mallorca, donde la dinámica de densidad sugiere una fracción sedentaria. La codorniz se encuentra actualmente en un controvertido acusado declive poblacional, que requiere una coordinación internacional e invertir esfuerzos en conocer sus patrones de movimiento para disponer de estimaciones más precisas de su abundancia.
Isolation and evaluation of beneficial microorganisms for their potential use in agriculture as microbial biostimulants
(Universitat de Barcelona, 2025-01-14) Briones Sendra, Miriam; Trillas Gay, M. Isabel; Segarra Braunstein, Guillem; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[eng] Conventional agricultural practices often rely on the extensive application of fertilizers to ensure maximum crop yields, leading to significant economic costs and negative environmental impacts. Nitrogen (N) and phosphorus (P) are critical nutrients for plant growth; however, excessive nitrogen use contributes to ecosystem pollution and disrupts the nitrogen cycle, while phosphorus, typically derived from limited mining sources, necessitates constant applications to maintain nutrient levels and high yields. In this context, microbial biostimulants emerged as a promising alternative to conventional chemical fertilizers, being defined as materials containing one or more microorganisms that, when applied to plants or the rhizosphere, stimulate natural processes to enhance nutrient use efficiency, seed quality, plant growth promotion, and accessibility on confined nutrients in soil. Promising microorganisms for biostimulant development include Bacillus subtilis, Pseudomonas fluorescens, Azospirillum spp., and Azotobacter spp., for their abilities to solubilize phosphorus, fix nitrogen, promote plant growth, and improve soil health. This thesis is part of an industrial PhD program, a scholarship from Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR, Resolution EMC/460/2020), Biocontrol Technologies, S.L. and Universitat de Barcelona. The general objective of the research was to isolate, characterize, and explore the potential application of these genera to plants, with the aim, to develop a microbial biostimulant that complies with Spanish regulations (Royal Decree 999/2017) or European regulations (Regulation (EU) 2019/1009) by combining in vitro characterization experiments, plant trials, and soil studies. The isolation and characterization identified several strains of interest, including 16 Bacillus subtilis, 16 Pseudomonas fluorescens, 4 Azotobacter spp., and 9 Azospirillum spp. with some P. fluorescens excelling for Indole-3-Acetic acid production (IAA), B. subtilis for IAA, siderophores production and phosphorus solubilizing capacities while Azotobacter spp. demonstrated higher mineral phosphorus solubilization and Azospirillum spp. nitrogen fixing capabilities. Plant trials revealed Bacillus subtilis B7 and B17 as promising candidates for the development of biofertilizers according to Spanish regulations when applied at the substrate at a concentration of 107 CFU mL-1 which significantly enhanced seed germination by 10% and 13%, respectively, and promoted plant growth in cucumber, lettuce, and maize compared to non-inoculated plants. Furthermore, with the inoculation of B7 and B17 applied at the plant rhizosphere at a concentration of 107 CFU mL-1 the maize phosphorus use efficiency was improved under conditions of soluble phosphorus limitation, where B7 increased maize biomass by 34% and B17 enhanced plant phosphorus accumulation by 59% compared to non-inoculated plants. Moreover, Azospirillum brasilense 21F221 and Azospirillum aestuarii 21F226 were selected as candidates for the development of microbial biostimulants under European regulations due to their significant increase in nitrogen use efficiency when applied to maize and rice seeds at 108 CFU g seed-1 cultivated with different N fertilization regimes. Strain 21F221 notably enhanced plant growth (16% and 4%) and plant nitrogen accumulation (33% and 34%) and 21F226 boosted plant biomass (20% and 11%) and yield (148% and 37%) compared to non- inoculated plants in maize and rice respectively, suggesting the possibility to significantly reduce fertilizer. The study of these Azospirillum spp. strains' effects on soil dynamic revealed no nitrogen fixing in the absence of plants and efficient nutrient mining from organic matter, as well as significant impacts on native microbial populations, underscoring the need for tailored application strategies. The studies conducted in the framework of this PhD thesis successfully bridges academic research with industrial application, supporting the initial steps for the development of a microbial biostimulant that meets stringent Spanish and European regulatory standards. Further studies would be necessary focused on development of growth, sporulation and formulation methods of selected strains, optimization of application strategies and field trials to validate these strains under diverse agricultural conditions.
Causes, effects, and management of river salinization in Spain with special attention to wastewater treatment
(Universitat de Barcelona, 2025-01-15) Moyano Salcedo, Alvaro Javier; Salvadó i Cabré, Humbert; Cañedo-Argüelles, Miguel; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[eng] Freshwater salinization (FS) represents a pressing global environmental challenge, significantly impacting aquatic ecosystems. Despite extensive research, critical gaps remain in understanding the full extent and implications of FS. This thesis aims to address and contribute to filling some of these gaps by providing global information necessary to explore FS patterns, temporal variability, and the interaction of FS with other pollutants, particularly nutrients. One of the key focuses of this thesis is the evaluation of the salinity effects on urban wastewater treatment plants (WWTPs), as well as WWTP contributions to FS. The objectives of this thesis are fourfold. First, it aims to compile a global database integrating river salinity parameters and both natural and anthropogenic drivers of freshwater salinization to explore patterns and temporal variability across various regions. Second, it seeks to examine the seasonal dynamics of primary salinization sources such as mining, transportation, agriculture, and urban wastewater discharges, and their effects on the temporal variability of river salinity in Spanish rivers. Third, the thesis investigates the interactive effects of nutrient and salt pollution on river ecosystems through controlled experiments in artificial channels. Fourth, it assesses how increasing salinity impacts microbial communities and pollutant removal efficiency in WWTPs. Chapter 1 presents a global dataset, GlobSalt, which includes 13 parameters related to river salinity and associated ions, with approximately 15 million records. This dataset reveals substantial spatial variability in salinity and serves as a crucial resource for understanding FS dynamics and identifying high-risk regions. Chapter 2 analyzes temporal variations in electrical conductivity (EC) across 91 Spanish rivers, demonstrating how human activities disrupt EC patterns and influence aquatic biodiversity. Chapter 3 explores the combined effects of nutrient and salt pollution on stream microcosms, highlighting significant declines in macroinvertebrate diversity and the complex interactions between pollutants. Chapter 4 assesses the impact of salinity on WWTP performance, revealing how high EC levels affect microbial communities and pollutant removal efficiency. Moreover, each chapter presents an application of the GlobSalt data: (i) the temporal variation of river EC influenced by WWTP discharges and seasonal patterns, (ii) the concentration of phytoplankton in rivers in relation to EC levels for pristine and impacted sites, and (iii) the increase in river EC associated with wastewater discharges in different seasons. In summary, this thesis not only advances scientific understanding of freshwater salinization and its drivers but also offers practical insights for managing and mitigating FS impacts. By integrating global and local data, addressing seasonal and interactive effects, and evaluating WWTP performance and contributions, this research provides valuable information for developing effective management strategies and guiding future studies in the field of freshwater ecology.
