Decline of Mammal Species Diversity Along the Yungas Forest of Argentina

OJEDA, R.A., BARQUEZ, R.M, STADDLER, J, BRANDL, R.

BIOTROPICA

The Ass for Trop Biol & Conserv (ATBC)

Año: 2008 vol. 40 p. 515 - 521

0006-3606

ABSTRACT The southernmost extension of tropical Andean–Amazonian forests protrudes into the arid to semiarid habitats in northwestern Argentina. We analyzed the decline of species richness of forest mammals along these Yungas forests. In particular, we tested whether species decline is due to a general latitudinal effect and whether the drop of species from the assemblages was independent from species’ traits and environmental variables. For these tests, we estimated the geographic range edges of 39 species of forest mammal and estimated the species richness with bands of 30. First, we compared the slope of the decline of species richness from north to south (5.8 species/degree) with the decline expected from the latitudinal species gradient (1–3 species/degree). The decline in species richness of forest mammals along the Yungas was significantly steeper than expected. Second, with a null model assuming a random drop of mammal species we derived confidence limits for the expected species richness and number of range edges within the bands. None of the forest mammals reached the tip of the forest, in marked contrast to nonforest mammals. More range edges than expected from the null model fell within the bands 23◦30–24◦00 S and a band near the tip of the Yungas indicating a nonrandom drop of species. The correlation between vulnerability traits and range edges suggests that processes associated with the availability of resources influence the drop of species. We propose that a suite of macroecological attributes interacting with a decrease in habitat quality determines the pattern of species richness in the Yungas forest. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp.◦30–24◦00 S and a band near the tip of the Yungas indicating a nonrandom drop of species. The correlation between vulnerability traits and range edges suggests that processes associated with the availability of resources influence the drop of species. We propose that a suite of macroecological attributes interacting with a decrease in habitat quality determines the pattern of species richness in the Yungas forest. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp. Key words: fragmentation; geographic range edges; macroniches; Neotropical forest mammals; North West Argentina; tropical–temperate ecotone; vulnerability.: fragmentation; geographic range edges; macroniches; Neotropical forest mammals; North West Argentina; tropical–temperate ecotone; vulnerability.