Long-term survival of a urodele amphibian despite depleted major histocompatibility complex variation

• Published in: Molecular ecology Vol. 18; no. 5; pp. 769 - 781
• Main Authors: BABIK, W., PABIJAN, M., ARNTZEN, J.W., COGALNICEANU, D., DURKA, W., RADWAN, J.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.03.2009
• Subjects: Amino Acid Sequence; Amino Acid Substitution - genetics; amphibian decline; Animals; Base Sequence; Codon - genetics; Conservation; Ecology; Europe; Gene Expression Regulation; Genes, MHC Class II - genetics; Genetic Loci - genetics; Genetics; Geography; glacial refugia; Histocompatibility Antigens Class II - chemistry; Histocompatibility Antigens Class II - genetics; Histocompatibility Antigens Class II - immunology; Isoenzymes - genetics; Major Histocompatibility Complex - genetics; Major Histocompatibility Complex - immunology; MHC class II; MHC pseudogenes; Microsatellite Repeats - genetics; Models, Genetic; Molecular biology; Molecular Sequence Data; Phylogeny; Polymorphism, Genetic; positive selection; Recombination, Genetic - genetics; Reptiles & amphibians; Salamandridae - genetics; Salamandridae - immunology; Selection, Genetic; Sequence Alignment; Survival Analysis; Time Factors; Triturus cristatus; Europe
• ISSN: 0962-1083; 1365-294X
• DOI: 10.1111/j.1365-294X.2008.04057.x

Depletion of polymorphism at major histocompatibility complex (MHC) genes has been hypothesized to limit the ability of populations to respond to emerging pathogens, thus putting their survival at risk. As pathogens contribute substantially to the global amphibian decline, assessing patterns of MHC variation is important in devising conservation strategies. Here, we directly compare levels of MHC class II and neutral variation between multiple populations of the great crested newt (Triturus cristatus) from refugial (REF: Romania) and postglacial expansion (PGE: Germany, Poland and UK) areas. REF populations harboured high levels of adaptive variation (24 expressed alleles), exhibiting clear signatures of historical positive selection, which points to the overall importance of MHC class II variation in this species. On the other hand, PGE populations were extremely depauperate (two alleles) but nevertheless have survived for c. 10 000 years, since the postglacial expansion. Variation in putative MHC class II pseudogenes, microsatellites and allozymes also showed a significant southern richness–northern purity pattern. The populations in the postglacial expansion area thus provide the clearest example to date of the long‐term survival of populations in which MHC variation, historically under positive selection, has been depleted.