Acanthopagrus butcheri completes its entire life history within estuaries and coastal lakes of southern Australia, although adults occasionally move between estuaries via the sea. Consequently, it is expected that populations of A. butcheri in different estuaries will be genetically distinct, with the magnitude of genetic divergence increasing with geographic isolation. However, previous genetic studies of A. butcheri from southeast Australia yielded conflicting results; allozyme variation exhibited minimal spatial structuring (è = 0.012), whereas mitochondrial DNA distinguished the majority of populations analyzed (è = 0.263) and genetic divergence was positively correlated with geographic isolation. This discrepancy could reflect high male gene flow, which impacts nuclear but not mitochondrial markers. Here we estimated allele frequencies at five nuclear microsatellite loci across 11 southeast Australian populations (595 individuals). Overall structuring of microsatellite variation was weaker (è = 0.088) than that observed for mitochondrial DNA, but was able to distinguish a greater number of populations and was positively correlated with geographic distance. Therefore, we reject high male gene flow and invoke a stepping-stone model of infrequent gene flow among estuaries for both sexes. Likewise, management of A. butcheri within the study range should be conducted at the scale of individual or geographically proximate estuaries for both sexes. The lack of allozyme structuring in southeast Australia reflects either the large variance in structuring expected among loci under neutral conditions and the low number of allozymes surveyed or a recent colonization of estuaries such that some but not all nuclear loci have approached migration-drift equilibrium.
History
Publication title
Marine Biotechnology
Volume
9
Pagination
33-44
ISSN
1436-2228
Department/School
School of Natural Sciences
Publisher
Springer-Verlag
Place of publication
175 Fifth Ave, New York, USA, Ny, 10010
Rights statement
The original publication is available at www.springerlink.com