Genetic signatures through space, time and multiple disturbances in a ubiquitous brooding coral

Abstract

The predominance of self-recruitment in many reef-building corals has fundamental and complex consequences for their genetic diversity, population persistence and responses to climate change. Knowledge of genetic structure over local scales needs to be placed within a broad spatial context, and also integrated with genetic monitoring through time to disentangle these consequences. Here, we examined patterns of genetic diversity over multiple spatio-temporal scales across tropical Australia in the ubiquitous brooding coral, Seriatopora hystrix. We also analysed complimentary environmental and demographic data to elucidate the seascape drivers of these patterns. Large genetic differences were detected between the east vs. west coasts of Australia. In northwest Australia, geographic differentiation dominated genetic structure over multiple scales. However, three sympatric lineages were detected at the largest offshore reef system (Scott Reef). Similar to the differences observed among putative species in eastern Australia, these lineages were associated with different levels of wave exposure. Local genetic structure within the Scott Reef system was relatively stable over 10 years, but temporal differences were observed that reflected small but important genetic changes over a few generations during recovery after severe bleaching. These results highlight the importance of self-recruitment together with occasional longer distance connectivity for the persistence of a metapopulation across spatially and temporally variable environments. Our multidimensional research provides a foundation for further long-term genetic monitoring to inform conservation strategies and highlights that sampling scales, ecological effects and cryptic diversity are important considerations to develop realistic understanding of the evolutionary resilience of corals.

Parentage analyses identify local dispersal events and sibling aggregations in a natural population of Millepora hydrocorals, a free‐spawning marine invertebrate

“…Although the adult population is predominantly sustained through asexual reproduction (85% are clones), our parentage analysis identified a moderate contribution from self‐recruitment with a minimum of 8% of offspring produced locally and a limited dispersal ability of early life stages. These results support earlier observations indicating that self‐recruitment at the reef scale (or finer) is critical for population replenishment in corals (Figueiredo et al., 2013; Gilmour et al., 2009; Underwood, Richards, Miller, Puotinen, & Gilmour, 2018).…”

“…a limited dispersal ability of early life stages. These results support earlier observations indicating that self-recruitment at the reef scale (or finer) is critical for population replenishment in corals (Figueiredo et al, 2013;Gilmour et al, 2009;Underwood, Richards, Miller, Puotinen, & Gilmour, 2018).…”

“…Because only 20% of the area covered was sampled to assess for parentage relationships, our sampling design might exclude potential parents occurring between our transects and surveyed habitats, which could potentially increase true values of self-recruitment in the studied population. In consideration of this, a relatively high investment in self-recruitment might well be an efficient process to sustain local populations in an isolated reef system such as Moorea (as described in Gilmour et al, 2009;Shinzato et al, 2015;Tsounis & Edmunds, 2016;Underwood et al, 2018;Zeng, Rowden, Clark, & Gardner, 2017 Marquesas, Austral, Gambier, Society, and Tuamotu; Boissin, Dubé, Bourmaud, Gravier-Bonnet, Planes, unpublished data). Consistently, no offspring were assigned to adult colonies collected in other reef locations located at 1.5-10 km away from our studied area, and the spatial autocorrelation analysis also showed a negative relationship at distances >200 m (i.e., overdispersion).…”

Long‐term dynamics and drivers of coral and macroalgal cover on inshore reefs of the Great Barrier Reef Marine Park

“…) at each monitoring site using the NOAA WAVEWATCH III global hindcast data set (December 2010 to December 2016, spatial resolution 0.5°, temporal resolution 1 h) to weight distances to the nearest wave blocking obstacle every 7.5° around each site (fetch) by the relative frequency at which waves approached the site and their average magnitude, as per previous studies (Underwood et al. , ). These distances were then summed and normalized to the maximum possible summed distances for the most exposed site within the study area (Halfway Island, exposure index 0.279187) to create a dimensionless index of relative wave exposure.…”

Reproduction of brooding corals at Scott Reef, Western Australia

“…Scott Reef experienced severe bleaching in 1998 and 2016 and moderate bleaching in 2010 [36] [37]. Exposure to potentially damaging cyclones also occurred in 2004,2005,2007 and 2012 [38]. Broadcast spawning corals synchronise the release of their gametes to one or a few nights of the year.…”