The Evolution of Male Form and Function in Nightshade Flowers
The overall objective of this study is to investigate the diversity of anther form (male floral organs) in the genus Solanum to allow greater understanding of the relationship between anther form and buzz pollination. This project takes a multidisciplinary approach to investigating the anther traits found within the genus Solanum. We bring together both morphological and developmental genetic approaches. These constitute the two halves of this thesis. In the morphological section (chapter 2) the epidermal cell surface of the anthers of Solanum is examined using scanning electron microscopy (SEM). This is the first study to examine many of these species with SEM, and the first to focus specifically on the presence, location and type of epidermal cell outgrowths on the anther surface. How anther shape varies throughout the genus is examined by measurement and analysis of anther dimensions of living and herbarium specimens. These anther dimension measurements are subjected to principal component analysis (PCA) and then analysed in a phylogenetic context using phylomorphospace approaches. The way in which anthers are arranged with respect to one another within a flower, whether separate or in a fused anther cone, is recorded and plotted onto the phylogeny to identify independent evolutions of the anther cone trait. The method of attachment between the anthers in fused anther cones is examined through SEM to better understand from a morphological perspective how this trait is created at a microscale, also shedding light on potential aspects of the trait’s evolution. The molecular section (chapter 3) of the thesis approaches the investigation of an important anther trait from a developmental genetic perspective. This trait is the fused anther cone of Solanum lycopersicum (tomato), which is held together by a mesh of trichomes along the edges of the anthers. This work aims to better understand this trait by identifying genes responsible for its development. A candidate gene approach is taken, focusing on the R2R3 Myb subgroup 9 family of transcription factors. Function of the tomato members of this family is investigated through ectopic expression in tobacco and expression analysis during stages of floral development using semi qRTPCR. This study has contributed significantly towards the understanding of the diversity of anther traits found in the genus Solanum from a morphological, evolutionary and developmental genetic perspective and paves the way for further studies which investigate the importance of these anther traits to the interactions of buzz-pollinating insects with these plants
Nightshade, Solanum, Buzz pollination, MIXTA, Developmental genetics, tomato, phylomorphospace
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