Phylogenetic relationships in the orchid genus Serapias L. based on non-coding regions of the chloroplast genome

A molecular phylogenetic analysis was performed on 14 species of the Mediterranean unrewardingorchid genus Serapias using sequences of four noncoding regions of chloroplast DNA. This study hasled to a new interpretation of the evolutionary relationships in this genus. The well-defined phylogenetictree supports a division of taxa into two main clades, each including two minor groups. The molecularrelationships found in this study differ from those defined by traditional systematic morphologicalassessments. By comparing the variation in sequence to variations in floral traits, we propose that thesplit in the two main lineages reflects an early differentiation of flower size, perhaps due to the shift fromallo- to self-pollination. Conversely, the relationships within each minor group do not reflect floral sizevariation; therefore, we presume that this diversification resulted from genetic drift, local selectionforces, and multiple, independent transitions towards self-pollination and polyploidy.