The role of the synaptic plasticity gene NRN1 in schizophrenia: integrating molecular and neuroimaging approaches
(Universitat de Barcelona, 2024-12-20) Almodóvar Payá, Carmen; Fatjó-Vilas Mestre, Mar; Arias Sampériz, Bárbara; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[eng] Schizophrenia, a psychiatric disorder affecting 24 million people worldwide, continues to present significant challenges despite notable progress in understanding its etiology. While advancements have been made, the fundamental pathophysiological mechanisms, molecular diagnostics, and precise biomarkers remain unclear. Consequently, ongoing psychiatric research must focus on unraveling the complex biological foundations of the disorder. A deeper understanding is crucial for identifying more appropriate diagnostic categories and developing innovative therapeutic strategies to improve the quality of life for individuals affected by schizophrenia. Currently, the leading etiological hypothesis suggests that schizophrenia arises from a complex interaction between genetic and environmental factors, which disrupt the processes governing brain development and maturation. From birth to adulthood, brain development depends on synaptic plasticity, the process by which neurons modify their connections in response to external signals, refining synapses and creating neural circuits. Accordingly, impaired synaptic plasticity is thought to play a pivotal role in the pathophysiology of schizophrenia, a notion strongly supported by evidence from multiple disciplines. Among the genes that play crucial roles in both development and adulthood by mediating synaptic plasticity, Neuritin-1 (NRN1) stands out. Prior to this thesis, extensive research using cell and animal models had explored the functions of NRN1 in the brain. In summary, NRN1 regulates apoptosis in proliferative neurons, promotes neuronal migration and synaptic maturation, modulates neurite outgrowth during differentiation, stimulates dendritic arbor growth, stabilizes active synapses, and as previously mentioned, supports synaptic plasticity. Additionally, several studies have highlighted NRN1's neuroprotective effects, its role in enhancing cognitive performance, and its sensitivity to neurotherapeutic agents through epigenetic mechanisms. This body of evidence suggests that NRN1 could be a promising target for developing therapeutic strategies for schizophrenia, as modulating its expression may positively impact brain functioning and, therefore, behavior and patient outcomes. However, despite these promising findings, human research on the role of NRN1 in schizophrenia remained limited, with only two previous studies examining its impact on schizophrenia risk, age at onset, and intelligence quotient. Given its potential importance, we focused on NRN1 as a key synaptic plasticity gene in schizophrenia, aiming to deepen our understanding of how this mechanism contributes to the disorder and how such knowledge could enhance patient care. To achieve this, we adopted a multilevel approach incorporating various layers of NRN1 molecular diversity. This strategy resulted in four articles that examined the association of NRN1 with age at onset, clinical and neuroimaging traits of schizophrenia, its interactions with related genes, its expression and methylation in post-mortem brain samples from schizophrenia patients, and its methylation changes in response to cognitive therapy. Overall, our results validate the efficacy of a multifaceted methodology in uncovering the role of candidate genes in modulating schizophrenia presentation. Specifically, we identified NRN1 genetic variants associated with an increased risk for early-onset schizophrenia-spectrum disorders, with carriers exhibiting altered dorsolateral prefrontal cortex activity during a working memory task. Additionally, epistatic interactions between NRN1, BDNF-rs6265, and CACNA1C-rs1006737 significantly modulated clinical severity and neuroanatomical features, with the interaction between NRN1 and BDNF in the left lateral orbitofrontal cortex fully mediating the effects on general psychopathology. In post-mortem brain samples, schizophrenia patients treated with clozapine displayed lower NRN1 expression and methylation differences in the prefrontal cortex compared to untreated patients and controls, with these methylation differences correlating with NRN1 expression and influenced by specific genetic variants. Lastly, we demonstrated the clinical applicability of our findings, showing that cognitive remediation therapy is associated with changes in NRN1 peripheral methylation, with increased methylation distinguishing responders from non-responders across cognitive domains, an effect also shaped by NRN1 genetic variability. Globally, the findings presented in this thesis highlight how understanding the role of specific genes involved in synaptic plasticity can not only deepen our insight into the etiology of schizophrenia but also potentially lead to improved patient care. Although studies focusing on candidate genes are constrained by the polygenic nature of the disorder, these studies provide compelling evidence and valuable clinical insights, laying the groundwork for further exploration of these key genes within broader molecular networks. Thus, this thesis serves as a steppingstone in the collective process of building knowledge about the etiology of psychosis, aiming to understand how individual genetic variations influencing neurodevelopment and synaptic plasticity contribute to the underlying causes of schizophrenia.
From Local to Regional: Demographic and Population Dynamics of a Long-lived Scavenger Species in a Changing Environment
(Universitat de Barcelona, 2024-12-17) Arévalo-Ayala, Diego José; Hernández Matías, Antonio, 1974-; Real, Joan; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[eng] In a rapidly changing world, the loss of global biodiversity presents a significant challenge. While sustainability has become a guiding principle for balancing the protection of the environment along with economic development and human well-being, its implementation can often be disjointed across various sectors. The incoherence in the integration of environmental policies can lead to unintended negative impacts on biodiversity, particularly for vulnerable species like vultures and the environmental services they provide. Vultures, as a highly threatened group of birds, are especially vulnerable to poisoning, but also to new circular economy and renewable energy policies such as the closure of landfills and wind energy. Thus, it is imperative to evaluate the mechanisms and demographic responses of vulture species to these new paradigms. My thesis examines the demography of the griffon vulture Gyps fulvus in northeast Iberian Peninsula, using long-term data to provide a comprehensive understanding of the population dynamics in response to a changing environment. In Chapter 1, we studied how the local griffon vulture population in Central Catalonia responded to reduced organic matter in an open landfill due to European sanitary measures aimed at closing landfills. Using the robust Schwarz and Arnason Jolly-Seber model, we estimated the vultures' apparent survival probability and annual abundance. We found that the available organic matter in the landfill significantly declined after a waste treatment centre was established, negatively impacting apparent survival. However, local abundance remained stable, with an increase attributed to the growth of the Catalonian breeding population. This suggests that local waste management measures had limited impact on vultures, as their high dispersal capacity allows them to find alternative food sources. In Chapter 2, we used a Bayesian hierarchical Cormack-Jolly-Seber model to analyze the age-specific demographic response of the local vulture population at the landfill, estimating apparent survival and permanent emigration probabilities under three scenarios of organic matter availability: no reduction, substantial decrease, and drastic decrease. We found a notable increase in transients among newly captured immatures and adults. Apparent survival in juveniles declined, while in immature residents increased and adult residents decreased. The results suggested that intensified intraspecific competition due to reduced food increased permanent emigration. However, resident immatures showed resilience, indicating that high-quality individuals persisted despite food scarcity. In Chapter 3, we used a multi-site Integrated Population Model (ms-IPM) to examine the dynamics of griffon vulture populations in Catalonia, Aragon, and the Valencian Community. We aimed to understand demographic processes and inform site-specific conservation strategies. We observed different trends: steady growth in Catalonia, stabilization in the Valencian Community after an initial increase, and a decline with a slight recovery in Aragon. Key growth factors varied by region: adult survival in Aragon, floater-to-breeder ratio and immigration in the Valencian Community, and all three factors in Catalonia. Density dependence affected the floater-to-breeder ratio and immigration in Catalonia and the Valencian Community, with higher emigration to the other two sites in the vultures of Valencian Community, likely due to nearing carrying capacity. Populations in Aragon and the Valencian Community are stable, while Catalonia is growing. Maintaining adult survival in Aragon is crucial, given its lower rate and potential non-natural mortality sources. This study highlights the value of ms-IPMs for understanding complex population dynamics and the need for targeted conservation strategies. In conclusion, by applying demographic models, including the ms-IPM, and addressing data heterogeneity and uncertainty, in this thesis we gained a deeper understanding of griffon vulture population dynamics. This approach helped identify key demographic drivers, identify possible environmental impacts, and inform conservation strategies, highlighting the need for cohesive policies across regions to effectively conserve vulnerable species like vultures.
