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

Abstract

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.

Functional Traits in Lichen Ecology: A Review of Challenge and Opportunity

“…Furthermore, the higher cost involved in measuring certain traits may not always contribute additional information within a hypothesis, compared to insights gained from using more easily obtained trait data. Thus, Hurtado et al [37][38][39] found that readily applied categorical traits of epiphytic lichens, such as the growth form and type of photobiont (considered at a high level of systematic classification), were highly relevant in explaining lichen response to macroclimate across a latitudinal gradient in Europe. Surprisingly, traits with a more direct physiological association (e.g., chlorophyll a, water holding capacity, specific thallus mass, tissue %N or %C) were little or not relevant at this scale of analysis.…”

Direct and Indirect Effects of Management Intensity and Environmental Factors on the Functional Diversity of Lichens in Central European Forests

“…Nevertheless, lichen functional traits are increasingly used in order to explore ecological processes, and measuring lichen traits for a particular set of sampled species is becoming more common (e.g., [ 16 , 17 , 18 , 19 , 20 ]). In fact, studies have recently been conducted to investigate how lichen functional diversity changes along ecological gradients (e.g., [ 21 , 22 , 23 ]) and how it is affected by forest management (e.g., [ 4 , 24 , 25 ]). However, a comprehensive assessment of how lichen functional diversity changes along a continuous gradient of forest management intensity across different regions and varying environmental conditions is still lacking.…”

Morphological and Chemical Traits of Cladonia Respond to Multiple Environmental Factors in Acidic Dry Grasslands

“…This high variability leads to a range of possible morphological combinations that have been almost overlooked in previous literature (e.g., [ 6 , 7 , 14 , 15 ]). Additionally, reproduction, which is a relevant trait in species life history [ 5 , 6 ], is achieved in variable ways, not only sexually (by means of ascospores), but also with different types of vegetative propagules [ 11 , 12 ], as well as by dispersion of thallus fragments [ 16 ]. The position of pycnidia may also vary, developing either on the primary or secondary thallus [ 12 , 13 ].…”

“…The analysis of functional traits to explore species' responses to environmental factors is increasingly applied also to lichens [1,2]. However, most studies have addressed epiphytes (e.g., [3][4][5]), whereas terricolous lichens are relatively less investigated (e.g., [6][7][8]) despite their ecological importance (e.g., [9]) and conservation concern [6,10]. It is therefore of utmost importance to understand the relationships driving terricolous species' responses to environmental stresses, particularly in the current context of global change [2,5,6] Terricolous lichen communities are often dominated by species of the genus Cladonia.…”