Master's Theses

Date of Award

2018

Document Type

Thesis

Department

Biology

First Advisor

Amy Berkov

Second Advisor

Fabian Michelangeli

Third Advisor

David Lohman

Keywords

Miconieae, Melastomataceae, floral evolution, floral symmetry, pollination, generalized pollination, pollination syndromes, diversification rates, BAMM, BiSSE

Abstract

Analyses of evolution of floral morphology and symmetry broaden our understanding of the drivers of angiosperm diversification. Integrated within a flower, labile floral characters produce different phenotypes that promote variable interactions with pollinators. Thus, investigation of floral evolution may help infer potential historic transitions in pollinator modes and ecological pressures that generated present diversity. This study aims to explore morphological evolution of flowers in Miconieae, a species-rich Neotropical tribe within family Melastomataceae. Despite a constrained floral plan, Melastomataceae manage to achieve a variety of floral traits appealing to diverse pollinator types, with majority of the species requiring specialized “buzz pollination” by bees. However, previous research in Miconieae documented several instances of convergent evolution of phenotypes associated with generalized pollination strategies. I explore morphological evolution of Miconieae in a phylogenetic context to understand how diversification relates to different phenotypes, and how common evolution of generalized pollination systems is within this tribe. I reconstructed the largest species-level phylogeny of Miconieae with maximum likelihood inference, and combined it with morphological data on a variety of floral characteristics for over 350 species scored from field photographs. I analyzed trait evolution with ancestral state reconstruction of discrete and continuous characters with R packages ape and phytools. Trait correlation was estimated with Pagel’s statistical method for discrete characters and with regression analysis of phylogenetically independent contrasts of continuous characters. I analyzed diversification in the tribe with Bayesian Analysis of Macroevolutionary Mixtures (BAMM) and explored the effect of character state evolution on diversification with Binary State Speciation and Extinction (BiSSE) approach. My analyses reveal rampant convergent and correlated evolution of multiple characters indicative of pollinator-mediated selective pressures. I confirm several parallel trends in evolution of generalized floral phenotypes. I find an association between generalization trends and increased diversification rates that may be related colonization of highland environments within the tribe.

Available for download on Friday, March 15, 2019

Share

COinS