Abstracts (first author)
Using seedbanks to investigate contemporary evolution of plant reproductive traits facing global changes
Global changes raise numerous concerns about the fate of natural populations. Beyond ecological responses, global changes are also expected to impose new selective pressures on populations and hence represent an unprecedented opportunity to study evolutionary processes at contemporary scales. As a facet of global changes, pollinator decline has been reported at the global scale. Because plants usually depend on pollinators for their reproduction, plant reproductive traits (mating systems and floral traits) are expected to adapt to pollinator decline.
Detecting contemporary evolution of natural populations is however a complicated task. For instance, advance in phenology has been reported for numerous plant species (from weeds to trees) in response to climate change, but it remains to be determined whether the mechanisms for such changes involve genetic evolution or reflect plasticity only.
In our study we took advantage of the possibility to store viable seeds on a long period of time to analyze evolutionary changes from temporal samples. We benefit from seed conservation in optimal conditions by French Botanical Gardens to investigate rapid evolution of reproductive trait of the cornflower (Centaurea cyanus, Fam. Asteraceae), a self-incompatible crop weed. We study two generations of the same population (20 years apart) from a region where important reduction of both pollinator richness and density has been documented. Common garden experiments allow us to detect the effect of genetic evolution for major reproductive traits. Compared to the ancestral population, our results show that today’s, plants flower earlier but also produce bigger flowers with longer receptivity, and exhibit bigger floral display. We used neutral markers to sort out the possibility that such differentiation in reproductive traits be due to drift only. We propose that such changes be in part adaptation to pollinator decline, through increased pollinator attraction.