Are Lizard Assemblages From the Atlantic Forest Under the Influence of Ecological Release?

Abstract

Ecological release is a key concept that describes how species increase their density and expand their niche in response to reduced competition. This phenomenon is commonly studied in island systems, but its occurrence in naturally isolated habitats within continents remains underexplored. To address this gap, we compared lizard assemblages between the remnants of the coastal Atlantic Forest (non-isolated areas) and naturally isolated forest relicts. Our predictions were that in isolated areas, lizard density and niche dimensions (e.g., diet) should be larger due to the absence of possible competitors, as well as a more generalised morphology. We verified that non-isolated areas had greater lizard richness than naturally isolated forest relicts. However, there was no difference between the type areas in relation to the average abundance and average breadths of the lizard niches (calculated from the volume of prey in the stomachs). In contrast, the average nearest neighbour Euclidean distance of lizard assemblages (from morphological data) was lower in isolated areas (more generalised) compared to non-isolated areas. We conclude that this study partially supports the ecological release hypothesis: the low number of competitors in naturally isolated forest enclaves (ecological opportunity) does not support density compensation and niche expansion (diet), emphasising the impact of historical factors on assemblage structure. In contrast, the more generalised morphology verified in lizards from isolated areas is considered evidence of ecological release, possibly driven by the expansion of microhabitat use. However, the lack of records on the spatial use of the studied lizards underscores the need for further research to confirm this relationship.