Disentangling functional trait variation and covariation in epiphytic lichens along a continent-wide latitudinal gradient.

Characterizing functional trait variation and covariation, and its drivers, is critical to understand the response of species to changing environmental conditions. Evolutionary and environmental factors determine how traits vary among and within species at multiple scales. However, disentangling their relative contribution is challenging and a comprehensive trait-environment framework addressing such questions is missing in lichens. We investigated the variation in nine traits related to photosynthetic performance, water use and nutrient acquisition applying phylogenetic comparative analyses in lichen epiphytic communities on beech across Europe. These poikilohydric organisms offer a valuable model owing to their inherent limitations to buffer contrasting environmental conditions. Photobiont type and growth form captured differences in certain physiological traits whose variation was largely determined by evolutionary processes (i.e. phylogenetic history), although the intraspecific component was non-negligible. Seasonal temperature fluctuations also had an impact on trait variation, while nitrogen content depended on photobiont type rather than nitrogen deposition. The inconsistency of trait covariation among and within species prevented establishing major resource use strategies in lichens. However, we did identify a general pattern related to the water-use strategy. Thus, to robustly unveil lichen responses under different climatic scenarios, it is necessary to incorporate both among and within-species trait variation and covariation.

Landscape effects on pollination networks in Mediterranean gypsum islands.

Habitat fragmentation is a major driver of global change that has operated historically on Mediterranean ecosystems. However, more needs to be understood about how fragmentation influences ecological interactions, particularly pollination. Gypsum outcrops are historically fragmented Mediterranean habitats and settings for the evolution of many endangered soil-specialist plants with narrow ranges. In this study, we aimed to determine how fragmentation (area and connectivity) affects: (i) pollinator community composition and (ii) structural properties of pollination networks; and whether there are differences in the effects of fragmentation on: (iii) the number of interactions and visits among pollinator functional groups; and (iv) the number of interactions and specialisation degree between soil-specialist and soil-generalist plants. We characterised the degree of fragmentation and the pollination network structures in 12 gypsum habitat fragments embedded in a cropland matrix during two consecutive years. We found significant relationships between fragmentation and network structure. The effects of fragmentation differed among pollinator functional groups, but not between soil-specialist and soil-generalist plants, in terms of number of interactions. However, the relatively higher pollinator specialisation of soil-specialist plants suggested greater dependence on pollinators. Inter-annual variations in the network structures demonstrated the importance of temporal replication. The observed patterns related to the landscape structure and pollination at both the network and species levels provide insights into the key ecological processes in gypsum islands. These findings may help to identify the potential drivers of species persistence, especially for endangered soil-specialist plants with narrow ranges in a changing scenario with exacerbated habitat fragmentation.