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Effective conservation requires that species recovery measures are informed by rigorous scientific research. For imperilled freshwater fishes and mussels in Canada, numerous research gaps exist, in part owing to the need for specialized research methods. The Canadian Freshwater Species at Risk Research Network (SARNET) was formed and identified or implemented approaches to address current research gaps, including (1) captive experimental research populations, (2) nonlethal methods for estimating abundance and distribution, (3) nonlethal field methods to measure life-history parameters, (4) species distribution models informed by co-occurring species, (5) conservation physiology to inform habitat and threat science, (6) evidence syntheses to evaluate threats and recovery measures, (7) disease-transmission models to understand mussel-host relationships, (8) experimental mesocosms and manipulative experiments to evaluate key habitat stressors, (9) threat and hazard models for predictive applications, and (10) rigorous evaluation of surrogate species. Over a dozen threat- and recovery-focused SARNET research applications are summarized, demonstrating the value of a coordinated research program between academics and government to advance scientific research on, and to support the recovery of, imperilled freshwater species. Des mesures de retablissement reposant sur des travaux de recherche scientifique rigoureux sont necessaires a une conservation efficace. Pour les especes de poissons d'eau douce et mulettes en peril au Canada, il existe de nombreuses lacunes dans la recherche, dues partiellement a la necessite de methodes de recherche specialisees. Le reseau canadien de recherche sur les especes d'eau douce en peril (SARNET) a ete cree et il a cerne ou applique differentes approches visant a combler ces lacunes, dont les suivantes : (1) des populations experimentales captives de recherche, (2) des methodes non letales d'estimation de l'abondance et de la repartition, (3) des methodes de terrain non letales de mesure de parametres du cycle biologique, (4) des modeles de repartition des especes integrant des donnees sur les especes cooccurrentes, (5) la physiologie de la conservation pour soutenir les travaux scientifiques sur les habitats et les menaces, (6) des syntheses de donnees probantes pour evaluer les menaces et measures de retablissement, (7) des modeles de transmission des maladies pour comprendre les relations mulettes-hotes, (8) des mesocosmes experimentaux et des experiences de manipulation pour evaluer des facteurs de stress cles des habitats, (9) des modeles de menaces et de dangers pour des applications predictives et (10) Revaluation rigoureuse d'especes substitutives. Un resume de plus d'une douzaine d'applications des travaux de recherche du SARNET axees sur les menaces et le retablissement est presente, qui demontre l'utilite d'un programme de recherche au sein duquel les travaux de chercheurs universitaires et gouvernementaux sont coordonnes afin de faire avancer la recherche scientifique sur les especes d'eau douce en peril et soutenir leur retablissement. [Traduit par la Redaction], Introduction An important goal of conservation biology is to prevent species extinctions caused by human activity (Soule 1985). When populations decline and become imperilled, various recovery measures are often enacted [...]

We compared the genetic diversity and structure of wild versus captive-propagated at-risk species of freshwater mussels in Canada, Lampsilis fasciola (wavy-rayed lampmussel; WRL) and Ptychobranchus fasciolaris (kidneyshell; KS), using microsatellite-generated genotypes. No significant differences were detected using Kruskal-Wallis tests that compared the genetic diversity metrics of wild and captive-propagated WRL (from 12 mothers) and KS (from seven mothers). After effective population size ([N.sub.e]) was estimated, considerable overlap was found in the estimated [N.sub.e] between wild and captive populations of both species. Pairwise [F.sub.ST] and [D.sub.est] values among wild WRL, hatchery-raised WRL juveniles, and across different time periods (2008-2018) were generally low ([F.sub.ST] = 0.007-0.043, [D.sub.est] = 0.005-0.282). Pairwise [F.sub.ST] and [D.sub.est] for KS were not significant and low (0.012, 0.017). When comparing captive-reared offspring with the wild population, STRUCTURE analysis revealed strong support for a single genetic population. With at least seven females contributing to brood stock, genetic diversity was maintained. Further research is needed to assess the male contribution to each glochidial brood as well as the variability of genetic diversity in individual glochidial broods. Nous avons compare la diversite et la structure genetiques de deux mulettes en peril au Canada, la lampsile fasciolee (Lampsilis fasciola, LF) et le ptychobranche reniforme (Ptychobranchusfasciolaris, PF), sauvages et issues de la propagation en captivite, en utilisant des genotypes generes a partir de microsatellites. Aucune difference significative n'est relevee entre les populations sauvages et propagees en captivite de LF (issues de 12 meres) ou de PF (issues de sept meres) a la lumiere de differents parametres de diversite genetique en utilisant des tests de Kruskal-Wallis. La taille effective de la population ([N.sub.e]) a ete estimee, et un chevauchement considerable est releve entre les [N.sub.e] estimees des populations sauvages et propagees en captivite des deux especes. Les valeurs de [F.sub.ST] et [D.sub.est] par paire de LF sauvages, de LF juveniles elevees en ecloseries et pour differentes periodes (de 2008 a 2018) sont generalement faibles ([F.sub.ST] = 0,007-0,043, [D.sub.est] = 0,005-0,282). Les valeurs de [F.sub.ST] et [D.sub.est] par paire de PF sont faibles (0,012, 0,017) et non significatives. Pour la comparaison de progeniture elevee en captivite a la population sauvage, les resultats de l'analyse avec le logiciel STRUCTURE appuient fortement l'interpretation d'une seule population genetique. Si au moins sept femelles contribuent au stock de geniteurs, la diversite genetique est maintenue. D'autres travaux de recherche sont necessaires pour evaluer la contribution des males a chaque emission de glochidies et la variabilite de la diversite genetique au sein de ces emissions. [Traduit par la Redaction], Introduction Freshwater mussels (Bivalvia: Unionida, unionids) are one of the most imperilled taxa on the planet, with 70% of unionid species in North America at risk of extinction (Williams et [...]

