Morphological variability decreases in populations living in less suitable environments and close to the range edges

Abstract

AbstractAimGeographical range expansion depends on ecological and evolutionary processes that may hamper local adaptations in populations living at range edges by constraining phenotypic variability. This study investigates the spatial patterns of the intraspecific variability of skull traits throughout the geographical range of a marsupial from the Brazilian Atlantic Forest. We aimed to answer whether the distance from the range edge and the environmental suitability explain the geographical variation of morphological variability of the species.LocationAtlantic Forest, Brazil.TaxonMarmosops incanus (Didelphimorphia, Didelphidae).MethodsWe analysed adult specimens deposited in the main biological collections in southeastern Brazil. The morphological variability extent and integration within populations were characterised by 13 linear measures of the skull, using a multivariate approach. Environmental suitability for the species' occurrence was estimated by ecological niche models, using climate variables and vegetation productivity as predictors and three different modelling methods. Distance from the range edge was calculated based on the minimum linear distance between populations and the closest range limit. We fitted linear regressions and selected the best models that explained the spatial variation of morphological variability based on the Akaike information criterion.ResultsThe extent of morphological variability of M. incanus is positively correlated with morphological integration and increases with local environmental suitability and distance from the range edges. However, the relationship between morphological variability and environmental suitability depends on the niche modelling method.Main ConclusionsUnfavourable environmental conditions constrain morphological variability within populations of the Gray slender opossum and may hamper local adaptation in peripheral populations living in less suitable environments. In addition to environmental conditions, geographical location of populations also plays an important role in phenotypic variability among populations. We stress the boundary effect of the species range on local adaptation of peripheral populations and its possible consequences for the range expansion dynamics.