Browsing by Author "Bourquin, Rebecca M."
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- Are Road Crossings Fragmenting Populations of Clinch Dace?Bourquin, Rebecca M.; Orth, Donald J.; Hallerman, Eric M.; Stauffer, Dean F. (Humboldt Field Research Institute, 2020-11-16)Chrosomus sp. cf. saylori (Clinch Dace) is a newly recognized species of minnow with a restricted distribution in southwestern Virginia. We analyzed genetic variation and abundance at paired sites above and below road crossings. Road crossings did not have a strong effect on presence, abundance, or genetic differentiation of Clinch Dace. Of all sites where Clinch Dace were found, only 1 perched culvert presented a barrier to upstream migration; however, no genetic differentiation was found between collections above and below that or any other culvert. Distribution and abundance of Clinch Dace populations were not influenced by habitat variables measured at the site level. Low abundance in small headwaters, nest association, and high mobility appear to be characteristics of this species of Chrosomus.
- Conservation Genetics of Clinch Dace Chrosomus sp. cf. sayloriBourquin, Rebecca M.; Moore, Michael J.; Orth, Donald J.; Hallerman, Eric M. (MDPI, 2023-07-13)Clinch Dace (Chrosomus sp. cf. saylori) is a newly recognized and yet-undescribed species of minnow with a restricted and fragmented distribution in the upper Tennessee River basin in southwestern Virginia, USA. We collected Clinch Dace from seven streams and observed variations at nine selectively neutral microsatellite DNA loci to infer population genetic processes and identify units for conservation management. Bayesian cluster analysis showed that three of the seven surveyed populations were genetically distinct, while the other four populations showed signs of recent admixture. Estimated effective population sizes and m-ratios were low within most populations, suggesting loss of alleles due to recent genetic drift. Positive FIS values, high average individual inbreeding coefficients, and high degrees of inferred relatedness among individuals suggested that inbreeding is taking place in some populations. FST values were high, and analysis of molecular variance indicated genetic divergence among populations. These indicators suggest that Clinch Dace populations are subject to the genetic processes that are characteristic of small and isolated populations.
- Fragmentation and Genetic Diversity in Clinch Dace PopulationsBourquin, Rebecca M.; Orth, Donald J.; Hallerman, Eric M. (Virginia Tech, 2019-07-25)In 1999 Clinch Dace, Chrosomus sp. cf. saylori, was discovered in the Tennessee drainage of Virginia. Subsequent sampling of southwest Virginia and portions of Tennessee indicated that Clinch Dace populations are small, fragmented, and of questionable viability. Further, riparian land use and mining pose significant threats to critical habitat. As such, Clinch Dace were listed as a Federal Species of Concern and on Virginia’s Wildlife Action Plan as Tier I - Critical Conservation Need. A management plan and species description for Clinch Dace is of utmost importance, but data on distribution and life history are needed before these objectives can be realized. The objectives of this study were to: 1) Monitor known populations of Clinch Dace to characterize at fine-scale distribution and status. The latter will be addressed in terms of relative abundance. 2) Analyze distribution data using geographic information systems and other approaches to identify habitat and landscape features that isolate Clinch Dace and associated fish populations, 3) Map stream crossings and assess likely barriers to upstream passage and measurements of specific conductance, 4) Screen molecular genetic markers in order to define demographic and any evolutionarily significant units for the species. Molecular genetic variation will be screened at nuclear microsatellite loci to assess levels of molecular genetic variability and population-level differentiation. We will examine the effect of geographic distance on genetic differentiation (Botta et al. 2015). Habitat use will be compared to assess whether genetic differentiation relates to any observed differences in adaptive characters among populations. 5) Use these findings to define demographic and evolutionarily significant units for the species and work toward estimating effective population size and protocols for translocating individuals. We sampled 29 reaches on ten streams for fish with a three-pass depletion method and measured eight habitat variables which might inform conservation actions. We also conducted statistical analyses on six habitat and fish community variables to determine whether habitat rather than fragmentation was influencing Clinch Dace presence and abundance. We conclude that seven Clinch Dace populations vary in their degree of isolation, with some populations showing signs of recent admixture and others not. Populations with the least admixture, such as Hurricane Fork and Hart Creek in Russell County, may represent distinct management units. However, they are also among the largest populations found in 2017 and may therefore be the best candidates for donor population for translocations. The effects of road crossings in our study area was minimal and most crossings were not obvious barriers to fish passage. Instream habitat metrics that we measured also seemed to have little effect on Clinch Dace presence and abundance. We recommend that further management actions be taken with an adaptive management approach, as it is not clear from our results that translocations should be ruled out, but rather undertaken initially as a pilot study with follow-up monitoring to determine whether outbreeding depression is taking place as a result of moving locally adapted fish. Stream restoration activities may not be warranted, as the Clinch Dace shows some resilience to habitat degradation, such as sedimentation and lack of woody debris. We only found one culvert on Hart Creek which could be considered for a retrofit and that does seem to be acting as a barrier to Clinch Dace movement. Further research could measure temporal changes in abundance and characterize the relationship between population size and extinction risk and identify minimum viable population thresholds. Further monitoring should include the seven populations characterized as well as nine streams (Hess, Indian, Laurel, Left Fork Coal, Mudlick, Pine, Town Hill, and West Fork Big Creeks).
- Population Fragmentation and Genetic Diversity of Chrosomus sp. cf. saylori (Clinch Dace)Bourquin, Rebecca M. (Virginia Tech, 2020-02-06)Clinch Dace (Chrosomus sp. cf. saylori) is a newly recognized species of minnow with a restricted distribution in southwestern Virginia. Field sampling and genetic analysis support the hypothesis that Clinch Dace populations are small and fragmented. Analysis of neutral genetic markers shows that most Clinch Dace populations have undergone past bottleneck events and are being operated upon by random genetic drift. Bayesian cluster analysis showed that three out of the seven populations found in 2017 are distinct, while the other four show signs of more recent admixture. However, Fst values among streams were high and analysis of molecular variance indicated differentiation among populations in all streams. These findings support the view that these populations are genetically isolated. Effective populations sizes were low at most sites, enhancing the likelihood of loss of alleles to genetic drift. Low M-ratios, non-zero Fis values, and high degrees of relatedness among individuals indicate that some inbreeding is taking place. Habitat analysis did not identify variables affecting distribution or abundance of Clinch Dace populations. As the collection sites were targeted near known Clinch Dace occupied sites, it is likely that habitat variables known to impact Clinch Dace, such as conductivity, were within the species' range of tolerance. Results showed that Clinch Dace seem particularly resilient to sedimentation, corroborating earlier work showing a negative relationship between Clinch Dace abundance to sediment size. That is, small sediment size does not seem to have a negative impact on Clinch Dace abundance. Of all sites where Clinch Dace were found, only one culvert at one site was clearly perched and may present a barrier to upstream migration, a possibility which is supported by the genetic differentiation found among collections above and below that culvert. While this study demonstrates that selectively neutral genetic differentiation has taken place among Clinch Dace populations, it does address any local adaptation that may be taking place which would render translocations a risk for outbreeding depression. The findings of this study can inform conservation management in identifying possible sources of individuals for translocations among populations or for augmentation following captive breeding.