Freshwater mussels (Mollusca: Bivalvia: Unionida) have a broad global distribution on every continent except Antarctica. However, owing to human activities, the diversity of freshwater mussels is seriously globally threatened. China is an important global biodiversity hotspot for this fauna.This article comprehensively reviews the 99 currently recognized species in China, collating for the first time their systematics, distribution, life‐history traits, habitat preferences, conservation status, and main threats to suggest future management actions.The review showed that the taxonomic status and species validity of many freshwater mussels are still not well resolved. The freshwater mussel diversity in the Yangtze River Basin is higher than that in other freshwater habitats in China. Life history characteristics and habitat preferences are poorly known for most species.Only half of the total number of species in China have been assessed for their conservation status. Among those assessed, around half of them are threatened with extinction with more than 10% being considered as Data Deficient.The key threats identified as potentially related to species declines are pollution, habitat loss and fragmentation, loss of access to host fishes and overharvesting of mussels or their host fishes.The review shows that there is a strong geographical bias in the amount of knowledge available for freshwater mussels, with most of the available data being concentrated in the middle and lower reaches of the Yangtze basin. Almost no data are available for these taxa north of the Yellow River basin and in the west and south‐west regions of China.To make future conservation and management more effective we suggest that efforts should be concentrated on: (i) increasing the amount of research on basic ecological and life‐history features, including growth, life‐span, reproductive cycle, host fish identification and habitat requirements of each species; (ii) establishing the interspecific and intraspecific genetic diversity patterns of Chinese freshwater mussels, to clarify their taxonomy, systematics and phylogeny, and to understand the phylogeography and population structure of each species; and (iii) urgently establishing protected areas for fish and mussels in locations of high species richness, such as Poyang Lake and Dongting Lake, and also in regions with high levels of endemism or genetic uniqueness, such as Guangxi Province, Yunnan Province and Heilongjiang Province. In addition, the need for habitat restoration and the conservation of freshwater mussels has become urgent in China, and an integrated systematic conservation and management plan should be developed and effectively implemented. [ABSTRACT FROM AUTHOR]

Obovaria olivaria is a species of freshwater mussel native to the Mississippi River and Laurentian Great Lakes‐St. Lawrence River drainages of North America. This mussel has experienced population declines across large parts of its distribution and is imperiled in many jurisdictions. Obovaria olivaria uses the similarly imperiled Acipenser fulvescens (Lake Sturgeon) as a host for its glochidia. We employed mitochondrial DNA sequencing and restriction site‐associated DNA sequencing (RAD‐seq) to assess patterns of genetic diversity and population structure of O. olivaria from 19 collection locations including the St. Lawrence River drainage, the Great Lakes drainage, the Upper Mississippi River drainage, the Ohioan River drainage, and the Mississippi Embayment. Heterozygosity was highest in Upper Mississippi and Great Lakes populations, followed by a reduction in diversity and relative effective population size in the St. Lawrence populations. Pairwise FST ranged from 0.00 to 0.20, and analyses of genetic structure revealed two major ancestral populations, one including all St. Lawrence River/Ottawa River sites and the other including remaining sites; however, significant admixture and isolation by river distance across the range were evident. The genetic diversity and structure of O. olivaria is consistent with the existing literature on Acipenser fulvescens and suggests that, although northern and southern O. olivaria populations are genetically distinct, genetic structure in O. olivaria is largely clinal rather than discrete across its range. Conservation and restoration efforts of O. olivaria should prioritize the maintenance and restoration of locations where O. olivaria remain, especially in northern rivers, and to ensure connectivity that will facilitate dispersal of Acipenser fulvescens and movement of encysted glochidia. [ABSTRACT FROM AUTHOR]

