Systematics of Monnina (Polygalaceae)

Endemic to the Neotropics, Monnina is the second largest genus in Polygalaceae, yet little is known about its phylogenetic history and morphological character evolution. Because Monnina demonstrates a great deal of morphological variability among species, a phylogenetic study was conducted to resolve where characters important in the diversification of the genus fit within an evolutionary framework. Bayesian and Maximum Likelihood analyses of nuclear ITS and plastid trnL-F regions were used to delimit the placement of Monnina in Polygalaceae and the infrageneric division within the genus. The results show that Monnina is a monophyletic genus subdivided into six clades. Ancestral character reconstructions point towards several synapomorphies in the genus. Indehiscent 1- to 2-seeded fruit is a synapomorphy for Monnina. Clade A is herbaceous, lacks extra-floral nectaries (EFN), and includes a tubular keel apex and 2-seeded dry fruits. The apex of the tubular keel is considered a synapomorphy for Clade A. Although, Clade B is also herbaceous, it lacks EFN in some species, glandular hairs and 2-seeded dry fruits. Glandular hairs are considered the synapomorphy for Clade B. Clade C includes herbaceous, shrub, and arborescent species that lack or exhibit EFN, and includes tri-lobed keels and 1- to 2-seeded fleshy or dry fruits. An irreversible reduction to 1-seeded fruits evolved in the ancestor to Clades D, E and F. While the external members of Clade D have similar characteristics to herbaceous members from Clade C, an internal subclade (D1) is denoted with fire adaptations and a distribution restricted to the Cerrado in southeastern South America. Clade E supports herbaceous plants with stipitate EFN (synapmorphic character). Clade F supports the greatest species range (northern Andes and Central America) and number of species (richness) that are characterized by shrub and arborescent species with fleshy fruits that lack EFN. Further phylogenetic studies that utilize molecular and morphological data will be required to elucidate biogeographical diversification rates.