Human density and sampling time explain richness of anurans in the brazilian biomes

Anuran richness patterns are strongly influenced by environmental factors. However, investigations on this issue have focused on the influence of abiotic factors without considering the joint effect of many existing variables, including the data sampling methodology and human demography. In this study we investigated the relationship between 21 environmental variables and anuran richness in brazilian biomes. Environmental variables represent a combination of human demographics, topographic, climatic and vegetation characteristics, and data sampling methodologies. We used principal component factorization and regressive and autoregressive models to select the most relevant variables for explaining anuran richness. Richness was correlated with demographic density, vegetation, accumulated rainfall, accumulated rainfall in the third and fourth quarter of the year, and accumulated rainfall in the first and second half of the year. However, the regressive and autoregressive models showed that human demographic density, sampling time, and sampling methodology were the best predictors of anuran richness. Our results highlight the importance of considering the effects of the human footprint and the methodology used for data collection on anuran species richness.