IS MANDEVILLA (APOCYNACEAE, MESECHITEAE) MONOPHYLETIC? EVIDENCE FROM FIVE PLASTID DNA LOCI AND MORPHOLOGY¹

In order to test the monophyly of Mandevilla Lindl., the largest genus in tribe Mesechiteae (Apocynaceae, Apocynoideae), and its affinities to other genera in the tribe, maximum parsimony analysis was conducted on a data set comprising DNA sequences from five plastid loci (rpl16, rps16, and trnK introns; trnSGCU-trnGUUC intergenic spacer; and matK gene), as well as morphological data for 65 taxa of Mesechiteae (48, Mandevilla) and nine taxa from other tribes of the subfamily. Mandevilla, as circumscribed by Pichon, was found to be monophyletic, whereas Woodson's circumscription proved to be polyphyletic. Thus defined, Mandevilla forms a strongly supported clade that can be divided into six clades of species groups. Most of the infrageneric taxa of Mandevilla proposed by Woodson and Pichon are polyphyletic. Many of the diagnostic characters previously used to define taxonomic groups are shown to have arisen multiple times, rendering them unsuitable for classificatory purposes. The similar growth form and tubular flowers of Macrosiphonia Müll. Arg. and Telosiphonia (Woodson) Henr., two geographically disjunct segregates, represent the most extreme case of parallel evolution within Mandevilla, with their striking similarities most likely correlated to colonization of open, dry habitats and pollination by hawkmoths.