Genetic diversity and connectivity of the reef-building coral Seriatopora hystrix along the East coast of Africa
Buitrago Lopez, C.N. (2015). Genetic diversity and connectivity of the reef-building coral Seriatopora hystrix along the East coast of Africa. MSc Thesis. Vrije Universiteit Brussel: Brussel.
Following the global trend, coral reefs in East Africa are declining rapidly due to the effect of direct and indirect anthropogenic stressors, such as pollution, destructive fishing practices, ocean acidification, and climate change. These ecosystems are of critical importance for the more than 39 million people living at the coasts of Kenya, Tanzania, and Mozambique. Therefore, conservation action that effectively protects coral reefs is urgently needed. This study aims to provide insightful information about the genetic diversity and population structure of the reef-building coral Seriatopora hystrix along the East African coast in relation with its particular life history traits. Herein, we utilise nine polymorphic microsatellite loci to assess the genetic variation in ten populations of S. hystrix. Analyses of genetic diversity distribution support the relation between biogeographical patterns of coral species distribution and genetic diversity of S. hystrix. Moreover, populations of S. hystrix were well structured (FST = 0.23; RST = 0.41) and strong differentiations were found over shorter distances, with no isolation-by-distance. Inbreeding associated with sexual reproduction rather than selfing seemed to explain better the deficits of heterozygotes found in some populations. Two genetic breaks were identified around latitude 4° S and 14° S, which corresponded with the most extreme populations and also coincide with dispersal barriers imposed by the oceanic currents. This study did not detected traces of recent bottleneck event, or admixture. Additionally, estimates of contemporary migration support that long distance gene flow can occur, yet still the long life span of scleractinian corals might blur the differences between contemporary and ancestral events. In conclusion, this study found that S. hystrix in East Africa exhibits characteristics of a metapopulation where migration takes place mostly from south to north throughout the East African Coastal Current. Therefore, efforts for conservation should be concentrated in protecting the Northern Mozambique Channel (NMC), which might act as seeding source for northern reefs enhancing the resilience of coral reefs after catastrophic events.
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