Efectos de la heterogeneidad del paisaje agrícola mediterráneo sobre los polinizadores y la eficacia de la polinización
(Universitat de Barcelona, 2024-11-22) Neira Vidal, Pablo; Sans, Xavier (Sans i Serra); Blanco Moreno, José Manuel; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[spa] La intensificación agrícola, que altera el uso de la tierra y las secuencias de cultivos en busca de maximizar la productividad y los ingresos, afecta la abundancia y diversidad de polinizadores, que son cruciales para la polinización. Esta tesis investiga cómo las características del paisaje agrícola afectan la abundancia de polinizadores en la región mediterránea noroccidental, con un enfoque en sírfidos y abejas. Durante un período de dos años, el estudio monitoreó la densidad de polinizadores y la efectividad de la polinización en veintidós campos de colza ubicados en paisajes que diferían en términos de diversidad de cultivos, extensión de hábitats seminaturales y tamaño del campo. Estas diferencias proporcionaron una base para analizar cómo las características específicas del paisaje influyen en la abundancia y efectividad de los polinizadores. Si bien muchos estudios se han centrado en la fracción no cultivada de los paisajes agrícolas, pocos han examinado los efectos temporales de la gestión de las tierras agrícolas, específicamente cómo la diversidad de cultivos y la prevalencia de ciertos cultivos que proporcionan recursos florales influyen en los polinizadores. Esta tesis adopta un enfoque más integral al considerar tanto el papel de los hábitats seminaturales como los efectos temporales de las prácticas agrícolas dentro de la matriz cultivada sobre la actividad de los polinizadores. Este doble enfoque subraya la importancia de comprender la interacción entre las áreas cultivadas y no cultivadas en la configuración de la abundancia de polinizadores y los servicios de polinización, mediante el examen de los efectos en una especie de cultivo alógamo facultativo. Esta tesis se organiza en dos secciones principales, cada una de las cuales aborda distintos aspectos de la matriz agrícola. En el primer apartado se aborda la diversidad de cultivos, mientras que el segundo se centra en la cobertura de cultivos de floración masiva, ambos analizados desde una perspectiva temporal. Se examinaron cuatro características del paisaje: la diversidad de cultivos equivalente en el año de muestreo (ERG), la diversidad de cultivos equivalente del año anterior (ERGp), el porcentaje de hábitats seminaturales (SNH) y el tamaño medio del campo (MFS). El estudio, realizado en veintidós campos de colza en paisajes con diferentes características, encontró que diferentes variables del paisaje influyeron en los grupos de polinizadores de distintas maneras. SNH influyó positivamente en la abundancia de abejorros, mientras que ERGp y MFS fueron importantes para otras abejas silvestres y para los sírfidos. Estos hallazgos proporcionan información práctica para priorizar estrategias para beneficiar a grupos específicos de polinizadores, mejorar la planificación del paisaje agrícola y promover la conservación de los polinizadores silvestres a través de la diversidad de cultivos. El estudio también exploró cómo ciertas características del paisaje (ERGp, SNH y MFS), así como las densidades de polinizadores (abejas silvestres [WB] y abejas melíferas [HB]) influyeron en los resultados de la polinización y en la cantidad y calidad de las semillas en los cultivos de colza. La investigación en un subconjunto de veinte campos de colza reveló una relación positiva entre el ERGp y la densidad de polinizadores. El experimento de exclusión en estos campos mostró que la polinización por insectos mejoró significativamente la calidad y cantidad de la colza. El ERGp surgió como una característica relevante del paisaje, que tuvo un impacto positivo en la densidad de WB y la efectividad de la polinización, mejorando así la producción de colza. Además, el estudio examinó los efectos de la cobertura de cultivos de floración masiva (MFC) del año anterior (MFC1) y acumulada durante tres años (MFC3). También se tuvieron en cuenta los hábitats seminaturales y los efectos del tamaño medio del campo sobre los polinizadores y el rendimiento de la colza. El modelo de ecuaciones estructurales indicó que MFC1 y MFC3 influyeron positivamente en las densidades de abejas silvestres (WB). Los tamaños de campo más pequeños promovieron densidades más altas de abejas grandes (LB). El número de semillas por vaina se relacionó positivamente con el WB en general y con el LB en particular. También se relacionó positivamente con MFC1 y MFS. El contenido de aceite de semilla se asoció positivamente con las densidades de LB y negativamente con MFS. La SNH se correlacionó con un aumento en el peso de mil semillas. En general, el estudio destaca la importancia de los hábitats fuera de los cultivos y de los recursos florales y su temporalidad para promover los servicios de polinización en paisajes agrícolas mediterráneos dominados por los cereales. Por lo tanto, la gestión del paisaje debe centrarse en estos factores para promover la sostenibilidad y maximizar los beneficios agrícolas y ecológicos.
Análisis de las respuestas ecofisiológicas de los bosques de Polylepis dentro del páramo andino al sur del Ecuador frente a las condiciones climáticas
(Universitat de Barcelona, 2024-10-18) Carabajo Hidalgo, Aldemar; Sabaté i Jorba, Santi; Asbjornsen, Heidi; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[spa] Los bosques de Polylepis cumplen un papel ecológico muy importante al ser los que se desarrollan a mayor altitud en el mundo. Dentro de este género, Polylepis reticulata es una de las especies arbóreas endémica de la cordillera de los Andes que se desarrolla entre 3800 y 4500 msnm, en la línea de bosque alto andino del ecosistema páramo. Al igual que las demás especies que viven en estos ecosistemas, está expuesta a condiciones ambientales extremas, tales como bajas temperaturas y periodos de alta nubosidad y niebla que crean una elevada variabilidad en la radiación solar incidente. Sin embargo, existen muy pocos estudios en estos bosques y se conoce muy poco sobre su ecofisiología. El objetivo de esta tesis es estudiar la ecofisiología de P. reticulata, evaluando la dinámica de su transpiración, sus tasas fotosintéticas potenciales y su eficiencia en el uso del agua en el crecimiento, así como sus rasgos funcionales. Para abordar estos objetivos, se midió la dinámica del flujo de savia utilizando técnicas de pulso de calor, se obtuvieron curvas de respuesta fotosintética a la luz y al CO2 para caracterizar la cinética de su fotosíntesis, se utilizaron medidas de flujo de savia y de crecimiento radial para determinar su eficiencia en el uso del agua y sus patrones intra- anuales de crecimiento y se describieron sus rasgos funcionales. Los resultados muestran que P. reticulata está adaptada para aprovechar los cortos momentos de condiciones más favorables en el páramo para transpirar, y que las condiciones óptimas ocurren cuando el déficit de presión de vapor (VPD) es mayor a 0,15 kPa y el contenido de agua en el suelo (VWC) es menor a 0,73 cm3 cm-3. Sin embargo, estas dos condiciones se cumplen solo en el 11% de nuestras mediciones, lo que sugiere que estas ventanas de oportunidad son breves y escasas. Las tasas de transpiración son mayores en árboles situados en el borde del bosque y en años menos lluviosos, en los que se producen las condiciones óptimas para la transpiración con mayor frecuencia. Para adaptarse a las condiciones del páramo, P. reticulata posee un aparato fotosintético altamente eficiente que responde rápido a las condiciones cambiantes, saturándose en valores relativamente bajos de radiación fotosintéticamente activa (PAR) y mostrando tasas fotosintéticas altas comparadas con las de otras especies que viven en condiciones ambientales más favorables. Por último, se ha encontrado que a pesar de la baja estacionalidad existente en la zona ecuatorial, tanto el crecimiento como la eficiencia en el uso de agua de P. reticulata presentan patrones de estacionalidad intra-anual marcados, incrementando en periodos con mayores temperaturas y PAR, y reduciéndose en periodos con mayor velocidad del viento. El estudio de los rasgos funcionales y estructurales de P. reticulata muestran características típicas de las especies que viven en altitud, como hojas gruesas o áreas foliares específicas bajas. Al relacionarlos con la eficiencia en el uso del agua se observa una relación positiva con el ratio C/N del suelo y el contenido de clorofila, y una relación negativa con el potencial hídrico al mediodía y el contenido de nutrientes en las hojas. Se concluye que la disponibilidad de energía es limitante para la transpiración y el crecimiento de la especie, por lo que ha desarrollado adaptaciones ecofisiológicas que le permiten aprovechar los escasos momentos en los que tiene acceso a la energía, manteniendo un balance de carbono positivo para sobrevivir en las condiciones extremas del páramo. Los resultados de esta tesis aportan conocimiento novedoso sobre la ecofisiología de P. reticulata y contribuyen a un mejor conocimiento de sus respuestas a las condiciones climáticas cambiantes en las que se desarrolla.
