Petr Dostál

This is a plain language summary of a Functional Ecology research article which can be found here.

Some invasive plants can substantially change the abiotic environment of invaded ecosystems. Many native plants cannot tolerate these novel conditions and are doomed to extinction. There are also plant species that can persist in invaded habitats because they can adapt to suboptimum environments created by invaders. In this study, I explored whether the decrease in light availability, due to an invasion of giant hogweed (Heracleum mantegazzianum)—a tall exotic umbellifer—drove the evolution of reproductive strategies in a native perennial plant, germander speedwell (Veronica chamaedrys). This species can reproduce vegetatively by clonal ramets and also sexually by seeds; however, it is not clear which of the two reproductive modes dominates when light becomes scarce.

To explore this, I used plant material of V. chamaedrys from 23 sites with distinct invasion history (from uninvaded sites, and sites invaded up to about 50 years) and light conditions, and measured seed and ramet production under common garden conditions. Growing plants in the same light conditions allowed me to identify whether population differentiation in reproduction had a genetic rather than plastic basis. I found that invaded populations increased investment in vegetative reproduction—a shift that was driven by the decreased light availability of sites which were recently invaded. However, as light availability rebounded in the more advanced stages of invasion, allocation to ramets decreased. If plant size differences were controlled, increased investment in ramets was paralleled by reduced seed production.

These results suggest that an exotic plant invasion can drive evolution of reproductive strategies, here observed on a timescale of decades. This knowledge is important not only for the prediction of long-term invasion impacts, but also, more generally, for the provision of novel insights into the process of adaptation of plants to changing abiotic conditions.