Genetic diversity, population structure, and dispersal patterns of wild and cultivated Cycas szechuanensis in China

Cycas szechuanensis (Cycadaceae) is an endemic and nationally protected species in China. To inform scientifically grounded conservation strategies of this rare and endangered plant, 19 wild and cultivated populations comprising 622 individuals from all known distribution localities were sampled, and their genetic diversity and population structure were assessed using microsatellite markers. Fine-scale spatial genetic structure (FSGS) and parentage analyses were conducted to evaluate pollen and seed dispersal in the two largest populations, Taishan and Yangjiang. Our results revealed high genetic diversity in C. szechuanensis , especially in wild populations. Bottlenecks were not detected in most wild populations, but inbreeding was evident. The persistence of cultivated populations primarily relied on clonal reproduction. Four genetic groups were identified in C. szechuanensis , corresponding to their geographic distribution from south to north, with the southern group exhibiting the highest genetic diversity. However, the greatest genetic differentiation was not observed between the southernmost and northernmost groups. Parentage analysis revealed restricted seed dispersal and long-distance pollen flow, with the farthest assigned paternity reaching 1.9 km, resulting in clustered recruitment and significant FSGS in juvenile individuals. Adult FSGS was not consistently significant after accounting for sex. Based on these findings, we make recommendations for in situ and ex situ species conservation .