Subpopulation genetic structure of a plant panmictic population of Castanea sequinii as revealed by microsatellite markers

Abstract

Castanea squinii Dode, an endemic tree widely distributed in China, plays an important role both in chestnut breeding and forest ecosystem function. The spatial genetic structure within and among populations is an important part of the evolutionary and ecological genetic dynamics of natural populations, and can provide insights into effective conservation of genetic resources. In the present study, the spatial genetic structure of a panmictic natural population of C. sequinii in the Dabie Mountain region was investigated using microsatellite markers. Nine prescreened microsatellite loci generated 29 33 alleles each, and were used for spatial autocorrelation analysis. Based on Moran s I coefficient, a panmictic population of C. sequinii in the Dabie Mountain region was found to be lacking a spatial genetic structure. These results suggest that a high pollen-mediated gene flow among subpopulations counteract genetic drift and/or genetic differentiation and plays an important role in maintaining a random and panmictic population structure in C. sequini populations. Further, a spatial genetic structure was detected in each subpopulation s scale (0.228 km), with all three subpopulations showing significant fine-scale structure. The genetic variation was found to be nonrandomly distributed within 61 m in each subpopulation (Moran s I positive values). Although Moran s I values varied among the different subpopulations, Moran s I in all the three subpopulations reached the expected values with an increase in distances, suggesting a generally patchy distribution in the subpopulations. The fine-scale structure seems to reflect restricted seed dispersal and microenvironment selection in C. sequinii. These results have important implications for understanding the evolutionary history and ecological process of the natural population of C. sequinii and provide baseline data for formulating a conservation strategy of Castanea species.