Ecological and phenotypic divergence in Iberian shrews (Soricidae)

Abstract

There are examples of coexisting species with similar morphology and ecology, in apparent contradiction to competition theory. Shrews (Soricidae) are a paradigmatic example of this because members of this group exhibit a conserved body form, relatively low variability in lifestyle, and, in many cases, a sympatric distribution. Here, we combined geometric morphometrics and ecological niche modeling to test whether diversification of soricid species inhabiting the Iberian Peninsula has been driven by niche divergence or, conversely, whether niche conservatism has played a paramount role in this process. We also examined whether pairwise morphological distances increase as the degree of niche overlap between species becomes greater, as would be expected if interspecific competition promotes morphological differentiation. Our results showed that water shrews (Neomys), white‐toothed shrews (Crocidurinae), and red‐toothed shrews (Soricinae) are clearly differentiated in terms of both skull shape and mandible shape. However, we found a lack of phylogenetic signal in most morphological traits, indicating that closely related species are not more similar than expected by random chance. Notably, water shrews show a more “triangular” or sharp skull than white‐toothed and red‐toothed shrews, probably as an adaptation to their semiaquatic lifestyle. In agreement with the phenotypic data, climatic traits (mean annual temperature and annual precipitation) were highly labile and sister taxa showed extensive differentiation in their realized niche space. Finally, we found that phenotypic distances between species tend to increase as the degree of niche overlap increases, suggesting that interspecific competition is an important factor in determining the level of morphological resemblance among relatives. Overall, our results indicate that the existence of limited morphological disparity in a given group does not necessarily imply the existence of a niche conservatism signature.

Resource competition drives an invasion‐replacement event among shrew species on an island

“…Sorex minutus is sympatric with multiple shrew species across the European mainland, including C. russula. Differential resource use and niche separation among these insectivorous small mammals is known to be integral for facilitating multi-shrew communities (Rey et al, 2019) and this has been proposed to facilitate the sympatric existence of S. minutus (albeit in low abundance) with larger species of shrews in mainland Europe (Churchfield & Rychlik, 2006). Indeed, S. minutus and C. russula are the only shrew species present on the small island of Belle Île off northwestern France.…”

Resource competition drives an invasion-replacement event among shrew species on an island

“…Sorex minutus is sympatric with multiple shrew species across the European mainland, including C. russula. Differential resource use and niche separation among these insectivorous small mammals is known to be integral for facilitating multi-shrew communities (Rey, Noguerales and García-Navas, 2019) and this has been proposed to facilitate the sympatric existence of S. minutus (albeit in low abundance) with larger species of shrews in mainland Europe (Churchfield and Rychlik, 2006). Indeed, S. minutus and C. russula are the only shrew species present on the small island of Belle Île off northwestern France and coexist with one another in large numbers amongst a similar small mammal community that is present in Ireland (McDevitt et al, 2014, Gargan et al, 2016.…”