Mechanisms of selection and MHC diversity in the montane vole and other wild mammals

Abstract

The loss of genetic diversity due to reduced gene flow, inbreeding and genetic drift can result in reduced fitness for individuals and extinction risks for populations and species. One locus for which genetic diversity is vitally important is the Major Histocompatibility Complex (MHC). The MHC is renowned for its unparalleled allelic diversity which facilities recognition of diverse parasites by vertebrate immune systems, and this genetic diversity has been maintained even in the face of repeated population bottlenecks in some species. Two selective processes could maintain this diversity: mate choice and parasitism. This research investigates the relative roles of sexual selection and parasite-mediated selection in maintaining MHC diversity both within populations and across species. At the population level, I employed both field work and molecular genetics using Second Generation (454) sequencing technology to investigate host-parasite interactions and neutral and adaptive genetic diversity in a cyclic montane vole population. For interspecies analysis, I employed comparative phylogenetic tests to ask whether parasites drive MHC diversity across species, and for the first time, determine if sexual selection is broadly important in explaining MHC diversity across a range of vertebrate species,. Knowledge obtained here will inform efforts to conserve genetic diversity in small wildlife populations and can suggest processes that can promote natural MHC diversity (e.g. mate choice coordinated through captive breeding).