Assessing changes in epiphytic lichen community after 45 years, a study case in white poplars from northern Iberian Peninsula (Jaca, Aragon)

Abstract

Epiphytic lichens are used broadly as bioindicators, as they are sessile organisms with slow growth and different species display a wide range of environmental sensitivity. Most studies on epiphytic lichens focus on their use as indicators of the present environmental conditions, but few studies assess the changes that occur over decades. Comparative temporal approaches in lichens are rare, since there are few old datasets and in most cases substrates have disappeared, especially trees. However, in 1973 one of us (X. Llimona) described the lichen community on urban Populus alba in Jaca, and those trees are still alive. Our aim was to study the epiphytic lichen community in 2018 and compare it with the study of 1973. Species richness decreased during these 45 years. While only 36% of species found in 1973 persisted until 2018, these species remaining were observed at a high frequency in the 2018 sampling. Lichens communities from both years were similar on its tolerance to environmental variables, and the locality and their surroundings had the same land use in both years. Thus, the changes in lichen composition between both samplings might be explained by autogenic succession or limitation on dispersion rather than habitat filtering. Our data suggests that, under stable environments, lichen community assembly over decades depends on other traits such as competition rather than lichen sensitivity.