Phylogeny and evolution of basils and allies (Ocimeae, Labiatae) based on three plastid DNA regions.

ABSTRACT

A phylogeny of basils and allies (Lamiaceae, tribe Ocimeae) based on sequences of the trnL intron, trnL-trnF intergene spacer and rps 16 intron of the plastid genome is presented. Several methods were used to reconstruct phylogenies and to assess statistical support for clades maximum parsimony with equally and successively weighted characters, bootstrap resampling, and Bayesian inference. The phylogeny is used to investigate the distribution of morphological, pericarp anatomy, chemical, and pollen characters as well as the geographical distribution of the clades. Tribe Ocimeae is monophyletic and easily diagnosable with morphological synapomorphies. There are monophyletic clades within Ocimeae that broadly correspond to currently recognised subtribes Lavandulinae, Hyptidinae, Ociminae, and Plectranthinae. Only Lavandulinae has clear non-molecular synapomorphies. Several currently recognised genera are not monophyletic. Floral morphology consistent with sternotribic pollination is most common in Ocimeae, but there are independent departures from this model. Buzz pollination is likely in some species, the only postulated occurrence of this within Lamiaceae. Quinone diterpenoids and flavones in the leaf exudates differ in their distributions across the phylogeny and this could contribute to differences in the recorded medicinal as well as pesticidal uses of the species in the different clades. Mapping geographic distribution on to an ultrametric phylogenetic tree produced using non-parametric rate smoothing supports an Asiatic origin for Ocimeae. There are several secondary occurrences in Asia arising from the African Ociminae and Plectranthinae clades. Colonisation of Madagascar occurred at least five times, and New World colonisation occurred at least three times.