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Pyganodon grandis and P. lacustris , widespread and common species in North America, are known to co-occur across parts of their distributions. These mussels are genetically distinguishable with a sequence divergence between 9% and 13% for the mitochondrial (mt) DNA barcoding region, cytochrome c oxidase subunit I (COI), which is well beyond thresholds for distinct species. The objectives of this study were to (1) confirm the presence of two genetically distinct species (P. grandis and P. lacustris) in Font Lake and Lake Geneserath on Beaver Island in northern Lake Michigan, (2) identify hybrids using mitogenotype mismatch and (3) compare species and populations morphometrically. Of the 212 specimens sequenced, 146 (68.9%) were found to be heteroplasmic, with successful amplifications of both maternally (F-type, from mantle tissue) and paternally (M-type, from gonad tissue) inherited mt DNA sequences. Mismatches in species identity of the F- and M-type COI sequences were found in 22 specimens (15.1% of heteroplasmic specimens), with these being considered putative hybrids. Geometric morphometric analyses of shell shape reliably differentiated specimens by species (identified using COI sequences) and between lakes, correctly assigning 97.4% of homoplasmic and heteroplasmic specimens with matching mitogenomes to both species and lake of origin. The shape of putative hybrids generally resembled those of the F-type mt DNA sequence that was recovered. This study confirms that hybridization does occur between sympatric Pyganodon species. Additionally, our results reemphasize the value of modern morphometric techniques for distinguishing among species and populations with overlapping morphological variability. [ABSTRACT FROM AUTHOR]

Freshwater mussels are one of the most diverse groups of freshwater organisms as well as one of the most endangered groups of organisms on Earth. Freshwater mussels have a life history that greatly influences their geographical distribution, genetic structure, and demographic characteristics. Here, we describe and compare the spatial genetic structure and diversity of 5 freshwater mussel species with different brooding periods and uses of larval parasitism. These 5 species co-occur in tributaries in Poyang Lake in south central China, and we studied their populations in the Gan and Fuhe Rivers, which are both large tributaries of Poyang Lake. Cytochrome c oxidase subunit-I (COI) haplotype richness and diversity of species with a spring or summer glochidia brooding period (Lamprotula caveata , Nodularia douglasiae , and Solenaia oleivora) were greater than richness and diversity in species with a winter brooding period (Anemina arcaeformis , S. carinata). In addition, the COI haplotype richness and diversity of A. arcaeformis , which does not have a parasitic portion of its life cycle, was lower than 3 species that require a host fish to complete their life cycles (L. caveata , N. douglasiae , and S. oleivora) and was higher than S. carinata. We also used the COI sequences and microsatellite datasets to determine whether the populations of each of the 5 species in the Gan and Fuhe Rivers are admixed or genetically distinct. Genetic differentiation was evident among collection populations of L. caveata , N. douglasiae , and S. carinata and largely absent in A. arcaeformis and S. oleivora. We conclude that differences in genetic diversity and patterns of genetic structure in these sympatric species could result from the different life-history attributes of these species, particularly timing and length of the brooding period, nonparasitic vs parasitic life cycles, and different host fish requirements. Therefore, we suggest increased emphasis on life history and reproductive biology research and urge managers to consider that these traits differ among freshwater mussels when making management decisions for the conservation of genetic and species diversity. [ABSTRACT FROM AUTHOR]

