A Nuclear DNA Perspective on Delineating Evolutionarily Significant Lineages in Polyploids: The Case of the Endangered Shortnose Sturgeon (Acipenser brevirostrum)

Abstract

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.

First verified occurrence of the shortnose sturgeon (Acipenser brevirostrum) in the James River, Virginia

“…After extensive sampling and work with commercial fishermen, they captured 2 shortnose sturgeon. Both fish were gravid females, and telemetric and recapture data indicated that one fish spawned in the Potomac River (Kynard et al, 2009). As with the genetic samples collected during the Chesapeake Bay reward program, the 2 gravid females could not be genetically differentiated from Delaware River shortnose sturgeon (King et al, 2014).…”

“…The shortnose sturgeon (Acipenser brevirostrum) is an amphidromous sturgeon reported to inhabit the continental slope of the Atlantic Ocean from New Brunswick, Canada, to Florida (Gruchy and Parker, 1980;Dadswell et al, 1984;Kynard, 1997). However, Dadswell et al (2013) documented a single shortnose sturgeon captured in a weir in the Minas Basin, an inlet of the Bay of Fundy in Nova Scotia, Canada, and that capture represents a modest extension of the northern range for this species.…”

“…There is a chance that some of the 26 shortnose sturgeon were unknowingly recaptured during the reward program. Results of analysis of the genetic samples taken from shortnose sturgeon as part of the reward program indicated no distinct difference between fish from the Chesapeake Bay and from the Delaware River and Bay; therefore, the 2 groups were assigned to the same population segment (Grunwald et al, 2002;Wirgin et al, 2010;King et al, 2014). Researchers did not mention milt production or egg release for any of the shortnose sturgeon captured during the programs.…”

“…Researchers did not mention milt production or egg release for any of the shortnose sturgeon captured during the programs. Only 2 studies (Welsh et al, 2002;Kynard et al, 2009) were focused specifically on the life history of shortnose sturgeon in the Chesapeake Bay. Welsh et al (2002) telemetered 13 shortnose sturgeon, which were initially captured and tagged in the marine part of the estuary.…”

“…Of these 13 fish, 3 shortnose sturgeon were later detected in the Chesapeake and Delaware Canal or in the Delaware River (Welsh et al, 2002). Kynard et al (2009) focused their research on the life history of shortnose sturgeon in the Potomac River. After extensive sampling and work with commercial fishermen, they captured 2 shortnose sturgeon.…”