Geographical Variation of Diversity in Argentine Passerine Birds

Abstract

The number of species, genera, and families of passerine birds is presented in the form of isoline maps, using a 100 x 100 km grid. The main features of these maps are discussed according to the biogeographic background. A similar procedure is performed for entropy (information content) of species per genera, species per family and genera per family. Simple linear and multiple correlations between taxa richness and entropy with precipitation, temperatures (mean annual, mean July, and mean January), minimum altitude, maximum altitude, and slope were performed, calculating also the beta coefficients weighing the importance of independent variables. Comparisons are given for the whole country as well as for four selected transects. Latitudinal variation of species' richness is also analysed. According to a phytogeographical map, a strata index was calculated for each quadrat according to proportions of different biomes and the number of contacts or ecotones which they have. The strata index, at a macrogeographical scale, accounts fairly wellfor the richness of taxa.