The effects of ozone on Mediterranean wheat in a changing environment
(Universitat de Barcelona, 2024-09-06) Chang Espino, Melissa; Araus Ortega, José Luis; Bermejo Bermejo, Victoria; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[eng] The assays were conducted in the La Higueruela/MNCN-CSIC Agricultural Research Station, situated within a climate typical of the Iberian Peninsula, where controlled exposure to ambient and elevated ozone levels was facilitated through open-top chambers. Chapter 1 focused on evaluating the impact of ozone fumigation on different aged cultivars, while Chapters 2 and 3 explored the interactive effect of ozone and nitrogen fertilization. Additionally, Chapter 4 examined the effect of ozone on the fungal pathogen Puccinia striiformis. To assess the impact of ozone on wheat, various factors were studied that are pertinent for crop management and policy-making. Chapter 1 delved into the effects breeding has had on wheat sensitivity to tropospheric ozone pollution, noting that the selection for a higher harvest index in the more modern varieties has led to an increased susceptibility to ozone, though the benefits of breeding mostly offset the effects of the pollutant. However, as landraces have a more extensive genetic base to improve ozone tolerance, they should be considered for future breeding processes. Expanding upon crop management, Chapter 2 investigated the potential mitigative effects of additional nitrogen fertilization on ozone-induced yield and quality reductions. While findings indicated a beneficial impact from the fertilizer, this effect was only observed until the highest levels of ozone concentration, beyond which the fertilizer effect was entirely eliminated, resulting in both yield and growth values resembling those of the lower fertilizer treatment under the same fumigation. This resulted in lower critical levels under the higher nitrogen treatment, prompting a policy-making-oriented consideration of the economic and environmental consequences associated with ineffective fertilizer use at elevated ozone levels. However, as additional nitrogen does provide some compensation at certain elevated ozone levels, the mechanisms through which this could be happening were explored in Chapter 3. It was noted that the additional nitrogen allowed the plant to invest more resources into the photosynthetic machinery, thereby enhancing assimilation to a certain extent. This can be considered for future research aimed at selecting varieties for a higher nitrogen use efficiency, particularly given the distinct nitrogen uptake and storage mechanisms of modern cultivars compared to landraces. Finally, Chapter 4 addressed another factor that could be essential for both crop management and policy-making, pathogens. The effect of ozone on a yellow rust infection was analyzed, noting its mitigation on yellow rust infection. While ozone exhibited beneficial effects at its current levels, higher concentrations – albeit lower than those reducing nitrogen use efficiency – proved detrimental to plant health. In Chapters 1 and 3, isotopic signatures were also investigated. For both, and regardless of nitrogen fertilization treatment, the grain carbon isotope proved to be an excellent indicator of chronic ozone stress, while nitrogen isotopes in both leaf and grain provided valuable insights into nitrogen remobilization in wheat. However, the interpretation of these findings depended on correlations with other measurements due to the intricate nature of nitrogen dynamics within the plant. In conclusion, this thesis underscores the importance of considering cultivar-specific tolerance mechanisms in breeding programs, acknowledging the limitations of crop management practices such as nitrogen fertilization, and recognizing the adaptation of modern wheat cultivars to current ozone levels, which provide them with protection against pathogens such as Puccinia striiformis.
Foraging and migratory ecology of tropicbirds (Phaethontidae)
(Universitat de Barcelona, 2024-09-10) Saldanha, Sarah Delphine; González-Solís, Jacob; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[eng] In polar and temperate regions, strong seasonality in environmental conditions often drives animal phenology, resulting in population-wide synchrony in the timing of critical biological events such as breeding and migration. The association between phenology and seasonality is less pronounced in tropical systems, where environmental conditions remain relatively constant throughout the year. As a result, many species exhibit asynchronous or year-round breeding patterns. This leads to the question of whether these species respond to seasonal changes, which may remain present albeit to a lesser extent, and what shapes their phenology. To assess the effects of seasonality on tropical species, we investigated the foraging and migratory ecology of the Red-billed Tropicbird (Phaethon aethereus), a poorly studied pantropical species that breed year-round in Cabo Verde, between 2017 and 2024. Along four chapters, this thesis presents novel insights into how tropicbirds cope with seasonal changes in resource availability and environmental conditions using a combination of biologging (GPS, GLS-immersion loggers, time-depth recorders (TDR), and accelerometry), nest monitoring, and diet analyses. In the first chapter, we used auxiliary biologging data from immersion loggers, TDR and accelerometry to evaluate and semi-supervise Hidden Markov Model to classify tropicbirds' behaviors at sea based on tropicbird GPS tracks. We found that although overall classification accuracy greatly improved with semi-supervision, these models failed to capture tropicbird the foraging state, and give a word of caution on using these models to classify behaviors in other opportunistic foragers. Building on the methodological insights of this first chapter, the second chapter of this thesis focuses on the effects of seasonality on the foraging behavior of tropicbirds during the breeding season. In this chapter, we found seasonal patterns in foraging behavior, occupancy, and diet, which affected fitness metrics. We relate these patterns to the increased availability of squid and nest site suitability at the end of the dry season and an increase in weather-related foraging costs in the wet season. In the third chapter, we investigated whether seasonal patterns persist during the non-breeding period and found individual and seasonal consistency in the areas used. We also found that seasonal shifts seem to be related to population-wide habitat preferences. In the fourth chapter, to decipher whether the observed seasonal patterns in foraging and migratory behavior reflect individual plasticity, or seasonal specialization we investigated the repeatability and heritability of tropicbird phenology. We found that individuals maintained remarkably consistent year-round phenology across subsequent years and that phenology appears heritable, with recruits returning to breed around the same time they fledged. Our results provide some of the first in-depth knowledge on the seasonal variation in the foraging behavior of a tropical seabird species, suggesting seasonality in tropical systems may be a stronger driver of the movements of top predators than previously thought. Moreover, we found strong individual repeatability and heritability of phenology, suggesting that these seasonal patterns remain consistent within generations. Therefore, we anticipate that, in changing environmental conditions, tropicbirds may have a restricted ability to modify their individual foraging and migratory strategies, rendering them more vulnerable to environmental change than previously anticipated.
