Bird diversity patterns in Neotropical temperate farmlands: the role of environmental factors and trophic groups in the spring and autumn.

MELISA F. APELLANIZ; M. ISABEL BELLOCQ; JULIETA FILLOY

AUSTRAL ECOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2012 vol. 37 p. 547 - 555

1442-9985

Productivity and habitat heterogeneity, and environmental similarity are some of the most widely accepted hypotheses to explain spatial patterns of species richness and taxonomic similarity, respectively. Environmental factors may exhibit seasonal changes affecting species distributions. We explore the seasonal constancy in spatial patterns of bird species richness and taxonomic similarity. Species feeding habits are likely to have a major influence in bird-environment associations and, given that the availability of food resources shows seasonal changes in temperate climates, we expect those associations to differ by trophic groups (insectivores or granivores). We surveyed birds and estimated environmental variables along line-transects covering an E-W gradient of annual precipitation in the Pampas of Argentina during the autumn and the spring. We assessed responses of bird species richness to spatial changes in habitat productivity and heterogeneity using regression analyses, and evaluated the seasonal constancy of those responses. Furthermore, we used Mantel tests to examine the relationship between species turnover and both the environmental similarity between sites and the geographic distance among sites, also assessing the seasonal constancy of those relationships. Richness of insectivorous birds was directly related to primary productivity in both seasons, whereas richness of seed-eaters showed a positive association with habitat heterogeneity during the spring. Taxonomic dissimilarity between assemblages was correlated with both climatic dissimilarity and geographic distance during the autumn and the spring, except for insectivore assemblages. The diversity within main trophic groups likely reflected seasonal differences in their spatial patterns as a response to seasonal changes in the spatial patterns of food resources. Our findings suggest that analyses incorporating seasonality and functional groups could contribute to better understand the determinants of biological diversity in temperate climates.