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Evolution and consequences of floral signaling in plants

Final Report Summary - FLORSIGNALS (Evolution and consequences of floral signaling in plants)

Floral signals mediate interactions of plants with different animals, for example pollinators (mutualists) and herbivores (antagonists), and are thus of key importance for ecosystem functioning as well as for human nutrition. In this project we studied the functions and evolution of floral signals using different interacting animals. We showed that specific floral signals are associated with floral rewards and these are used by pollinators to find the most rewarding flowers. The same signals are also used by herbivores, thus imposing conflicting selection on them. This has various consequences, on the one hand, such signals can be decreased through phenotypic plasticity after herbivore attack, on the other hand, plant populations adapt to produce different strengths of such signals, depending on the abundances of mutualists and antagonists in natural habitats. Adaption of plants to different pollinators was studied by using experimental evolution. Here it was shown that different pollinators select for different signals and mating system, and already after 9 generations, plants evolve strong differences in these traits under such divergent selection. We have also shown that floral volatile signal variation has a significant genetic component, i.e. heritability, and models can be used to successfully predict scent evolution using heritability, selection and genetic variance/covariance (G matrix). Selection on few volatiles can, as a consequence of pleiotropies, lead to changes in gene expression in a range of other genes as well. Thus floral traits do not evolve in isolation but in a concerted manner. Whereas in a generalized pollination system, pollinator adaptation does not lead to floral isolation, this differs in specialized pollination system, where few scent compounds, mediate the attraction of specific pollinators and lead to strong reproductive isolation mediated by the attraction of different pollinators.