Functional Diversity of Amphibians and Reptiles in Tropical Dry Forest Remnants and Anthropogenic Cover Types in the Lower Bogotá River Sub-Basin (Department of Cundinamarca, Colombia)

Landscape transformation drives global biodiversity loss by altering species assemblages. Species respond to habitat changes based on their functional traits, with those unable to tolerate new environmental conditions being eliminated. As a result, changes in assemblage structure affect ecosystem functioning, since the functional roles of species also depend on their trait values and ranges. This study aims to analyze the structure of amphibian and reptile assemblages in the tropical dry forest of the Lower Bogotá River sub-basin, classify species into functional groups based on morphological and natural history traits, and evaluate the effect of natural and anthropogenic land cover types on functional diversity indices. The structure of amphibian and reptile assemblages varied among land cover types, reflecting differences in species composition and abundance. Amphibians showed significant variation between natural and anthropogenic cover types, with rice fields acting as strong environmental filter that increased functional dispersion (FDis) and functional divergence (RAOQ). In contrast, reptile assemblages exhibited high functional homogenization, likely due to landscape transformation and the biological invasion of two gecko species, with no significant variation in functional diversity indices across land cover types. The study also recorded two critically endangered reptile species of high conservation priority: Podocnemis lewyana, an endemic species and Mabuya mabouya. Species were classified into six functional groups for both amphibians and reptiles, based on key functional traits such as body size, reproductive strategy, habitat use, and diet. Among amphibians, two functional groups were only present in natural land covers and disappeared in anthropogenic ones: the group of diurnal and poisonous species, and the group of species with nocturnal habits, terrestrial habitat use, insectivorous diets, oval body shape (high surface-to-volume ratio) and intermediate biomass, suggesting that species with these specialized traits failed to persist in transformed landscapes. In contrast, five of the six reptile functional groups were present in natural covers, with only the group of nocturnal, large-bodied carnivorous species absent from anthropogenic covers, reflecting a greater capacity for tolerance to habitat transformation in the remaining functional groups; while the viviparous and venomous species were exclusively found in anthropogenic covers. The high level of functional homogenization between natural and anthropogenic land covers, particularly among reptiles, suggests that historical deforestation has driven environmental filtering, leading to the simplification of herpetofaunal assemblages, despite significant species turnover between land cover types. This, in turn, has resulted in the loss of amphibian and reptile functional groups, reducing niche differentiation and potentially reducing ecosystem functionality. The observed changes in functional diversity may contribute to an extinction debt, which could be further explored through the study of biotic interaction networks in fragmented tropical dry forest landscapes. Future research should also consider investigating these networks from a functional trait perspective, as this approach may provide deeper insights into the long-term implications for resource use efficiency and ecological processes in fragmented landscapes.