Designatable Units Research Articles

Genomic population structure and inbreeding history of Lake Superior caribou.

Caribou (Rangifer tarandus) have experienced dramatic declines in both range and population size across Canada over the past century. Boreal caribou (R. t. caribou), 1 of the 12 Designatable Units, has lost approximately half of its historic range in the last 150 years, particularly along the southern edge of its distribution. Despite this overall northward contraction, some populations have persisted at the trailing range edge, over 150 km south of the continuous boreal caribou range in Ontario, along the coast and nearshore islands of Lake Superior. The population history of caribou along Lake Superior remains unclear. It appears that these caribou likely represent a remnant distribution at the trailing edge of the receding population of boreal caribou, but they may also exhibit local adaptation to the coastal environment. A better understanding of the population structure and history of caribou along Lake Superior is important for their conservation and management. Here, we use high-coverage whole genomes (N = 20) from boreal, eastern migratory, and barren-ground caribou sampled in Manitoba, Ontario, and Quebec to investigate population structure and inbreeding histories. We discovered that caribou from the Lake Superior range form a distinct group but also found some evidence of gene flow with the continuous boreal caribou range. Notably, caribou along Lake Superior demonstrated relatively high levels of inbreeding (measured as runs of homozygosity; ROH) and genetic drift, which may contribute to the differentiation observed between ranges. Despite inbreeding, caribou along Lake Superior retained high heterozygosity, particularly in genomic regions without ROH. These results suggest that they present distinct genomic characteristics but also some level of gene flow with the continuous range. Our study provides key insights into the genomics of the southernmost range of caribou in Ontario, beginning to unravel the evolutionary history of these small, isolated caribou populations.

Lineage diversity within a widespread endemic Australian skink to better inform conservation in response to regional-scale disturbance.

Much attention is paid in conservation planning to the concept of a species, to ensure comparability across studies and regions when classifying taxa against criteria of endangerment and setting priorities for action. However, various jurisdictions now allow taxonomic ranks below the level of species and nontaxonomic intraspecific divisions to be factored into conservation planning—subspecies, key populations, evolutionarily significant units, or designatable units. Understanding patterns of genetic diversity and its distribution across the landscape is a key component in the identification of species boundaries and determination of substantial geographic structure within species. A total of 12,532 reliable polymorphic SNP loci were generated from 63 populations (286 individuals) covering the distribution of the Australian eastern three‐lined skink, Bassiana duperreyi, to assess genetic population structure in the form of diagnosable lineages and their distribution across the landscape, with particular reference to the recent catastrophic bushfires of eastern Australia. Five well‐supported diagnosable operational taxonomic units (OTUs) existed within B. duperreyi. Low levels of divergence of B. duperreyi between mainland Australia and Tasmania (no fixed allelic differences) support the notion of episodic exchange of alleles across Bass Strait (ca 60 m, 25 Kya) during periods of low sea level during the Upper Pleistocene rather than the much longer period of isolation (1.7 My) indicated by earlier studies using mitochondrial sequence variation. Our study provides foundational work for the detailed taxonomic re‐evaluation of this species complex and the need for biodiversity assessment to include an examination of cryptic species and/or cryptic diversity below the level of species. Such information on lineage diversity within species and its distribution in the context of disturbance at a regional scale can be factored into conservation planning regardless of whether a decision is made to formally diagnose new species taxonomically and nomenclaturally.

A Phylogeographic Contact Zone for Arctic Grayling in Alberta, Canada

AbstractArctic Grayling Thymallus arcticus are a salmonid with a Holarctic distribution, extending from northeastern Eurasia through northwestern North America. Throughout their range, Arctic Grayling face a number of threats, including angling mortality, habitat fragmentation and loss, and climate change. Thus, there is a need to protect the species through targeted management actions. Genetic information can assist in determining the appropriate scale for these actions through the description of designatable units. Here we use newly collected mitochondrial DNA sequence data to assess the phylogeographic structure of Arctic Grayling in Alberta, Canada, and link these with previously collected mitochondrial and microsatellite data to determine how many designatable units may exist across Canada. Our assessment of 831 base pairs of sequence data in 96 individuals found two deeply divergent lineages in Alberta. When combined with 22 previously collected sequences, our results highlight that Alberta is a contact zone for the observed lineages of Arctic Grayling in North America. A reassessment of nine microsatellites that were genotyped in 1,116 individuals further highlighted interbasin divergence, likely the result of historical processes. Given the divergence and geographic distribution of the genetic diversity, Arctic Grayling in Canada merit consideration for separate designatable units in future species status assessments and management plans. Continuing research should attempt to expand sampling geographically (e.g., regions east of Great Slave Lake and along the Arctic coastline) to clarify possible colonization routes and add to or synthesize the work on Arctic Grayling behavior, morphology, and life history to address the limited understanding of local adaptions within this species.

