Genetic diversity in fragmented populations of Berchemiella wilsonii var. pubipetiolata (Rhamnaceae)

BACKGROUD AND AIMS: Berchemiella wilsonii var. pubipetiolata (Rhamnaceae) is distributed in fragmented habitat patches in eastern China. It is highly endangered because of severe disturbance by anthropogenic activities. Information on genetic variation and structure is critical for developing successful conservation strategies for this species. METHODS: Allozyme variation of population genetic diversity and structure was investigated for a total of 98 individuals sampled from four extant populations using isoelectric focusing in thin-layer polyacrylamide slab gels. KEY RESULTS: Based on 20 loci scored from the nine enzymes examined, a high genetic diversity was detected at both the species and population level, while there was a loss of low frequency alleles (<0.1) in all populations. Most loci showed deviation from Hardy-Weinberg equilibrium due to excess of heterozygotes in all populations, suggesting that selection for heterozygotes has occurred in this species. The genetic diversity was mainly found within populations with a moderate genetic differentiation (F(ST) = 0.13), but the two geographically discontinuous population groups showed significant differences, with F-statistic values of 0.078 for the Zhejiang populations and 0.014 for the Anhui populations, respectively. CONCLUSIONS: It appears most likely that this species has experienced a recent decrease in population size, and genetic drift in small populations has resulted in a loss of alleles occurring at low frequency. The differentiation into two population groups reflects a population genetic consequence that has been influenced by the different land-use in the two regions. Some conservation concerns are discussed together with possible strategies for implementing in situ and ex situ conservation.