Population genetics of the brooding coral Seriatopora hystrix reveals patterns of strong genetic differentiation in the Western Indian Ocean

Asymmetric genetic population structures at the range edges of a mangrove whelk

Many marine species are distributed across incredibly wide geographical ranges spanning thousands of kilometers often due to movement along prevailing ocean currents. However, data are lacking on genetic connectivity among populations of such widespread species within or among ecoregions, possibly due to the lack of appropriate datasets. In this study, we investigated the genetic structure of populations of the mangrove whelk, Terebralia palustris, using mitochondrial cytochrome oxidase subunit I (COI) sequences. Sequences generated for this study from Okinawa, Japan, were compared to samples from the coast of East Africa analyzed in a previous study. Interestingly, despite considerable distance separating them, the African and Japanese populations share major haplotypes and do not show clear genetic differentiation. At lower latitudes, core African populations exhibited higher genetic diversity than either the more southerly African and Japanese populations. Genetic β-diversity revealed that the northern edge population in Japan has a greater proportion of βSNE (the nestedness-resultant component), indicating contemporary migration, whereas the southern edge population in Africa is characterized by a predominant βSIM (the turnover component), suggesting historical demography. A potential cause of this dissimilarity could be due to the strong Kuroshio Current along the Ryukyu Islands, which may promote larval dispersal. These differing patterns suggest that there may be divergent responses to future climate change at the population level at the periphery of the range of T. palustris.

Population genetics assessment of two pocilloporid coral species from the northern red sea: Implications for urbanized reef sustainability

Understanding the genetic makeup of key coral species is vital for effective coral reef management, as heightened genetic diversity directly influences long-term survival and resilience against environmental changes. This study focused on two widespread Indo-Pacific branching corals, Pocillopora damicornis (referred as Pocillopora cf. damicornis (as identified only morphologically) and Seriatopora hystrix, by genotyping 222 and 195 colonies, respectively, from 10 sites in the northern Gulf of Eilat, Red Sea, using six and five microsatellite markers, respectively. Both species exhibited low observed heterozygosity (0.47 for P. cf. damicornis, 0.32 for S. hystrix) and similar expected heterozygosity (0.576 for P. cf. damicornis, 0.578 for S. hystrix). Pocillopora cf. damicornis showed minimal deviations from Hardy-Weinberg equilibrium (HWE) and low but positive F values, indicating high gene flow, while S. hystrix exhibited higher diversion from HWE and positive F values, suggesting isolation by distance and possible non-random mating or genetic drift. As the Gulf of Eilat undergoes rapid urbanization, this study highlights the anthropogenic impacts on the population genetics of key ecosystem engineering species and emphasizes the importance of managing genetics of Marine Protected Areas while implementing active coral reef restoration. The differences in reproductive traits between the two species (S. hystrix being a brooder, while P. cf. damicornis a broadcast spawner), underscore the need for sustainable population genetics management of the coral reefs for the future and resilience of the coral reef ecosystem of the northern Red Sea region.

Integration of population genetics with oceanographic models reveals strong connectivity among coral reefs across Seychelles

Many countries with tropical reef systems face hard choices preserving coral reefs in the face of climate change on limited budgets. One approach to maximising regional reef resilience is targeting management efforts and resources at reefs that export large numbers of larvae to other reefs. However, this requires reef connectivity to be quantified. To map coral connectivity in the Seychelles reef system we carried out a population genomic study of the Porites lutea species complex using 241 sequenced colonies from multiple islands. To identify oceanographic drivers of this connectivity and quantify variability, we further used a 2 km resolution regional ocean simulation coupled with a larval dispersal model to predict the flow of coral larvae between reef sites. Patterns of admixture and gene flow are broadly supported by model predictions, but the realised connectivity is greater than that predicted from model simulations. Both methods detected a biogeographic dispersal barrier between the Inner and Outer Islands of Seychelles. However, this barrier is permeable and substantial larval transport is possible across Seychelles, particularly for one of two putative species found in our genomic study. The broad agreement between predicted connectivity and observed genetic patterns supports the use of such larval dispersal simulations in reef system management in Seychelles and the wider region.

Reduced genetic diversity and restricted gene flow of broadcast-spawning coral Galaxea fascicularis in the South China Sea reveals potential degradation under environmental change

Under the dual effects of climate change and anthropogenic activities, coral reefs in the South China Sea (SCS) are at serious risk of degradation. Galaxea fascicularis is a widely distributed species in the SCS, and the study of its genetics, survival, and adaptability is conducive to further understanding the future characteristics of coral reefs in the SCS. In this study, 146 G. fascicularis samples were selected from 9 survey stations across 12 latitudes in the SCS, and 8 pairs of microsatellite markers were used to characterize their genetic diversity and structure. The results showed moderate genetic diversity index values (Ar = 3.444-4.147, He = 0.634-0.782, Ho = 0.367-0.586). The AMOVA results and pairwise FST values showed a moderate level of genetic differentiation (ΦST = 0.119, P < 0.05) among G. fascicularis populations in the SCS, whereas its genetic structure showed high genetic differentiation (FST = 0.062-0.225) among relatively high-latitude populations (n = 3) and low genetic differentiation (FST = 0.012-0.064) in low-latitude populations (n = 6). The living environment of relatively high-latitude populations is disturbed by high-intensity human activities, leading to the specialization of local populations. Mantel test results showed a significant positive correlation between genetic differentiation among G. fascicularis populations and sea surface temperature (SST) variance (R2 = 0.4885; Mantel test, p = 0.010 < 0.05) in addition to geographical distance (R2 = 0.1134; Mantel, test p = 0.040 < 0.05), indicating that SST and geographical isolation were primary factors affecting the genetic structure of this species in the SCS. The lower genetic diversity and limited gene flow of G. fascicularis indicate limited genetic adaptation, and corresponding vulnerability may be more pronounced under future environmental changes. These findings provide a theoretical basis for the conservation and restoration of coral reefs in the SCS.