Evolution and Biogeography of the Slipper Orchids: Eocene Vicariance of the Conduplicate Genera in the Old and New World Tropics

Abstract

Intercontinental disjunctions between tropical regions, which harbor two-thirds of the flowering plants, have drawn great interest from biologists and biogeographers. Most previous studies on these distribution patterns focused on woody plants, and paid little attention to herbs. The Orchidaceae is one of the largest families of angiosperms, with a herbaceous habit and a high species diversity in the Tropics. Here we investigate the evolutionary and biogeographical history of the slipper orchids, which represents a monophyletic subfamily (Cypripedioideae) of the orchid family and comprises five genera that are disjunctly distributed in tropical to temperate regions. A relatively well-resolved and highly supported phylogeny of slipper orchids was reconstructed based on sequence analyses of six maternally inherited chloroplast and two low-copy nuclear genes (LFY and ACO). We found that the genus Cypripedium with a wide distribution in the northern temperate and subtropical zones diverged first, followed by Selenipedium endemic to South America, and finally conduplicate-leaved genera in the Tropics. Mexipedium and Phragmipedium from the neotropics are most closely related, and form a clade sister to Paphiopedilum from tropical Asia. According to molecular clock estimates, the genus Selenipedium originated in Palaeocene, while the most recent common ancestor of conduplicate-leaved slipper orchids could be dated back to the Eocene. Ancestral area reconstruction indicates that vicariance is responsible for the disjunct distribution of conduplicate slipper orchids in palaeotropical and neotropical regions. Our study sheds some light on mechanisms underlying generic and species diversification in the orchid family and tropical disjunctions of herbaceous plant groups. In addition, we suggest that the biogeographical study should sample both regional endemics and their widespread relatives.

Evolution of the climatic tolerance and postglacial range changes of the most primitive orchids (Apostasioideae) within Sundaland, Wallacea and Sahul

“…Separation between the two genera occurred approximately 43-41 Ma ago (Gustafsson, Verola & Antonelli, 2010) while the diversification of currently recognized species started around 21 to 10 Ma ago (Guo et al, 2012). This pattern was also observed in other flowering plants, e.g., palaeotropical genus Pseuduvaria (Annonaceae; Su & Saunders, 2009).…”

Assessment of genetic diversity among four orchids based on ddRAD sequencing data for conservation purposes

“…The value of h was slightly higher than the value of p. Due to less SNP variation, the value of h and p was similar and according to the neutrality test statistics it tends to be negative. The slipper orchids were analyzed to trace the phylogenetic relationship among the orchids species based on chloroplastic gene sequences (accD, rbcL, matK, rpoC1, rpoC2, ycf1, ycf2, and ndhF) in PAUP version 4.0b10 (Guo et al 2012).…”

Orchid historical biogeography, diversification, Antarctica and the paradox of orchid dispersal

“…On one hand, the broad distribution of orchids (and their great diversity) might partly reflect their excellent dispersal, conferred by the dust-like seeds of almost all species. Such disjunctions are seen within genera or pairs of closely related genera in all orchid subfamilies except Apostasioideae, suggesting that they may often have arisen early enough for continental drift to affect present-day distributions (Dressler, 1981;Chase, 2001; but see Guo et al, 2012). Dressler (1981) suggested that only 34 orchid genera had been able to cross tropical oceans and establish disjunct distributions on continents long isolated from each other (i.e.…”