Rodent endemism, turnover and biogeographical transitions on elevation gradients in the northwestern Argentinian Andes

FERRO IGNACIO

MAMMALIAN BIOLOGY

ELSEVIER GMBH

Año: 2013 p. 322 - 331

1616-5047

The aim of this research is to relate patterns of endemism and turnover along a local elevation gradient in northwest Argentina with continental biogeographical transitions. Specimen based records constituted the principal source of information to infer rodent distribution along the elevation gradient. I assessed elevational variation of richness, endemism and turnover by means of non-linear regression analysis. Then I identified five distributional patterns based on the overlap of species geographic range. Their frequency along elevation was used to validate biogeographical boundaries inferred by turnover rates. Eleven species out of 37 (30%) are endemic to the study area. Species richness and endemism were humpshaped. The rate of endemism reached its maximum value at the upper limit of the forest (2500 m). By contrast, species turnover was U-shaped, with a small peak at 1500 m and a maximum at 3500 m. The species? geographic range patterns were not randomly distributed along elevation but agglomerated at specific elevation. Species turnover and chorological analysis suggest two biogeographical boundaries, a weaker at 1500 m and a stronger at 3500 m. The 1500 m boundary marks the transition from assemblages dominated by Lowland-widespread fauna at lower elevation to Montane (Andean eastern slopes) species at middle elevation. This boundary is characterized by moderate species turnover and high species richness. The strong turnover rate at 3500 and the dominance of highland Andean and Andean-Patagonian species above this elevation suggest the occurrence of the transition between the Neotropical and Andean regions; which is characterised by an almost complete species replacement.