Efectes de l'associació de varietats de blat sobre l’abundància d’espècies arvenses, de pugons i la producció en cultius ecològics
(Universitat de Barcelona, 2024-10-11) Tous Fandos, Alba; Sans, Xavier (Sans i Serra); Chamorro Lorenzo, Lourdes; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[cat] La major part de la producció ecològica mundial de blat prové de conreus de varietats modernes en règim de monocultiu. La sembra de varietats tradicionals és poc comuna per la baixa disponibilitat en el mercat i perquè l’agricultura ecològica copia alguns aspectes dels models agronòmics convencionals intensius, on les varietats tradicionals resulten menys productives. A més, la implementació de policultius és limitada, per una banda, pel sobreesforç logístic i econòmic que genera el cultiu simultani de varietats i espècies diferents (Lin 2011; Di Bene et al. 2022). Per l’altra banda, perquè l’associació de varietats d’una mateixa espècie és una pràctica poc estesa a Europa, tot i suposar una gestió agrícola i una inversió econòmica similars als monocultius (Vanloqueren & Baret 2009). Tanmateix, en els darrers anys, ha crescut l’interès per part d’investigadors i agricultors per l’ús de policultius i la sembra de varietats tradicionals en conreus herbacis extensius ecològics amb la finalitat d’incrementar la complexitat i la salut global del sistema i de reduir la dependència a les aportacions externes (Wezel et al. 2014; Reiss & Drinkwater 2018; Di Bene et al. 2022). La tesi doctoral pretén avançar en el coneixement dels beneficis i perjudicis de la diversificació dels cultius sobre la regulació de les poblacions arvenses, el control de pugons i la producció de gra en conreus de blat mitjançant estudis en condicions naturals i controlades d’hivernacle i laboratori. Gran part de la recerca en aquest àmbit s’ha dut a terme mitjançant experiències en condicions controlades de laboratori o hivernacle. En aquests estudis, no es valora la influència dels factors ambientals o agronòmics sobre la funcionalitat dels policultius ni l’efecte de la diversitat planificada sobre la diversitat associada. A més, pocs experiments consideren els trets funcionals a l’hora de dissenyar els policultius, fet que pot propiciar l’establiment de policultius poc avantatjosos a causa de redundàncies o interaccions negatives entre les varietats associades. Finalment, els estudis que avaluen els trets funcionals de distintes varietats o espècies, acostumen a caracteritzar els trets en individus crescuts en règim de monocultiu. Així doncs, no es té en compte la possible modificació dels trets funcionals fruit de la interacció planta- planta present en els policultius (Gaba et al. 2015; Barot et al. 2017; Brooker et al. 2021). Amb la finalitat d’aprofundir en el paper de les varietats de blat associades sobre el funcionament dels policultius en condiciones naturals, s’ha dissenyat un experiment de dos anys amb l’associació de tres varietats de blat, una relativament moderna i dues de tradicionals i, un altre estudi també de dos anys de duració, amb dues associacions cadascuna d’elles formada per una varietat moderna i una de tradicional, a més de la incorporació d’una coberta de lleguminosa. En tots els experiments s’ha avaluat simultàniament el funcionament de les associacions i els respectius monocultius. La selecció de les varietats de blat i el cultiu de cobertura estudiats s’ha dut a terme mitjançant un procés participatiu amb els agricultors de l’Associació Agroecològica de Gallecs i els fariners locals, així com amb la direcció tècnica del Consorci de l’Espai d’Interès Natural (EIN) de Gallecs. L’EIN de Gallecs és una àrea rural periurbana de 698,91 ha situada a 15 km al nord de Barcelona (Mollet del Vallès) predominantment agrícola. Des del 2005, l’Associació Agroecològica de Gallecs ha promogut activament un procés de reconversió i transició cap a l’agricultura ecològica, on destaca la sembra de varietats tradicionals de blats i lleguminoses (Chamorro et al. 2017). La tria de les varietats de blat s'ha basat en criteris com la representativitat de l’ús de les varietats a Catalunya, el valor nutritiu, el valor cultural i el potencial de comercialització en el cas de la barreja de varietats de blat (Serra-Gironella 2020). Des d’una perspectiva científica, també s’ha tingut en compte els aspectes morfològics i fenològics i els atributs fisiològics, com ara la susceptibilitat als pugons, de les diferents varietats (Taula 1). Aquest enfocament basat en l’expertesa col·lectiva dels actors implicats assegura que les varietats seleccionades s'ajustin adequadament als objectius dels investigadors i al mateix temps propicia que els productors adoptin els policultius de blat dissenyats. Les varietats escollides han estat tres varietats de blat d’hivern tou Triticum aestivum L. subsp. aestivum (Florence-Aurora, Xeixa i Montcada) i una varietat de blat d’hivern dur Triticum turgidum L. subsp. durum Desf. (Husn.) (Forment). Tot i que estrictament el blat Forment sigui una espècie diferent, per simplificar, d’ara endavant ens hi referirem com a varietat. Com a coberta de lleguminosa es va sembrar el melgó (Medicago polymorpha L.), triat per la seva adaptació al clima mediterrani i perquè el seu port prostrat el fan una excel·lent elecció com a cultiu de coberta.
El cultiu del blat a l’ambient mediterrani davant la crisi climàtica: Perspectives geogràfiques des de la teledetecció i l’ecofisiologia
(Universitat de Barcelona, 2024-09-20) Segarra Torruella, Joel; Araus Ortega, José Luis; Kefauver, Shawn Carlisle; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[cat] OBJECTIUS: L’objectiu general de la tesi és emprar dades de teledetecció i sistemes d’informació geogràfica per estimar i comprendre el rendiment i qualitat de varietats de blat mediterrani tot considerant els efectes ambientals, del paisatge i el maneig agrícola. Per dur a terme aquest objectiu, es van proposar els objectius específics següents: 1. Desenvolupar models de teledetecció multiescala per estimar els paràmetres de rendiment i qualitat. 2. Desenvolupar classificacions de tipus de cultius per tal de mapejar els camps i cultius agrícoles. 3. Comprendre els efectes ambientals, topogràfics i de maneig a nivell de camp i regional sobre el rendiment del blat i la qualitat. 4. Explorar els canvis d'ús del sòl i els efectes del paisatge en el cas del blat mediterrani. 5. Definir la idoneïtat del cultiu del blat pel que fa a les característiques regionals en diferents àrees climàtiques. 6. Entendre si cal una millora vegetal per un ambient específic o si els genotips tenen una plasticitat genètica que els permet adaptar-se a diferents agroclimes. 7. Avaluar les diferències entre el maneig convencional i ecològic del blat per definir zones d'idoneïtat del maneig.