An assessment of terminology for intraspecific diversity in fishes, with a focus on "ecotypes" and "life histories".

Understanding and preserving intraspecific diversity (ISD) is important for species conservation. However, ISD units do not have taxonomic standards and are not universally recognized. The terminology used to describe ISD is varied and often used ambiguously. We compared definitions of terms used to describe ISD with use in recent studies of three fish taxa: sticklebacks (Gasterosteidae), Pacific salmon and trout (Oncorhynchus spp., “PST”), and lampreys (Petromyzontiformes). Life history describes the phenotypic responses of organisms to environments and includes biological parameters that affect population growth or decline. Life‐history pathway(s) are the result of different organismal routes of development that can result in different life histories. These terms can be used to describe recognizable life‐history traits. Life history is generally used in organismal‐ and ecology‐based journals. The terms paired species/species pairs have been used to describe two different phenotypes, whereas in some species and situations a continuum of phenotypes may be expressed. Our review revealed overlapping definitions for race and subspecies, and subspecies and ecotypes. Ecotypes are genotypic adaptations to particular environments, and this term is often used in genetic‐ and evolution‐based journals. “Satellite species” is used for situations in which a parasitic lamprey yields two or more derived, nonparasitic lamprey species. Designatable Units, Evolutionary Significant Units (ESUs), and Distinct Population Segments (DPS) are used by some governments to classify ISD of vertebrate species within distinct and evolutionary significant criteria. In situations where the genetic or life‐history components of ISD are not well understood, a conservative approach would be to call them phenotypes.

Assessing biodiversity hotspots below the species-level in Canada using designatable units

The biodiversity hotspot approach is commonly used to identify key regions of conservation priority based on species richness and uniqueness. Like other countries, Canada uses below species-level conservation units, called Designatable Units (DUs), for assessing extinction risk on a case-by-case basis. Researchers have yet to investigate conservation unit hotspots below the species level, despite the potential benefits to optimize the impact of conservation strategies. Across taxa, we: (i) identified at-risk DU hotspots, eco-geographic regions in Canada with a disproportionate number of at-risk DUs relative to species richness; and (ii) compared at-risk DU hotspots using two sets of eco-geographic maps adopted by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). DU richness counts were based on COSEWIC assessed species and hence biased towards at-risk DUs; species richness values were obtained from the International Union for Conservation of Nature (IUCN) Red List. At-risk DU hotspots were consistently found in the Pacific and Great Lakes regions. A positive correlation was observed between at-risk DUs and species richness using both eco-geographic maps, but important regional nuances were also detected, i.e., hotspots were not always found in regions of high species richness. Moreover, there were 3.45 at-risk DUs for every at-risk species across all taxa, providing greater resolution for refining conservation prioritization across regions. For Canada, the at-risk DU hotspot approach permits the identification of regions with a high number of at-risk DUs relative to species richness, enabling the targeting of multiple DUs and taxa in one management plan. More generally, these results emphasize the importance of incorporating below species-level metrics into conservation decisions to better account for different components of biodiversity and extinction risk.

