Performance of Cerrado lizards: a test of the center–periphery hypothesis

The center–periphery hypothesis (CPH) states that species' demographic performance declines from the center towards the periphery of their geographic range due to increasingly suboptimal environmental conditions. We tested the predictions under the CPH using two lizard lineages with different activity patterns and distributions, taking lizard body condition and gastrointestinal parasitism as proxies of demographic performance. We sampled Ameiva ameiva , Tropidurus itambere , and T. madeiramamore from core localities and peripheral Cerrado isolates in southwestern Amazonia. To assess predictions under the CPH, we built generalized linear mixed models using the indicators of demographic performance as the response variables. Environmental (climate, elevation, soil) and spatial (landscape parameters, distance to Cerrado's center and periphery) variables were predictor variables, along with lizard genus and their interactions. We applied generalized dissimilarity modeling (GDM) and variance partitioning to assess geographic, environmental, and spatial influences on parasite beta diversity. Lizard lineage was the most important predictor of body condition and lizard parasite abundance/richness. Centrality, connectivity, and precipitation of the warmest quarter significantly predicted lizard gastrointestinal parasitism. Soil, centrality, landscape, and elevation had a non‐zero sum of coefficients in GDM's I‐spline for lizard parasite beta diversity. Geographic distance had a negligible influence, and environmental variation was the primary driver of parasite beta diversity. For Ameiva , demographic performance did not vary across the sampled central and peripheral areas, both central to Ameiva 's distribution, consistent with CPH predictions of stable demographic performance between central areas. Tropidurus displayed better body condition and higher parasite abundance in peripheral isolates, contrary to predictions under the CPH, likely due to ecological release. Soil and proximity to the Cerrado's center were the strongest predictors of parasite beta diversity, suggesting environmental and spatial factors outweigh biotic or climatic influences. These results suggest that the CPH's predictions may not always hold, especially when ecological release affects demographic performance.