Abstract. DELFORGE, P. - Gymnadenia rubra WETTSTEIN 1889 and the taxonomy of apomictic Vanilla Orchids  [Natural. belges 92 (Orchid. 24): 87-116].
The history and context of the description of the Red Vanilla Orchid, Gymnadenia rubra, apomictic, and its allied, G. stiriaca, G. dolomitensis, G. minor, G. bicolor, and G. hygrophila, all apomictic too, are evoked. The descriptions of the last 4 species, recently published, are based almost exclusively on the subjective evaluation of some morphological characters without explanation of the basis for these statements nor attempts to investigate the extent to which these characters might be prone to environmentally induced variation. Furthermore, the morphological characters used for the delimitation of these 4 species do not work in many cases in the field. Taxonomy of agamous complexes present in 47 families of Angiosperms has always been considerated as very difficult. Surveys of apomictic species in numerous genera have found significant levels of intrapopulation genetic diversity, frequently a paradoxically high level, which is not significantly different from those of congeneric sexual relatives. As a result, the morphological intrapopulational plasticity of apomictic species can be larger than specific differences between two closely related species, because of differential responses among genotypes to a temporally and spatially fluctuating environment. This mecanism contributes to the maintenance of within-population genetic diversity and renders determination very difficult. More objective interpretations of morphological and genetical data of apomictic species complexes have led to grant species status to groups of related apomictic or partly apomictic variants rather than to individual morphotypes. As it seems that G. minor, G. bicolor, and G. hygrophila constitute only morphotypes (or ecomorphs) of G. rubra, they are better treated as forms. They are formally named here G. rubra f. minor, G. rubra f. rosea, and G. rubra f. hygrophila respectively. As the rank of variety seems more appropriate for G. dolomitensis, it is named G. rubra var. dolomitensis.

Key-Words: Orchidaceae, Gymnadenia, Gymnadenia sectio Nigritella, Gymnadenia rubra, Gymnadenia rubra var. rubra f. hygrophila (W. FOELSCHE & HEIDTKE) P. DELFORGE comb. et stat. nov., Gymnadenia rubra var. rubra f. minor (W. FOELSCHE & K. ZERNIG) P. DELFORGE comb. et stat. nov., Gymnadenia rubra var. rubra f. rosea (C. BOILLAT & V. BOILLAT) P. DELFORGE comb. nov., Gymnadenia rubra var. dolomitensis (TEPPNER & KLEIN) P. DELFORGE comb. nov. Taxonomy, apomixis.