COS 100-1
Towards understanding plant invasions: Centaurea stoebe conquering North America

Thursday, August 14, 2014: 8:00 AM
Golden State, Hyatt Regency Hotel
Heinz MuellerSchaerer, Biology, University of Fribourg, Fribourg, Switzerland
Background/Question/Methods

Biological invasions still remain an enigma to ecologists and evolutionary biologists. A detailed study of the plant invader’s biology under different environmental settings to elucindate genotype by environment interactions and their consequences for populations growth my help to unveil the success of some plant species to invade new regions and habitats. I will illustrate this for the European native and highly invasive Centaurea stoebe (Asteraceae), which experienced an exceptionally high shift in cytotype frequency and climatic niche towards drier and warmer habitats during its invasion into North America. Thus, this represents a great opportunity to elucidate potential underlying life history and performance traits. Both diploid (EU2x) and tetraploid (EU4x) cytotypes occur in Europe, but only tetraploids have been recorded so far in North America (NA4x). In the talk, main emphasis will be given to disentangle pre-adaptation (through differences in traits and plasticity of EU2x vs. EU4x) from post introduction evolution (EU4x vs. NA4x) to explain differences in the spatio-temporal dynamics of the observed range expansions and invasion routes, using our extensive experimental data and ecological niche models.  

Results/Conclusions

In NA, we identified two focal introduction points both around 1890, one in the pacific North West (SW Canada) and one at the Atlantic coast (NY). Niche limits changed only little during the invasion in the East, but they largely expanded in the West, being more pronounced in disturbed habitats. Our results showed that multiple introductions, biotic release, plasticity (for early establishment) and directional selection allowed to conquer the novel environment within less than a century. Invasion into drier habitats in the West - constituting a niche shift - allowed to dominate the less competitive vegetation (C. stoebe as a “driver” in the West!). Both pre-adaptation and rapid evolutionary change contributed to the invasion of the tetraploid cytotype, but at the demographic level, it was only post-introduction evolutionary change through positive selection for traits related to increased reproduction in 4xNA vs. 4xEU that promoted the invasion success. I will conclude by outlining the strengths and limitations of this novel multi-forked approach and advocate its broader use for other study systems.