Which Caribou? Misnaming Caribou Population Units Leads to Conservation Errors

In reviewing the genetic, morphological, behavioural, and ecological distinctiveness of caribou throughout Canada, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) (2011) divided “Southern Mountain caribou” (c.f. COSEWIC 2002) into three designatable units (DU) for conservation purposes: Northern Mountain (DU7), Central Mountain (DU8), and Southern Mountain (DU9) populations of woodland caribou. These new designations mean that each is considered a “wildlife species” according to the Species at Risk Act. Recent federal and provincial government reports refer to “Southern Mountain caribou,” conflating Southern Mountain, Central Mountain, and nine of the 45 subpopulations of Northern Mountain caribou into one pseudo-population, with clear conservation consequences. For example, in 2018, a federal decision on an emergency order required the Minister of Environment and Climate Change Canada (ECCC) to ascertain whether there were immediate threats to the survival or recovery of the Southern Mountain population of woodland caribou. By conflating two ecotypes and part of another into “Southern Mountain caribou”—an obsolete, geographical grouping not used since2002—ECCC’s assessment falsely informed the Minister that there were 3,764 “Southern Mountain caribou,” when in fact there were only 1,240 in the Southern Mountain (DU9)mpopulation. Other errors arising from the first distorted the number and trajectories of extant subpopulations. Instead of issuing the emergency order, the Minister entered into protracted negotiations with the province on recovery planning that continue at this writing. The nomenclatural ambiguity can be resolved by 1) using the currently accepted taxonomy naming Osborn’s caribou a valid subspecies, R. t. osborni, instead of Northern Mountain population of woodland caribou, 2) using original English names for Mountain caribou and Rocky Mountain caribou, and 3) basing conservation actions on these distinct phylogenetic units as per COSEWIC (2011, 2014).

Absence of genetic structure reflects post-glacial history and present-day host use in Mapleleaf (Quadrula quadrula) mussel from Manitoba, Canada

Our study documents and analyzes the absence of genetic diversity and structure of the Mapleleaf (Quadrula quadrula (Rafinesque, 1820)) (Bivalvia: Unionidae) mussel in the Lake Winnipeg, Assiniboine River, and Red River drainages (Manitoba, Canada). Previous studies have revealed patterns of genetic diversity and structure in the Mississippi and Ohio river drainages, as well as in the Laurentian Great Lakes drainage. Genotypes from six variable microsatellite loci showed that the Q. quadrula population in Manitoba was significantly differentiated from the population in the Great Lakes drainage (Ontario, Canada), supporting the existence of two Designatable Units in Canada. Conversely, there was no evidence of genetic structure within the sampled range of Q. quadrula in Manitoba. The lack of genetic structure in Q. quadrula across its distribution in Manitoba reflected its post-glacial history and use of a vagile host and necessitates that efforts should be made to ensure connectivity and maintain gene flow across the region. Given that the evidence suggests that Manitoba Q. quadrula belong to a single genetic population, movement of hatchery-propagated juvenile Q. quadrula, adult Q. quadrula, or glochidia-carrying host catfish sourced from any location in Manitoba could be used to augment declining populations or at-risk locations in Manitoba.

The role of introgression and ecotypic parallelism in delineating intraspecific conservation units.

Parallel evolution can occur through selection on novel mutations, standing genetic variation or adaptive introgression. Uncovering parallelism and introgressed populations can complicate management of threatened species as parallelism may have influenced conservation unit designations and admixed populations are not generally considered under legislations. We examined high coverage whole‐genome sequences of 30 caribou (Rangifer tarandus) from across North America and Greenland, representing divergent intraspecific lineages, to investigate parallelism and levels of introgression contributing to the formation of ecotypes. Caribou are split into four subspecies and 11 extant conservation units, known as designatable units (DUs), in Canada. Using genomes from all four subspecies and six DUs, we undertake demographic reconstruction and confirm two previously inferred instances of parallel evolution in the woodland subspecies and uncover an additional instance of parallelism of the eastern migratory ecotype. Detailed investigations reveal introgression in the woodland subspecies, with introgressed regions found spread throughout the genomes encompassing both neutral and functional sites. Our investigations using whole genomes highlight the difficulties in unequivocally demonstrating parallelism through adaptive introgression in nonmodel species with complex demographic histories, with standing variation and introgression both potentially involved. Additionally, the impact of parallelism and introgression on conservation policy for management units needs to be considered in general, and the caribou designations will need amending in light of our results. Uncovering and decoupling parallelism and differential patterns of introgression will become prevalent with the availability of comprehensive genomic data from nonmodel species, and we highlight the need to incorporate this into conservation unit designations.

The Currency of Conservation: How Is Landscape Extent Applied in Conservation Planning?