The eastern pondmussel, Sagittunio nasutus (Bivalvia: Unionida), has declined in abundance and distribution in eastern North America over the last few decades. The declines are predominantly the result of infestation by invasive dreissenid mussels and changes in habitat. The species is now considered imperilled across large portions of its distribution, especially in the Laurentian Great Lakes region.The genetic diversity and structure of the remnant populations in the Great Lakes region were assessed using 10 newly developed microsatellite DNA loci for S. nasutus. Understanding the remaining populations can inform future management projects and determine whether the remnant populations have experienced a genetic bottleneck or a founder effect. We hope that this will inform the conservation of other species in regions founded by, and isolated from, a more genetically diverse source population or with disjointed geographical distributions.Focusing on the Great Lakes region, samples (n = 428) from 62 collection sites in 28 water bodies were collected. Across the locations sampled for S. nasutus 11 genetic populations were identified, with significant genetic differentiation among them. The genetic structure of the species was assessed, with genetic similarities among populations compared and with geographical routes of colonization and gene flow evaluated.Initial colonization from the Atlantic coast into Lake Erie and Lake Ontario is evident, followed by colonization events into nearby inland rivers and lakes. Analyses found evidence of inbreeding in all but one population and evidence of past genetic bottlenecks or strong founder effects in all but four populations. This study deepens our understanding of the genetic past and present of this imperilled species, providing conservation suggestions for the future management of the species. [ABSTRACT FROM AUTHOR]

Among the highest profile invasive species in the Laurentian Great Lakes region are Dreissena polymorpha and D. rostriformis bugensis (collectively dreissenids). Despite their abundance and ecosystem-wide effects, little is known about dreissenid distributions in large connecting channels between lakes. The objectives of this study were to estimate and document dreissenid densities and their habitat characteristics throughout the St. Clair River, to compare dreissenid species demographics, and predict spatial distributions between two connecting waters of the Great Lakes: the St. Clair and Detroit rivers. Two types of species distribution models (SDMs), MaxEnt and classification and regression tree analysis (CART), were created using dreissenid and habitat data collected in both the Detroit and St. Clair rivers. The SDMs were then used to predict presence of dreissenids in the St. Clair River. The St. Clair River had more D. r. bugensis (mean density = 486 ± 152 individuals/m2) than D. polymorpha (mean density = 3 ± 1 individuals/m2). The SDMs created from the Detroit River data reliably predicted presence of dreissenids in the St. Clair River. Depending on the river and species, CART models identified velocity and depth to be important predictor variables, while distance to river inlet/outlet were the most influential variables in the MaxEnt models. Most research on dreissenid distribution modeling is focused on determining areas for potential spread; however, this study presents a unique perspective by modeling dreissenid presence, both D. polymorpha and D. r. bugensis separately and together, where they have been established for more than 30 years. [ABSTRACT FROM AUTHOR]

Freshwater mussels are a critically imperiled group of mollusks that play key ecological roles and provide important services to humans. The Ambleminae is the only subfamily of these mussels, endemic to North America. Complete mitogenomes have only been sequenced for two of five tribes of the subfamily. Pleurobema oviforme, Amblema plicata, and Popenaias popeii each belong to tribes Pleurobemini, Amblemini, and Popenaidini, respectively, and have not had published mitogenomes. Thus, this study aims to present the complete mitogenomes for these species, to provide a phylogeny of the Ambleminae and confirm the gene arrangements with representation from each of its tribes. The newly sequenced mitogenomes range from 15,852 to 15,993 nucleotides, are composed of 13 PCGs, 22 tRNAs, and two rRNAs and all share the same (UF1) gene order. [ABSTRACT FROM AUTHOR]

The middle and lower portions of the Yangtze River basin is the most species-rich region for freshwater mussels in Asia. The management and conservation of the taxa in this region has been greatly hampered by the lack of a well-developed phylogeny and species-level taxonomic framework. In this study, we tested the utility of two mitochondrial genes commonly used as DNA barcodes: the first subunit of the cytochrome oxidase c gene (COI) and the first subunit of the NADH dehydrogenase gene (ND1) for 34 putative species representing 15 genera, and also generated phylogenetic hypotheses for Chinese unionids based on the combined dataset of the two mitochondrial genes. The results showed that both loci performed well as barcodes for species identification, but the ND1 sequences provided better resolution when compared to COI. Based on the two-locus dataset, Bayesian Inference (BI) and Maximum Likelihood (ML) phylogenetic analyses indicated 3 of the 15 genera of Chinese freshwater mussels examined were polyphyletic. Additionally, the analyses placed the 15 genera into 3 subfamilies: Unioninae (Aculamprotula, Cuneopsis, Nodularia and Schistodesmus), Gonideninae (Lamprotula, Solenaia and Ptychorhychus) and Anodontinae (Cristaria, Arconaia, Acuticosta, Lanceolaria, Anemina and Sinoanodonta). Our results contradict previous taxonomic classification that placed the genera Arconaia, Acuticosta and Lanceolaria in the Unioninae. This study represents one of the first attempts to develop a molecular phylogenetic framework for the Chinese members of the Unionidae and will provide a basis for future research on the evolution, ecology, and conservation of Chinese freshwater mussels. [ABSTRACT FROM AUTHOR]

