Phylogenetic relationships and character evolution in Govenia (Orchidaceae)

Abstract

Govenia Lindl. (Orchidaceae) is a neotropical terrestrial deciduous genus of approximately 28 species of the higher Epidendroids. To determine if Govenia is monophyletic and what are the relationships among its species, a phylogenetic analysis based on a detailed morphological study was conducted. Furthermore, the evolution of eight vegetative and floral characters is explored and explained in relation to pollination syndrome. Three most parsimonious trees were retrieved from heuristic searches. Govenia is corroborated as monophyletic with six recognized groups: three monotypic groups (G. ciliilabia, G. powellii, and G. boliviensis) and three major clades (Purpusii, Capitata, and Superba groups). The Purpusii group is characterized by a well-developed rhizome, a solitary leaf, and 3–12 white flowers. The Capitata group is characterized by the lack of a rhizome, two leaves, and 10–30 white flowers. The Superba group is characterized by the lack of a rhizome, two leaves, and numerous yellow flowers. Two trends were identified in Govenia. The first trend is represented by plants with a rhizome and reduced leaf and flower numbers that occur in taxa from the Purpusii group. The second trend has been to increase inflorescence length and the number of flowers, to change flower colour from white to yellow with an ascending position of the column, and is represented in taxa from the Superba group. The evolution of floral characters leads to the hypothesis that there was a shift in pollinator from small bumblebees to larger bumblebees.