Human-Induced Landscape Changes Homogenize Atlantic Forest Bird Assemblages through Nested Species Loss.

The increasing number of quantitative assessments of homogenization using citizenscience data is particularly important in the Neotropics, given its high biodiversity and ecological peculiarity, and whose communities may react differently to landscape changes. We looked for evidence of taxonomic homogenization in terrestrial birds by investigating patterns of beta diversityalong a gradient of human-altered landscapes (HAL), trying to identify species associated with this process. We analyzed bird data from 87 sites sampled in a citizen scienceprogram in the south Brazilian Atlantic Forest. Regional-scale taxonomic homogenization was assessed by comparing beta diversityamong sites in different HALs (natural, rural or urban landscapes) accounting for variation derived from geographical distanceand zoogeographical affinities by georeferencing sites and determining their position in a phytogeographical domain. Beta diversitywas calculated by multivariate dispersion and by testing compositional changes due to turnover and nestednessamong HALs and phytogeographical domains. Finally, we assessed which species were typical for each group using indicator speciesanalysis. Bird homogenization was indicated by decreases in beta diversityfollowing landscape changes. Beta diversityof rural sites was roughly half that of natural habitats, while urban sites held less than 10% of the natural areas’ beta diversity. Species composition analysis revealed that the turnover component was important in differentiating sites depending on HAL and phytogeography; the nestednesscomponent was important among HALs, where directional species loss is maintained even considering effects of sampling effort. A similar result was obtained among phytogeographical domains, indicating nested-pattern dissimilarity among compositions of overlapping communities. As expected, a few native generalists and non-native urban specialists were characteristic of rural and urban sites. We generated strong evidence that taxonomic homogenization occurs in the south Brazilian Atlantic Forest as a result of a directional and nested species loss, with the resultant assemblages composed of few disturbance-tolerant birds.