Chin J Plant Ecol ›› 2006, Vol. 30 ›› Issue (1): 147-156.DOI: 10.17521/cjpe.2006.0021

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SUBPOPULATION GENETIC STRUCTURE IN A PANMICTIC POPULATION AS REVEALED BY MOLECULAR MARKERS: A CASE STUDY OF CASTANEA SEQUINII USING SSR MARKERS

WANG Ying, KANG Ming, HUANG Hong-Wen*()   

  1. Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
  • Received:2005-01-06 Accepted:2005-04-10 Online:2006-01-06 Published:2006-01-30
  • Contact: HUANG Hong-Wen

Abstract:

Castanea squinii, an endemic tree widely distributed in China, has great value both for chestnut breeding and in natural forest ecosystems. 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 natural population of C. sequinii in the Dabie Mountain region, including three subpopulations, was investigated using SSR markers. Nine prescreened SSR loci generated 29-33 alleles and were used for spatial autocorrelation analysis. Based on Moran's I coefficient, a panmictic population of C. sequinii was revealed that lacked spatial genetic structure in the Dabie Mountain region. These results suggested that high pollen flow among subpopulations counteracted genetic drift or genetic differentiation and played an important role in maintaining a random and panmictic population structure in the region. However, spatial genetic structure was detected in the geographic range of each subpopulation's scale (0.228 km) indicating that spatial genetic structure occurred at a fine scale within each subpopulation. All three subpopulations showed significant fine-scale structure. The genetic variation was not randomly distributed within 61 m in each subpopulation (Moran's I positive values). However, 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 distance suggesting a general patchy distribution in the subpopulations. The fine-scale structure seemed to be influenced by restricted seed dispersal and microenvironment selection. These results have important implications for understanding the evolutionary history and ecological process of natural populations of C. squinii and provide baseline data for formulating conservation strategies of Castanea species.

Key words: Castanea sequinii, SSR, Panmictic large population, Subpopulation, Genetic structure, Spatial autocorrelation, Genetic diversity, Gene flow