Colonizing the world in spite of reduced MHC variation

Journal of Evolutionary Biology
By: , and 

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Abstract

Reduced immune gene diversity is thought to negatively affect the capacity of organisms to adapt to pathogen challenges, which represent a major force in natural selection. Genes of the Major Histocompatibility Complex (MHC) are the most widely invoked adaptive loci in conservation biology, and have become the most popular genetic markers to investigate pathogen-host interactions in vertebrates. Although MHC genes are the most polymorphic genes described in the vertebrate genome, the extent to which MHC diversity determines the long-term persistence of populations is, unclear and often debated, as recent studies have documented the occurrence of natural populations thriving even after a depletion of MHC diversity caused by genetic drift. Here, we show that some phylogenetically related species belonging to the Falco genus (Aves: Falconidae) present a dramatically low MHC variability that has not precluded, nevertheless, the successful colonization of almost all existing regions and habitats worldwide. We found evidence for two remarkably different patterns of MHC variation within the genus. While kestrels show a high MHC variation according to the general theory, falcons exhibit an ancestrally low intra- and inter-specific MHC allelic diversity. We provide compelling evidence that this pattern is not caused by the degeneration of functional genes into pseudogenes, the inadvertent analyses of paralogous MHC genes, or the devastating action of genetic drift. Instead, our results strongly support the idea of an evolutionary transition driven and maintained by natural selection from primarily highly variable towards low polymorphic, but functional and expressed, MHC genes with species-specific pathogen-recognition capabilities.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Colonizing the world in spite of reduced MHC variation
Series title Journal of Evolutionary Biology
DOI 10.1111/j.1420-9101.2012.02529.x
Volume 25
Issue 7
Year Published 2012
Language English
Publisher European Society of Evolutionary Biology
Publisher location Malden, MA
Contributing office(s) Alaska Science Center Biology WTEB
Description 10 p.
First page 1438
Last page 1447
Online Only (Y/N) N
Additional Online Files (Y/N) N