Divergent adaptations in different parts of introduced range in tetraploid Vicia cracca

- Vicia cracca is known to occur in two cytotypes in the native range.
- Only polyploid Vicia cracca individuals occur in the invasive range.
- Tetraploids from the native range are not strongly differentiated from the diploids.
- Performance of tetraploids from the invasive range differs between regions.
- Plants from different areas in the invasive range could adapt to differential novel conditions.

Understanding causes of species invasiveness is a necessary condition for effective mitigation of invasive species. One of the key characteristics supporting species invasiveness may be species ability to adapt to wide range of environmental conditions. It has been hypothesized that increased ability to adapt to wide range of conditions may be related to polyploidization. Experimental studies comparing the ability to adapt to novel conditions between native and invasive populations of different cytotypes of the same species are, however, still largely missing.We used Vicia cracca, a species known to occur in two different cytotypes in its native range in Europe and being an important invader in North America. We investigate if known cytotypes of Vicia cracca from the native and invasive range differ in their ability to adapt to environmental variation. To do this, we grew plants of both cytotypes from the native and invasive range in a common garden and exposed half of the plants to experimental shading to simulate environmental variation potentially occurring at the localities of the species.The study confirmed previous expectation that only polyploid plants occur in the invasive range. The study, however, did not support the expectation that the tetraploids would be superior to the diploids from the native range or have better ability to cope with shading. The performance and plasticity of tetraploids from the invasive range was in most cases different from the European tetraploids and differed between the two areas in the invasive range. This may suggest that the tetraploids underwent strong post-invasive evolution and have adapted in different ways to the specific condition of the different parts of the invaded area. Alternatively, it may indicate that the invasive range was created by colonizers from different areas possessing distinct adaptations.