Ecoacústica del gall fer Tetrao urogallus al Pirineu català
(Universitat de Barcelona, 2024-09-20) Jordi Torres, Olga; Mañosa, Santi; Farina, Angelo; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[cat] La comunicació animal té lloc en ambients amb un paisatge sonor específic, compost pels sons generats pels éssers vius (biofonia), els sons d'origen antròpic com el de la maquinària o els cotxes (antropofonia) i el so generat pels elements com el vent, la pluja o els terratrèmols (geofonia). A causa de les interferències que aquest paisatge sonor i les característiques de l'entorn físic poden causar durant la comunicació animal, els animals adopten estratègies que optimitzen la transmissió del seu missatge. El missatge que cada individu envia a la resta dels individus a través de les seves vocalitzacions, tant intra com interespecífiques, té importància en el dia a dia dels animals, tant amb finalitats territorials com reproductives. Els sons generats pels animals contenen característiques d'estructura, durada, espectre i intensitat que donen als animals una signatura vocal que els distingeix d'altres individus. Hem trobat que les característiques de la veu dels mascles de gall fer Tetrao urogallus que componen la signatura vocal individual són aquelles que fan referència a la freqüència i la durada dels components de la seva veu. D'aquesta manera, els individus es poden identificar i diferenciar entre si a través de les seves característiques bioacústiques. Aquesta informació es pot utilitzar en el futur per crear identificadors automàtics que diferencien a escala individual les vocalitzacions enregistrades amb gravadores autònomes. Les dades obtingudes mitjançant monitoratge acústica passiva, tant a escala individual com d'espècie, també poden ser útils per al monitoratge de la biodiversitat. Això requereix un protocol de mostreig bioacústic òptim que cobreixi una zona de mostreig ben definida i que proporcioni gravacions d'alta qualitat. Per aconseguir- ho, cal calcular la distància de propagació i la distància de detecció dels senyals acústics. Això es pot fer coneixent el valor real d'amplitud (dB) i les característiques del micròfon. Vam ser capaços de determinar per primera vegada l'amplitud real de la veu d'un mascle tot obtenint la distància de propagació i la distància de detecció del seu so. Aquesta informació es pot utilitzar per planificar protocols de mostreig bioacústic amb qualsevol mena de micròfon per obtenir les dades acústiques necessàries a efectes de monitoratge. L'estructura de l'hàbitat pot influir en la persistència d'una determinada espècie en una zona per diferents vies, incloent-hi l'alteració de la disponibilitat d'aliments o la provisió de refugis entre d'altres. En aquest sentit, hem explorat com les característiques de la propagació del so en un entorn també poden jugar un paper determinant en la persistència del gall fer en parcel·les forestals prèviament ocupades, facilitant o deteriorant la comunicació. Per investigar-ho, vam comparar l'estructura forestal i les propietats de propagació del so en parcel·les forestals ocupades i abandonades. Les característiques de propagació del so dels llocs abandonats poden afectar la comunicació dels individus creant distorsió i emmascarament del senyal acústic per reverberació excessiva i presència de soroll de fons. Per tant, els nostres resultats suggereixen que la gestió forestal del gall fer no només hauria d'afavorir una estructura forestal per proporcionar refugi i menjar, sinó també per mantenir les propietats d'hàbitat acústic adequades per millorar la seva comunicació.
Species interactions, ecosystem functioning and the resilience of marine vegetated ecosystems in a global change era
(Universitat de Barcelona, 2024-07-29) Minguito Frutos, Mario; Alcoverro i Pedrola, Teresa; Boada García, Jordi; Adams, Matthew Philip; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[eng] Human domination of Earth’s Systems is transforming life at a planetary scale. A plethora of anthropogenic pressures disrupt environmental conditions, degrading ecosystem functioning and posing unprecedented threats to global biodiversity and human life support systems. In this context of global anthropogenic change, acquiring accurate ecological knowledge is crucial for identifying warning indicators and ecosystem tolerance limits. Such knowledge can inform ecosystem managers and aid in mitigating stressors at local and/or regional scales that further fuel this global change. Marine vegetated ecosystems, including seagrass meadows and macroalgal forests, rank among the most productive habitats on Earth. They support a significant portion of the world’s biodiversity and fisheries while contributing to carbon sequestration. However, these ecosystems face severe threats from global change, which vary according to their tolerance limits and eventually shape their vulnerability against human pressures. In addition, macrophyte ecosystems often exhibit nonlinear responses to stress, including abrupt and catastrophic shifts. These inherent ecosystem properties further complicate predictions about their resistance and resilience (and, therefore, their management), making these systems excellent models for assessing the effects of global change in nature. In this thesis, I focus on key ecological mechanisms that shape the functioning and resilience of marine macrophytes and explore their interactions with herbivores under various global-change-related stressors, such as eutrophication, overfishing, or tropicalization. Specifically, I investigate (i) seagrass responses to cope with light limitation, (ii) how species-specific attributes allow seagrasses to colonize distinct depth ranges on a global scale, (iii) the influence of abiotic and biotic factors in shaping ecological contexts and thus macrophytes vulnerability to herbivory, and (iv) how mixed-shoaling behaviours between range-extending and native herbivorous fishes influence their specific foraging activity and efficiency in the tropicalized environments of the eastern Mediterranean Sea. 20 The first results in this thesis emphasize the importance of physiological photo-acclimatization for macrophyte resistance and recovery (i.e., resilience) against light limitation. While such acclimatization can reduce minimum light requirements, only self-facilitation mechanisms alleviating mortality rates lead to bistability in seagrass meadows. Secondly, the species-specific ability of seagrasses to persist across depth ranges depends on their acclimatization potential in key physiological, morphological, and structural traits, regardless of species size or functional group. Third, plant-herbivore interactions in marine macrophyte ecosystems are mediated by an array of endogenous and exogenous factors of biotic and abiotic nature. These factors include the identity of both biotic interactors, herbivore size, or the fear imposed by predators, and the nutrients, temperature, and depth conditions. Lastly, the global redistribution of tropical and warm-adapted species results in novel species interactions in temperate environments. In the eastern Mediterranean, range-extending herbivorous fish species engaged more in mixed-species shoaling behaviours, forming larger groups and increasing their foraging activity and efficiency. In contrast, native Mediterranean herbivores do not exhibit that ability to shoal in mixed-species groups nor obtain such foraging benefits. Overall, this thesis focuses on species features and ecological contexts to understand how species and marine vegetated ecosystems cope and respond to stressors of human origin. This thesis highlights (i) the role of species-specific acclimatization capacities of marine macrophytes in shaping their vulnerability to anthropogenic impacts degrading water quality, especially at their deep limits, (ii) the highly species-specific and context-specific vulnerability of macrophyte communities to herbivory, and (iii) that the mixed-species shoaling behaviour of range-extending species with temperate species results in a mechanism that partially explains the enormous herbivory pressures experienced by macrophytes in tropicalized reefs. Consequently, management at local scales is critical for maintaining healthy and resilient macrophyte ecosystems in the face of global anthropogenic pressures.
