Major histocompatibility complex selection dynamics in pathogen-infected túngara frog (Physalaemus pustulosus) populations

Kosch, Tiffany A., Bataille, Arnaud, Didinger, Chelsea, Eimes, John A., Rodríguez-Brenes, Sofia, Ryan, Michael J., and Waldmann, Bruce (2016) Major histocompatibility complex selection dynamics in pathogen-infected túngara frog (Physalaemus pustulosus) populations. Biology Letters, 12 (8). 20160345.

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Abstract

Pathogen-driven selection can favour major histocompatibility complex (MHC) alleles that confer immunological resistance to specific diseases. However, strong directional selection should deplete genetic variation necessary for robust immune function in the absence of balancing selection or challenges presented by other pathogens. We examined selection dynamics at one MHC class II (MHC-II) locus across Panamanian populations of the túngara frog, Physalaemus pustulosus, infected by the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd). We compared MHC-II diversity in highland túngara frog populations, where amphibian communities have experienced declines owing to Bd, with those in the lowland region that have shown no evidence of decline. Highland region frogs had MHC variants that confer resistance to Bd. Variant fixation appeared to occur by directional selection rather than inbreeding, as overall genetic variation persisted in populations. In Bd-infected lowland sites, however, selective advantage may accrue to individuals with only one Bd-resistance allele, which were more frequent. Environmental conditions in lowlands should be less favourable for Bd infection, which may reduce selection for specific Bd resistance in hosts. Our results suggest that MHC selection dynamics fluctuate in túngara frog populations as a function of the favourability of habitat to pathogen spread and the vulnerability of hosts to infection.

Item ID: 45259
Item Type: Article (Research - C1)
ISSN: 1744-957X
Keywords: amphibian population declines, chytridiomycosis, directional selection, host–pathogen interactions, major histocompatibility complex, resistance alleles
Funders: National Research Foundation of Korea (NRF), National Scientific Foundation, Korea (NSF)
Projects and Grants: NRF 2015R1D1A1A01057282, NSF IBN 0517328
Date Deposited: 22 Aug 2016 22:30
FoR Codes: 06 BIOLOGICAL SCIENCES > 0604 Genetics > 060406 Genetic Immunology @ 33%
06 BIOLOGICAL SCIENCES > 0603 Evolutionary Biology > 060307 Host-Parasite Interactions @ 34%
06 BIOLOGICAL SCIENCES > 0605 Microbiology > 060505 Mycology @ 33%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960806 Forest and Woodlands Flora, Fauna and Biodiversity @ 100%
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