Historic divergence with contemporary connectivity in a catadromous fish, the estuary perch (Macquaria colonorum)
Shaddick, K., Gilligan, D.M., Burridge, C.P., Jerry, D.R., Truong, K., Beheregaray, L.B., 2011. Historic divergence with contemporary connectivity in a catadromous fish, the estuary perch (Macquaria colonorum). Canadian Journal of Fisheries & Aquatic Sciences, 68(2): 304–318.
Estuary perch provide an important recreational fishery within estuaries along the NSW coastline. Detailed genetic analysis was used to study the current population structure of the species throughout their distribution and to study how historical changes in sea level and oceanic currents may have influenced their evolution. Genetic data from mitochondrial DNA clearly separated the species into two populations, with the two separated in the vicinity of Jervis Bay on the NSW south coast. In contrast, genetic data from nuclear DNA suggested no marked population structure across large distances. Together, these analyses suggest that the two separate populations may have formed during the Pleistocene ice ages when the exposed landbridge between Tasmania and mainland Australia isolated estuary perch populations in NSW and eastern Victoria from populations in western Victoria. The two populations subsequently expanded towards the end of the Pleistocene. Current connectivity between populations appears to be maintained by movement of fish between estuaries, facilitated by both large and fine-scale oceanic currents such as the Eastern Australian Current and Zeehan Current. This is consistent with genetic analyses undertaken on other marine/estuarine fishes in SE Australia and highlights the important role of the marine environment in driving population genetic processes in estuarine species.