Development of microsatellite markers for the seagrass Zostera japonica using next-generation sequencing

The seagrass Zostera japonica Asch. & Graebn. is among the few seagrass species that thrive both in temperate and tropical intertidal zones. The degradation of Z. japonica in its native range and continued expansion in some localities have raised concerns with regard to its conservation and management. Population genetic studies of Z. japonica across its biogeographic range and within meadows are scarce. Previously developed microsatellites via traditional methods are not sufficient in quantity and perform inconsistently between the temperate and tropical populations. Thus, this study aimed to develop more reliable polymorphic markers for Z. japonica using next generation sequencing. In total, 6479 sequences containing loci were identified and 1619 pairs of primers were successfully designed. Of these, 63 loci were selected for primary validation in 16 individuals from four populations, with 48 (76.2%) polymorphic loci detected. Seventeen polymorphic loci were selected for further evaluation in 62 individuals from one temperate and one tropical population. The overall probability of identity (PID) for both populations was 2.375e^-22 (PID_sib = 3.557e^-08). The number of alleles, and expected and observed heterozygosity in the two populations were both relatively high and not significantly different from each other. The pairwise F_ST = 0.232 (p < 0.0001) and Principal Coordinates Analysis both suggested a large and significant genetic divergence between the two populations. This study makes abundant molecular markers available for genetic studies in Z. japonica, and facilitates its conservation and management strategies.