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At least 127 records · Page 7Linked to original sources
USGS2026

Genomic data reveal historical introgression and genetic erosion across an imperiled radiation of Caribbean Spondylurus skinks

Understanding how island biodiversity originates and persists is central to evolutionary biology and conservation. Caribbean islands, shaped by repeated cycles of isolation and connectivity, provide a natural laboratory to evaluate how dispersal, divergence, and introgression interact during diversification. Here we use low-coverage whole-genome data from modern and historical specimens of Caribbean Spondylurus skinks, sampling 14 of 17 described species, to reconstruct the evolutionary history and assess current genetic diversity of this insular radiation. Phylogenomic analyses of mitochondrial and nuclear single nucleotide polymorphisms reveal pervasive discordance among gene trees, extensive introgression, and reject a simple stepping-stone model of diversification across the Caribbean. Instead, Spondylurus diversification reflects repeated long-distance dispersal, gene flow following divergence, and persistence on small islands and cays. Genomic patterns of diversity, runs of homozygosity, effective population sizes, and genetic loads show strong contrasts among species with different recent demographic histories, including severe inbreeding, elevated realized genetic load, and sharp population declines associated with invasive predators. Historical specimens exhibit higher heterozygosity and lower genetic load than contemporary samples, indicating rapid genomic erosion over the last century. Together, our results highlight introgression as a persistent force shaping Caribbean skink evolution and reveal urgent conservation risks driven by recent demographic collapse and loss of genomic resilience.

Evolutionary Journal of the Linnean Society↗
USGS2016

Genome sequence of the photoarsenotrophic bacterium Ectothiorhodospira sp. strain BSL-9, isolated from a hypersaline alkaline arsenic-rich extreme environment

The full genome sequence of Ectothiorhodospira sp. strain BSL-9 is reported here. This purple sulfur bacterium encodes an arxA -type arsenite oxidase within the arxB2AB1CD gene island and is capable of carrying out “photoarsenotrophy” anoxygenic photosynthetic arsenite oxidation. Its genome is composed of 3.5 Mb and has approximately 63% G+C content.

Genome Announcements↗
USGS2017

Virulence of a chimeric recombinant infectious haematopoietic necrosis virus expressing the spring viraemia of carp virus glycoprotein in salmonid and cyprinid fish

Infectious haematopoietic necrosis virus (IHNV) and spring viraemia of carp virus (SVCV) are both rhabdoviruses of fish, listed as notifiable disease agents by the World Organization for Animal Health. Recombinant rhabdoviruses with heterologous gene substitutions have been engineered to study genetic determinants and assess the potential of these recombinant viruses for vaccine development. A recombinant IHNV (rIHNV), containing the full-length genome of a European IHNV strain, was modified by deleting the glycoprotein (G) gene and replacing it with a European SVCV G-gene to make the rIHNV-Gsvcv. The chimeric rIHNV-Gsvcv level of virulence in rainbow trout, common carp and koi was assessed, and its ability to induce a protective immune response in surviving koi against wild-type SVCV infection was tested. The rIHNV-Gsvcv infection of trout led to high mortality, ranging from 78% to 92.5%, after immersion. In contrast, no deaths occurred in juvenile common carp after infection with rIHNV-Gsvcv by either immersion or intraperitoneal (IP) injection. Similarly, koi infected with rIHNV-Gsvcv via IP injection had little to no mortality (≤9%). Koi that survived initial infection with a high dose of recombinant virus rIHNV-Gsvcv were protected against a virulent SVCV challenge resulting in a high relative per cent survival of 82.5%.

Journal of Fish Diseases↗
USGS2023

Environmental antimicrobial resistance gene detection from wild bird habitats using two methods: A commercially available culture-independent qPCR assay and culture of indicator bacteria followed by whole-genome sequencing

