In this new post, Petr Dostál—from the Institute of Botany, Czech Republic—presents his work ‘Reproductive strategies of native plant populations altered by a plant invasion’. He highlights the connection between native and exotic plant species, discusses how evolution can progress faster than expected, and shares the greenness of central European grasslands. 

About the paper

A dump site, brownfield, or an abandoned garage are sites where you can find Tree of heaven, Japanese knotweed, or Giant hogweed during your city walks. These exotic plants sometimes escape and invade more natural habitats such as grasslands, forest edges, or wetlands. Unfortunately, the invasion of exotic plants is often coupled with decline of native species. They go extinct from invaded habitats not only because of competitive superiority of invaders, but also because some exotic plants significantly modify habitat conditions.

Not all native species are displaced after invasion—some of them persist, though in suboptimum conditions because they can tolerate a broad range of environments, including the one created by invaders. Survival of the others depends on their ability to adapt evolutionarily to novel conditions. So far, many studies have shown that exotic plants can evoke rapid evolutionary changes in native populations.

Despite increasing evidence of invasion-induced evolution in native plants, it remains unclear whether plant invaders—namely those that significantly change abiotic environment—can modify reproductive strategies of native plants. A decision whether plants allocate more energy to seeds or rather to vegetative propagation depends on environmental contexts, such as amount of soil nutrients, light availability, or disturbance intensity.

In this paper I explored whether the reproductive strategy of Veronica chamaedrys, a native perennial plant combining sexual and clonal reproduction, has changed due to alteration of light conditions by invasion of giant hogweed (Heracleum mantegazzianum). Specifically, I asked whether investments to clonal (vegetative) reproduction is a preferred option in populations from invaded sites characterized by low light availability.

About the research

Heracleum mantegazzianum, giant hogweed, is a monocarpic perennial umbellifer originating from the western Greater Caucasus that was introduced as a garden ornamental worldwide. With stems up to 5 m high and production of numerous seeds, it can form dense and extensive stands. Due to significant reduction of light availability, many native plant species disappear from sites invaded by giant hogweed. It was not, however, the case of Veronica chamaedrys, growing in the invaded grasslands in the western part of the Czech Republic.

In this study I used plant material of Veronica chamaedrys collected at 23 sites with and without presence of giant hogweed. Thanks to aerial photographs, I was also able to estimate age of hogweed populations at invaded sites (11, 28, 42 and 48 years on average). Further, light conditions were measured at the same sites. In the common garden experiment, I then linked differences in reproductive strategies of Veronica chamedrays populations with field-measured data on light conditions.

I found that invaded populations indeed increased investment to vegetative reproduction, a shift that was driven by the decreased light availability of sites invaded only recently. However, as light availability rebounded in the more advanced stages of giant hogweed invasion, so decreased allocation to ramets. 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 tens of years. However, whether and why clonal reproduction is more adaptive in shaded (invaded) conditions remained unclear in the research. It could be due to greater recruitment success of clonal propagules compared to seeds. Alternatively, clonal multiplication may be beneficial as ramets may forage for light, which is a limited resource after the giant hogweed invasion. Finally, it can also be assumed that a low-light environment may reduce pollinator abundance and their pollination activity, leading to reproductive failure. A more thorough field experiment examining how sexual versus clonal origin of the propagules contributes to individual fitness and population performance—conducted across different light conditions—could identify adaptive value of the two reproductive modes in distinct environments.

About the author

I am a scientist at the Institute of Botany of the Czech Academy of Sciences, Czech Republic. I am a plant ecologist with focus on biotic interactions. I am interested in how biotic interactions determine species distributions patterns at different spatial scales, drive species population dynamics and determine plant community diversity. More recently, I have started to explore how abiotic contexts modulate plant competitive interactions and species coexistence.

My research has been focused on the interactions between exotic and native organisms, namely plants of temperate grasslands. I have examined whether the success of invasive plants can be linked to a reduced load of enemies or to better competitive ability. I have also explored how native plants can adapt to the presence of invaders and to coexist with them.

Enjoyed the blogpost? Read the research here!