Phylogeny and Historical Biogeography of Pfitzer (Orchidaceae) Based on Nuclear and Plastid DNA.

The phylogeny and biogeography of the genus were evaluated by using phylogenetic trees derived from analysis of nuclear ribosomal internal transcribed spacer (ITS) sequences, the plastid L intron, the L-F spacer, and the B-L spacer. This genus was divided into three subgenera: , , and . Each of them is monophyletic with high bootstrap supports according to the highly resolved phylogenetic tree reconstructed by combined sequences. There are five sections within the subgenus , including , , , , and . The subgenus is phylogenetic basal, which suggesting that is comprising more ancestral characters than other subgenera. The evolutionary trend of genus was deduced based on the maximum likelihood (ML) tree and Bayesian Evolutionary Analysis Sampling Trees (BEAST). Reconstruct Ancestral State in Phylogenies (RASP) analyses based on the combined sequence data. The biogeographic analysis indicates that species were firstly derived in Southern China and Southeast Asia, subsequently dispersed into the Southeast Asian archipelagoes. The subgenera was likely derived after these historical dispersals and vicariance events. Our research reveals the relevance of the differentiation of in Southeast Asia and geological history. Moreover, the biogeographic analysis explains that the significant evolutionary hotspots of these orchids in the Sundaland and Wallacea might be attributed to repeated migration and isolation events between the south-eastern Asia mainland and the Sunda Super Islands.