Genetic diversity and population structure of the endangered basal angiospermBrasenia schreberi(Cabombaceae) in China

Brasenia schreberi J.F. Gmelin (Cabombaceae), an aquatic herb that occurs in fragmented locations in China, is rare and endangered. Understanding its genetic diversity and structure is crucial for its conservation and management. In this study, 12 microsatellite markers were used to estimate the genetic diversity and variation in 21 populations of B. schreberi in China. A total of 61 alleles were found; assessment of allelic richness ( A r = 1.92) and observed and expected heterozygosity ( H O = 0.200, H E = 0.256) suggest lower genetic diversity compared to some endangered species, and higher variation was observed within populations (58.68%) rather than among populations (41.32%). No significant correlation between geographical and genetic distance among populations was detected (Mantel test, r = 0.0694; P = 0.7985), which may have likely resulted from barriers to gene flow ( N m = 0.361) that were produced by habitat fragmentation. However, Bayesian and neighbor-joining cluster analyses suggest a population genetic structure consisting of two clusters (I and II) or four subclusters (I-1, 2 and II-1, 2). The genetic structure and distribution of B. schreberi in China may have involved glacial refugia that underwent range expansions, introgression, and habitat fragmentation. The findings of the present study emphasize the importance for both in situ and ex situ conservation efforts.