Little is known regarding the maintenance of range-edge populations in the absence of gene flow from core populations. In this study, we used 7 microsatellite markers to investigate genetic diversity and differentiation of the broadcast-spawning coral species Acropora solitaryensis among range-edge populations that are disjunct from the core range, and cautiously infer what this means in terms of connectivity. Acropora solitaryensis in sub-tropical eastern Australia is effectively isolated from conspecifics thousands of kilometers away and cannot rely on immigration from core populations for population maintenance. The range-edge region in this study consists of nearshore (Solitary Island) and offshore (Lord Howe Island) populations separated by >630 km. Despite the presence of null alleles, genetic diversity was within the range of that observed in other Acropora species. Nearshore and offshore populations were found to be genetically differentiated, with some indication of a small number of long-distant migrants in both directions. From both a demographic and a genetic perspective, this result may be important for the long-term persistence of A. solitaryensis at this range edge.
Noreen, AME, van Oppen, MJH & Harrison, PL 2013, 'Genetic diversity and differentiation among high-latitude broadcast-spawning coral populations disjunct from the core range', Marine Ecology Progress Series, vol. 491, pp. 101-109.