Small clones dominate a population of the short-lived perennial seagrass Zostera japonica

Clonality and sexual reproduction are important drivers of spatial genetic structure (SGS) in seagrass meadows. However, few genetic studies have focused on the annual or short-lived perennial seagrass Zostera japonica, which has been declining dramatically along coastal regions of China. In this study, we assessed the effects of asexual and sexual reproduction on the dispersal of Z. japonica using spatial autocorrelation analysis at both the genet and ramet levels. Clonal richness was moderate (0.6) at a ramet sampling interval of 1 m. The clone subrange was short (5.1 m) relative to other known seagrass species, which may be related to its short life history. The Sp statistic (reflecting the rate of decrease of pairwise kinship with the logarithm of the distance) was stronger at the ramet than the genet level, indicating that clonality intensified the SGS pattern for Z. japonica. Comparisons of sexual and asexual variances of gene dispersal suggested that sexual reproduction was more important than clonal spread for seagrass meadow persistence in this population.