Distribution and dispersion patterns of individuals in nine species of Lepanthes (Orchidaceae)

Dispersion of individuals and patches of individuals are presented for nine species of epiphytic and lithophytic orchids in the genus Lepanthes. Patches is defined as the group of individuals present on a phorophyte. Mean number and standard error of reproductive individuals per patch range from 11.6 ± 5.1 in Lepanthes eltoroensis, to 45.5 ± 5.2 in L. rupestris. Most patches contain few reproductive individuals and usually a few patches had most of the adults. The distribution of patch sizes is skewed and most patches carry fewer individuals than the mean. Therefore means may not be an appropriate measure of central tendency as shown by mean crowding and mean patchiness indices. Mean distances between patches range from 4.8 m in L. rupestris to 95.5 m in L. dodiana. Most species have a mean nearest neighbor patch further than 50 m. A regular pattern of dispersion is often observed at distances of 5 and 10 m while at larger distances patches are more frequently aggregated. Large distances between patches and few individuals per patch suggest that small effective population sizes may be common in these orchids if gene flow is restricted.