Avian β-defensin variation in bottlenecked populations : the Seychelles warbler and other congeners

Gilroy, DL; van Oosterhout, C; Komdeur, J; Richardson, DS

Abstract

β-defensins are important components of the vertebrate innate immune system responsible for encoding a variety of anti-microbial peptides. Pathogen-mediated selection is thought to act on immune genes and potentially maintain allelic variation in the face of genetic drift. The Seychelles warbler, Acrocephalus sechellensis, is an endemic passerine that underwent a recent bottleneck in its last remaining population, resulting in a considerable reduction in genome-wide variation. We genotyped avian β-defensin (AvBD) genes in contemporary (2000–2008) and museum samples (1876–1940) of the Seychelles warbler to investigate whether immunogenetic variation was lost through this bottleneck, and examined AvBD variation across four other Acrocephalus species with varying demographic histories. No variation was detected at four of the six AvBD loci screened in the post-bottleneck population of Seychelles warbler, but two silent nucleotide polymorphisms were identified at AvBD8 and one potentially functional amino-acid variation was observed at AvBD11. Variation in the Seychelles warbler was significantly lower than in the mainland migratory congeneric species investigated, but it similar to that found in other bottlenecked species. In addition, screening AvBD7 in 15 museum specimens of Seychelles warblers sampled prior to the bottleneck (1877–1905) revealed that this locus possessed two alleles previously, compared to the single allele in the contemporary population. Overall, the results show that little AvBD variation remains in the Seychelles warbler, probably as a result of having low AvBD diversity historically rather than the loss of variation due to drift associated with past demographic history. Given the limited pathogen fauna, this lack of variation at the AvBD loci may currently not pose a problem for this isolate population of Seychelles warblers, but it may be detrimental to the species’ long-term survival if new pathogens reach the population in the future.

Citation

Gilroy, D., van Oosterhout, C., Komdeur, J., & Richardson, D. (2016). Avian β-defensin variation in bottlenecked populations : the Seychelles warbler and other congeners. Conservation Genetics, 17(3), 661-674. https://doi.org/10.1007/s10592-016-0813-x

• Journal Article Type: Article
• Acceptance Date: Jan 18, 2016
• Online Publication Date: Feb 1, 2016
• Publication Date: Jun 1, 2016
• Deposit Date: Sep 29, 2021
• Publicly Available Date: Sep 29, 2021
• Journal: Conservation Genetics
• Print ISSN: 1566-0621
• Electronic ISSN: 1572-9737
• Publisher: Springer Verlag
• Volume: 17
• Issue: 3
• Pages: 661-674
• DOI: https://doi.org/10.1007/s10592-016-0813-x
• Publisher URL: http://dx.doi.org/10.1007/s10592-016-0813-x
• Related Public URLs: http://www.springer.com/journal/10592
• Additional Information: Funders : Natural Environment Research Council (NERC);Earth and Life Systems Alliance (ELSA);Natural Environment Research Council; Projects : Telomeres as biomarkers of cost and quality in a wild vertebrate population; Grant Number: NE/F02083X/1