The genetic basis of tropical diversity

Work in my lab aims to discover the genes responsible for natural variation in plant form. These genes are the raw material of evolution and for plant breeding. A better understanding of them will permit informed decisions about the conservation of genetic diversity as well as understand the limits to diversity. Most of the Earth's diversity is found in the tropics. Working with tropical plant Begonia gives us a wide range of variation to study and will help explain how evolution produced such a large (1,6000 species) and variable group. We will make a genetic map of Begonia which will allow us to see where in the genome the genes controlling particular aspects of form or behavoir are found. We will be able to compare the organisation in Begonia to that in other species and find out how many genes control each trait and how strong the effects are. Comparisons of the links between traits and genes in the different Begonia species will help us understand how the very different forms have evolved. We will study natural variation in leaf shape. This is very variable between species and is part of a plant's adaptation to a particular environment as leaves are the site of photosynthesis and of much of the plant's interactions with the environment (sunlight, rain, insects etc...). Geneticists using a few species of model plants have been able to describe a number of genes that are involved in making a leaf. One group of genes, the KNOX genes are thought to be involved in making leaves with many leaflets instead of a single leaf, and a second group of genes (ARP genes) may control where the leaf blade grows out from its stalk. We wish to extend these studies to plants from the tropics, which harbour most of the world's plant species. Different species of tropical Begonias have many leaflets or a single leaf or have leaf blade all around the leaf stalk (like nasturiums) or just at the top (like an ordinary leaf). We intend to use genetics to determine if KNOX and ARP genes control leaf shape in Begonia. We will make a genetic map of Begonia which will allow us to see where in the genome the genes controlling particular aspects of form or behaviour are found. We will be able to compare the organisation in Begonia to that in other species and find out how many genes control each trait and how strong the effects are. We will also be able to see if KNOX and ARP genes are responsible for any of the variation in leaf form. Comparisons of the links between traits and genes in the different Begonia species will help us understand how such a diverse and large group as the Begonias has evolved.

A genetic map for Begonia will be produced using fluorescent AFLPs anchored using co-dominant markers. QTL mapping will determine the location and strength of loci affecting leaf morphology, in particular peltate or compound leaf development. Markers associated with these traits in the mapping population and markers derived from key developmental regulators of leaf form will be used for association maping in a number of F1BC1 populations to determine the conservation of associations between species. This work will determine whether key developmental genes identified in model species are involved in the variation of leaf form in the natural world and whether convergent evolution of the same traits within a lineage occurs by effects on the same loci. It will also provide a genetic map of a widespread, diverse tropical genus opening the field for studies of evolution in this group.