Phylogenetic relationships within the tropical dade of Orobanchaceae.

The tropical dade of Orobanchaceae contains approximately forty genera, typically with fewer than ten species each, and contributes significantly to the variation in floral morphology found within the family. Despite the economic importance of this dade, which contains three of four most important genera of crop parasites within the family, it has been under-sampled in previous phylogenies. We tested the monophyly of the tropical dade and its major genera using DNA sequences from the nuclear (internal transcribed spacer) and plastid (rpll6, trnT-L) genomes. The tropical dade was strongly supported as mono-phyletic in all analyses, and four main clades were recovered. The earliest diverging lineage from the remainder of the tropical dade is comprised of the shrubby genera Asepalum and Cyclocheilon, previously placed within Cyclocheilaceae. The atypical holoparasitic Alectra alba was shown to belong within the primarily holoparasitic Harveya, and the hemiparasitic Harveya obtusifolia was shown to belong to an otherwise holoparasitic lineage within Harveya. Both New World Melasma species were included here for the first time, and these were shown to be more closely related to the Neotropical hem iparasitic Escobedia than the African Melasma lineage. These results support a previous study recognizing Nesogenes within the tropical dade of Orobanchaceae rather than the separate family Nesogenaceae. [ABSTRACT FROM AUTHOR]