Herpetofaunal responses to anthropogenic forest habitat modification across the neotropics: insights from partitioning β-diversity

Habitat change is the primary cause of biodiversity loss worldwide. Large tracks of primary forest can be (1) degraded by human-induced disturbance to the point of total conversion into alternative non-forest land-use types, or (2) reduced into small forest fragments isolated within an anthropogenic matrix. Such disturbed habitats are further prone to be colonized by disturbance-adapted species, which can offset species extinctions therein. Here we investigate amphibian and lizard responses to different degrees of habitat degradation and fragmentation, in terms of both species richness and composition, across the neotropics. We then partitioned the beta-diversity into its species replacement and richness-difference components to further examine changes in amphibian and lizard species composition. Based on a comprehensive compilation of 67 studies, we observed increasing rates of amphibian and lizard species loss, particularly along the habitat degradation gradient. There were considerable shifts in species composition for both taxa at human-disturbed sites, which were compounded by species replacements. Novel environmental features of disturbed sites clearly benefited synanthropic generalists at the expense of strict forest habitat specialists. As such, we recommend avoiding the use of species richness as a single metric in evaluating the effects of habitat disturbance on biodiversity. Our findings further highlight the critical importance of retaining large expanses of relatively undisturbed forest within anthropogenic landscapes to prevent pervasive species losses and changes in community structure.