We asked how the concept of landscape extent is used in conservation planning. To narrow the scope of our review, we focused on four iconic species depicted on Canadian currency: the beaver (Castor canadensis), the caribou (Rangifer tarandus), the common loon (Gavia immer), and the polar bear (Ursus maritimus). Landscape ecology research suggests that a landscape is a species-specific construct arising from the spatial scales over which ecological processes occur. Species traits can be correlated with the scales of important effects and thus can identify relevant landscape extents for research and conservation. It is unclear, however, how the theoretical concept of landscape extent is applied in conservation practice. For the four iconic species in our study, we found an inconsistent use of species-specific traits in definitions of landscape extent for conservation planning. For two species, the caribou and the polar bear, species-specific traits were used to define conservation units, for defining either Designatable Units for assessment of at-risk status or for defining herds or subpopulations for management actions. No species-specific traits were identified in spatial frameworks used in loon or beaver conservation planning, as both were included in multi-species management approaches. Our review suggests a type of research implementation gap. Conservation units are often defined based on political or administrative boundaries rather than by species-specific processes. We suggest that landscape extent be implemented as a hypothesis in an adaptive management framework when possible. Additionally, we encourage research approaches that explicitly incorporate policy considerations into research design.

Reintroduction of fishes in Canada: a review of research progress for SARA-listed species

Fishes are among the most threatened taxa in Canada with over 70 species, subspecies, and (or) designatable units presently listed for protection under the Species at Risk Act (SARA). Protecting these species requires a diverse set of strategies based on the best-available data and information. One approach identified under SARA and in Canadian federal recovery strategies for improving the status of SARA-listed fishes is species reintroduction, which involves the release of individuals into areas from which they have been extirpated with the goal of re-establishing self-sustaining populations. The success of reintroduction relies on a comprehensive understanding of species ecology and life history, with considerations around population genetics and genomics. However, SARA-listed species are some of the most poorly known species in Canada due to their rarity and relative lack of research investment prior to the enactment of SARA. As a result, SARA-listed species have the most to lose if reintroduction activities are not carefully researched, planned, and executed. Therefore, the purpose of this review is to present an accessible summary on the state of reintroduction science for SARA-listed fishes in Canada with the hope of motivating future research to support reintroduction activities. We focus our review on 14 SARA-listed freshwater or anadromous fishes identified as candidates for reintroduction in federal recovery strategies. We follow the species-specific summaries with guidance on how basic research questions in population ecology, habitat science, and threat science provide a critical foundation for addressing knowledge gaps in reintroduction science. Subsequently, we identify the importance of genetic and genomic techniques for informing future research on the reintroduction of SARA-listed species. We conclude with recommendations for active, experimental approaches for moving reintroduction efforts forward to recover Canadian fishes.

Evaluating evolutionary history and adaptive differentiation to identify conservation units of Canada lynx (Lynx canadensis)

Protection and management of adaptively diverse populations is critical to meet the goals of conservation policy and to conserve the evolutionary potential of species into the future. The identification of conservation units below the species level can be a helpful tool in this regard. In Canada, such conservation units are referred to as Designatable Units (DUs) which are required to be both discrete and significant. Significance criteria are related to the evolutionary significance of species, or populations below the species level. Evaluating evolutionary significance often concerns adaptive differentiation, which can be difficult to demonstrate empirically, and challenging to establish for wide-ranging species. Such species are often genetically panmictic across their range, and, as a result, lumped into a single or few DUs, even though they may have unique population histories or evolutionary lineages. Here, we use Approximate Bayesian Computation to differentiate between hypotheses of contemporary versus historic phylogenetic histories, and a candidate gene approach using coding trinucleotide repeat markers within functional genes to assess the potential for local adaptation of insular and peripheral populations of Canada lynx (Lynx canadensis). We demonstrate that these populations have evolutionary histories consistent with divergence following the last glacial maximum, and show patterns at cTNR loci that suggest the potential for adaptive divergence as well. We demonstrate how, in concert with previously published evidence of genetic discreteness, our results suggest at least four DUs for Canada lynx: lynx (1) north and (2) south of the St. Lawrence River on mainland Canada, and lynx on the islands of (3) Newfoundland and (4) Cape Breton.

