Clonal diversity and recruitment strategy of the two dominant seagrass species Cymodocea rotundata and Enhalus acoroides in the southern Philippines

The studied fifteen populations of Cymodocea rotundata and Enhalus acoroides in Mindanao, southern Philippines revealed a remarkable strategy for reproduction and dispersal. E. acoroides populations exhibits high rates of sexual recruitment with high clonal richness ranged from 0.9 to 1.0, while C. rotundata exhibited monoclonal to high clonal richness ranged from 0 to 1.0. Overall, clonal richness was high indicating sexual reproduction is prevalent, but varied for C. rotundata. The largest genet found in the study was at Rizal (RIZ), northern Mindanao wherein throughout the sampling area only one genet was identified, maybe influenced by environmental condition and hydrodynamic of the water currents and tidal fluctuation in this range-edge population. Significant pairwise population genetic differentiation was found among many sites. Isolation by distance (IBD) was detected in C. rotundata (P < 0.05) but not in E. acoroides (P = 0.253). IBD manifested among populations maybe influenced by the ocean currents in Mindanao, but it has to be confirmed yet in the future study. The results have implications for understanding on how the environmental conditions can influenced the dispersal strategy of these species in natural settings. These species manifested high plasticity most likely to adopt to environmental conditions favoring natural selection for long term demographic stability and fitness. The genetic diversity, structure, reproduction and dispersal strategies observed in this study may prove useful for eventual genetic conservation plans of these two foundational seagrass species.