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Canine distemper virus (CDV) is a multi-host pathogen with variable clinical outcomes of infection across and within species. We used whole-genome sequencing (WGS) to search for viral markers correlated with clinical distemper in African lions. To identify candidate markers, we first documented single-nucleotide polymorphisms (SNPs) differentiating CDV strains associated with different clinical outcomes in lions in East Africa. We then conducted evolutionary analyses on WGS from all global CDV lineages to identify loci subject to selection. SNPs that both differentiated East African strains and were under selection were mapped to a phylogenetic tree representing global CDV diversity to assess if candidate markers correlated with documented outbreaks of clinical distemper in lions (n = 3). Of 54 SNPs differentiating East African strains, ten were under positive or episodic diversifying selection and 20 occurred in the clinical strain despite strong purifying selection at those loci. Candidate markers were in functional domains of the RNP complex (n = 19), the matrix protein (n = 4), on CDV glycoproteins (n = 5), and on the V protein (n = 1). We found mutations at two loci in common between sequences from three CDV outbreaks of clinical distemper in African lions; one in the signaling lymphocytic activation molecule receptor (SLAM)-binding region of the hemagglutinin protein and another in the catalytic center of phosphodiester bond formation on the large polymerase protein. These results suggest convergent evolution at these sites may have a functional role in clinical distemper outbreaks in African lions and uncover potential novel barriers to pathogenicity in this species.more » « less
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Abstract Environmental DNA (eDNA) sampling—the detection of genetic material in the environment to infer species presence—has rapidly grown as a tool for sampling aquatic animal communities. A potentially powerful feature of environmental sampling is that all taxa within the habitat shed DNA and so may be detectable, creating opportunity for whole‐community assessments. However, animal DNA in the environment tends to be comparatively rare, making it necessary to enrich for genetic targets from focal taxa prior to sequencing. Current metabarcoding approaches for enrichment rely on bulk amplification using conserved primer annealing sites, which can result in skewed relative sequence abundance and failure to detect some taxa because of PCR bias. Here, we test capture enrichment via hybridization as an alternative strategy for target enrichment using a series of experiments on environmental samples and laboratory‐generated, known‐composition DNA mixtures. Capture enrichment resulted in detecting multiple species in both kinds of samples, and postcapture relative sequence abundance accurately reflected initial relative template abundance. However, further optimization is needed to permit reliable species detection at the very low‐DNA quantities typical of environmental samples (<0.1 ng DNA). We estimate that our capture protocols are comparable to, but less sensitive than, current PCR‐based eDNA analyses.
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Abstract Identification of genes underlying genomic signatures of natural selection is key to understanding adaptation to local conditions. We used targeted resequencing to identify
SNP markers in 5321 candidate adaptive genes associated with known immunological, metabolic and growth functions in ovids and other ungulates. We selectively targeted 8161 exons in protein‐coding and nearby 5′ and 3′ untranslated regions of chosen candidate genes. Targeted sequences were taken from bighorn sheep (Ovis canadensis ) exon capture data and directly from the domestic sheep genome (Ovis aries v. 3; oviAri3). The bighorn sheep sequences used in the Dall's sheep (Ovis dalli dalli ) exon capture aligned to 2350 genes on the oviAri3 genome with an average of 2 exons each. We developed a microfluidic qPCR‐basedSNP chip to genotype 476 Dall's sheep from locations across their range and test for patterns of selection. Using multiple corroborating approaches (lositan andbayescan ), we detected 28SNP loci potentially under selection. We additionally identified candidate loci significantly associated with latitude, longitude, precipitation and temperature, suggesting local environmental adaptation. The three methods demonstrated consistent support for natural selection on nine genes with immune and disease‐regulating functions (e.g. Ovar‐DRA ,APC ,BATF 2,MAGEB 18), cell regulation signalling pathways (e.g.KRIT 1,PI 3K,ORRC 3), and respiratory health (CYSLTR 1). Characterizing adaptive allele distributions from novel genetic techniques will facilitate investigation of the influence of environmental variation on local adaptation of a northern alpine ungulate throughout its range. This research demonstrated the utility of exon capture for gene‐targetedSNP discovery and subsequentSNP chip genotyping using low‐quality samples in a nonmodel species. -
Abstract The boom of massive parallel sequencing (
MPS ) technology and its applications in conservation of natural and managed populations brings new opportunities and challenges to meet the scientific questions that can be addressed. Genomic conservation offers a wide range of approaches and analytical techniques, with their respective strengths and weaknesses that rely on several implicit assumptions. However, finding the most suitable approaches and analysis regarding our scientific question are often difficult and time‐consuming. To address this gap, a recent workshop entitled ‘ConGen 2015’ was held at Montana University in order to bring together the knowledge accumulated in this field and to provide training in conceptual and practical aspects of data analysis applied to the field of conservation and evolutionary genomics. Here, we summarize the expertise yield by each instructor that has led us to consider the importance of keeping in mind the scientific question from sampling to management practices along with the selection of appropriate genomics tools and bioinformatics challenges.