Temporal stability of nuclear gene (allozyme) and mitochondrial DNA genotypes among red drums from the gulf of mexico

Allelic variation in nine polymorphic nuclear genes and restriction-site variation in mitochondrial DNA (mtDNA) were assayed among 194 adult red drums Sciaenops ocellatus from the northern Gulf of Mexico. Data were combined with those of previous studies in order to examine patterns of temporal genetic variation among four year-classes (1984-1987) and individuals spawned prior to 1984. Tests of heterogeneity among year-classes in both nuclear gene allele frequencies and mtDNA haplotype frequencies were nonsignificant, and estimated fixation (F_ST) values were 0.009 (nuclear genes) and 0.002 (mtDNA). Estimates of Nei's unbiased genetic distance (nuclear genes) and nucleotide sequence divergence (mtDNA) among year-classes also indicated the absence of temporal genetic differentiation. Estimates of average heterozygosity (nuclear genes) and nucleon and nucleotide sequence diversities (mtDNA) indicated that levels of genome-wide variation within and among year-classes of red drum are equivalent to (or higher than) those in most marine fish species examined to date. Estimates of effective female population size suggest that the total size of the female red drum population in the northern Gulf of Mexico could be 10 million individuals.