Objectives A variety of methods have been developed to detect antimicrobial resistance (AMR) in different environments to better understand the evolution and dissemination of this public health threat. Comparisons of results generated using different AMR detection methods, such as quantitative PCR (qPCR) and whole-genome sequencing (WGS), are often imperfect, and few studies have analysed samples in parallel to evaluate differences. In this study, we compared bacterial culture and WGS to a culture-independent commercially available qPCR assay to evaluate the concordance between methods and the utility of each in answering research questions regarding the presence and epidemiology of AMR in wild bird habitats. Methods We first assessed AMR gene detection using qPCR in 45 bacterial isolates from which we had existing WGS data. We then analysed 52 wild bird faecal samples and 9 spatiotemporally collected water samples using culture-independent qPCR and WGS of phenotypically resistant indicator bacterial isolates. Results Overall concordance was strong between qPCR and WGS of bacterial isolates, although concordance differed among antibiotic classes. Analysis of wild bird faecal and water samples revealed that more samples were determined to be positive for AMR via qPCR than via culture and WGS of bacterial isolates, although qPCR did not detect AMR genes in two samples from which phenotypically resistant isolates were found. Conclusions Both qPCR and culture followed by sequencing may be effective approaches for characterising AMR genes harboured by wild birds, although data streams produced using these different tools may have advantages and disadvantages that should be considered given the application and sample matrix.

Journal of Global Antimicrobial Resistance↗
USGS2015

Phylogenetic and pathogenic characterization of novel adenoviruses from long-tailed ducks ( Clangula hyemalis )

Novel adenoviruses were isolated from a long-tailed duck ( Clangula hyemalis ) mortality event near Prudhoe Bay, Alaska in 2000. The long-tailed duck adenovirus genome was approximately 27 kb. A 907 bp hexon gene segment was used to design primers specific for the long-tailed duck adenovirus. Nineteen isolates were phylogenetically characterized based on portions of their hexon gene and 12 were most closely related to Goose adenovirus A . The remaining 7 shared no hexon sequences with any known adenoviruses. Experimental infections of mallards with a long-tailed duck reference adenovirus caused mild lymphoid infiltration of the intestine and paint brush hemorrhages of the mucosa and dilation of the intestine. This study shows novel adenoviruses from long-tailed ducks are diverse and provides further evidence that they should be considered in cases of morbidity and mortality in sea ducks. Conserved and specific primers have been developed that will help screen sea ducks for adenoviral infections.

Alaska↗
USGS2017

Acetoclastic Methanosaeta are dominant methanogens in organic-rich Antarctic marine sediments

Despite accounting for the majority of sedimentary methane, the physiology and relative abundance of subsurface methanogens remain poorly understood. We combined intact polar lipid and metagenome techniques to better constrain the presence and functions of methanogens within the highly reducing, organic-rich sediments of Antarctica’s Adélie Basin. The assembly of metagenomic sequence data identified phylogenic and functional marker genes of methanogens and generated the first Methanosaeta sp. genome from a deep subsurface sedimentary environment. Based on structural and isotopic measurements, glycerol dialkyl glycerol tetraethers with diglycosyl phosphatidylglycerol head groups were classified as biomarkers for active methanogens. The stable carbon isotope (δ 13 C) values of these biomarkers and the Methanosaeta partial genome suggest that these organisms are acetoclastic methanogens and represent a relatively small (0.2%) but active population. Metagenomic and lipid analyses suggest that Thaumarchaeota and heterotrophic bacteria co-exist with Methanosaeta and together contribute to increasing concentrations and δ 13 C values of dissolved inorganic carbon with depth. This study presents the first functional insights of deep subsurface Methanosaeta organisms and highlights their role in methane production and overall carbon cycling within sedimentary environments.

ISME Journal↗
USGS2018

The complete maternal mitochondrial genome sequences of two imperiled North American freshwater mussels: Alasmidonta heterodon and Alasmidonta varicosa (Bivalvia: Unionoida: Unionidae)

The freshwater mussels Alasmidonta heterodon and A. varicosa historically inhabited rivers along the North American Atlantic coast from the Carolinas, U.S.A., to New Brunswick, CA. However, many populations have been extirpated, and A. heterodon is now federally listed in the U.S.A. as endangered, and both A. heterodon and A. varicosa are listed as vulnerable on the IUCN Red List. To facilitate genetic study of these species, we sequenced the complete female mitochondrial genomes of A. heterodon (15,909 bp; GenBank accession no. MG905826), and A. varicosa (15,693 bp; GenBank accession no. MG938673). Both mitogenomes contained 14 protein coding genes, 2 rRNA genes, and 22 tRNAs with the same gene order as reported for other members of the subfamily Anodontinae. When these two genomes were put into a phylogenetic context with other members of the Unionidae, they clustered together with other species in the subfamily Anodontinae, Tribe Anodontini.

