Phylogenetics, biogeography, and evolutionary trends of the Phalaenopsis sumatrana complex inferred from nuclear and chloroplast DNA

Phylogenetic trees inferred from the internal transcribed spacers 1 and 2 (ITS1 + ITS2) region from nuclear ribosomal DNA (nrDNA) and the intergenic spacer of atpB-rbcL from chloroplast DNA (cpDNA) were used to clarify the phylogenetics and evolutionary trends of the Phalaenopsis sumatrana complex. The P. sumatrana complex includes the two species P. sumatrana and Phalaenopsis corningiana as well as a problem species, Phalaenopsis zebrina, according to the concepts of Sweet (1980) and Christenson (2001). Based on the phylogenetic tree inferred from the ITS sequence, the accessions of P. sumatrana cannot be separated from those of P. corningiana. In contrast, the accessions of P. zebrina can be separated from those of both P. sumatrana and P. corningiana. However, analyses of the sequences of the atpB-rbcL spacer apparently cannot discriminate among these three species of the P. sumatrana complex. An inspection of the morphological characters of the plants of the P. sumatrana complex and the floral fragrances of P. zebrina can be used to separate it from both P. sumatrana and P. corningiana. Based on the molecular data and floral fragrances, P. zebrina perhaps should not be treated as a synonym of P. sumatrana. On the evolutionary trend of the P. sumatrana complex, P. zebrina was suggested to be the relative origin group of the P. sumatrana complex based on the phylogenetic tree and biogeography.