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

► Nei's genetic identity (I) has been used to solve taxonomic relationships. ► We provide a summary statistics for mean I values for orchid populations and species. ► Allozyme-based average I values for conspecific populations were 0.955. ► Allozyme-based average I values for congeneric species pairs were 0.453. ► We found that allozyme markers still are useful to delimit orchid species boundaries.