Karyology of the genus E pidendrum ( O rchidaceae: L aeliinae) with emphasis on subgenus A mphiglottium and chromosome number variability in E pidendrum secundum

E pidendrum is one of the largest N eotropical genera of O rchidaceae and comprises approximately 1500 species. Only 2.8% of these species have been studied cytologically, demonstrating chromosome numbers ranging from n  = 12 in E . fulgens to n  = 120 in E . cinnabarinum . The present work evaluated the evolution of the karyotypes of E pidendrum spp. based on data gathered from the literature and from analyses of the karyotypes of 16 B razilian species (nine previously unpublished). The appearance of one karyotype with n  = 12 with one larger chromosome pair in subgenus A mphiglottium appears to have occurred at the beginning of the divergence of this lineage, and x  = 12 probably represents the basic number of this subgenus. E pidendrum secundum exhibits wide variation in chromosome numbers, with ten different cytotypes found in 22 B razilian populations, seven of which were new counts: 2 n  = 30, 42, 50, 54, 56, 58 and 84. Most lineages of E pidendrum seem to have been secondarily derived from one ancestral stock with x  = 20, as is seen in the majority of the present‐day representatives of the genus. © 2013 The Linnean Society of L ondon, Botanical Journal of the Linnean Society , 2013, 172 , 329–344.