Systematics of the neotropical genus drymonia (gesneriaceae)

Abstract

Understanding the patterns and processes that have shaped the current distribution of biodiversity in the Neotropics is a major focus in biological research. Robust phylogenetic hypotheses are fundamental to infer these patters, and address hypotheses of character and range evolution. Drymonia, which is the third largest genus of Neotropical Gesneriaceae, encompasses remarkable variation in floral, fruit and growth habit traits. This research explores several aspects of the systematics and evolutionary biology of the genus Drymonia. First, we evaluate the evolutionary context for changes in corolla throat constriction across the genus. We show that open, bell-shaped (campanulate) corollas are supported as the ancestral state for Drymonia, with multiple independent origins of constriction in the corolla tube. From observations of pollinator’s visits, we infer an association of hummingbird pollination with constricted corolla tubes, suggesting that narrowing evolved as a barrier mechanism to limit the visitation by bees. Second, we propose an extensive taxon-sampled phylogenetic hypothesis for Drymonia and its closest relatives, which are part of the core Andean-centered clade. The monophyly of Drymonia is strongly supported. However, the infra-generic relationships, and the relationships within the core Andean-centered clade remain poorly supported. We investigate the historical biogeography of the genus, and estimate a Tropical Andes origin. Drymonia rapidly diversified in the Andes during the late Miocene with subsequent movements to Central America, the Pacific Andean slopes, and more recently to the Amazon. We explore patterns of morphological evolution in five characters. The estimated ancestral states for Drymonia are entomophilous syndrome, funnelform/campanulate corolla, anther dehiscence by basal pores, fleshy capsules, and climber growth. Independent origins of ornithophilous corollas, berries, and epiphytism suggest a very dynamic pattern of morphological evolution in Drymonia. We suggest that a combination of interaction with pollinators, and adaptation to different habits created by the Andes orogeny may have played an important role in the diversification of the group. Finally, we focus on the taxonomical aspects of the genus. Based on the study of ~3600 herbarium specimens, and additional living plants in the field and botanical gardens, we discovered five new species of Drymonia, which are described here.