More than meets the eye: a morphological and phylogenetic comparison of long‐spurred,white‐flowered Satyrium species (Orchidaceae) in South Africa

Superficial similarities among unrelated species are often a result of convergent evolution and can cause considerable taxonomic confusion. A case in point is Satyrium eurycalcaratum , described here as a new species, which has been confused with several other Satyrium spp. with similar long‐spurred, white flowers. A phylogenetic analysis, based on molecular data, indicated that S. eurycalcaratum is not closely related to any of the species with which it has been previously confused. A comparative analysis of morphological characters in the seven South African Satyrium spp. with long‐spurred, white flowers showed that each of these, including S. eurycalcaratum , is characterized by a unique combination of traits. Despite the similarity in pollination syndrome characters, such as spur length and flower colour, variation in rostellum structure was particularly pronounced and four distinctive forms were present. There was no phylogenetic signal in patterns of interspecific rostellum variation, as some closely related species had different rostella, whereas some distantly related species shared similar rostellum structures. We therefore conclude that the use of rostellum traits in conjunction with phylogenetic evidence can resolve species delimitations among orchid species that share the same pollination syndrome. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 166 , 417–430.