Mitochondrial DNA Part B↗
USGS2020

The transformative impact of genomics on sage-grouse conservation and management

For over two decades, genetic studies have been used to assist in the conservation and management of both Greater Sage-grouse ( Centrocercus urophasianus ) and Gunnison Sage-grouse ( C. minimus ), addressing a wide variety of topics including taxonomy, parentage, population connectivity, and demography. The field of conservation genetics has been transformed by dramatic improvements in sequencing technology, facilitating genomic studies in many wildlife species. The quality and amount of data generated by genomic methods vastly exceed that of traditional genetic studies, allowing for increased precision in estimating genetic parameters of interest. Perhaps more importantly, genomic methods can provide insight into non-neutral evolution such as adaptive divergence. Here we recount the shift from genetic to genomic methods using two wildlife species of substantial conservation interest, focusing on the improved capabilities and advantages of genomic methods. For instance, reassessment of divergence in sage-grouse using genomic methods confirmed strong differentiation between the two species and revealed that a small population in the state of Washington was more genetically distinct than previously recognized. Further, new genomic resources and approaches have been used to identify a family of genes linked to local dietary adaptation suggesting that sage-grouse may possess digestive and metabolic adaptations that mitigate the effects of consuming plant secondary metabolites like those found in sagebrush. Genetic variation among populations in these gene regions is thought to be involved with local dietary adaptations, and therefore maintaining the tie between sage-grouse and the chemistry of local sagebrush may be an important management consideration. We posit that the integration of newly developed genomic resources combined with the vast wealth of ecological and behavioral data for sage-grouse has the potential to shed light on mechanistic relationships that ultimately are vital to the conservation and management of these species.

Book chapter↗
USGS2022

Genome resequencing clarifies phylogeny and reveals patterns of selection in the toxicogenomics model Pimephales promelas

Background The fathead minnow ( Pimephales promelas ) is a model species for toxicological research. A high-quality genome reference sequence is available, and genomic methods are increasingly used in toxicological studies of the species. However, phylogenetic relationships within the genus remain incompletely known and little population-genomic data are available for fathead minnow despite the potential effects of genetic background on toxicological responses. On the other hand, a wealth of extant samples is stored in museum collections that in principle allow fine-scale analysis of contemporary and historical genetic variation. Methods Here we use short-read shotgun resequencing to investigate sequence variation among and within Pimephales species. At the genus level, our objectives were to resolve phylogenetic relationships and identify genes with signatures of positive diversifying selection. At the species level, our objective was to evaluate the utility of archived-sample resequencing for detecting selective sweeps within fathead minnow, applied to a population introduced to the San Juan River of the southwestern United States sometime prior to 1950. Results We recovered well-supported but discordant phylogenetic topologies for nuclear and mitochondrial sequences that we hypothesize arose from mitochondrial transfer among species. The nuclear tree supported bluntnose minnow ( P. notatus ) as sister to fathead minnow, with the slim minnow ( P. tenellus ) and bullhead minnow ( P. vigilax ) more closely related to each other. Using multiple methods, we identified 11 genes that have diversified under positive selection within the genus. Within the San Juan River population, we identified selective-sweep regions overlapping several sets of related genes, including both genes that encode the giant sarcomere protein titin and the two genes encoding the MTORC1 complex, a key metabolic regulator. We also observed elevated polymorphism and reduced differentation among populations (F ST ) in genomic regions containing certain immune-gene clusters, similar to what has been reported in other taxa. Collectively, our data clarify evolutionary relationships and selective pressures within the genus and establish museum archives as a fruitful resource for characterizing genomic variation. We anticipate that large-scale resequencing will enable the detection of genetic variants associated with environmental toxicants such as heavy metals, high salinity, estrogens, and agrichemicals, which could be exploited as efficient biomarkers of exposure in natural populations.