Watersheds influence the wood turtle’s (Glyptemys insculpta) genetic structure

The wood turtle (Glyptemys insculpta) is a freshwater species endemic to eastern North America and is currently listed as endangered by the International Union for Conservation of Nature. Wood turtle local populations are considered units for the species recovery, and are defined as discrete interbreeding populations in a distinct watershed; however, there are no studies to date supporting this definition. The main objective of this paper was to genetically characterize wood turtles from a northern portion of their range, and test an isolation-by-watershed hypothesis, the first of its kind at such a large geographical scale. Turtles were sampled in 24 watercourses from 12 different watersheds for a total of 331 individuals, each genotyped for nine microsatellite loci. Within each watershed, genetic diversity was similar between sites, and observed heterozygosity ranged from 0.677 to 0.754. Partial redundancy analyses then confirmed that watershed isolation contributed to 18% of the total observed genetic variation, while spatial autocorrelation and the post-glacial Expansion Model did not significantly explain any variation. Clustering methods revealed substantial spatial genetic structure, with sampled groups falling into ten nested hierarchical clusters. We recommend further consideration of these ten clusters to determine if they meet the evolutionary significance criterion to become designatable units, whose genetic structures were influenced by watershed structure.

Looking for Striped Bass in Atlantic Canada: The Reconciliation of Local, Scientific, and Historical Knowledge

Morone saxatilis (Striped Bass) occurs throughout the provinces of Atlantic Canada, but its full distribution in the region is undescribed. Canadian Striped Bass populations are grouped by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) into 3 geographically distinct Designatable Units: Saint Lawrence River, Southern Gulf of St. Lawrence, and Bay of Fundy. Striped Bass also occurs in many other unclassified Canadian regions, and growing evidence suggests that some of these locations may support distinct, uncharacterized populations. The recreational fisheries for Striped Bass are rapidly increasing in popularity in Canada, and thus, it has become of great importance to both recognize the species' full distribution and manage the fisheries therein. We compiled recent research, certified angling catches, historic accounts, grey literature, and anecdotal reports to identify coastal sites and rivers where Striped Bass have been reported. Our findings will help managers and researchers target rivers and coastal areas for assessment and study to encompass the entirety of the species' range in Canadian waters. Our report suggests that a fourth Designatable Unit for Eastern Cape Breton Island and Northeastern Nova Scotia is needed to both monitor and manage assemblages of Canadian Striped Bass.

Lines on a map: conservation units, meta‐population dynamics, and recovery of woodland caribou in Canada

AbstractDelineating conservation units is a fundamental step in recovery planning for endangered species. Yet, challenges remain in the application and validation of scientifically evaluated conservation units in management practice. The Canadian government makes use of Designatable Units (DUs) as the primary conservation unit under their Species‐at‐Risk Act. DUs must be ecologically discrete and have demonstrated evolutionary significance, which, in the case of woodland caribou (Rangifer tarandus caribou), has led to the definition of multiple DUs across Canada. Simultaneously, Environment and Climate Change Canada has released two recovery strategies affecting four DUs, wherein DUs are subdivided into smaller conservation units. However, the two recovery strategies adopt different definitions for the conservation unit. For the Boreal DU, the Local Population is considered the conservation unit for recovery management, whereas for Southern Mountain DU, the conservation unit for recovery is the subpopulation, which may or may not be comprised of several Local Populations. The scientific rationale for the difference between recovery strategies is unclear, not necessarily supported by genetic or demographic evidence, and highlights a policy challenge facing caribou conservation. We argue that the current emphasis on protecting subpopulations within a DU might be inconsistent and unviable for recovery planning. Instead, the recognition and emphasis on maintaining meta‐population dynamics within DUs is essential and currently underutilized in the long‐term recovery of woodland caribou in Canada.

Population structure of caribou in an ice‐bound archipelago

AbstractAimArchipelagos provide ideal natural systems for testing the effects of isolation and fragmentation of habitats on the genetic makeup of populations—an important consideration, given that many insular species are of conservation concern. Two theories predominate: Island Biogeography Theory (IBT) posits that proximity to the mainland drives the potential for migrants and gene flow. The Central Marginal Hypothesis (CMH) predicts that island populations at the periphery of a species range may experience low gene flow, small population size and high rates of genetic drift. We investigated population genetic structure, genetic diversity and key drivers of diversity for Arctic island‐dwelling caribou (Rangifer tarandus). Our aim was to inform intraspecific units for conservation and decipher how IBT and CMH could act in an archipelago where isolation is highly variable due to sea ice and open water.LocationCanadian Arctic Archipelago, Canada (Latitude, 55–82°N; Longitude, 61–123°W).MethodsWe genotyped 447 caribou at 16 microsatellite loci; these caribou represented two subspecies (R. t. groenlandicus, R. t. pearyi) and three designatable units. We used hierarchical Bayesian clustering and ordination to determine genetic groups. We evaluated the influence of ecological and geographic variables on genetic diversity using linear mixed‐effects models and compared diversity among mainland and island herds.ResultsBayesian clustering revealed nine genetic clusters with differentiation among and within caribou subspecies. Genetic differentiation was explained predominantly by isolation‐by‐distance across all caribou, even at the scale of subspecies. Island caribou were less genetically diverse than mainland herds; individual heterozygosity was negatively correlated with distance‐to‐mainland and the extent of autumn ice‐free coastline and positively correlated with unglaciated island size.Main conclusionsOur findings underscore the importance of hierarchical analysis when investigating genetic population structure. Genetic diversity and its key drivers lend support to both IBT and CMH and highlight the pending threat of climate change for Arctic island caribou.

