Rapid adaptations to novel environments: the example of dispersal in urban environment

Background/Question/Methods

Dispersal ecology and the spatio-temporal dynamics of populations are closely linked to habitat structure, which in turn conditions the adaptive response of dispersal traits. Human-altered-habitats represent interesting models to analyse the evolutionary ecology of dispersal.  We used the recent colonization of the heterocarpic plant Crepis sancta (Asteraceae) in urban environment as a model system. Specifically, we studied dispersal evolution and metapopulation processes in a typical urban habitat: the small patches on sidewalks around trees, where more than hundred weeds (mostly annuals) grow.  We first demonstrate a colonization/extinction dynamics for the urban populations of Crepis sancta thanks to Stochastic Patch occupancy Modelling. Second, the urban system was used as an evolutionary experience to analyse adaptive change in dispersal traits.

Results/Conclusions

Compared to large rural unfragmented populations (around the cities), we showed that seed dispersal is significantly reduced in urban patchy populations, which is in line with the high cost of dispersal for dispersing seeds measured in the city. Finally, quantitative genetic tools allowed quantifying the evolutionary process. The quantitative genetics model revealed that dispersal shift is consistent with short-term evolution that occurs over 10–20 generations of selection driven a high cost of dispersal in the city. The urban system has turned to be a simple and manageable metapopulation system and provided the first experimental demonstration for a rapid evolution of dispersal in plants as a consequence extreme fragmentation.