The Importance of Environmental Heterogeneity in Evaluating the Conservation Status of Two Frog Species in a Changing Amazonian Interfluve

ABSTRACT Identifying the most effective criterion to assess the conservation status of vulnerable species in threatened tropical regions is crucial to evaluate recovery plans. We investigated the influence of environmental heterogeneity on the extent of occurrence (EOO), area of occupied habitat (AOH), and density variation of two Amazonian riparian frog species, Allobates sumtuosus and Amazophrynella manaos . We searched for the species in 86 sites in the Negro–Nhamundá Rivers interfluve between 2016 and 2019, using visual and acoustic searches in 250 × 10 m plots established on banks of small streams in terra‐firme dense rainforests. EOO greatly overestimated the AOH for the studied species. This is likely due to the contrasting responses of the species to broad‐scale environmental heterogeneity. The density index of the species varied in response to both abiotic and biotic factors, and few locations harbored high densities. Therefore, reserves to enhance the conservation of both species should be based on environmental determinants of intermediate density indices. The large EOO indicates resistance to threats at the species level. However, the species' restricted AOH suggests low resilience at the population level. This is critical given the current habitat degradation across the studied region. Extent of occurrence is likely to be a poor indicator of conservation status for many Amazonian frogs.