The Yangtze River basin has the highest species richness for freshwater mussels in East Asia, but little is known about the reproductive biology of most species. Here, the reproductive biology of nine freshwater mussel species (Unionidae) found in Poyang Lake, Jiangxi province, China was studied. Sex ratios were not significantly different from 1:1 in eight of the nine species examined. The minimum size and age of sexual maturity (0.2–5.6 yr for males and 0.3–5.9 yr for females) and of females first becoming gravid (0.6–8.9 yr) varied among species. Brooding seasons for glochidia varied among species, but seven of the nine species examined brooded glochidia through the spring and summer. In all species, high frequencies (mean 87.5%) were found to be gravid during their peak brooding period. Fecundity was positively correlated with shell length in the five species in which this was examined. Mean annual fecundity showed wide interspecific variation, ranging from 7,800 to 328,000 propagules/mussel. The findings of this study have implications for the ecology and conservation of unionid species in China and contributes to knowledge of the evolution of reproductive and life history characters of the Unionidae. [ABSTRACT FROM AUTHOR]

Information on the genetic diversity and population genetic structure of threatened species is important for guiding management decisions. Margaritifera margaritifera (freshwater pearl mussel) occurs across western Russia, north and central Europe, and Atlantic drainages of north-eastern North America (NA). European populations of M. margaritifera are considered endangered, whereas NA populations are thought to be relatively secure. As such, the population genetics of M. margaritifera occurring in European rivers is relatively well studied while that of NA populations is not known. In this study, we investigated the genetic diversity and differentiation of M. margaritifera in Canada and the USA. Genetic diversity indices calculated from nine microsatellite loci were relatively high in the NA population. Analyses of genetic structure indicated that a single panmictic population exists for M. margaritifera in NA. However, there was evidence of substructure in some tributaries of the St. Lawrence River in Québec, Canada. The NA population of M. margaritifera has low genetic differentiation and high diversity, possibly resulting from large population size and high gene flow. Consequently, conservation of this species should focus primarily on maintaining favourable habitat conditions and connectivity for host fish. [ABSTRACT FROM AUTHOR]

Contemporary species distributions and geographic patterns of genetic structure largely reflect pre-historic events, often with subsequent alterations from human influences. The geographic genetic structure of a relatively common and widespread unionid species, Quadrula quadrula, was investigated to reconstruct its postglacial history. Hypotheses regarding colonization routes of Q. quadrula into the Great Lakes basin after the most recent glacial retreat were tested. Samples were collected from Q. quadrula at sites spanning hypothesized glacial refugia and postglacial expansion routes in the Mississippi River drainage, including the Ohio and Missouri rivers, and the Great Lakes. Broad-scale phylogeography and population structure were assessed by sequencing a fragment of the mitochondrial CO1 gene and genotyping eight microsatellites. Results of analyses showed marked differences among the Great Lakes, Mississippi River, and Ohio River drainages, and suggested colonization of the Great Lakes basin from a Mississippian source. Populations showed patterns of isolation by distance: geographic and genetic distances were significantly correlated among Great Lakes populations based on colonization through the Chicago–Illinois outlet, but not when following the Wabash–Maumee outlet. All evidence indicates that postglacial colonization of the Great Lakes basin occurred almost exclusively through the Chicago–Illinois outlet, with subsequent expansion into the lower Great Lakes. [ABSTRACT FROM AUTHOR]

Understanding genetic diversity across large spatial scales helps to reveal patterns of population structure. Mitochondrial DNA sequences and microsatellite loci were used to analyze the phylogeography of a common unionid species (Lasmigona costata) from the Laurentian Great Lakes and historically connected river drainages. Phylogeographic patterns were assessed to determine colonization routes into the Great Lakes following glacial recession. A suite of seven microsatellite loci were genotyped and a fragment of the mitochondrial gene COI was sequenced. Multiple analyses using microsatellite allele frequencies suggest at least two distinct genetic populations for L. costata. A total of seven hypothesized post-glacial dispersal scenarios were compared using isolation by distance to test the various dispersal models. Evidence was strongest for two post-glacial dispersal routes into the Great Lakes: one utilizing a connection between the Wabash and Maumee River watersheds, and one utilizing a connection between the Wisconsin River and Green Bay watersheds. A highly differentiated and monophyletic population of L. costata was identified in the Ozark Highlands, which may constitute a unique taxonomic entity. [ABSTRACT FROM AUTHOR]

