Genetics and Evolution

As the only native insular Newfoundland canid between the extinction of the wolf in the 1930s and the recent arrival of coyotes, the red fox (Vulpes vulpes deletrix Bangs 1898) poses interesting questions about genetic distinctiveness and the post-glacial colonization history of the island's depauperate mammalian fauna. Here, we characterized genetic variability at the major histocompatibility complex (MHC) class II DR β1 domain (DRB1) locus in 28 red foxes from six sampling localities island-wide and compared it with mitochondrial control region (CR) diversity and DRB1 diversity in other canids. Our goals were to describe novel DRB1 alleles in a new canid population and to make inferences about the role of selection in maintaining their diversity. As in numerous studies of vertebrates, we found an order-of-magnitude higher nucleotide diversity at the DRB1 locus compared with the CR and significantly positive nonsynonymous-to-synonymous substitution ratios, indicative of selection in the distant past. Although the evidence is weaker, the Ewens-Watterson test of neutrality and the geographical distribution of variation compared with the CR suggest a role for selection over the evolutionary timescale of populations. We report the first genetic data from the DRB1 locus in the red fox and establish baseline information regarding immunogenetic variation in this island canid population which should inform continued investigations of population demography, adaptive genetic diversity, and wildlife disease in red foxes and related species.

Two hundred and eighty-seven longnose sucker Catostomus catostomus were collected from 14 lakes in Labrador, 52 from three lakes in Ontario, 43 from two lakes in British Columbia and 32 from a lake in Yukon; a total of 414 in all. The resulting 34 haplotypes (20 in Labrador) contained moderate haplotypic diversity (h = 0·657) and relatively low nucleotide diversity (í µí¼‹ = 3·730 × 10 −3. Mean í µí¼™ ST (0·453, P < 0·05) over all populations revealed distinct genetic structuring among C. catostomus populations across Canada, based on province, which was validated by the analysis and spatial analysis of molecular variance (c. 80% variation between provinces). These results probably reflect the historical imprint of recolonization from different refugia and possibly indicate limited ongoing gene flow within provinces. A haplotype network revealed one major and two minor clades within Labrador that were assigned to the Atlantic, Beringian and Mississippian refugia, respectively, with tests of neutrality and mismatch distribution indicative of a recent population expansion in Labrador, dated between c. 3500 and 8300 years ago.

Two tribes of subterranean dytiscid diving beetles independently colonised groundwater systems of the Western Australian arid zone, a habitat transition that was most likely driven by the contraction of surface water bodies following late Neogene aridification of the Australian continent. These &#39;stygofauna&#39; are now trapped within discrete calcrete aquifers that have formed in palaeodrainage valleys, resulting in the world&#39;s most diverse radiations of subterranean dytiscid beetles. Approximately 100 species from three genera exhibit partial or fully regressed visual systems and are essentially blind. This unique study system, with multiple independent transitions to subterranean life enables regressive and adaptive evolutionary processes to be studied in parallel at an unheralded comparative scale. Here we provide an overview of the progression of dytiscid beetle research and undertake a literature survey of published research within the field of regressive evolution as i...

Phylogeographic studies have provided evidence for speciation underground within the confines of a cave environment, questioning the assumption that cave animals evolved from surface ancestors (Juan et al. 2010). However, for many of these studies, it is difficult to rule out the possibility that phylogeographic patterns may have resulted from multiple colonisation events from the same ancestral surface species, introgressive hybridisation among related species, and/or the extinction of surface ancestral lineages. Such is the case for the subterranean diving beetle species (Dytiscidae) of the groundwater calcrete archipelago of central Western Australia, where more than 100 species have been described that appear to have evolved by a combination of ecological/allopatric speciation and in some cases possibly sympatric speciation. We have further explored these speciation theories by phylogeographic analyses of nuclear gene data (WG, TOPO, ARK, Cn) from 86 species in the genera Limbod...

Neutral evolution theory predicts that genes specific to the development/function of eyes in subterranean animals will evolve under relaxed selection, ultimately becoming pseudogenes. Independently evolved (3-8 million years ago) subterranean beetle (Dytiscidae) species of Western Australia have converged on eye loss, providing a powerful system to explore changes to the genome with respect to troglomorphic characters. Using next generation sequence data, we investigated the molecular evolution of ‘eye genes’ of subterranean beetle species to test if they are evolving neutrally. We used transcriptome data from five beetle species (three subterranean and two surface) to design baits for hybrid enrichment of 60 pigmentation and phototransduction genes from 31 subterranean and surface species. The current talk focuses on the results from the study of 8 photoreceptor genes that showed evidence for a lack of transcription or possible pseudogenisation in stygobitic species when compared t...

Teleosts exhibit extensive diversity of sex determination (SD) systems and mechanisms, providing the opportunity to study the evolution of sex determination and sex chromosomes. Here we sequenced the genome of the Common Lumpfish (Cyclopterus lumpus Linnaeus), a species of increasing importance to aquaculture, and identified the SD region and master SD locus using a 70K SNP array and tissue-specific expression data. The chromosome-level assembly identified 25 diploid chromosomes with a total size of 572.89 Mb, a scaffold N50 of 23.86 Mb, and genome annotation predicted 21,480 protein-coding genes. Genome wide association analysis located a highly sex-associated region on chromosome 13, suggesting that anti-Müllerian hormone (AMH) is the putative SD factor. Linkage disequilibrium and heterozygosity across chromosome 13 support a proto-XX/XY system, with an absence of widespread chromosome divergence between sexes. We identified three copies of AMH in the Lumpfish primary and alternat...

The negative genetic impacts of gene flow from domestic to wild populations can be dependent on the degree of domestication and exacerbated by the magnitude of pre-existing genetic differences between wild populations and the domestication source. Recent evidence of European ancestry within North American aquaculture Atlantic salmon (Salmo salar) has elevated the potential impact of escaped farmed salmon on often at-risk wild North American salmon populations. Here we compare the ability of single nucleotide polymorphism (SNP) and microsatellite (SSR) marker panels of different sizes (7-SSR, 100-SSR, and 220K-SNP) to detect introgression of European genetic information into North American wild and aquaculture populations. Linear regression comparing admixture predictions for a set of individuals common to the three data sets showed that the 100-SSR panel and 7-SSR panels replicated the full 220K-SNP-based admixture estimates with low accuracy (r2of 0.64 and 0.49 respectively). Addit...

ABSTRACTAdaptation to ocean climate is increasingly recognized as an important driver of diversity in marine species despite the lack of physical barriers to dispersal and the presence of pelagic stages in many taxa. A robust understanding of the genomic and ecological processes involved in structuring populations is lacking for most marine species, often hindering management and conservation action. Cunner (Tautogolabrus adspersus), is a temperate reef fish that displays both pelagic early life history stages and strong site-associated homing as adults; the species is also presently of interest for use as a cleaner fish in salmonid aquaculture in Atlantic Canada. Here we produce a chromosome-level genome assembly for cunner and characterize spatial population structure throughout Atlantic Canada using whole genome resequencing. The genome assembly spanned 0.72 Gbp and resolved 24 chromosomes; whole genome resequencing of 803 individuals from 20 locations spanning from Newfoundland ...