The Role of Geographical and Ecological Factors on Population Divergence of the Neotropical otter Lontra longicaudis (Carnivora, Mustelidae)

Abstract

The geographic distribution of the populations of a species are influenced by the spatial structure of the ecosystems, the environmental factors and the presence of geographic barriers. The Neotropical otter, Lontra longicaudis, is widely distributed throughout the Americas, where a wide range of environmental conditions and geographical features could promote genetic and morphological variation on the three currently recognized subspecies. In this study, we combined phylogeographic, morphometric and environmental niche modelling analyses to examine whether: (1) genetic variation is associated with the presence of barriers to gene flow and/or hydrography; (2) genetic and morphologic variation are associated with environmental variation; and (3) the observed variation in L. longicaudis populations corresponds to the previously defined subspecies. We found strong phylogeographic structure between the northern (L. l. annectens) and the two-southern subspecies (L. l. longicaudis and L. l. enudris), and although shallower, we also detected genetic differentiation between the two South American subspecies. Such genetic differentiation corresponds to the hydrography and to the geographical barriers characteristic of the distributional area of the species. We found a correlation between the shape of the skull and mandible with the environmental variation through the distribution of the species, and we rejected the hypothesis of niche equivalency and similarity between the three identified genetic lineages, suggesting adaptations to different environmental conditions. Our results support that the variation in environmental conditions, in concert with geographical barriers to gene flow and hydrography, have led to population divergence of L. longicaudis along the Neotropics. These results have important taxonomic implications for the species and its conservation.