Floral fragrance variation in Cypripedium: Implications for evolutionary and ecological studies

The floral fragrance compositions of eight species (including two putative varieties) of Cypripedium were determined by GC-mass spectrometry. Substantial diversity in fragrance compound skeletal type was detected and included benzenoid, terpenoid and fatty alcohol derivatives. Qualitative fragrance variation was investigated within and between two populations of Cypripedium calceolus var. parviflorum. The clustering algorithm, unweighted pair group method arithmetic average (UPGMA) was used as an objective analytical means to assess population-level fragrance variation relative to species-level variation. Members from two populations of C. calceolus var. parviflorum formed a single cluster with similarity values ranging from 0.36 to 1.0, indicating a high degree of biogenetic uniformity among some individuals as well as substantial relative divergence between others. The results of this study indicate that conclusions about taxonomic or pollinator relationships, based upon limited infraspecific sampling of floral fragrance, should be considered tentative until the extent of population variation is investigated.