Biogeography and designatable units of Bombus occidentalis Greene and B. terricola Kirby (Hymenoptera: Apidae) with implications for conservation status assessments

Conservation action for species of concern requires that “designatable units” (e.g., species, subspecies, geographic races, genetically distinct forms) are clearly defined, or that the species complex is treated as a whole. Several species of bumble bee are currently threatened, and some of these have cryptic colouration (resembling other species), or form complexes that vary considerably in colour patterning. Here we address the taxonomy and distribution of Bombus occidentalis Greene and B. terricola Kirby, both of which are currently of conservation concern in North America. Bombus occidentalis includes two apparently monophyletic groups of COI barcode haplotypes (recently considered as subspecies) with ranges mostly separated by that of their sister species, B. terricola. The southern B. o. occidentalis ranges throughout the western United States and into western Canada from southern Saskatchewan and Alberta, and throughout British Columbia north to ca. 55°N; the northern B. o. mckayi Ashmead, is restricted to north of this in British Columbia, westernmost Northwest Territories, Yukon Territory and Alaska. Bombus o. mckayi exists, as far as is known, only with a “banded” colour pattern. By contrast, B. o.occidentalis occurs in both banded and non-banded colour patterns, although the southern banded colour pattern is geographically isolated from the northern subspecies. Bombus o. occidentalis has declined throughout its range, perhaps due in part to exposure to novel parasites. Despite having similar levels of parasitism (ca. 40 %) as the southern subspecies, B. o. mckayi appears to have stable populations at present. There is therefore compelling evidence that the two subspecies should be distinguished for conservation and management purposes. We present the evidence for their distinction and provide tools for subspecies recognition.

Conservation status of caribou in the western mountains of Canada: Protections under the species at risk act, 2002-2014

In April 2014, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) reviewed the status of caribou in the western mountains of Canada, in keeping with the ten-year reassessment mandate under the Species at Risk Act. Assessed as two ‘nationally significant’ populations in 2002, COSEWIC revised the conservation units for all caribou in Canada, recognising eleven extant Designatable Units (DUs), three of which -- Northern Mountain, Central Mountain, and Southern Mountain -- are found only in western Canada. The 2014 assessment concluded that the condition of many subpopulations in all three DUs had deteriorated. As a result of small and declining population sizes, the Central Mountain and Southern Mountain DUs are now recognised as endangered. Recent declines in a number of Northern Mountain DU subpopulations did not meet thresholds for endangered or threatened, and were assessed as of special concern. Since the passage of the federal Species at Risk Act in 2002, considerable areas of habitat were managed or conserved for caribou, although disturbance from cumulative human development activities has increased during the same period. Government agencies and local First Nations are attempting to arrest the steep decline of some subpopulations by using predator control, maternal penning, population augmentation, and captive breeding. Based on declines, future developments and current recovery effects, we offer the following recommendations: 1) where recovery actions are necessary, commit to simultaneously reducing human intrusion into caribou ranges, restoring habitat over the long term, and conducting short-term predator control, 2) carefully consider COSEWIC’s new DU structure for management and recovery actions, especially regarding translocations, 3) carry out regular surveys to monitor the condition of Northern Mountain caribou subpopulations and immediately implement preventative measures where necessary, and 4) undertake a proactive, planned approach coordinated across jurisdictions to conserve landscape processes important to caribou conservation.