PeerJ↗
USGS2022

Salmonella enterica serovar Typhimurium from wild birds in the United States represent distinct lineages defined by bird type

Salmonella enterica serovar Typhimurium is typically considered a host generalist; however, certain isolates are associated with specific hosts and show genetic features of host adaptation. Here, we sequenced 131 S. Typhimurium isolates from wild birds collected in 30 U.S. states during 1978-2019. We found that isolates from broad taxonomic host groups including passerine birds, water birds (Aequornithes), and larids (gulls and terns) represented three distinct lineages and certain S. Typhimurium CRISPR types presented in individual lineages. We also showed that lineages formed by wild bird isolates differed from most isolates originating from domestic animal sources, and genomes from these lineages substantially improved source attribution of Typhimurium genomes to wild birds by a machine learning classifier. Furthermore, virulence gene signatures that differentiated S. Typhimurium from passerines, water birds, and larids were detected. Passerine isolates tended to lack S. Typhimurium-specific virulence plasmids. Isolates from the passerine, water bird, and larid lineages had close genetic relatedness with human clinical isolates, including those from a 2021 U.S. outbreak linked to passerine birds. These observations indicate that S. Typhimurium from wild birds in the United States are likely host-adapted, and the representative genomic dataset examined in this study can improve source prediction and facilitate outbreak investigation.

Applied and Environmental Microbiology↗
USGS2024

Ecology shapes the genomic and biosynthetic diversification of Streptomyces bacteria from insectivorous bats

Streptomyces are prolific producers of secondary metabolites from which many clinically useful compounds have been derived. They inhabit diverse habitats but have rarely been reported in vertebrates. Here, we aim to determine to what extent the ecological source (bat host species and cave sites) influence the genomic and biosynthetic diversity of Streptomyces bacteria. We analysed draft genomes of 132 Streptomyces isolates sampled from 11 species of insectivorous bats from six cave sites in Arizona and New Mexico, USA. We delineated 55 species based on the genome-wide average nucleotide identity and core genome phylogenetic tree. Streptomyces isolates that colonize the same bat species or inhabit the same site exhibit greater overall genomic similarity than they do with Streptomyces from other bat species or sites. However, when considering biosynthetic gene clusters (BGCs) alone, BGC distribution is not structured by the ecological or geographical source of the Streptomyces that carry them. Each genome carried between 19–65 BGCs (median=42.5) and varied even among members of the same Streptomyces species. Nine major classes of BGCs were detected in ten of the 11 bat species and in all sites: terpene, non-ribosomal peptide synthetase, polyketide synthase, siderophore, RiPP-like, butyrolactone, lanthipeptide, ectoine, melanin. Finally, Streptomyces genomes carry multiple hybrid BGCs consisting of signature domains from two to seven distinct BGC classes. Taken together, our results bring critical insights to understanding Streptomyces -bat ecology and BGC diversity that may contribute to bat health and in augmenting current efforts in natural product discovery, especially from underexplored or overlooked environments.

Microbial Genomics↗
USGS2024

High inter-population connectivity and occasional gene flow between subspecies improves recovery potential for the endangered Least Bell’s Vireo

Increasingly, genomic data are being used to supplement field-based ecological studies to help evaluate recovery status and trends in endangered species. We collected genomic data to address two related questions regarding the Least Bell’s Vireo ( Vireo bellii ), an endangered migratory songbird restricted to southern California riparian habitat for breeding. First, we sought to delineate the range limits and potential overlap between Least Bell’s Vireo and its sister subspecies, the Arizona Bell’s Vireo, by analyzing samples from the deserts of eastern California, southwestern Nevada, Utah and Arizona. Second, we evaluated genetic structure among Least Bell’s Vireo populations in coastal California and estimated effective population size. Clustering analyses based on 10,571 single nucleotide polymorphisms (SNPs) from 317 samples supported two major groups that aligned closely to the previously defined subspecies ranges. The first cluster included birds in the Central Valley, all coastal drainages, and westernmost deserts of California, with no further sub-structuring among coastal drainages. Almost all birds from the Amargosa River in eastern California and eastward assigned to the second cluster; however, low levels of gene flow were detected across the subspecies groups, with greater rates of gene flow from Arizona Bell’s Vireo to Least Bell’s Vireo than the reverse. Admixed individuals occurred in the California deserts; and although smaller than coastal populations, desert populations may be important for maintaining and replenishing genetic diversity and facilitating the movement of potentially adaptive genes between subspecies. Within Least Bell’s Vireo, local populations in coastal drainages comprised a single genetic population, with some evidence of close relatives distributed across drainages, suggesting these could function as a well-connected metapopulation. These results are consistent with previous Least Bell’s Vireo banding studies that reported high rates of dispersal among drainages. Effective population size for both subspecies was high, suggesting that adaptive potential has been maintained despite previous declines.

