Microplate tectonics and environmental factors as distribution drivers in Western Mediterranean freshwater planarians

Abstract

Aim: Species biogeography mainly focuses on palaeogeographical events, while en-vironmental factors are generally overlooked despite their importance in species diversification. Here, we use an integrative approach to understand how palaeogeo-graphical and environmental processes shape species distribution and focus on fresh-water planarians as the model system. Location: Western Mediterranean. Taxon: Dugesia. Methods: We inferred the phylogenetic relationships of most known Dugesia species in the area using six molecular markers. We then estimated their divergence times and reconstructed their ancestral distribution ranges. We also performed environmental niche modelling analyses using Dugesia subtentaculata as a model to evaluate the ef-fects of several hydro-environmental variables and the likely existence of interspecific competition on Dugesia distributions. Results: Our results provide a new phylogenetic scheme for Dugesia from the Western Mediterranean and show that the time splits between the lineages and their putative ancestral distribution ranges are correlated with microplate tectonic dynamics within the region during the Oligocene-Miocene period. Our environmental niche modelling analyses indicate that the type of land cover and the slope of the terrain are the most important abiotic factors driving the distribution of Dugesia from this region. Finally, we found a partial niche overlap between D. subtentaculata and two other common planarian species from the Iberian Peninsula. Main conclusions: The microplate tectonic dynamics of the Western Mediterranean during the Oligocene-Miocene period, together with the position of the mountain ranges and posterior climate changes, may have played crucial roles in driving the biogeographical history of Dugesia in this region. Moreover, both interspecific com-petition and changes in fluvial characteristics driven by human activities may affect the current diversity and distribution of Dugesia in the Western Mediterranean. This study highlights the importance of integrating different types of information to study the biogeographical history of a species.