Increasing abundance of an invasive C4 grass is associated with larger community changes away than at home

Prepared by Alida A. Hábenczyus, Csaba Tölgyesi, Róbert Pál, András Kelemen, Eszter Aradi, Zoltán Bátori, Judit Sonkoly, Edina Tóth, Nóra Balogh & Péter Török

Maps and photographs of the localities of the surveyed sites in the native (North American) and the non-native (Hungarian) ranges of Sand Dropseed. (a) Map of the North American sites; (b) map of the Hungarian sites; (c) Sand Dropseed in its native habitat in Montana, US (Photo credit: Robert Pál); (d) invaded open grassland in the Hungarian Kiskunság region (Photo credit: András Kelemen)

As a combined consequence of globalization and climate change, some species are able to escape their original distribution range, and not only enter a new area but also establish a stable population. Most of these species do not harm their new environment but a few of them can expand and severely transform the invaded ecosystem and related ecosystem services. This phenomenon is called biological invasion. It is, however, not always clear at the beginning of the spread of a newcomer species whether it really can transform the native vegetation or it will eventually find its place and get integrated in the vegetation without altering it significantly. Nature conservation interventions should obviously focus on the former type, and, for this, timely assessment of a potential invader is of paramount importance.

Here we evaluated the effect of Sand Dropseed (Sporobolus cryptandrus) in its recent non-native range in Hungary, Europe, and compared it to the effects in its native, North American range. Since there are only a handful of plant species that occur in both ranges, we applied a trait-based approach, which allows for capturing the functional effects of Sand Dropseed. We scrutinized traits related to plant metabolism, reproduction, interspecific interactions, and functional diversity, which is a general measure of ecological functionality. This functional approach gives the opportunity to define ecosystem services and disservices, and help translate them into monetary dimensions.

Tint-drawing of Sand Dropseed (Sporobolus cryptandrus). Illustration credit: Jana Táborská.

Our results revealed that an increasing abundance of Sand Dropseed is associated with heavier changes in diversity and functional characteristics in its non-native, European range, than in its native, North-American range, where a long history of co-evolution could allow for other plant species to live with Sand Dropseed. In the non-native range, the C4 metabolism of Sand Dropseed, which enables extreme water use efficiency, makes it a strong competitor even in harsh environmental conditions. As a result, an increasing abundance of Sand Dropseed leads to the loss of many plant species from the grasslands in its non-native range, but not in the native one. Besides impoverishing the species composition of the host plant communities, it reduces the abundance of floral resources for pollinators and makes the overall vegetation less palatable for herbivores. Losing natural pollinators may be of regional scale importance, concerning pollinator-dependent cultivated lands surrounding the stands of Sand Dropseed. Grasslands’ food provisioning capacity for cattle or sheep is also a crucial ecosystem service, which may be compromised by this invader. Hence, Sand Dropseed represents a high conservation risk, and tackling its spread must be a priority task in Hungary. A high level of vigilance is needed in other European grasslands, too, where it may appear in the future.

This is a plain language summary of the paper by Hábenczyus et al. published in Applied Vegetation Science (