Spatial genetic structure in populations of Cymbidium goeringii (Orchidaceae)

The fine-scale population genetic structure of Cymbidium goeringii (Orchidaceae), a small herbaceous perennial, was analyzed using spatial autocorrelation statistics. All visible individuals,(138 and 110, respectively) within 20 x 40 m areas of each of two populations were sampled and their locations were mapped. Individual plants were genotyped for 14 allozyme loci, and Moran's spatial autocorrelation statistics were calculated for a large numbers of alleles. Values of Moran's I-statistics were statistically significant in 35 (19.4%) to 36 (16.4%) of 180 and 220 cases respectively for the two populations, and the overall correlograms were significant for 11 (61.1%) to six (27.3%) of 18 and 22 alleles, respectively. The results also indicate that genetic similarity was shared among individuals within up to a scale of 14 m distance, and this is partly due to a combination of limited pollen dispersal and long distance seed dispersal by wind. One important implication is that, from the viewpoint of conservation genetics, sampling within populations should be conducted at 14-16 m intervals in order to optimize the genetic diversity in collections from population.