Integrated analysis of species richness and functional traits highlights the functional vulnerability of liverworts along the entire altitudinal gradient in Colombia

Investigating diversity patterns along altitudinal clines brings important insights about the responses of biodiversity to changes in environmental conditions, with implications for conservation actions. We analyzed the species richness and functional patterns of liverworts along the entire altitudinal gradient (0-5000 m) in Colombia, the country with the richest liverwort flora in tropical America. Published data on the elevation ranges of the 705 liverwort species and functional traits related ecological strategies were compiled. The elevation gradient was divided into 100-m vertical bands. General linear and additive models were used to investigate trends in liverwort richness. Functional entities richness and functional diversity (Functional Redundancy, Functional Over-redundancy and Functional Vulnerability) were evaluated along the altitudinal gradient. We also assessed the species richness-dependency in the functional patterns through NMDS. A unimodal hump-shaped relationship was observed for species richness and functional diversity, with the highest values recorded in the intermediate zones (2000-3000 m) of the altitudinal gradient. The most representative traits explaining the functional differentiation were the presence of monoicous and dioicous reproductive system, lobules, inflated lobules, and thalloid and leafy gametophytes. Functional vulnerability showed an exponential pattern, with higher values at altitudes above 4000 m, where life forms tolerant to high humidity and dark pigmentation were the most relevant traits. The unimodal hump-shaped pattern was explanatory of the distribution of species and functional diversity of liverworts along the altitudinal gradient. These functional patterns indicated that environmental filters select functional traits, mainly those related to water uptake and retention, as adaptive strategies. We found a high functional vulnerability generated by functional entities with a single liverwort species in high-Andean areas (4000-5000 m), implying a threat to the ecosystem functions provided by liverworts in these areas