Allozyme variation among and within eleven Orchis species (fam. Orchidaceae), with special reference to hybridizing aptitude

The electrophoretic variability of nine enzymatic loci was studied in 31 populations of eleven species of the genus Orchis (fam. Orchidaceae). This orchid group shows a higher degree of genetic variability ( ) than reported by Gottlieb (Progr. Phytochem. 7:1–46, 1981) for other outbreeding plant species ( ).Furthermore, the Nei coefficients of genetic identity show a higher biochemical-genetic similarity between species pairs of which we found the hybrids ( ) than between other species pairs ( ). These results seem to indicate a correlation between hybridizing aptitude and degree of genetic similarity. High values could be partially attributed to the presence of a gene flow between two species which, by hybridizing, would join their genetic pools. But they could also indicate that hybridizing species are not well differentiated: the isozyme similarity would reflect a more general similarity of the gene pool that could lead to hybrid formation.