Landscape-scale forest loss promotes the taxonomic homogenization of bird assemblages in a human-modified mountain region

Abstract

Background and Research Aims: The ongoing deforestation process across the globe is reducing the extent of suitable habitat for forestspecialist species. The cross-habitat spillover hypothesis posits that in such a scenario, some species may be compelled to use supplementary resources from the adjacent anthropogenic matrix. Consequently, the compositional differentiation (beta diversity) between forest remnants and the matrix should decrease (i.e. biotic homogenization) in more deforested landscapes. We tested this prediction by assessing bird assemblages in a mountain region of Guerrero, Mexico. Methods: We surveyed birds in nine landscapes with different forest cover. Within each landscape, we measured bird beta diversity (D?) between forest fragments and the surrounding anthropogenic matrix and then assessed the relationship between D? and landscape forest cover. We separately assessed the complete bird assemblage, and forestspecialist and habitat-generalist birds, because the cross habitat spillover hypothesis posits that the loss of D? in more deforested landscapes should be particularly evident when assessing forest-dependent birds.