ABSTRACT:Frog virus 3 (FV3) and FV3-like viruses, are members of the genus Ranavirus (family Iridoviridae), and they have been associated with infectious diseases that may be contributing to amphibian population declines. We examined the mode of transmission of an FV3-like virus, and potential hosts and reservoirs of the virus in a local amphibian community. Using the polymerase chain reaction to detect infected animals, we found an FV3-like virus in south-central Ontario, Canada, amphibian communities, where it infects sympatric amphibian species, including ranid and hylid tadpoles (Rana sylvatica, Hyla versicolor, and Pseudacris spp.), larval salamanders (Ambystoma spp.), and adult eastern-spotted newts (Notophthalmus viridescens). The high prevalence of FV3-like infections in caudate larvae suggests that salamanders are likely to be both hosts and reservoirs. In laboratory FV3 challenges of R. sylvatica, the rate of infection was dependent on the amount of virus to which the animals were exposed. In addition, although vertical transmission was suspected, horizontal transmission through exposure to infected pond water is the most likely route of infection in tadpoles. Based on our observations, a simple model of FV3/FV3-like virus transmission postulates that, in aquatic amphibian communities, transmission of the virus occurs between anuran and urodele species, with ambystomatid salamanders the most likely reservoir for the ranavirus in our study.
Lake sturgeon (Acipenser fulvescens) are of conservation concern throughout their range. Many populations are dependent on fluvial habitats which have been increasingly impacted and fragmented by dams and human development. Although lake sturgeon were once abundant in the Ottawa River and its tributaries, historical commercial harvests and other anthropogenic factors caused severe declines and low contemporary numbers in lake sturgeon populations. Contemporary habitat fragmentation by dams may be increasing isolation among habitat patches and local rates of decline, raising concerns for persistence of local populations. We used microsatellite DNA markers to assess population structure and diversity of lake sturgeon in the Ottawa River, and analyzed samples from 10 sites that represent more than 500 km of riverine habitat. To test for evidence of anthropogenic fragmentation, patterns of genetic diversity and connectivity within and among river segments were tested for concordance with geographic location, separation by distance and obstacles to migration, considering both natural and artificial barriers as well as barrier age. Despite extensive habitat fragmentation throughout the Ottawa River, statistical analyses failed to refute panmixia of lake sturgeon in this system. Although the long generation time of lake sturgeon appears to have effectively guarded against the negative genetic impacts of habitat fragmentation and loss so far, evidence from demographic studies indicates that restoring connectivity among habitats is needed for the long-term conservation and management of this species throughout this river system.
SummaryLake sturgeon (Acipenser fulvescens) are a species of conservation concern across their range, with impoundments and exploitation acting as significant impediments to their recovery. Northern Ontario contains some of the few remaining intact systems with healthy lake sturgeon populations because of low exploitation and undammed, unregulated watersheds. Although preliminary research suggests that northern Ontario lake sturgeon are genetically distinct from depleted sturgeon populations in the Great Lakes basin, this region represents a large gap in our understanding of genetic diversity of lake sturgeon. Recent identification of hydroelectric development potential in four major rivers in northern Ontario may pose future threats to these populations. The two goals of this study were to address the lack of genetic information from a significant portion of the species range, and to compare levels of local and regional diversity between relatively intact systems and more intensively studied (and fragmented) areas to the south. Comparison of 23 putative populations from three major drainages identified three divergent genetic groups which corresponded with historical drainages more than contemporary watersheds. The three groups reflected colonization from Mississippian and Missourian glacial refugia, as well as a novel third group in western Ontario characterized by low genetic variability. Diversity within populations similarly reflected historical influences more than anthropogenic stressors, including impoundments and population abundances resulting from harvest. Genetic similarities among geographically separated populations within major drainages underscore their historical connections, reflecting lake sturgeon dispersal abilities and the importance of habitat connectivity.
Summary1. Environmental DNA (eDNA) is increasingly used for surveillance and detection of species of interest in aquatic and soil samples. 2. A significant risk associated with eDNA methods is potential false-positive results due to laboratory contamination. 3. To minimize and quantify this risk, we designed and validated a set of synthetic oligonucleotides for use as species-specific positive PCR controls for several high-profile aquatic invasive species. 4. The controls consist of species-specific sequences for the species of interest, with the addition of a synthetic insert containing recognition sites for several restriction enzymes. 5. Following PCR, the presence of the synthetic insert can be detected using gel electrophoresis, restriction enzyme digests or DNA sequencing. For quantitative PCR (qPCR), false positives in environmental samples can also be detected using a fluorescent probe designed to detect the synthetic insert. 6. The generation of synthetic controls is a cost-effective, reproducible method that increases the power and reliability of eDNA testing by eliminating misinterpretation of false-positive results from laboratory contamination.
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