Ecological segregation in allochronic populations of storm-petrels
(Universitat de Barcelona, 2024-07-16) Medrano Martinez, Fernando Anand; González-Solís, Jacob; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[eng] Divergence in reproductive timing, known as allochrony, is an evolutionary process that in some cases has led to sympatric speciation. However, the mechanisms that could drive the existence of allochrony (e.g., environmental variability), and the role of the ecological adaptations to different seasons in the process of speciation are less known. Further, considering that several allochronic species of birds are threatened, it is important to improve our understanding of their ecology and their management and protection. Our work assessed whether seasonal allochrony has led to phenotypic and ecological differentiation and identified the environmental factors favoring it in Northern storm-petrels (Hydrobatidae). First, considering that a key aspect in the study of allochrony is a good understanding of the species’ phenology, we assessed breeding phenology using several approaches (e.g. nest monitorin or deployment of geolocators). This included an evaluation of whether brood patch scoring serves as a reliable method for describing phenology in allochronic populations. Second, to understand the role of body size in the seasonal adaptations to the environmental temperature, we assessed whether Bergmann’s rule was met across all allochronic species and populations of Northern storm-petrels. Third, to assess the role of other ecological adaptations to the environment, we focused on two contrasting systems of allochronic storm petrels, whose genetic differentiation have been well stablished but there is little knowledge on their ecological differentiation. In the first system, comprising the spring-breeding (hot season) and autumn-breeding (cool season) populations of the Cape Verde storm-petrel (Hydrobates jabejabe), which breed in Cabo Verde within the Eastern Tropical Atlantic, minimal genetic differentiation exists between them. In the second system, the summer- breeding Townsend’s storm-petrel (Hydrobates socorroensis) and the winter- breeding Ainley’s storm-petrel (Hydrobates cheimnomnestes), which breed in Guadalupe Island within the subtropical Mexican Pacific, allochrony has led to a relevant genetic differentiation and they are regarded as sister species. For both systems, we compared the spatial ecology using GPS (for the breeding season) and geolocators (for the non-breeding season), and trophic ecology using isotopes between the allochronic populations. Overall, we found a greater ecological differentiation between populations with a greater genetic differentiation than in those with little differentiation. That is, body size and all the explored axes of the ecological niche were more differentiated between allochronic populations in Guadalupe than in Cabo Verde. Regarding factors promoting allochrony and differentiation between populations, we found that Guadalupe shows a more pronounced temporal variation in marine productivity and night length compared to Cabo Verde. This implies that differentiation is more likely to occur within highly seasonal systems, encompassing variables such as air temperature, night length and oceanic productivity. These conditions favour reproductive isolation between populations, thereby facilitating differentiation and, ultimately, speciation. In addition, our research revealed that individuals from the allochronic populations of Guadalupe visited previously unrecognized and primarily non-overlaping areas during both, the breeding and the non-breeding periods. This discovery brings new challenges to the management of the waters between United States and México. Further research is needed in other allochronic organisms, such as mice and fishes, to ascertain whether phenotypic, ecological, physiological and genetic differentiation among allochronic populations co-vary with the intensity of the seasonality and the allochronic speciation process.
Spatial Ecology of the Endangered Egyptian Vulture: from Distribution and Movement to Biological Conservation
(Universitat de Barcelona, 2024-06-14) Cerecedo Iglesias, Catuxa; Real, Joan; Pretus Real, Joan Lluís; Cortés-Avizanda, Ainara; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[eng] The current rampant loss of biodiversity is known to be affecting human well-being the world over. Sustainability has become the global go-to solution to ensure the balance between economic growth, social well-being and environmental care is maintained. This concept implies the need for a reduction in human environmental impact if wildlife species are to be preserved and the adequate functioning of ecosystems is to be guaranteed. Obligate avian scavengers, one of the most globally threatened of all groups of vertebrates, play a vital role in the nature-ecosystem services-human well-being dynamic. However, the pursuit of sustainable development can negatively impact vulture conservation and all that it entails. In this thesis, we explore the conservation challenges facing the Egyptian vulture Neophron percnopterus, a globally threatened migrant species, within the current context of sustainability. Specifically, we assess the impact of human-driven transformations, changes in food availability and on-going conservation measures on the spatial ecology of this species of great conservation concern. By using novel technologies such as GPS and information generated by classical long-term monitoring schemes, we aimed to increase the knowledge of the environmental factors that have shaped the spatial distribution and movement patterns of this species up to the present day and asses the spatial coverage of the main conservation tool, the Protected Areas (PAs), committed to safeguarding this species. To do so, we focused on the populations of continental and NE of Spain. First, we found that the breeding population of Egyptian vultures in continental Spain has been stable since 2000 but that its abundance is distributed heterogeneously across the whole region. The availability of food sources such as the presence of livestock and supplementary feeding stations and the abundance of griffon vultures were found to be the main factors aggregating breeding pairs and increased local densities in certain areas. By contrast, the increasing number of wind farms correlated with low-density Egyptian vulture areas. However, some of these environmental factors were only significant at specific spatial scales, a significant finding that has practical implications. Second, we found that predictable food sources such as landfills influence the foraging behaviour and movement patterns of tagged vultures in Catalonia (N=16). Whilst the feeding strategy of non-breeding individuals is centred on predictable sources such as landfills, breeders have a more diversified approach and incorporate less predictable food sources such as extensive farms. Additionally, the novel spatial network analysis used in this thesis proves to be a valuable tool for understanding the behavioural dynamics of vultures and this approach highlights the vulnerability of this species to the loss of predictable food sources. The potential closure of landfills will foreseeably prompt behavioural shifts towards other less predictable food sources such as extensive livestock, with non-breeding individuals being particularly affected. Third, an assessment of the coverage of PAs reveals the need to adequately protect key areas of the Egyptian vulture population in Catalonia, especially those linked to feeding areas that are currently unprotected. During PA planning, criteria should be based on ecological and behavioural aspects of breeding and non-breeding vultures rather than on purely administrative factors if the entire population is to be conserved efficiently. This thesis presents new methods for studying the spatial ecology of vultures and provides a greater understanding of the distributions and movements of these long-lived mobile species, thereby contributing to a more complete explanation of these spatial patterns. Finally, it sheds light on the detrimental effects of possible future sustainable actions on vulture populations –keystone species in ecosystems and providers of services at zero cost– and provides essential knowledge that will help inform future guidelines and conservation efforts.
Ecological patterns of Antarctic benthic communities and the biodiversity they harbour
(Universitat de Barcelona, 2024-05-16) Baena Cabrera, Patricia; López González, Pablo José; Ambroso, Stefano; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[eng] The exploration of marine environments, especially the deep sea, has been an ongoing effort. With the majority of Earth’s surface covered by oceans, the invention of SCUBA and subsequent deep-sea expeditions has expanded our understanding of marine ecosystems. However, much of the ocean remains underexplored due to its vast depths. Understanding the biodiversity and functioning of marine ecosystems is crucial for developing effective management plans to protect the oceans. In this regard, this thesis aims to understand biodiversity from various perspectives and how it can vary depending on biological or abiotic factors. Utilizing non-invasive methods with Remotely Operated Vehicles (ROVs), we investigated benthic communities in the area located in front of the Filchner-Ronne Ice-Shelf, in the southernmost part of the Weddell Sea, and in the easternmost part of the same sea, specifically at Maud Rise and Astrid Ridge, covering a depth range from 251 to 1989 meters. Firstly, we examined the relationship between different demersal fish species and benthic communities comprised of various ecosystem engineers. The study demonstrated that the majority of observed fish species were positively associated with structurally complex ecosystems, with juvenile specimens predominantly found resting or hiding among the engineer organisms. Secondly, we described anthozoan communities on two seamounts and revealed significant biodiversity differences compared to the nearby plain and even between the two seamounts. The reason for these observed differences is partly due to the factor defined by the seamount itself, the region within it (summit vs. slope), the type of substrate and hydrodynamics. Lastly, with the aim of further understanding the biodiversity of one of these seamounts, a Chrysogorgia colony was sampled, revealing that the colony belonged to an undescribed species. After the recent review of this genus, it appears that this new species is the only representative of Chrysogorgia in the Southern Ocean. While only one sample of this species exists, its colonial morphology characteristics and proximity suggest potential sightings on two other occasions on the same seamount. However, the oceanographic peculiarities of seamounts raise the question of whether this species has an endemic distribution limited to a small region of seamounts or is more widely distributed. Overall, this thesis enhances ecological knowledge of different Antarctic benthic communities, highlighting that seemingly similar environments can exhibit significant different benthic communities and that even at small scales, notable community-level differences can be observed.
