Dissertations, Theses, and Capstone Projects

Date of Degree

2-2014

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

Fabian Michelangeli

Subject Categories

Biology

Keywords

Conostegia, Melastomataceae, Morphology, Morphometrics, Phylogeny, Taxonomy

Abstract

The genus Conostegia comprises 77 species of shrubs and trees ranging from Central America to northern South America and the Caribbean. They are ecologically important as they provide pollen for native bees and fruits for birds. One of the main questions of this study is if the genus Conostegia is actually monophyletic. I address this question for the first time by gathering genetic data from four chloroplast regions and two nuclear ribosomal regions of DNA. Phylogenetic analyses of these data revealed that Conostegia is not monophyletic and that a group of species in the genera Clidemia and Miconia fall within it. It is noteworthy that species of these genera that fall within Conostegia are for the most part restricted to southern Central America. Morphological studies that include the use of anatomy, morphometrics, as well as different types of microscopy were conducted to attempt and identify potential characters that support a more broadly circumscribed Conostegia. These studies revealed several characters such as structured variation in herkogamy, a stele within the style and presence of mucilage inside the ovary in many species as potential synapomorphies for clades within the Conostegia clade. Not only are some of these characters useful but also novel in the systematics of the family Melastomataceae. Having identified a broader Conostegia clade, a taxonomic revision was conducted, including ample documentation of the morphology of all the species in the clade, descriptions and maps for 77 species. Lastly, taking advantage of the results of the molecular phylogeny as guidance, three main hypotheses were tested using morphometric approaches. The first hypothesis stated that diversification in floral morphology had indeed occurred within the Conostegia clade, all species of which are buzz pollinated. It has been said in the past that groups in which buzz pollination has evolved, tend to conserve their floral morphology and pollinators. That being said, no study has addressed how conserved flowers in these lineages actually are. This question was addressed by quantifying floral morphology over a broad sample of species within the Conostegia clade and found four major floral types. Transitions between floral types and their possible biological significance are discussed. The second hypothesis that was tested was that leaf venation in Conostegia is in fact quantifiable using geometric morphometrics and that such variation has a phylogenetic component. Variation in leaf venation, in particular the position of origin of the main parallel veins that characterize the family, has been historically used to distinguish groups of species. These different types of leaf veins have also been proposed as potential synapomorphies for major clades within the family. Possibly because variation in leaf venation is a continuous character, its use in Melastomataceae systematics has been difficult. A general framework is here proposed and it is shown that geometric morphometrics is an efficient tool for grasping leaf venation. In addition, it is shown that one of the three major clades in Conostegia is in fact different in its leaf venation from the other two clades and that the other two clades are similar to each other. The third and last hypothesis tested was that seeds in Conostegia can be quantified using elliptic Fourier analysis (EFA). The latter is a powerful geometric morphometric technique based on outlines. Traditionally, seeds in the Melastomataceae have been used in the systematics of many groups in a qualitative framework by coding binary or multistate discrete variables. For the first time a continuous framework using EFA was attempted. The results show that EFA can efficiently quantify many seeds in a small amount of time and summarize their variation using multivariate statistics in few axes. Furthermore, the EFA analyses revealed that one of the clades within Conostegia is significantly different than the other two but that the latter two are not different between each other. These results corroborate, in a different structure, the results obtained in the leaf venation analyses. In conclusion, identifying a natural or monophyletic group allowed for a revision of the taxonomy of a noteworthy component of Neotropical forests providing a tool to the general public for their identification. Subsequently, having clarity with respect to the relationships and identity of the species within the clade, biological questions were addressed experimenting with new available tools. This process yielded several discoveries.

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