Ornithological Applications↗
USGS2015

Convergent evolution of the genomes of marine mammals

Marine mammals from different mammalian orders share several phenotypic traits adapted to the aquatic environment and therefore represent a classic example of convergent evolution. To investigate convergent evolution at the genomic level, we sequenced and performed de novo assembly of the genomes of three species of marine mammals (the killer whale, walrus and manatee) from three mammalian orders that share independently evolved phenotypic adaptations to a marine existence. Our comparative genomic analyses found that convergent amino acid substitutions were widespread throughout the genome and that a subset of these substitutions were in genes evolving under positive selection and putatively associated with a marine phenotype. However, we found higher levels of convergent amino acid substitutions in a control set of terrestrial sister taxa to the marine mammals. Our results suggest that, whereas convergent molecular evolution is relatively common, adaptive molecular convergence linked to phenotypic convergence is comparatively rare.

Nature Genetics↗
USGS2019

A novel host-adapted strain of Salmonella Typhimurium causes disease in olive ridley turtles (Lepidochelys olivacea) in the Pacific.

Salmonella spp. are frequently shed by wildlife including turtles, but S. enterica subsp. enterica serovar Typhimurium or lesions associated with Salmonella are rare in turtles. Between 1996 and 2016, we necropsied 127 apparently healthy pelagic olive ridley turtles ( Lepidochelys olivacea ) that died from drowning bycatch in fisheries and 44 live or freshly dead stranded turtles from the west coast of North and Central America and Hawaii. Seven % (9/127) of pelagic and 47% (21/44) of stranded turtles had renal granulomas associated with S. Typhimurium. Stranded animals were 12 times more likely than pelagic animals to have Salmonella -induced nephritis suggesting that Salmonella may have been a contributing cause of stranding. S. Typhimurium was the only Salmonella serovar detected in L. olivacea , and phylogenetic analysis from whole genome sequencing showed that the isolates from L. olivacea formed a single clade distinct from other S. Typhimurium. Molecular clock analysis revealed that this novel clade may have originated as recently as a few decades ago. The phylogenetic lineage leading to this group is enriched for non-synonymous changes within the genomic area of Salmonella pathogenicity island 1 suggesting that these genes are important for host adaptation.

California, Hawaii, Oregon, Washington↗
USGS2002

Comparison of mitochondrial DNA control region sequence and microsatellite DNA analyses in estimating population structure and gene flow rates in Atlantic sturgeon Acipenser oxyrinchus

Atlantic sturgeon Acipenser oxyrinchus is large, long-lived, and anadromous with subspecies distributed along the Atlantic (A. oxyrinchus oxyrinchus) and Gulf of Mexico (A. o. desotoi) coasts of North America. Although it is not certain if extirpation of some population units has occurred, because of anthropogenic influences abundances of all populations are low compared with historical levels. Informed management of A. oxyrinchus demands a detailed knowledge of its population structure, levels of genetic diversity, and likelihood to home to natal rivers. We compared the use of mitochondrial DNA (mtDNA) control region sequence and microsatellite nuclear DNA (nDNA) analyses in identifying the stock structure and homing fidelity of Atlantic and Gulf coast populations of A. oxyrinchus. The approaches were concordant in that they revealed moderate to high levels of genetic diversity and suggested that populations of Atlantic sturgeon are highly structured. At least six genetically distinct management units were detected using the two approaches among the rivers surveyed. Mitochondrial DNA sequences revealed a significant cline in haplotype diversity along the Atlantic coast with monomorphism observed in Canadian populations. High levels of nDNA diversity were also observed among populations along the Atlantic coast, including the two Canadian populations, probably resulting from the more rapid rate of mutational and evolutionary change at microsatellite loci. Estimates of gene flow among populations were similar between both approaches with the exception that because of mtDNA monomorphism in Canadian populations, gene flow estimates between them were unobtainable. Analyses of both genomes provided high resolution and confidence in characterizing the population structure of Atlantic sturgeon. Microsatellite analysis was particularly informative in delineating population structure in rivers that were recently glaciated and may prove diagnostic in rivers that are geographically proximal along the south Atlantic coast of the US.

