Spatial autocorrelation of genetic variation in three stands of Ophiopogon xylorrhizus (Liliaceae s.l.)

Using spatial autocorrelation analysis, the spatial distribution of genotypes and gene frequencies at three allozyme loci, as well as the spatial distribution of family outcrossing rates were investigated in three stands of the tropical rainforest endangered perennial Ophiopogon xylorrhizus in Southwest China. Similar spatial patterns of the different allozymes were found both in individual stands and among stands, particularly at the whole distance classes. There were slightly different associations between like-homozygous and like-heterozygous plants. Most like-homozygous plant pairs exhibited a significant positive autocorrelation in shorter distance classes, and a random distribution or slightly negative autocorrelation in the following one or two distance classes. In contrast, a significant positive autocorrelation was found in the last one or two distance classes, indicating that like-homozygous plants were clustered in patches with a diameter of 5-10 m. Most like-heterozygous plant pairs exhibited a random distribution or a slightly negative autocorrelation in shorter distance classes, a significantly positive autocorrelation in the next one or two distance classes, and tended to a random distribution in the last one or two distance classes. Fifty-five per cent of unlike-homozygous plant pairs existed in different patches with similar patch sizes and these patches did not overlap. Highly consistent patterns were found in the spatial distribution of gene frequencies. Different genes existed in different patches, with a highly consistent average patch size in all three stands. Family outcrossing rates were randomly distributed in space. These results imply that it is not possible to sample the genetic variation of a population by merely conserving one part of it because the population is unlikely to be homogenous. (C) 2000 Annals of Botany Company.