Genetic structure of Atlantic and Gulf of Mexico populations of sea bass, menhaden, and sturgeon: Influence of zoogeographic factors and life-history patterns

Abstract

Abstract.To assess the influence of zoogeographic factors and life-history parameters (effective population size, generation length, and dispersal) on the evolutionary genetic structure of marine fishes in the southeastern USA, phylogeographic patterns of mitochondrial DNA (mtDNA) were compared between disjunct Atlantic and Gulf of Mexico populations in three coastal marine fishes whose juveniles require an estuarine or freshwater habitat for development. Black sea bass (Centropristis striata), menhaden (Brevoortia tyrannus and B. patronus) and sturgeon (Acipenser oxyrhynchus) samples were collected between 1986 and 1988. All species showed significant haplotype frequency differences between the Atlantic and Gulf, but the magnitude and distribution of mtDNA variation differed greatly among these taxa: sea bass showed little within-region mtDNA polymorphism and a clear phylogenetic distinction between the Atlantic and Gulf; menhaden showed extensive within-region polymorphism and a paraphyletic relationship between Atlantic and Gulf populations; and sturgeon exhibited very low mONA diversity both within regions and overall. Evolutionary effective sizes of the female populations (N:(e)) estimated from the mtDNA data ranged from N:(e) = 50 (Gulf of Mexico sturgeon) to N:(e) = 800 000 (Atlantic menhaden), and showed a strong rank-order agreement with the current-day census sizes of these species. The relationship between N:(e) and the estimated times of divergence (t) among mtDNA lineages (from conventional clock calibrations) predicts the observed phylogenetic distinction between Atlantic and Gulf sea bass, as well as the paraphyletic pattern in menhaden, provided the populations have been separated by the same long-standing zoogeographic barriers thought to have influenced other coastal taxa in the southeastern USA. However, vicariant scenarios alone cannot explain other phylogenetic aspects of the menhaden (and sturgeon) mtDNA data and, for these species, recent gene flow between the Atlantic and Gulf coasts is strongly implicated. These data are relevant to management and conservation issues for these species.

Genetic Variability and Population Structure of Gulf Menhaden Compared with Yellowfin Menhaden

“…In addition to the instability in LD estimates, high gene flow and insufficient sampling could also create downward bias in estimates of N e using the temporal method (Wang and Whitlock 2003;Waples and Do 2010;Hare et al 2011). In general, these estimates that suggest N e > 1,000 are supported by previous examinations of Gulf Menhaden reporting exceptionally high genetic variability based on mtDNA (Bowen and Avise 1990;Anderson 2007;Lynch et al 2010) and microsatellite (Anderson 2007;Lynch et al 2010) diversity.…”

“…However, the method used in that study was based on nucleotide diversity at a single mitochondrial DNA (mtDNA) locus and relied upon rough estimation under a coalescent model. The estimate of Bowen and Avise (1990) thus may simply reflect long-term (evolutionary) effective size among mtDNA lineages only. In comparison, a short-term estimate of N e would more accurately reflect the effective size of the contemporary population and would be more useful for estimating existing adaptive potential (Hare et al 2011).…”

“…Thus, one question that might be answered with genetic data is whether there are observable negative impacts on genetic diversity in the center of the range of B. patronus due to fishing. Bowen and Avise (1990) previously estimated the effective size of the female population in menhaden (N fe ) to be~250,000 individuals, suggesting very high genetic diversity. However, the method used in that study was based on nucleotide diversity at a single mitochondrial DNA (mtDNA) locus and relied upon rough estimation under a coalescent model.…”

Allozyme and mitochondrial DNA variation in three species of oreos (Teleostei: Oreosomatidae) from Australasian waters

“…These values, unlike the allozyme heterozygosity values, are not unusual. Although there appears to be no comprehensive and up-to-date review of this topic, it is easy to find marine fish species that show more (e.g., Atlantic menhaden, Bowen & Avise (1990); jackass morwong, Grewe et al (1994); yellowfin tuna, Ward Table 6 Smooth oreo (Pseudocyttus maculatus), black oreo (A llocyttus niger), and warty oreo (A. verrucosus). Summary allozyme statistics.…”

“…(P = the percentage of loci polymorphic (frequency of the most common allele < 0.95). H = mean heterozygosity per locus (Nei 1978, unbiased estimate Gold et al (1993)) and less (e.g., black sea bass, Bowen & Avise (1990); weakfish, Graves et al (1992)) mtDNA variation.…”