Projectdetails

The evolution of orchids has been shaped dramatically by pollinators affecting a huge diversity of changes in floral morphology, especially in the shape of the column, anther and pollinia. I propose to apply a series of techniques to increase understanding of developmental mechanisms when formulating evolutionary explanations for pollinia shape variation using the speciose and morphologically diverse genus Bulbophyllum as model system: (l). Expansion of the existing molecular phylogeny of Bulbophyllum to 100 species to reconstruct the evolution of pollinia deposition in this genus. (ll), Screening of gene expression of B function genes not yet identified in petaloid monocots in different developmental stages of Bulbophyllum flowers from species with different pollinia numbers with/without stipes using RT-ISPCR and cDNA libraries. (lll). Test for a causal relationship of spatial and temporal expression patterns and mutations in newly identified B function genes with evolvement of pollinia morphology. If the two/four pollinia and stipes absence/presence transitions represent unique events, then these abrupt morphological innovations would conform to a model of evolution that proceeds by rare changes. If, however, morphological transitions are homoplastic, genetically controlled developmental variability would allow repeated variation of pollinia morphology. If stamen identity in orchids is determined in a similar way as in dicots, genes specifically expressed during pollinia development should share sequence motifs with B function genes of model species. If these genes are controlling pollinia number and stipes presence, changes in their expression and sequences should correlate with tracks followed by different pollinia morphologies during the evolution of Bulbophyllum.