Abstract: The spatial structure of genetic variation is an important part of evolutionary and ecological genetic processes in natural populations of plants, and may provide deep insights into the conservation of species. In this paper, the spatial distribution patterns of genetic variation of two closely related sympatric species, Actinidia chinensis and A. deliciosa, were investigated using SSR markers. A total of 104 alleles was scored by nine pairs of SSR primers in two natural populations, and the alleles with frequency ranging from 20% to 80% were chosen and then used to calculate Moran’s I spatial autocorrelation coefficients for the two individual species or the species complex (A. chinensis/A. deliciosa) based on equal numbers of paired samples. Over half of the alleles were found to have a random distribution pattern within populations, while a large proportion of alleles occurred as cline, depression, double depression or intrusion patterns (29.6–48.0% within populations of each individual species, 51.0–44.7% for the two species complex, in Xixia of Henan and Shangnan of Shaanxi populations, respectively). This suggests that a moderate spatial structure of genetic variation occurred within the natural populations of the two species. Moreover, a similar spatial distribution pattern of genetic variation was found within the two populations of each individual species and in the species complex at the two sampled loca-tions. The results showed that allelic variation for individual plants within 100 m (and especially within 30 m) distance had significant positive correlation, but changed into a negative correlation with increasing distance, which may imply that the distances for pollen dispersal is about 100 m, and seed dispersal might be restricted to within 30 m. The different spatial structures of genetic variation of Actinidia natural populations were influ-enced by a combination of the biological characteristic of pollination, seed dispersal, and natural habitat. The restricted seed and pollen dispersal, and intervention of human activities were the main factors influencing the spatial pattern. The results should be of importance for further understanding of population genetic structure, population spreading and phylogeography in Actinidia, and provide baseline data for the conservation and management of these species, especially for sampling strategies for ex situ conservation.

Key words: rhizobial resource, leguminous crops, nitrogenase activity