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

<p><strong><span>Aim</span></strong><span><strong>:</strong> We evaluated the stands of the invasive grass, <em>Sporobolus cryptandrus</em> in its native North American and non-native European range, where it is a recent invader. Our aim was to reveal how the species' increasing abundance affects functional diversity and ecosystem service provisioning capacities of plant communities in both ranges.</span></p> <p><strong><span>Location</span></strong><span><strong>:</strong> Sand</span> <span>grasslands in the Kiskunság, Hungary, and in Montana, USA.</span></p> <p><strong><span>Methods</span></strong><span><strong>:</strong> All vascular plant species and their relative abundances were recorded </span><span>in a stratified random manner in 1</span><span>m×1m </span><span>plots in</span><span> each range, using the following cover categories of <em>Sporobolus</em> as strata: 1–25%, 26–50%, 50–75%, and 75–100%. The functional characteristics of the plant communities of the two continents were compared. We performed the comparisons of the communities both with and without including Sporobolus.</span></p> <p><strong><span>Results</span></strong><span><strong>: </strong>Increasing <em>Sporobolus</em> cover resulted in a lower functional diversity and species richness, reduced average specific leaf area, and increased height of the whole plant communities in both ranges but these effects were significantly stronger in the non-native stands. <em>Sporobolus</em> also negatively affected the cover of insect-pollinated plant species and the proportion of native perennials, switching the rest of the community from perennial-dominated to annual-dominated. In the plant communities without <em>Sporobolus</em>, increasing <em>Sporobolus</em> cover led to higher specific leaf area and seed mass in both ranges, but average height was decreasing along the <em>Sporobolus</em> abundance gradient in the native range, while it was increasing in the non-native range. </span></p> <p><strong><span>Conclusions</span></strong><span><strong>:</strong> The spread of <em>Sporobolus</em>, away from its native range, leads to the impoverishment of host communities and compromises the biomass and floral resource provisioning capacity of the vegetation to higher trophic levels. Tackling the spread of this new invader should therefore be a priority task.</span></p>