Journal of Applied Ichthyology↗
USGS2015

Genomics and introgression: Discovery and mapping of thousands of species-diagnostic SNPs using RAD sequencing

Invasive hybridization and introgression pose a serious threat to the persistence of many native species. Understanding the effects of hybridization on native populations (e.g., fitness consequences) requires numerous species-diagnostic loci distributed genome-wide. Here we used RAD sequencing to discover thousands of single-nucleotide polymorphisms (SNPs) that are diagnostic between rainbow trout (RBT, Oncorhynchus mykiss ), the world’s most widely introduced fish, and native westslope cutthroat trout (WCT, O. clarkii lewisi ) in the northern Rocky Mountains, USA. We advanced previous work that identified 4,914 species-diagnostic loci by using longer sequence reads (100 bp vs . 60 bp) and a larger set of individuals ( n = 84). We sequenced RAD libraries for individuals from diverse sampling sources, including native populations of WCT and hatchery broodstocks of WCT and RBT. We also took advantage of a newly released reference genome assembly for RBT to align our RAD loci. In total, we discovered 16,788 putatively diagnostic SNPs, 10,267 of which we mapped to anchored chromosome locations on the RBT genome. A small portion of previously discovered putative diagnostic loci (325 of 4,914) were no longer diagnostic (i.e., fixed between species) based on our wider survey of non-hybridized RBT and WCT individuals. Our study suggests that RAD loci mapped to a draft genome assembly could provide the marker density required to identify genes and chromosomal regions influencing selection in admixed populations of conservation concern and evolutionary interest.

Montana↗
USGS2022

Using landscape genomics to delineate future adaptive potential for climate change in the Yosemite toad (Anaxyrus canorus)

An essential goal in conservation biology is delineating population units that maximize the probability of species persisting into the future and adapting to future environmental change. However, future-facing conservation concerns are often addressed using retrospective patterns that could be irrelevant. We recommend a novel landscape genomics framework for delineating future “Geminate Evolutionary Units” (GEUs) in a focal species: (1) identify loci under environmental selection, (2) model and map adaptive conservation units that may spawn future lineages, (3) forecast relative selection pressures on each future lineage, and (4) estimate their fitness and likelihood of persistence using geo-genomic simulations. Using this process, we delineated conservation units for the Yosemite toad ( Anaxyrus canorus ), a U.S. federally threatened species that is highly vulnerable to climate change. We used a genome-wide dataset, redundancy analysis, and Bayesian association methods to identify 24 candidate loci responding to climatic selection ( R 2 ranging from 0.09 to 0.52), after controlling for demographic structure. Candidate loci included genes such as MAP3K5, involved in cellular response to environmental change. We then forecasted future genomic response to climate change using the multivariate machine learning algorithm Gradient Forests. Based on all available evidence, we found three GEUs in Yosemite National Park, reflecting contrasting adaptive optima: YF-North (high winter snowpack with moderate summer rainfall), YF-East (low to moderate snowpack with high summer rainfall), and YF-Low-Elevation (low snowpack and rainfall). Simulations under the RCP 8.5 climate change scenario suggest that the species will decline by 29% over 90 years, but the highly diverse YF-East lineage will be least impacted for two reasons: (1) geographically it will be sheltered from the largest climatic selection pressures, and (2) its standing genetic diversity will promote a faster adaptive response. Our approach provides a comprehensive strategy for protecting imperiled non-model species with genomic data alone and has wide applicability to other declining species.

California↗
USGS2021

Implications of historical and contemporary processes on genetic differentiation of a declining boreal songbird: The rusty blackbird

The arrangement of habitat features via historical or contemporary events can strongly influence genomic and demographic connectivity, and in turn affect levels of genetic diversity and resilience of populations to environmental perturbation. The rusty blackbird ( Euphagus carolinus ) is a forested wetland habitat specialist whose population size has declined sharply (78%) over recent decades. The species breeds across the expansive North American boreal forest region, which contains a mosaic of habitat conditions resulting from active natural disturbance regimes and glacial history. We used landscape genomics to evaluate how past and present landscape features have shaped patterns of genetic diversity and connectivity across the species’ breeding range. Based on reduced-representation genomic and mitochondrial DNA, genetic structure followed four broad patterns influenced by both historical and contemporary forces: (1) an east–west partition consistent with vicariance during the last glacial maximum; (2) a potential secondary contact zone between eastern and western lineages at James Bay, Ontario; (3) insular differentiation of birds on Newfoundland; and (4) restricted regional gene flow among locales within western and eastern North America. The presence of genomic structure and therefore restricted dispersal among populations may limit the species’ capacity to respond to rapid environmental change.

Diversity↗