Drivers of species richness in Amazonian amphibians and reptiles: testing diversity hypotheses across taxonomic groups

Investigating the ecological drivers of species richness in the Amazon Basin enhances our understanding of the eco‐evolutionary processes shaping biodiversity across taxonomic groups. Our study investigates the roles of energy availability, water balance, and habitat heterogeneity in shaping the distribution of amphibians and reptiles by testing five ecological hypotheses: energy–environment, energy–water dynamics, productivity, metabolic theory and habitat heterogeneity. We found distinct patterns across taxa. The energy–environment hypothesis received the strongest support overall, with temperature exerting a positive effect on species richness in all groups, while potential evapotranspiration negatively impacted on Gymnophiona and snakes. The energy–water dynamics hypothesis showed moderate, taxon‐specific support, performing best for Anura, snakes, Crocodylia and Testudines. Precipitation had a positive effect across groups, whereas actual evapotranspiration had mixed impacts, with positive impacts on Anura, lizards and snakes but negatively impacting on Crocodylia and Testudines. The productivity hypothesis received weak overall support; net primary productivity positively influenced Anura and snakes but negatively affected lizards. The metabolic theory was moderately supported, with the inverse of absolute temperature (1/kT) consistently showing a negative effect across groups. The habitat heterogeneity hypothesis was generally poorly supported, except for Gymnophiona; landscape heterogeneity negatively influenced Anura, Caudata and snakes, but positive influences on the remaining taxa. Our findings highlight that, although the energy–environment hypothesis has emerged as the most robust across taxa, species richness patterns in amphibians and reptiles are best understood when considering the joint influence of energy, environment, and water availability (i.e. energy + environment + water). This integrated understanding underscores the need for conservation strategies that account for the unique ecological requirements of different taxonomic groups. Our findings highlight that sustaining biodiversity in the Amazon Basin depends primarily on the balance of energy and water dynamics, while the role of landscape heterogeneity appears to be taxon‐specific and context‐dependent.