A meta-analysis of the effects of habitat loss and fragmentation on genetic diversity in mammals

Human activities have led to global changes with direct consequences for biodiversity. For this reason, special concerns have arisen, particularly in respect to global threats such as habitat loss and fragmentation, because they decrease population size, promote the loss of species genetic diversity, contract species geographical distribution and facilitate species loss. Interest in the genetic consequences related to habitat changes has increased in the last decades, so it became crucial to understand how genetic diversity changes due to habitat loss and fragmentation and if the degree of genetic losses is related with species traits. Thus, we conduct a meta-analysis to test if genetic diversity of mammalian populations that live in fragments is lower than those living in continuous habitats and we also explore which species traits could be related with the observed patterns. Through this meta-analysis we detected an overall decrease in allelic diversity, allelic richness, observed heterozygosity and expected heterozygosity in mammalian species that live in situations of high habitat fragmentation. However, not all species are affected the same way. We found that species with larger body mass are the most negatively affected by fragmentation; terrestrial and arboreal mammals are more negatively affected than flying species; herbivores suffer consistent negative effect of fragmentation in the four genetic measures analysed; and forest-dependent species are the most susceptible to the negative effects of fragmentation. We expected to detect an increase in inbreeding coefficients in fragments when compared to continuous habitats; however, this pattern did not arise, probably because time since fragmentation was not enough and/or species have ways to avoid inbreeding. The patterns here described allow a better understanding of which mammalian species are more susceptible to the negative effects of habitat loss and fragmentation, potentially giving support for the conservation and management of their populations.