Do anthropogenic matrix and life-history traits structure small mammal populations? A meta-analytical approach

Understanding the genetic responses of different species to the landscape attributes is essential to improve conservation actions and decision-making. However, making generalizations about such responses is not trivial, since they can be influenced by several factors. Aspects related to landscape matrix quality, for example, such as contrast and heterogeneity, may play a relevant role in the spatial-genetic structuring of populations since functional connectivity is influenced by the degree of matrix permeability. Intending to identify trends of genetic responses to habitat fragmentation and the aspects influencing these responses, we employed a meta-analytical approach to investigate the degree of genetic structuring of small mammal populations, measured through the fixation index (FST), in anthropogenic landscapes. For this, we obtained data of 28 species from 38 studies worldwide. We investigated the heterogeneity among species’ responses by focusing on the influence of matrix quality (contrast and heterogeneity), and species’ life-history traits (mean dispersal distance, generation time, and locomotor mode), controlling the influence of the marker type used in the study and the isolation by distance (IBD) among the patches habitat. We found a consistent pattern of genetic structuring of small mammal populations in anthropogenic landscapes, which present a significant genetic differentiation. Genetic structure is mostly influenced by matrix quality characteristics so that populations established in landscapes with high contrast and more heterogeneous matrices tend to be more structured. Also, populations of species with long generation time and high dispersal capacity exhibit a greater degree of genetic structure. Besides, accounting for IBD as a fixed effect was crucial to understand the variation among studies’ findings. Thus, the degree of genetic structuring of small mammal populations reflects the functional connectivity of the landscape, resulting from a balance between landscape attributes (matrix contrast and heterogeneity) and species’ life-history traits. Overall, our findings suggest that small mammals may be more susceptible to fragmentation than previously recognized, calling for special attention to this group considering their importance to maintain community structure and ecosystem functioning.