Biology subjects

Dicks, K. L.

Publications and source records attributed to Dicks, K. L..

3 recordsLinked to original sources

bioRxiv2022

Genetic diversity in global populations of the Critically Endangered addax (Addax nasomaculatus) and its implications for conservation

Threatened species are frequently patchily distributed across small wild populations, ex situ populations managed with varying levels of intensity, and reintroduced populations. Best practice advocates for integrated management across in situ and ex situ populations. Wild addax (Addax nasomaculatus) now number fewer than 100 individuals, yet thousands of addax remain in ex situ populations, which can provide addax for reintroductions, as has been the case in Tunisia in the mid-1980s. However, integrated management requires genetic data to ascertain the relationships between wild and ex situ populations that have incomplete knowledge of founder origins, management histories and pedigrees. We undertook a global assessment of genetic diversity across wild, ex situ, and reintroduced populations in Tunisia to assist conservation planning for this Critically Endangered species. We show that the remnant wild populations retain more mitochondrial haplotypes which are more evolutionarily diverse than the entirety of the ex situ populations across Europe, North America and the United Arab Emirates, and the reintroduced Tunisian population. Additionally, 1704 SNPs revealed that whilst population structure within the ex situ population is minimal, each population carries unique diversity. Finally, we show that careful selection of founders and subsequent genetic management is vital to ensure genetic diversity is provided to, and minimise drift and inbreeding within, reintroductions. Our results highlight a vital need to conserve the last remaining wild addax population, and we provide a genetic foundation for determining integrated conservation strategies to prevent extinction and optimise future reintroductions.

genetics↗

bioRxiv2021

Associations between MHC class II variation and phenotypic traits in a free-living sheep population

Pathogen-mediated selection (PMS) is thought to maintain the high level of allelic diversity observed in the major histocompatibility complex (MHC) class II genes. A comprehensive way to demonstrate contemporary selection is to examine associations between MHC variation and individual fitness. As individual fitness is hard to measure, many studies examine associations between MHC diversity and phenotypic traits which include direct or indirect measures of adaptive immunity thought to contribute to fitness. Here, we tested associations between MHC class II variation and five representative phenotypic traits measured in August: weight, strongyle faecal egg count, and plasma IgA, IgE and IgG immunoglobulin titres against the gastrointestinal nematode parasite Teladorsagia circumcincta in a free-living population of Soay sheep. We found no association between MHC class II variation and August weight or strongyle faecal egg count. We did however find associations between MHC class II variation and immunoglobulin levels which varied with age, isotype and sex. Our results suggest associations between MHC and phenotypic traits are more likely to be found for traits more closely associated with pathogen defence than integrative traits such as body weight and highlight a useful role of MHC-antibody associations in examining selection on MHC genes.

evolutionary biology↗

bioRxiv2020

Haplotyping MHC class IIa by high throughput screening in an isolated sheep population

Investigating the current evolutionary processes acting on a highly polymorphic gene region, such as the major histocompatibility complex (MHC), requires extensive population data for both genotypes and phenotypes. The MHC consists of several tightly linked loci with both allelic and gene content variation, making it challenging to genotype. Eight class IIa haplotypes have previously been identified in the Soay sheep (Ovis aries) of St. Kilda using Sanger sequencing and cloning, but no single locus is representative of all haplotypes. Here, we exploit the closed nature of the island population of Soay sheep and its limited haplotypic variation to identify a panel of SNPs that enable imputation of MHC haplotypes. We compared MHC class IIa haplotypes determined by Sanger sequence-based genotyping of 135 individuals to their SNP profiles generated using the Ovine Infinium HD BeadChip. A panel of 11 SNPs could reliably determine MHC diplotypes, and two additional SNPs within the DQA1 gene enabled detection of a recombinant haplotype affecting only the SNPs downstream of the expressed genes. The panel of 13 SNPs was genotyped in 5951 Soay sheep, of which 5349 passed quality control. Using the Soay sheep pedigree, we were able to trace the origin and inheritance of the recombinant SNP haplotype. This SNP-based method has enabled the rapid generation of locus-specific MHC genotypes for large numbers of Soay sheep. This volume of high-quality genotypes in a well-characterized population of free-living sheep will be valuable for investigating the mechanisms maintaining diversity at the MHC.

evolutionary biology↗