Abstract
Host race formation, the accumulation of genetic divergence within a species as a consequence of differential exploitation host-species, may eventually lead to sympatric speciation and is as such currently at the center of interest in evolutionary biology. Galerucella nymphaeae is one of the best examples of horst race formation, with strong among-races variation in morphology, life history, feeding and oviposition preference and with clear fitness consequences associated with exploitation of one of the four host plant species. While the requirements for host race formation are met and have been described in great detail in this species (Pappers 2001), we now take the logical next step towards the underlying processes that drive the observed reproductive isolation phenomena. To that end we will perform a hierarchy of experiments, starting with elucidation of the allopatric or sympatric origin of the observed host race differentiation, followed by estimation of the strength of positive assortative mating within races. Three hypothesis on the mechanism of host choice as driving force behind the reproductive isolation will be investigated (temporal niche differentiation, host signaling, and imprinting). Finally we will assess the contribution of mate choice to the reproductive isolation observed. The project will deliver the empirial dat, that are indispensable for testing the controversial theories (and their accompanying models) on host race formation and sympatric speciation, and will thus fill an important gap in current evolutionary theory.
Netherlands