Copy number variation and genetic diversity of MHC Class IIb alleles in an alien population of Xenopus laevis.
Xenopus laevis (the African clawed frog), which originated through hybridisation and whole genome duplication, has been used as a model for genetics and development for many years, but surprisingly little is known about immune gene variation in natural populations. The purpose of this study was to use an isolated population of X. laevis that was introduced to Wales, UK in the past 50 years to investigate how variation at the MHC compares to that at other loci, following a severe population bottleneck. Among 18 individuals, we found nine alleles based on exon 2 sequences of the Class IIb region (which includes the peptide binding region). Individuals carried from one to three of the loci identified from previous laboratory studies. Genetic variation was an order of magnitude higher at the MHC compared with three single-copy nuclear genes, but all loci showed high levels of heterozygosity and nucleotide diversity and there was not an excess of homozygosity or decrease in diversity over time that would suggest extensive inbreeding in the introduced population. Tajima's D was positive for all loci, which is consistent with a bottleneck. Moreover, comparison with published sequences identified the source of the introduced population as the Western Cape region of South Africa, where most commercial suppliers have obtained their stocks. These factors suggest that despite founding by potentially already inbred individuals, the alien population in Wales has maintained substantial genetic variation at both adaptively important and neutral genes.
Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK. Barbara.mable@glasgow.ac.uk.
Barbara K
http://orcid.org/0000-0001-7118-4116
BK
Mable
Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK.
Elizabeth
E
Kilbride
School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK. Mark.Viney@bristol.ac.uk.
Mark E
ME
Viney
School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK.
Richard C
RC
Tinsley
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D056915:DNA Copy Number Variations; D014644:Genetic Variation; D005828:Genetics, Population; D005838:Genotype; D006239:Haplotypes; D000949:Histocompatibility Antigens Class II / Q000145:classification / Q000235:genetics*; D007178:Inbreeding; D008969:Molecular Sequence Data; D010802:Phylogeny; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013019:South Africa; D014852:Wales; D029867:Xenopus Proteins / Q000235:genetics*; D014982:Xenopus laevis / Q000235:genetics*
D000949:Histocompatibility Antigens Class II; D029867:Xenopus Proteins
Bottlenecks; Genetic diversity; Introduced species; MHC; Polyploidy; Xenopus laevis