Morphological and genetic variation in Cisco (Coregonus artedi) and Shortjaw Cisco (C. zenithicus): multiple origins of Shortjaw Cisco in inland lakes require a lake-specific conservation approach

The study of cisco diversity in inland lakes of North America has been plagued by taxonomic uncertainty linked to high phenotypic plasticity and an ongoing reliance on morphology to differentiate species. More recently, this uncertainty has hindered the development of conservation plans and status assessments of ciscoes. This study presents the first range-wide comparison of morphological and genetic variation between Cisco (Coregonus artedi) and Shortjaw Cisco (C. zenithicus). Using morphological and genetic data from 17 lakes, three sets of analyses were undertaken to evaluate alternate hypotheses explaining the pattern of cisco phenotypic diversity in inland lakes. Morphotypes (MTs) representing the two taxa were phenotypically distinct (largely reflective of differences in gill raker number and jaw morphology) within lakes but highly variable across lakes. Shortjaw Cisco was only recognizable when compared to sympatric Cisco and some populations were morphologically similar to Cisco from other lakes. Analysis of AFLP data revealed two genetic clusters that conformed to differences in geography (eastern and western groups), rather than hypothesized taxonomic boundaries. Genetic variation strongly suggests that each of these unique sympatric pairs of MTs originated recently and locally, in parallel, from the ancestral Cisco. Phenotypic and genetic distinctiveness between MTs were not related. MTs were sometimes clearly recognizable despite a lack of genetic differentiation, suggesting that the canalization of phenotypic plasticity is unevenly completed across lakes. These results provide evidence that the taxon-based approach is clearly inadequate for the protection of Shortjaw Cisco. In Canada, status assessment should aim to identify lake-specific designatable units (DU). Given the idiosyncratic nature of each instance of Shortjaw Cisco, it is expected that the strength of morphological, biological, ecological and genetic evidence for individual DUs will vary among lakes.

Genetic analysis of Dolly Varden (Salvelinus malma) across its North American range: evidence for a contact zone in southcentral Alaska

Contact zones between divergent lineages of aquatic taxa have been described from the northeastern Pacific Ocean. We surveyed samples of Dolly Varden (Salvelinus malma) from their North American range for variation at 14 microsatellite DNA loci. After accounting for hybridization between Dolly Varden and co-occurring bull trout (Salvelinus confluentus) and Arctic char (Salvelinus alpinus), we found evidence for two genetic lineages of Dolly Varden consistent with the previously recognized subspecies, northern Dolly Varden (S. m. malma) and southern Dolly Varden (S. m. lordii). We documented a contact zone between the two subspecies from the eastern Alaska Peninsula to Cook Inlet, Alaska, where admixture values (i.e., the proportion of the genome estimated to be composed of northern Dolly Varden, QNDV) ranged between QNDV= 0.245 and 0.754 across about 700 ocean kilometres. Populations of Dolly Varden showing low admixture (i.e., less than 5%) were located a minimum of 346 km to the west to 1200 km to the southeast, respectively, from the contact zone. The two lineages of Dolly Varden probably stem from isolation and subsequent divergence in, and dispersal from, distinct northern and southern Pleistocene glacial refugia and substantiate the treatment of S. malma as two subspecies and as at least two designatable units under Canada’s Species at Risk Act.

Identifying designatable units for intraspecific conservation prioritization: a hierarchical approach applied to the lake whitefish species complex (Coregonus spp.).

The concept of the designatable unit (DU) affords a practical approach to identifying diversity below the species level for conservation prioritization. However, its suitability for defining conservation units in ecologically diverse, geographically widespread and taxonomically challenging species complexes has not been broadly evaluated. The lake whitefish species complex (Coregonus spp.) is geographically widespread in the Northern Hemisphere, and it contains a great deal of variability in ecology and evolutionary legacy within and among populations, as well as a great deal of taxonomic ambiguity. Here, we employ a set of hierarchical criteria to identify DUs within the Canadian distribution of the lake whitefish species complex. We identified 36 DUs based on (i) reproductive isolation, (ii) phylogeographic groupings, (iii) local adaptation and (iv) biogeographic regions. The identification of DUs is required for clear discussion regarding the conservation prioritization of lake whitefish populations. We suggest conservation priorities among lake whitefish DUs based on biological consequences of extinction, risk of extinction and distinctiveness. Our results exemplify the need for extensive genetic and biogeographic analyses for any species with broad geographic distributions and the need for detailed evaluation of evolutionary history and adaptive ecological divergence when defining intraspecific conservation units.