How traffic facilitates population expansion of invasive species along roads: The case of common ragweed in Germany

Abstract

1. Because common ragweed (Ambrosia artemisiifolia L., henceforth Ambrosia) has negative effects on human health, it is a common focus for management, which would benefit from a better understanding of the underlying mechanisms by which the species spreads. Road systems are known to be invasion corridors, but the conduit function of vehicles for the rapid spread of Ambrosia along roads and for population extension along roadside verges has not yet been demonstrated convincingly.2. To quantify the effect of different traffic volumes on the dispersal and population extension of Ambrosia, we used two approaches: First, by combining field experiments along roads with records of the seed rain around single plants, we simulated a combined dispersal kernel that revealed the interactions between primary dispersal and traffic-mediated secondary dispersal. Second, we recorded the seedling recruitment around isolated roadside populations over 2 years to determine how traffic-related parameters affect population extension. 3. The longest traffic-mediated dispersal distances exceeded those of primary dispersal by about one order of magnitude. Traffic volume had a significant positive effect on dispersal distances and on the lateral deposition of seeds on the road verge.4. Seedling recruitment around isolated roadside populations was significantly higher in the driving direction than against, but only at the distance where the major seed rain of traffic-mediated dispersal is to be expected according to the combined dispersal kernel (3-15 m). Synthesis and applications.This study isolates the effects of road traffic from confounding mechanisms (e.g. mowing machinery, propagule pressure from infested fields) on common ragweed (Ambrosia artemisiifolia L.) invasions. Results demonstrate the traffic-mediated dispersal in Ambrosia invasions as a routine and predictable process that facilitates population extension in the direction of traffic along roadsides, depending on traffic volume. This highlights the importance of prioritizing mowing along high use roads and mowing of isolated populations to prevent seed abscission and further spread of common ragweed. K E Y W O R D Scombined dispersal kernel, common ragweed, human-mediated dispersal, invasive species, population dynamics, road ecology, seed dispersal, traffic | 415Journal of Applied Ecology LEMKE Et aL.

Drivers of Ambrosia artemisiifolia abundance in arable fields along the Austrian-Hungarian border

“…This was followed by a gradual opening up of the state border, which eventually led to a very permeable green border with a high number of local crossings between neighbouring settlements after Hungary's accession to the EU (2004) and the Schengen treaty (2007). Traffic and transportation has also increased within both of these countries and also between them, which could provide further corridors facilitating the spread of ragweed (Joly et al 2011, Lemke et al 2019.…”

Total vegetation control: a comprehensive summary of herbicides, application timings, and resistance management options

“…Starting in the late 2000s, ever more cases of glyphosate-resistant weeds were reported along railroads and roadsides (Heap 2014(Heap , 2018 possibly resulting from movement from cropping systems to noncrop areas. Herbicide use patterns for both crop and noncrop areas have contributed to the selection of herbicide resistance weed biotypes; however, transportation corridors (railroads, roads) exacerbate the spread of these herbicide-resistant weeds (Lemke et al 2019).…”

Interaction of traffic intensity and habitat features shape invasion dynamics of an invasive alien species (Ambrosia artemisiifolia) in a regional road network

“…These vectors are commonly related to construction work, road maintenance and roadside management, agriculture, transportation industry and private vehicles. Depending on factors like vector velocity (Taylor et al 2012), seed accrual rate (Rew et al 2018) and seed adhesion time (Bajwa et al 2018) the achieved dispersal distances can range from some tens of meters to hundreds of kilometers for road vehicles (von der Lippe and Taylor et al 2012;Lemke et al 2019). An estimation from experimental data on dispersal by adhesion to vehicles revealed that approximately every hundredth seed transported by road vehicle is likely to be dispersed more than 5 km in road networks (Taylor et al 2012).…”