Morphometric circumscription of species and infraspecific taxa in Calopogon R. Br. (Orchidaceae)

The orchid genus Calopogon contains five species, the widespread C. tuberosus containing three varieties. The members of this small genus have a history of circumscriptional uncertainty, suggesting the need for further taxonomic evalua- tion. To determine characters distinguishing differ- ent groups and to examine their circumscription, we performed morphometric analyses on two different subsets of Calopogon, one of all the currently recognized species of the genus and another of only C. tuberosus, based on 40 vegeta- tive and floral variables measured from live plants. Principal components analyses (PCA) generally did not detect highly distinct groups, but canonical variate analyses (CVA) identified numerous char- acters that readily distinguish most of these groups, the least distinguishable of these being C. tuberosus var. latifolius. Furthermore, generalized patterns of similarity between taxonomic and geographic sub- divisions within C. tuberosus were further examined on a plant-by-plant basis using squared Mahalan- obis distances determined from the CVA of this species. Finally, using three different tests, the degree of morphological diversity was examined for each of the different groups of C. tuberosus, finding that the northern range of the species contained less diversity whereas the southern range generally contained more. We maintain the recognition of all Calopogon taxa except C. tuberosus var. latifo- lius, and do not recognize any new taxa based on our examinations of geographic partitions of the typical variety of C. tuberosus. However, morphol- ogy was observed to vary substantially over the geographic range of the typical variety and this species overall.