Genetic Diversity and Structure of Dominant Seagrass Species in the Southern Philippines for Conservation and Adaptive Management

This study is the first large‐scale genetic population study of the three dominant tropical species of seagrass in the southern Philippines. The aim was to understand the genetic diversity, population structure, and clonality of Enhalus acoroides, Thalassia hemprichii, and Cymodocea rotundata for appropriate ecosystem management and conservation. Population genetics analysis for the 15 sites was performed by using polymorphic microsatellite markers within the regional geographical scale. The results showed that the population genetic parameters across the Mindanao region are low to high. Overall, Clonal richness was highest in E. acoroides, followed by T. hemprichii and C. rotundata, indicating sexual reproduction is prevalent. The largest genet found in the study was at Rizal, Northern Mindanao, wherein throughout the sampling area only one genet was identified. The mean FIS (coefficient of local inbreeding) values were positive (heterozygous deficit) with some sites deviating from Hardy-Weinberg equilibrium. Significant pairwise population genetic differentiation was found among many sites. Isolation by distance (IBD) was detected in T. hemprichii and C. rotundata (P < 0.05) but not in E. acoroides (P = 0.253). IBD is present among populations, maybe influenced by the ocean current system in the southern Philippines, but it has to be confirmed yet in the future study. If the goal is to maintain the genetic connectivity of these ecologically important seagrass species, conservation planning and implementation of marine protection should be considered at the regional scale – following the Mindanao Ocean currents.