Unravelling seabird-fishery dynamics through bird-borne technologies
(Universitat de Barcelona, 2024-04-15) Navarro Herrero, Leia; González-Solís, Jacob; March Morla, David; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[eng] Seabirds and fisheries share the same fishing resources and grounds, resulting in their inevitable interaction, with significant conservation implications for the firsts. Seabirds scavenging on fishery waste modify their foraging ecology, behaviour and diet with potential consequences on their health. In addition, these interactions often result in the incidental capture of seabirds by fisheries, known as bycatch and thought to drive the decline of a hundred seabird species. While the dynamics of seabird- fishery interactions have been assessed through onboard observations and, more recently, by using tracking technologies at large spatiotemporal scales, studies at fine spatiotemporal scales are still scarce and with uneven results. This thesis aims to enhance the understanding of the dynamics of seabird-fishing interactions with industrial fisheries, with two parallel objectives: (1) unravel fine-scale seabird-fishery dynamics by identifying which, where and when seabird species interact with specific fisheries, uncovering the drivers behind these dynamics, and assessing the legal and political status of the fisheries involved; (2) explore methods for examining seabird-fishery interactions when vessel tracking is unavailable, which is often difficult to obtain and may have gaps due to faulty equipment, illicit manipulation (e.g., Illegal, Unreported, and Unregulated fishing activity; IUU), or lack of adoption in some fleets. To pursue these objectives, we generally used bird-borne GPS data and, in some specific cases, in combination with accelerometers, wet-dry, pressure and radar detectors sensors (capable of scanning seabird surroundings to identify vessels) and coupled it with gridded or raw Automatic Identification System (AIS) data from vessels. The thesis focused on NW Africa and the NW Mediterranean regions. The first is recognised as one of the most important seabird hotspots and upwelling systems worldwide, with intensive fishing activity and a significant presence of IUU fishing. The second holds high marine traffic activity by fishing, merchant, and recreational vessels. Unlike western Africa, where seabird-fishing interactions are poorly studied, it is well known that in this NW Mediterranean region, bycatch is the primary driver of population decline for endemic sea- bird species. The combination of bird-borne GPS and AIS data showed only three out of the nine seabird species in NW Africa, and the only species examined in NW Mediterranean frequently attended industrial fishing vessels: Cory’s shearwaters (Calonectris borealis), Cape Verde shearwaters (Calonectris edwardsii), Audouin’s gulls (Ichthyaetus audouinii) in NW African waters, and Scopoli’s shear- waters (Calonectris diomedea) in NW Mediterranean. All of them primarily attended trawlers, indicating these species feed on fishing discards but are also at risk of bycatch. The drivers of seabird-fishery interactions encompassed environmental factors (e.g., coastline distance) and vessel characteristics (e.g., vessel length or gear type). In NW Africa, seabirds traversed boundaries, foraging on up to five Exclusive Economic Zones and interacted with fishing vessels holding flags from 24 countrie By combining GPS, accelerometers, and wet-dry sensors, alongside machine learning techniques, we showed that seabird-vessel interactions can be inferred through movement analysis. In addition, when combined with radar detectors, this method demonstrated effectiveness in monitoring vessel activity when vessel tracking may be lacking. This thesis provided new approaches to the study of the dynamics of seabird-fishery interactions and to monitoring vessel activity through the use of bird-borne technologies. We showed that these approaches can be beneficial when applied to largely understudied regions where onboard observation and fishing surveillance are scarce or when vessel tracking data is unavailable, establishing an evidence-based framework that can help focus conservation efforts.
Facing Global Change: Impacts of drying and human pressures on invertebrate diversity and organic matter processing in a Mediterranean stream network
(Universitat de Barcelona, 2024-04-04) Viza, Aida; Muñoz Gràcia, Isabel; Menéndez López, Margarita; Universitat de Barcelona. Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals
[eng] Intermittent rivers and ephemeral streams (IRES) currently constitute half of the global river network, occurring ubiquitously. Characterised by natural and periodic cessations of flow, IRES are proliferating due to global change, but face threats from different human-induced impacts such as water pollution, soil erosion, and habitat fragmentation. Notably, agriculture is one of the human activities with the greatest impact on freshwater ecosystems. This thesis examines the effects of drying and different land uses (natural and agricultural) on biodiversity and ecosystem functioning in a Mediterranean intermittent stream network, the Algars. These aspects are crucial for sustaining biogeochemical cycles and energy transfer within a system. Additionally, the thesis investigates the role of resistance strategies during dry phases in preserving aquatic diversity. Chapter 1 focuses on the impact of drying and land use on the functional and taxonomic α- and β-diversity of aquatic invertebrate communities during a hydrological year. Chapter 2 evaluates the roles of hyporheic refuges and invertebrate seedbanks during the dry phase in benthic assemblages under flowing conditions, assessing the taxonomic and functional responses across six intermittent streams. Chapter 3 investigates the influence of drying and land use on organic matter (OM) decomposition and fungal biomass throughout an intermittent stream network during a hydrological year. Chapter 1 reveals that drying negatively affects the taxonomic and functional α- diversity of aquatic invertebrates, but positively influences β-diversity. Land use predominantly affects α-diversity. Notably, habitat heterogeneity and elevated water nutrient levels in the stream network positively correlate with invertebrate diversity. The adverse effects of drying are less pronounced in upstream forested areas, which exhibit higher habitat heterogeneity, when compared to downstream agricultural regions. Chapter 2 identifies that seedbanks and hyporheic assemblages support up to 16% and 40% of the benthic assemblages, respectively. Diversity metrics vary between assemblage types in terms of taxonomic and functional richness. While no clear relationship can be established for diversity or the abundance of resistance traits with the dry phase duration, a negative linear relationship is observed between the abundance of resilience traits and the dry phase duration. Chapter 3 demonstrates that decomposition rates across the stream network negatively correlate with the duration of flow interruption. Dissolved inorganic nitrogen derived from agricultural activities mitigates the negative impact of drying on mass loss, enhancing it by up to threefold.However, with prolonged dry conditions, this effect diminishes. Increased canopy cover, particularly in natural areas, enhances OM processing. In summary, moderate agricultural activity within the small network studied can enhance diversity and ecosystem functioning. Nonetheless, increases in the frequency and duration of dry phases due to global change will reduce water availability, exacerbating the impacts of human pressures and threatening the survival strategies of aquatic species. This thesis significantly contributes to the understanding of the interactions between drying and land use in OM processing and biodiversity across a stream network. It underscores the importance of conserving natural and forested streams, especially in headwater regions, as potential refuges in intermittent networks.

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