Adaptive Tolerance To A Pathogenic Fungus Drives Major Histocompatibility Complex Evolution In Natural Amphibian Populations

Keywords

Adaptation; Amphibian; Batrachochytrium dendrobatidis; Chytridiomycosis; Immunogenetics; Major histocompatibility complex

Abstract

Amphibians have been affected globally by the disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), and we are just now beginning to understand how immunogenetic variability contributes to disease susceptibility. Lineages of an expressed major histocompatibility complex (MHC) class II locus involved in acquired immunity are associated with chytridiomycosis susceptibility in controlled laboratory challenge assays. Here, we extend these findings to natural populations that vary both in exposure and response to Bd. We find that MHC alleles and supertypes associated with Bd survival in the field show a molecular signal of positive selection, while those associated with susceptibility do not, supporting the hypothesis that heritable Bd tolerance is rapidly evolving. We compare MHC supertypes to neutral loci to demonstrate where selection versus demography is shaping MHC variability. One population with Bd tolerance in nature shows a significant signal of directional selection for the same allele (allele Q) that was significantly associated with survival in an earlier laboratory study. Our findings indicate that selective pressure for Bd survival drives rapid immunogenetic adaptation in some natural populations, despite differences in environment and demography. Our field-based analysis of immunogenetic variation confirms that natural amphibian populations have the evolutionary potential to adapt to chytridiomycosis.

Publication Date

3-23-2016

Publication Title

Proceedings of the Royal Society B: Biological Sciences

Volume

283

Issue

1827

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1098/rspb.2015.3115

Socpus ID

84961653065 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/84961653065

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