Alterations to watercourses affect connectivity in aquatic systems and can influence dispersal of aquatic biota. Dams fragment populations and act as isolating barriers, but canals create connections between waterbodies that can be used as corridors for dispersal by opportunistic invaders. The Niagara Peninsula of Ontario, Canada, has a 200-y history of canal operation, resulting in major modification of the watercourses in the region. This modification allowed numerous invasive species to enter the upper Great Lakes (e.g., sea lamprey) and probably has facilitated dispersal in native species. The purpose of our study was to explore the effects of canal and dam construction on the genetic structure of Mapleleaf (Quadrula quadrula), a widespread and relatively common species in the central Great Lakes that has been found only recently in several western Lake Ontario harbors. Establishment of Q. quadrula in Lake Ontario may have been a recent event, facilitated by the Niagara Peninsula’s history of canal operation. We used analyses of microsatellite DNA genotypes to examine the effect of canals on the genetic structure of mussel populations. Structure analysis revealed a pattern of gene flow between lakes that cannot be explained by watercourse connections prior to the creation of the Welland Canal. Evidence suggestive of historical bottlenecks at some Lake Ontario sites may indicate that these populations became established after canal creation. After considering genetic structure, hydrogeography and isolation-by-distance (IBD) analysis, the first iteration of the canal (1829–1833) is most supported as the configuration that facilitated colonization. However, weak IBD signals across canal models may signify continued gene flow across configurations. Our study demonstrates the connective effect of canals on freshwater mussel populations and has the potential to improve conservation strategies for this and other unionid species at risk. [ABSTRACT FROM AUTHOR]

Abstract: The freshwater mussels (Unionidae) in the Yangtze River basin of China are among the most diverse assemblages on Earth. Freshwater mussels provide valuable ecosystem services (e.g. natural water filtration) and economic value (shell, pearls, and food), but are experiencing global declines as a result of pollution, habitat alteration, and overharvest. Despite the diversity and value of freshwater mussels in the Yangtze River basin, relatively little is known about the biology of the many species endemic to the region. Solenaia carinata is an endemic and potentially imperilled freshwater mussel (Bivalvia: Unionidae) in China that is distributed in a single major tributary of the middle Yangtze; the Poyang Lake basin in Jiangxi Province. This study represents the first analyses of the genetic diversity and population genetic structure of S. carinata. Solenaia carinata specimens (n=64) were collected from three sites in large tributary rivers of Poyang Lake. Using 19 polymorphic microsatellite markers, the results showed that S. carinata had a moderate level of genetic diversity (PIC ranged from 0.464 to 0.484), limited evidence of a recent genetic bottleneck, little genetic differentiation (FST ranged from 0.021 to 0.045), high levels of gene flow (Nm ranged from 3.675 to 33.227) and limited genetic structure among the three sampling locations. Given that S. carinata inhabits a highly interconnected system of large rivers and lakes, the results of low differentiation and high gene flow among geographically proximate sampling locations (sites separated by between 8 and 20 km of water) are not surprising. The results indicate that specimens can be used and moved from anywhere across the distribution of S. carinata for the purposes of captive propogation and translocation. [ABSTRACT FROM AUTHOR]

The Yangtze River drainage in China is among the most species rich rivers for freshwater mussels (order Unionida) on Earth with at least 68 species known. The freshwater mussels of the Yangtze River face a variety of threats with indications that species are declining in abundance and area of occupancy. This study represents the first analyses of the genetic structure and diversity for the common and widespread freshwater mussel Nodularia douglasiae based on microsatellite DNA genotypes and mitochondrial DNA sequences. Phylogenetic analysis a fragment of the COI mitochondrial gene indicated that N. douglasiae collected from across the middle and lower Yangtze River drainage are monophyletic with N. douglasiae from Japan, Russia, and South Korea. The results of the analysis of both the mtDNA and microsatellite datasets indicated that the seven collection locations of N. douglasiae in the middle and lower Yangtze River drainage showed high genetic diversity, significant genetic differentiation and genetic structure, and stable population dynamics over time. Moreover, we found that the connections among tributaries rivers and lakes in the Yangtze River drainage were important in maintaining gene flow among locations that N. douglasiae inhabits. An understanding of the genetic structure and diversity of a widespread species like N. douglasiae could be used as a surrogate to better understand the populations of other freshwater mussel species that are more rare in the Yangtze River drainage. At the same time, these results could provide a basis for the protection of genetic diversity and management of unionid mussels diversity and other aquatic organisms in the system. [ABSTRACT FROM AUTHOR]

