SYSTEMATICS AND REPRODUCTIVE BIOLOGY OF Tacca J.R. Forst. & G. Forst.

Abstract

The genus Tacca comprises an enigmatic group of tropical perennial acaulescent herbs. These plants are characterized by unique bracteate reproductive displays, which have excited interest in their reproductive biology. This dissertation examines aspects of systematics and reproductive biology in Tacca. The first chapter puts forward a phylogenetic study of relationships within Tacca J.R. Forst. & G. Forst., supplementing previous molecular phylogenetic and pre-cladistic taxonomic studies. Species, exemplar, and outgroup sampling are expanded. Multiple sources of data, molecular and morphological, are used for phylogenetic inference. This is used to interpret morphological evolution in various plant organs in the genus. The second chapter presents a comparative analysis of the genes and plastome structures of single representatives from Tacca and sister genus Thismia. The plastomes were sequenced using next-generation technology and generated using de novo assembly programs. The plastid genome of Thismia is among the smallest known quadripartite plastomes. The plastome of Tacca is more similar to other autotrophic members of Dioscoreaceae than to Thismia The third chapter documents an investigation into floral visitors of Tacca cristata Jack. Existing research on the pollination and reproductive biology of Tacca demonstrate low levels of outcrossing and likely autogamous selfing. Based on visual observations and field collections of insect visitors to natural populations, this study suggests that insect visitation may result in pollination of showy members of Tacca to some extent. The fourth chapter proposes to resurrect and lectotypify Tacca artocarpifolia Seem., a species currently in taxonomic synonymy. This is done based on examination and measurements made from photographs, live material, and herbarium specimens, including all named syntypes.