Strong genetic but not spatial subdivision of two reef fish species targeted by fishers on the Great Barrier Reef

Abstract

The density and biomass of two coral reef fish species targeted by line fishers, Plectropomus maculatus and Lutjanus carponotatus, have increased within no-take marine protected areas on inshore reefs of the Great Barrier Reef (GBR). This phylogenetic and population genetic study, using mitochondrial DNA (mt DNA) from the control region, is a broad scale analysis of the genetic connectivity of P. maculatus (n = 164) and L. carponotatus (n = 188) within and between inshore islands of the GBR (latitudinal gradient 800 km) that contain the aforementioned no-take areas. Analysis of molecular variance (AMOVA) indicated high levels of gene exchange between locations within (P. maculatus oCT = −0.011; L. carponotatus oCT = 0.004) and between each island group (P. maculatus oSC = 0.003; L. carponotatus oSC = 0.003). Phylogenetic analysis showed no geographic partitioning but identified two distinct lineages for both species that were distributed throughout the sampled range, suggesting that both species are admixtures of differentiated lineages rather than stable populations. This study shows that populations of both species within the sampling range are panmictic and under current conditions, they may be managed as a single stock across the entire GBR. Thus, the study suggests that the island groups and the no-take marine protected areas within them are connected by larval transport to each other and to fished areas. This study cannot confirm if this connectivity is historical (evolutionary) or contemporary (ecological).