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Four morphologically similar species of insectivorous bats in the genus Lasiurus (Chiroptera: Vespertilionidae) regularly occur in the American Southern Cone. Three of them (Lasiurus cinereus, L. blossevillii and L. ega) are sympatric over many regions, whereas the remaining species (L. varius, closely related to L. blossevillii) is allopatric, occurring in the Patagonian Temperate Rainforest. A multivariate analysis of 14 craniodental variables for 99 specimens from the four species confirmed size separating two small species from two large ones, and revealed morphofunctional aspects of mastication segregating the two large species on the basis of differences in temporal muscle function (coronoid process height and length of rostrum). We predict ecological (trophic) differences among these lasiurines consistent with their segregation in the morphofunctional space and in combination with the sympatric vs. allopatric condition of species pairs or triads.

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Vespertilionid species are widely distributed in South America. They are highly diverse, with physiological and behavioral adaptations which allow them to extend their distributions into temperate areas. In Patagonia, this family is represented by seven species in three genera (Histiotus, Lasiurus and Myotis). In this study, we analyzed the distribution of two vespertilionid species, Lasiurus villosissimus and Myotis dinellii, including new southernmost records, and their relationship with environmental variables. Two different spatial scales were analyzed: a continental approach for species distribution analyses (South America), and local trapping of bats in northwestern Chubut province, Argentina. We present new southern limits for L. villosissimus and M. dinellii, and included new records for Patagonian bats. The big hoary bat L. villosissimus was recorded as the largest bat inhabiting Patagonia, relating it as a bat mainly inhabiting low, humid and temperate/warm areas. The little yellow bat M. dinellii, instead, is the smallest mammal and the smallest bat recorded in Patagonia to date, related mainly with dry, mid-altitude and temperate/warm areas.