摘要：The Balsas’ province of southern Mexico has been defined as a natural unite based on its endemic taxaand environmental variables. It is recognized as a center of diversification, endemism and biogeographic transition.However, there are elements that allow us to distinguish 2 different biotic components within the province.Weanalyzed the distribution patterns of richness and beta diversity of birds, both total (migratory + resident) and resident.We used 2 coefficients of dissimilarity (1-Jclásicoy 1-Jmod.) to analyze beta diversity within the province. There are 3areas with high species richness: 1) Northeastern; 2) Western and 3) in the center of the province of the Balsas. Thebeta diversity pattern suggests the existence of 2 components in the bird community that correspond to Eastern andWestern sectors of the Balsas province. This is consistent with studies concerning the tendencies of the distributionof other taxa within the Balsas province. Therefore, we propose the division of the province into 2 faunal districts:Eastern and Western.
关键词：birds;richness;species replacement;biogeographic province.;aves;riqueza;reemplazo de especies;provincia biogeográfica.
