Significance of ecological vicariance and long-distance dispersal in the diversification of Carex sect. Spirostachyae (Cyperaceae)

Plant disjunctions have provided one of the most intriguing distribution patterns historically addressed by biogeographers. Carex sect. Spirostachyae (Cyperaceae) displays an interesting pattern of disjunction to evaluate these scenarios, with species occurring in the main continental landmasses and in oceanic islands of the two hemispheres. Internal transcribed spacer and 5'-trnK intron plastid gene sequences were analyzed to determine (1) the times of diversification using penalized likelihood, and (2) reconstructions of the regions using maximum likelihood and Bayesian approaches of origin of sect. Spirostachyae and internal main lineages. The times for the diversification of sect. Spirostachyae are dated to between the end of the Eocene and the Oligocene, whereas the two main lineages are dated to between the end of the Oligocene and the beginning of Miocene. The phylogenetic analyses reveal a Mediterranean-Eurasian center of differentiation for sect. Spirostachyae and subsection Spirostachyae, whereas no clear, single ancestral area could be inferred for subsection Elatae. Both long-distance dispersal and ecological vicariance appear to have been involved in the evolutionary history of the disjunct distribution of the main lineages of sect. Spirostachyae. These organisms appear to have a special ability to colonize remote areas (through transoceanic and interhemispherical colonizations), but special long-distance dispersal mechanisms are not evident.