Brook trout (Salvelinus fontinalis) often exist as highly differentiated populations, even at small spatial scales, due either to natural or anthropogenic sources of isolation and low rates of dispersal. In this study, we used molecular approaches to describe the unique population structure of brook trout inhabiting the Shavers Fork watershed, located in eastern West Virginia, and contrast it to nearby populations in tributaries of the upper Greenbrier River and North Fork South Branch Potomac Rivers. Bayesian and maximum likelihood clustering methods identified minimal population structuring among 14 collections of brook trout from throughout the mainstem and tributaries of Shavers Fork, highlighting the role of the cold-water mainstem for connectivity and high rates of effective migration among tributaries. In contrast, the Potomac and Greenbrier River collections displayed distinct levels of population differentiation among tributaries, presumably resulting from tributary isolation by warm-water mainstems. Our results highlight the importance of protecting and restoring cold-water mainstem habitats as part of region-wide brook trout conservation efforts. In addition, our results from Shavers Fork provide a contrast to previous genetic studies that characterize Appalachian brook trout as fragmented isolates rather than well-mixed populations. Additional study is needed to determine whether the existence of brook trout as genetically similar populations among tributaries is truly unique and whether connectivity among brook trout populations can potentially be restored within other central Appalachian watersheds.

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Acoustic telemetry and ichthyoplankton surveys were used to characterize the migratory behavior and spawning grounds of American shad Alosa sapidissima in the James River, Virginia. Seven acoustic monitoring stations spanned a distance of 95 river kilometers extending downstream from just below the fall line in Richmond to the estuarine portion of the river at Hog Island. Ninety-three fish were tagged in the estuarine portion of the river near Hog Island on 21 March 2005. Eighty-six fish exhibited fallback behavior, and 45 of these fish eventually abandoned the migration. Forty-six fish were eventually detected upstream at the mouths of the two major James River tributaries (Appomattox and Chickahominy rivers), within the main-stem James River up to the fall line, or both. Upstream movements detected by stationary hydrophones during the prespawning migration were significantly related to flooding tides, and movements downstream during the postspawning emigration were significantly related to ebbing tides. However, there was no significant relationship between time of day and movements during the prespawning or postspawning migration phase. Movement patterns suggested three primary areas of residency located within the 65-km reach below the fall line downstream to Upper Brandon Plantation, although some fish exhibited behaviors that were inconsistent with a specific residence area. Ichthyoplankton collections of eggs and yolk sac larvae indicated that the principal spawning grounds were located in a 33.5-km reach extending downstream from the fall line, a finding consistent with repeated detection of a majority of the tagged cohort within this reach.

The mitochondrial genomes of three North American stygobiont amphipods Stygobromus tenuis potomacus, S. foliatus and S. indentatus collected from Caroline County, VA, were sequenced using a shotgun sequencing approach on an Illumina NextSeq500 (Illumina Inc., San Diego, CA). All three mitogenomes displayed 13 protein-coding genes, 22 tRNAs and two rRNAs typical of metazoans. While S. tenuis and S. indentatus displayed identical gene orders similar to the pancrustacean ground pattern, S. foliatus displayed a transposition of the trnL2-cox2 genes to after atp8-atp6. In addition, a short atp8 gene, longer rrnL gene and large inverted repeat within the Control Region distinguished S. foliatus from S. tenuis potomacus and S. indentatus. Overall, it appears that gene order varies considerably among amphipods, and the addition of these Stygobromus mitogenomes to the existing sequenced amphipod mitogenomes will prove useful for characterizing evolutionary relationships among various amphipod taxa, as well as investigations of the evolutionary dynamics of the mitogenome in general.ARTICLE HISTORY

The shortnose sturgeon, Acipenser brevirostrum, oft considered a phylogenetic relic, is listed as an “endangered species threatened with extinction” in the US and “Vulnerable” on the IUCN Red List. Effective conservation of A. brevirostrum depends on understanding its diversity and evolutionary processes, yet challenges associated with the polyploid nature of its nuclear genome have heretofore limited population genetic analysis to maternally inherited haploid characters. We developed a suite of polysomic microsatellite DNA markers and characterized a sample of 561 shortnose sturgeon collected from major extant populations along the North American Atlantic coast. The 181 alleles observed at 11 loci were scored as binary loci and the data were subjected to multivariate ordination, Bayesian clustering, hierarchical partitioning of variance, and among-population distance metric tests. The methods uncovered moderately high levels of gene diversity suggesting population structuring across and within three metapopulations (Northeast, Mid-Atlantic, and Southeast) that encompass seven demographically discrete and evolutionarily distinct lineages. The predicted groups are consistent with previously described behavioral patterns, especially dispersal and migration, supporting the interpretation that A. brevirostrum exhibit adaptive differences based on watershed. Combined with results of prior genetic (mitochondrial DNA) and behavioral studies, the current work suggests that dispersal is an important factor in maintaining genetic diversity in A. brevirostrum and that the basic unit for conservation management is arguably the local population.