|Regional genetic connectivity of seagrasses in relation to their survival strategy|
Wouters, B. (2019). Regional genetic connectivity of seagrasses in relation to their survival strategy. MSc Thesis. Universiteit Antwerpen/Ghent University/VUB: Antwerpen, Ghent, Brussel. 32 pp.
Thalassia hemprichii (Ehrenberg) Ascherson, 1871 [WoRMS]
survival strategy, genetic connectivity and structure
Knowledge about genetic diversity and connectivity provides an ecological perspective for growth and persistence of local seagrass populations. Understanding their spatial population structure and identifying meadows with limited as well as high connectivity is integral to maximizing coastal ecosystem conversation effectiveness and to forecast how populations might recover after major disturbances. Thalassia hemprichii is a widely-distributed seagrass species in the SE Asian region. The current population genetic status of this species was examined in two separated geographic regions within the South China Sea. The levels of genetic diversity, gene flow and genetic structure of 7 populations were analysed using 14 species-specific microsatellite markers. Lower levels of genetic and genotypic diversity were found for populations in Lập An lagoon [allelic richness (Ar) = 2.52, unbiased heterozygosity (uHe) = 0.32, clonal richness (R) = 0.385], which is a semi-enclosed lagoon in Vietnam located in the province of Thừa Thiên-Huế, than for the populations in eastern Visayas (Ar = 2.93, uHe = 0.4, R = 0.69), which is an open coastal system in the Philippine Archipelago. Two different meadow-level sampling techniques were superimposed in Lập An lagoon and showed indication that the choice of sampling strategy can affect estimates of within-population spatial genetic structure. The Vietnamese and the Philippines populations were significantly genetically divergent from each another (Frt = 0.344, p-value < 0.001), which are found to be two major genetic demes based on Bayesian clustering. Populations within Lập An lagoon were found to be genetically divergent from one another (Fst = 0.133–0.401), suggesting that limited gene flow has been taking place among populations. In contrast, the populations in eastern Visayas show very small genetic differentiation (Fst = 0.078). In addition, the fine-scale genetic structure within the populations indicated that the main survival strategy of T. hemprichii is through within-meadow propagule dispersal over very short distances and that local clonal extension is a very prevalent reproduction strategy. Furthermore, spatial morphological variability among genetically divergent populations in Lập An lagoon advocates that genetic variation could have measurable effects on a seagrass community structure.