Molecular and cytological examination ofCalopogon(Orchidaceae, Epidendroideae): circumscription, phylogeny, polyploidy, and possible hybrid speciation

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Abstract
The orchid genusCalopogonR.Br. (Orchidaceae), native to eastern North America and the northern Caribbean, currently contains five species and up to three varieties. Using nuclear internal transcribed spacer (ITS) ribosomal DNA sequences, amplified fragment length polymorphisms (AFLPs), chloroplast DNA restriction fragments, and chromosome counts, we present a phylogenetic and taxonomic study of the genus.Calopogon multiflorusandC. pallidusare consistently sister species, but the relationships ofC. barbatus,C. oklahomensis, andC. tuberosusare not as clear. In the ITS analysisC. oklahomensisis sister toC. barbatus, whereas it is sister toC. tuberosusin the plastid restriction fragment analysis. Furthermore, all species were found to have chromosome numbers of 2n= 38 and 40, with the exception of the putatively hybrid‐derivedC. oklahomensiswith 2n= 114 and 120. The hexaploidy of the latter, plus the discrepancy in its position between the ITS and plastid restriction fragment trees, could suggest that it is of hybrid origin. However, the presence of unique morphological and molecular characters might indicate that it is either an ancient hybrid or not of hybrid derivation at all. Finally, using these molecular methods all taxa appear to generally be discrete groups, with the exception ofC. tuberosusvars.latifoliusandtuberosus, the former of which is best combined with the latter.
Funding Information
  • American Orchid Society