Genetic diversity and connectivity in a brooding reef coral at the limit of its distribution

Abstract

Remote populations are predicted to be vulnerable owing to their isolation from potential source reefs, and usually low population size and associated increased extinction risk. We investigated genetic diversity, population subdivision and connectivity in the brooding reef coral Seriatopora hystrix at the limits of its Eastern Australian (EA) distribution and three sites in the southern Great Barrier Reef (GBR). Over the approximately 1270 km survey range, high levels of population subdivision were detected (global F ST ¼ 0.224), with the greatest range in pairwise F ST values observed among the three southernmost locations: Lord Howe Island, Elizabeth Reef and Middleton Reef. Flinders Reef, located between the GBR and the more southerly offshore reefs, was highly isolated and showed the signature of a recent bottleneck. High pairwise F ST values and the presence of multiple genetic clusters indicate that EA subtropical coral populations have been historically isolated from each other and the GBR. One putative first-generation migrant was detected from the GBR into the EA subtropics. Occasional long-distance dispersal is supported by changes in species composition at these high-latitude reefs and the occurrence of new species records over the past three decades. While subtropical populations exhibited significantly lower allelic richness than their GBR counterparts, genetic diversity was still moderately high. Furthermore, subtropical populations were not inbred and had a considerable number of private alleles. The results suggest that these high-latitude S. hystrix populations are supplemented by infrequent longdistance migrants from the GBR and may have adequate population sizes to maintain viability and resist severe losses of genetic diversity.

Genetic diversity and differentiation among high-latitude broadcast-spawning coral populations disjunct from the core range

“…However, the large geographic distances between subtropical Eastern Australian nearshore coral communities and offshore reefs (> 630 km) likely limit dispersal between these locations. The observation that 2 species of brooding reef coral among subtropical Eastern Australian locations showed limited gene flow supports this hypothesis (Miller & Ayre 2008, Noreen et al 2009. A large proportion of subtropical-dwelling corals are tropical species surviving at or near their range limit, and environmental stress is known to negatively affect coral reproduction as well as survival (Harrison 2011).…”

“…Ayre & Hughes 2000, Ridgway et al 2008, Nakajima et al 2010. In contrast, significant population differentiation between sites at Lord Howe Island has previously been detected in 3 brooding and one broadcast-spawning reef coral species (Ayre & Hughes 2004, Miller & Ayre 2004, Noreen et al 2009). In this study, the STRUC-TURE results show that most Lord Howe Island samples belong to the same genetic cluster (Fig.…”

The influence of irradiance on tolerance to high and low temperature stress exhibited by Symbiodinium in the coral, Pocillopora damicornis, from the high‐latitude reef of Lord Howe Island

“…It appears that rapid increases in sea surface temperature beyond the normal range are enough to cause bleaching, and possibly death, even in corals adapted to thermally variable environments. Further, geographically and genetically isolated reefs such as LHI are especially vulnerable to climate change, with infrequent long-distance dispersal (Noreen et al 2009) likely to be insufficient to enable recovery from fatal bleaching events.…”

Intracolonial genetic variation in the scleractinian coral Seriatopora hystrix

“…In recent years, a number of species-specific microsatellites were developed (Maier et al 2001(Maier et al , 2005Underwood et al 2006) and successfully applied to investigate population genetic processes on different spatial scales (e.g., Maier et al 2005Maier et al , 2009Underwood et al 2007Underwood et al , 2009van Oppen et al 2008van Oppen et al , 2011Noreen et al 2009). Given that these and other surveys include individual-based analyses, the aims of our study were to (1) investigate whether genetically heterogeneous colonies occur in natural S. hystrix stands and (2) distinguish between the two underlying mechanisms, mosaicism and chimerism.…”