Sequence analysis of three pigmentation genes in the Newfoundland population of Canis latrans links the Golden Retriever Mc1r variant to white coat color in coyotes.

Three genes, Mc1r, Agouti, and CBD103, interact in a type-switching process that controls much of the pigmentation variation observed in mammals. A deletion in the CBD103 gene is responsible for dominant black color in dogs, while the white-phased black bear ("spirit bear") of British Columbia, Canada, is the lightest documented color variant caused by a mutation in Mc1r. Rare all-white animals have recently been discovered in a new northeastern population of the coyote in insular Newfoundland and Labrador, Canada. To investigate the causative gene and mutation of white coat in coyotes, we sequenced the three type-switching genes in white and dark-phased animals from Newfoundland. The only sequence variants unambiguously associated with white color were in Mc1r, and one of these variants causes the amino acid variant R306Ter, a premature stop codon also linked to coat color in Golden Retrievers and other dogs with yellow/red coats. The allele carrying R306Ter in coyotes matches that in the Golden Retriever at other variable amino acid sites and hence may have originated in these dogs. Coyotes experienced introgression with wolves and dogs as they colonized northeastern North America, and coyote/Golden Retriever interactions have been observed in Newfoundland. We speculate that natural selection, with or without a founder effect, may contribute to the observed frequency of white coyotes in Newfoundland, as it has contributed to the high frequency of white bears, and of a domestic dog-derived CBD allele in gray wolves.

Microsatellite variation and genetic structure of brook trout (Salvelinus fontinalis) populations in Labrador and neighboring Atlantic Canada: evidence for ongoing gene flow and dual routes of post-Wisconsinan colonization.

In conservation genetics and management, it is important to understand the contribution of historical and contemporary processes to geographic patterns of genetic structure in order to characterize and preserve diversity. As part of a 10-year monitoring program by the Government of Newfoundland and Labrador, Canada, we measured the population genetic structure of the world's most northern native populations of brook trout (Salvelinus fontinalis) in Labrador to gather baseline data to facilitate monitoring of future impacts of the recently opened Trans-Labrador Highway. Six-locus microsatellite profiles were obtained from 1130 fish representing 32 populations from six local regions. Genetic diversity in brook trout populations in Labrador (average H(E)= 0.620) is within the spectrum of variability found in other brook trout across their northeastern range, with limited ongoing gene flow occurring between populations (average pairwise F(ST)= 0.139). Evidence for some contribution of historical processes shaping genetic structure was inferred from an isolation-by-distance analysis, while dual routes of post-Wisconsinan recolonization were indicated by STRUCTURE analysis: K= 2 was the most likely number of genetic groups, revealing a separation between northern and west-central Labrador from all remaining populations. Our results represent the first data from the nuclear genome of brook trout in Labrador and emphasize the usefulness of microsatellite data for revealing the extent to which genetic structure is shaped by both historical and contemporary processes.

A comparative study of the ocular skeleton of fossil and modern chondrichthyans.

Many vertebrates have an ocular skeleton composed of cartilage and/or bone situated within the sclera of the eye. In this study we investigated whether modern and fossil sharks have an ocular skeleton, and whether it is conserved in morphology. We describe the scleral skeletal elements of three species of modern sharks and compare them to those found in fossil sharks from the Cleveland Shale (360 Mya). We also compare the elements to contemporaneous arthrodires from the same deposit. Surprisingly, the morphology of the skeletal support of the eye was found to differ significantly between modern and fossil sharks. All three modern shark species examined (spiny dogfish shark Squalus acanthias, porbeagle shark Lamna nasus and blue shark Prionace glauca) have a continuous skeletal element that encapsulates much of the eyeball; however, the tissue composition is different in each species. Histological and morphological examination revealed scleral cartilage with distinct tesserae in parts of the sclera of the porbeagle and blue shark, and more diffuse calcification in the dogfish. Strengthening of the scleral cartilage by means of tesserae has not been reported previously in the shark eye. In striking contrast, the ocular skeleton of fossil sharks comprises a series of individual elements that are arranged in a ring, similar to the arrangement in modern and fossil reptiles. Fossil arthrodires also have a multi-unit sclerotic ring but these are composed of fewer elements than in fossil sharks. The morphology of these elements has implications for the behaviour and visual capabilities of sharks that lived during the Devonian Period. This is the first time that such a dramatic variation in the morphology of scleral skeletal elements has been observed in a single lineage (Chondrichthyes), making this lineage important for broadening our understanding of the evolution of these elements within jawed vertebrates.