A review of the use of genetic markers in orchid systematics with emphasis on allozymes

Abstract

Conservation of orchids is sometimes hampered by taxonomic problems, primarily due to the difficulty in delimiting species and/or genus boundaries. In this respect, a summary statistics for Nei’s genetic identity (I) for conspecific orchid populations and congeneric species pairs could be useful to delimit species boundaries. In this review, we summarized Nei’s genetic identity for conspecific populations and congeneric species by performing a literature survey. Average I values for conspecific populations ranged from 0.756 to 1.000 with a mean of 0.95 from 84 allozyme-based studies. In contrast, average I values for congeneric orchid species considerably varied, ranging from 0.000 to 0.978 with a mean of 0.453 from 190 allozyme-based studies. Most orchid species examined so far exhibit ‘diagnostic alleles’ at several allozyme loci, which strongly suggests that allozyme markers are still useful for delimiting species boundaries.