Population genetic analyses of species inhabiting fragmented landscapes are essential tools for conservation. Occasionally, analyses of fragmented populations find no evidence of isolation, even though a barrier to dispersal is apparent. In some cases, not enough time may have passed to observe divergence due to genetic drift, a problem particularly relevant for long-lived species with overlapping generations. Failing to consider this quality during population structure analyses could result in incorrect conclusions about the impact of fragmentation on the species. We designed a model to explore how lifespan and population size influence perceived population structure of isolated populations over time. This iterative model tracked how simulated populations of variable lifespan and population size were affected by drift alone, using a freshwater mussel, Quadrula quadrula (mapleleaf), as a model system. In addition to exhibiting dramatic lifespan variability among species, mussels are also highly imperiled and exhibit fragmentation by dams throughout the range of many species. Results indicated that, unless population size was small (<50 individuals) or lifespan short (<22 years), observing genetic divergence among populations was unlikely. Even if wild populations are isolated, observing population structure in long-lived mussels from modern damming practices is unlikely because it takes longer for population structure to develop in these species than most North American dams have existed. Larger population sizes and longer lifespans increase the time needed for significant divergence to occur. This study helps illuminate the factors that influence genetic responses by populations to isolation and provides a useful model for conservation-oriented research. [ABSTRACT FROM AUTHOR]

Freshwater mussel populations have declined, in part, from changes in host communities. However, it is unknown if fish from adjacent catchments could be used to augment mussel populations in the Great Lakes inland rivers, and if so, whether this association would be impacted by known genetic structure in mussels and fish., This study tested how host fish origin (i.e. catchment) impacts the transformation of the endangered unionid Epioblasma triquetra from larval into juvenile life stages while concurrently considering potentially genetically distinct populations of mussels and hosts., We quantitatively determined if Percina caprodes and Percina maculata from the Lake Michigan, Erie and Huron basins are laboratory-successful hosts for E. triquetra. Experiments were performed in autumn and spring to document any seasonal effects on transformation., Percina caprodes was reconfirmed to be a successful host for E. triquetra, and for the first time, P. maculata was also determined to be a successful host in the Great Lakes region. Results suggest no differences in juvenile transformation with allopatric and sympatric fish and mussel pairings based on Great Lakes basin origin; therefore, transformation success may not parallel differences in genetic structure. In addition, results suggest seasonal differences in the developmental stages of E. triquetra juveniles., Knowing the most efficient strategy to optimise juvenile transformations can make reintroductions, augmentation and overall conservation efforts of E. triquetra successful. These data will help in developing recovery strategies for E. triquetra in the Laurentian Great Lakes by understanding variation in host use and nuances in this host-parasite relationship. [ABSTRACT FROM AUTHOR]

Physical barriers, habitat fragmentation, invasive species and geographic distance have isolated remnant populations of unionids in Great Lakes coastal refuges. Dreissenid species ( Dreissena polymorpha and Dreissena rostriformis bugensis ) may be the greatest threat to the survival of unionids in the Great Lakes since their introduction in the late 1980s and early 1990s; however, native unionids remain in coastal habitats of western Lake Erie. One of the most abundant unionid species in Lake Erie, Quadrula quadrula , was collected along coastal areas within the lake and from three tributaries, the Maumee River, Huron River (Ohio), and Grand River (Ontario, Canada) and genotyped at six polymorphic microsatellite loci to determine population structure. There was evidence of genetic differentiation by geographic distance, and genotypes clustered into three geographic regions: Lake Erie, the Maumee River, and the Grand River. Lack of fine-scale genetic differentiation, admixture among these regions, and significant isolation by distance, indicate connectivity and are consistent with a stepping-stone model of divergence across the lake and its tributaries. A diverse gene pool remains should Q. quadrula be able to repopulate more of their historic distribution across the region, but studies of other unionid species are needed to determine whether low levels of differentiation among lake populations or divergence from tributary populations is a common pattern. [ABSTRACT FROM AUTHOR]

