Abstract
A geospatial database of spotted seatrout (Cynoscion nebulosus) abundance along the Texas shoreline was generated, using 33 years of intensive gill net sampling data by the Texas Parks and Wildlife Department. The resulting landscape demographic data was used to identify areas of low individual abundance, which were evaluated as putative subpopulation boundaries. Quantitative population genetic analysis was conducted using a recently published genetic data set of mitochondrial DNA haplotypes, and a new data set of nuclear microsatellites. A significant mtDNA AMOVA result was obtained when samples were pooled into northern, mid-coast and southern spatial partitions based upon geospatial data (Fct = 0.030, P = 0.003). This three-partition model captured more genetic divergence at the group level than any other model examined. Similarly, the three-partition model resulted in a small but significant group association in the microsatellite AMOVA (Fct = 0.003, P = 0.009). Multivariate cluster analyses of both data sets indicated that at least three distinctive subpopulations of spotted seatrout exist within Texas waters. The genetic data are consistent with previous studies that indicate the presence of distinctive subpopulations of spotted seatrout in Texas coastal waters, and with geospatial abundance data indicating areas of low abundance, between adjacent subpopulations along the northern and southern Texas coastline.
Highlights
The spotted seatrout (Cynoscion nebulosus Cuvier) is the most popular recreational marine finfish in Texas [1] and is common throughout the Gulf of Mexico
Gold et al [3] used the distribution of mitochondrial DNA RFLP haplotypes to conclude that samples taken of spotted seatrout throughout the northern Gulf and Atlantic generally represented distinct subpopulations, and suggested that these subpopulations may be organized by natal estuaries, as expected from short dispersal distances in tagging studies and the affinity of spotted seatrout for inshore areas
The effective genetic differences between distinctive subpopulations, versus a single population operating under IBD, are likely to be subtle because the genetic drift that is expected among distinctive subpopulations can potentially be offset by the large census sizes that generally characterize marine finfish populations
Summary
The spotted seatrout (Cynoscion nebulosus Cuvier) is the most popular recreational marine finfish in Texas [1] and is common throughout the Gulf of Mexico (hereafter Gulf). In contrast with the finding of discreet subpopulations, Ramsey and Wakeman [4] and King and Pate [5] used allozymes and found low measures of population subdivision (Fst) and high gene flow (Nem) in Gulf samples, indicating that individuals in the western/northern Gulf http://astonjournals.com/faj comprise a single large population. Both studies found isolation-by-distance (IBD) among locales, suggesting that genetic differentiation occurred on a broad (but continuous) geographic scale. Gold et al [7] suggested that subpopulations centered in natal estuaries may have distinctive short-term demographic characteristics, recurrent gene flow among adjacent estuaries results in a genetic pattern which resembles IBD, rather than distinct subpopulations
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