My interest is in the genetic basis of natural variation. Leaf form is very responsive to the environment - both by plasticity during the lifetime of a single plant and genetically, as demonstrated by the differing leaf form of closely related species living in different habitats. The pathways controlling leaf form, therefore, will show to a high degree the effects of selection and adaptation. I am based at the Institute of Molecular Plant Sciences and in the Royal Botanic Garden Edinburgh, allowing me to use the expertise in developmental biology and Arabidopsis genetics at IMPS and the taxonomic and phylogenetic expertise of the RBGE and its extensive collections of living plants.
Although Arabidopsis is used primarily as a genetically uniform model plant there is a considerable amount of variation within the species and stock centres have collections of accession from throughout the world. The completed genome sequence of Arabidopsis has allowed many of these accessions to be genetically characterised. This allows the phenotypic differences between accessions to be mapped using quantitative trait analysis. Ecological studies have shown that the shape of the leaf margin is associated with climate, and Arabidopsis ecotypes show extensive variation in this trait. I am using QTL mapping to discover the genetic basis of the differences in leaf margins between accessions. As well as identifying new genes involved in leaf development, by using multiple populations for mapping this work will reveal whether the same changes have been selected each time this trait has evolved.
I am also studying the evolution of variation between species. Begonia is a huge genus (>1,400 spp.) found throughout the tropics. Large living and herbarium collections of Begonia are held at RBGE and the Botanic gardens in Glasgow and have been the subject of detailed study in phylogeny, population genetics and development in recent years. This genus shows a great diversity of leaf form, encompassing simple, serrated, lobed, peltate (Nasturtium-like) and compound (the leaf divided into leaflets). Peltate leaves have evolved at least eight times in this genus and compound leaf forms at least three times (Laura Forrest PhD Thesis, Glasgow 2000). The figure below shows some of the members of section Gireoudia which display a particularly wide range of leaf form and are readily hybridisable. Using in situ analysis of gene expression, molecular phylogeny of leaf developmental genes and by mapping traits in the F2 of hybrids I hope to determine the genetic basis of the differences in leaf form between some of these species.