Determining when and where the ecological impacts of invasive species will be most detrimental and whether the effects of multiple invaders will be superadditive, or subadditive, is critical for developing global management priorities to protect native species in advance of future invasions. Over the past century, the decline of freshwater bivalves of the family Unionidae has been greatly accelerated by the invasion of Dreissena. The purpose of this study was to evaluate the current infestation rates of unionids by zebra (Dreissena polymorpha) and quagga (D. rostriformis bugensis) mussels in the lower Great Lakes region 25 years after they nearly extirpated native unionids. In 2011–2012, we collected infestation data for over 4000 unionids from 26 species at 198 nearshore sites in lakes Erie, Ontario, and St. Clair, the Detroit River, and inland Michigan lakes and compared those results to studies from the early 1990s. We found that the frequency of unionid infestation by Dreissena recently declined, and the number of dreissenids attached to unionids in the lower Great Lakes has fallen almost ten-fold since the early 1990s. We also found that the rate of infestation depends on the dominant Dreissena species in the lake: zebra mussels infested unionids much more often and in greater numbers. Consequently, the proportion of infested unionids, as well as the number and weight of attached dreissenids were lower in waterbodies dominated by quagga mussels. This is the first large-scale systematic study that revealed how minor differences between two taxonomically and functionally related invaders may have large consequences for native communities they invade. [ABSTRACT FROM AUTHOR]

Populations of native unionids have been in steady decline over the past century. The invasion of dreissenid mussels (Dreissena polymorpha and Dreissena rostriformis bugensis) in the mid-1980's impacted already imperiled unionid populations by greatly increasing their regional extinction rates. A selection of Great Lakes coastal wetlands around Michigan was surveyed to locate remnant populations of native unionids. Physical and chemical parameters were measured in coastal wetlands to evaluate the importance of these habitat parameters to remnant unionid assemblages. We assessed fouling rates by dreissenids on unionids and used artificial substrates to estimate dreissenid colonization densities. Live unionids were found in coastal wetlands of the Les Cheneaux Islands, the Lake St. Clair delta, and North Maumee Bay with significantly higher unionid fouling in the Les Cheneaux Islands compared to the other two sampling areas (F2.76 = 4.97, p = 0.0095). No live unionids were documented in Beaver Island, Garden Island, Grand Traverse Bay, or Saginaw Bay wetlands. Dreissena colonization densities on artificial substrates averaged 19,213 m-2 at one site in North Maumee Bay, and 10,425 m-2 in Saginaw Bay, but no colonization occurred in the wetlands of Beaver Island, Garden Island, the Les Cheneaux Islands, or Grand Traverse Bay while Dreissena presence in the open water of these regions was evident. Dreissena colonization densities on artificial substrates increased with measures of anthropogenic disturbance and decreased with higher water level fluctuations and aerial exposure. Specific conductance, turbidity, and magnitude of water level fluctuations were important predictors of Dreissena colonization on artificial substrates. [ABSTRACT FROM AUTHOR]

The macrogeographic dispersal of unionoid mussels is largely dependent on movement by their host fish. The snuffbox mussel Epioblasma triquetra (Unionoida) and other congeners use a novel trapping behaviour to parasitize potential host fish with their larvae (glochidia). Common logperch ( Percina caprodes) trapped by E. triquetra survive the trapping behaviour, whereas other darter species ( Etheostoma and Percina) do not, thus, making the P. caprodes- E. triquetra relationship a good candidate system for a coevolutionary study. We hypothesized that the geographic genetic structure of E. triquetra should closely match that of its host, albeit with greater interpopulation divergences as a result of its dependency on the host for dispersal. Mantel tests of parallel pairwise matrices of population divergence (Jost's D) and genetic assignment tests based on microsatellite DNA data showed that the genetic population structures of both species were broadly, but not perfectly, congruent. Therefore, it appears that P. caprodes are not solely responsible for the genetic population structure observed for snuffbox and may not necessarily be the mussel's only host across its entire range. This suggests the potential for a geographic mosaic for coevolution in unionoids and darters. The findings of the present study reinforce the need for a joint study and conservation of unionoids and host fish aiming to protect these coevolved taxa. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, , 669-685. [ABSTRACT FROM AUTHOR]

Abstract: Concern exists that the introduction of dreissenid mussels following long-term effects of pollution may have completely eliminated native mussel species from Lake Erie. Natural seiche events were used to facilitate surveys for live unionids on five occasions in the western basin of Lake Erie and Sandusky Bay between 2007 and 2009, and beach and estuary surveys were conducted at numerous additional sites between 2004 and 2009. Sixteen unionid species were found living in or near Lake Erie, including six sites in the nearshore zone of the lake. Each community consisted of live individuals from two to eight species, and evidence included live and/or fresh dead material from several state listed species at multiple sites. Where estimated, the mean overall density was low at 0.09unionids/m2, although similar to other known unionid refuges in the lower Great Lakes. While the ephemeral nature of seiche events makes them a limited survey tool, their application combined with increasing numbers of fresh shells washing ashore over the past few years indicates that unionids are extant in the western basin of Lake Erie, and may further suggest that conditions may be improving for native mussel species. [Copyright &y& Elsevier]