The role of true viviparity in Amphibolis antarctica: implications for the genetic diversity in the context of seagrass restoration

Amphibolis antarctica (Labill.) Asch. produces large, well-developed viviparous seedlings, raising a fundamental question: Are these seedlings the result of sexual or asexual reproduction? This distinction carries significant implications for understanding dispersal, genetic diversity, and ecosystem resilience. Here, we present our observations on population structure, the development of embryos, morphological features of A. antarctica and testing genetic variability using new microsatellite markers, leading us to conclude that there is sexual reproduction in this species. While direct evidence of zygote fusion is lacking in the species, the application of new methods for detecting genetic diversity data suggest the presence of genetic variability allowing inference that there is no obligate asexual production of seedlings. We further evaluate the effectiveness of Amphibolis seedlings within the broader context of seagrass reproductive strategies. We argue that understanding whether reproduction is sexual or asexual is critical: asexual reproduction implies clonal dispersal, favoring spatial colonization, while sexual reproduction supports gene flow and long-distance dispersal. We review existing observational data, placing Amphibolis at the extreme end of the spectrum of mobile propagule dispersal and how this strategy may optimize recruitment success in marine environments. Our findings underscore the necessity of recognizing sexual reproduction and wide-scale genetic dispersal as pivotal components of effective seagrass conservation.