The invasion of common milkweed (Asclepias syriaca) in sandy old‐fields – is it a threat to the native flora?

Abstract

Questions Common milkweed (Asclepias syriaca L.) is an invasive ‘super species’ that has invaded extensive areas in Europe, forming novel ecosystems. One study has reported neutral effects of common milkweed on the native flora of sand dune grasslands in Hungary after the removal of invasive pine plantation. However, the effects of common milkweed on native flora more generally are unknown. Focusing on the potential effect of milkweed, we tested the following hypotheses: (1) the cover of native grassland species decreases with increasing cover of common milkweed; and (2) native species with low specific leaf area (SLA), height, seed mass and clonal spreading ability (i.e. low competitive ability) are more likely suppressed by milkweed compared with natives with high competitive ability. Location Late successional sandy old‐fields invaded by milkweed in the Great Hungarian Plain (Kiskunság, central Hungary). Methods We recorded the cover of vascular plants in seven old‐fields; in each old‐field we sampled 12 plots including plots with different milkweed cover and control plots without milkweed. We used linear mixed effect models for exploring the effects of milkweed on the species richness and cover of native grassland species. To identify the common traits of the most affected native species, we used trait‐based analyses; we studied leaf–height–seed traits and clonal spreading ability. Results We detected no effect of common milkweed on total species richness, but it had a negative effect on the cover of grassland species. The negative effect of common milkweed was most pronounced on the cover of species with low SLA, low seed mass and low clonal spreading ability. Conclusions Our results suggest that native, late successional sandy grasslands invaded by common milkweed form undesirable novel ecosystems because of significant negative impacts on the cover of native grassland species, especially those species with low competitive ability. For these species, management of milkweed might be needed to ensure their persistence in sandy grasslands in this landscape.

Disturbance maintains native and exotic plant species richness in invaded grassy woodlands

“…; Kelemen et al. ). Weed invasion, on top of habitat loss, fragmentation and other threats, make grassy ecosystems some of the most threatened on the planet (Veldman et al.…”

Mapping an ecological network of green habitat patches and their role in maintaining urban biodiversity in and around Debrecen city (Eastern Hungary)

“…Surveying invasive species is especially important in urban environments, because many plants are able to escape from cultivation and can easily spread to other habitats due to their good dispersal ability (Lososová et al, 2012). As biological invasion is a global phenomenon threatening biodiversity (Catford et al, 2012), it is crucial to identify the endangered habitats and initiate steps to prevent the dispersal of invasive species (Botta-Dukát, 2008;Kelemen et al, 2016).…”

Invasive plant management must be driven by a holistic understanding of invader impacts

“…Kelemen et al. () found that the invasive common milkweed ( Asclepias syriaca L.) does not change species richness of Hungarian sand dunes (Fig. ).…”

“…Kelemen et al. () demonstrate how management conclusions may differ depending on how impact is assessed, thus reinforcing the need for more holistic approaches to understanding invader impact.…”