Genetic Analysis of Quantitative Traits Contributing to Adaptive Evolution and Hybrid Speciation in Wild, Annual Sunflowers (Helianthus spp.): Exploring the Evolution Habitat Divergence in Helianthus paradoxus

Erwin Schrödinger Fellowship J 1960 The Evolution of Habitat Divergence in Wild Sunflowers Christian LEXER 09.10.2000 Habitat divergence is widely regarded as a key motivating force behind speciation in plants, and speciation resulting from hybridization processes represents an exceptionally useful model to investigate aspects of its evolution. The aim of the proposed work is to test vital hypotheses about the evolution of habitat divergence in the context of hybrid speciation in wild annual sunflowers (Helianthus spp.). One aspect will be to study the genetic architecture of traits contributing to the speciation process that gave rise to the wild sunflower Helianthus paradoxus. This hybrid species is isolated from its parental species, Helianthus annuus and Helianthus petiolaris, by altered habitat preference through novel adaptation (extreme salt tolerance), and by a shift in flowering time. Salt tolerance and flowering time are likely to be controlled by few quantitative trait loci (QTL) of major effect. Through a genome scan with molecular markers I will be able to study the genomic distribution of both classes of QTL relative to each other. This will allow me to test the hypothesis that linkage among QTL conferring altered habitat preference (salt tolerance) and QTL conferring assortative mating (flowering time) has driven the speciation process in this model system. Moreover, I propose to study the effect of the salt tolerance phenotype on fitness of an experimental population grown in natural "hybrid habitat". Fitness parameters will be recorded for this population at several stages of the plant life cycle, enabling me to study the effect of an ecologically adaptive trait conferring altered habitat preference (salt tolerance) on various components of fitness in the wild. The proposed experiments will allow me to explore the evolution of habitat divergence in a naturally occurring hybrid species from different perspectives, ranging from the genomic level to the level of the organism in its natural habitat.