Stronger effect of gastropods than rodents on seedling establishment,irrespective of exotic or native plant species origin |
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| Authors: | Lotte Korell Claudia Stein Isabell Hensen Helge Bruelheide Katharine N Suding Harald Auge |
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| Affiliation: | 1. Inst. of Biology, Martin Luther Univ. Halle‐Wittenberg, DE‐06108 Halle, Germany;2. Inst. of Biology, Germany;3. Dept of Environmental Science, Policy and Management, Univ. of California Berkeley, Berkeley, USA;4. Biology Dept and Tyson Research Center, Washington Univ. St. Louis, USA;5. German Centre for Integrative Biodiversity Research (iDiv) Halle‐Jena‐Leipzig, Leipzig, Germany;6. Dept of Community Ecology, Helmholtz Centre for Environmental Research ‐ UFZ, Germany |
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| Abstract: | Experimental evidence about how generalist consumers affect exotic plant invasions is equivocal, but most tests have been limited to few plant species, single herbivore guilds, and single locations. Using a seed‐addition experiment, we studied effects of gastropods and rodents on recruitment success of 37 exotic and 37 native plant species affiliated to three different functional groups (i.e. grasses, legumes and non‐legume herbs). We replicated our seed addition x herbivore exclusion experiment at multiple grassland sites, located within a few km of each other in two regions, coastal central California (USA) and southern Saxony–Anhalt (Germany). The two study regions differed in climate, land‐use, invasion history and species pools which allowed us to disentangle general from context‐specific effects. In both regions, herbivory by gastropods had a stronger impact on the proportion of recruited seedlings and the proportion of recruited species than rodent herbivory, but this effect was much more pronounced in California than in Germany. Especially, seedling recruitment of non‐legume herbs and legumes suffered from gastropod herbivory. Contrastingly, the effect of rodents was negative at the German sites and positive at the Californian sites, likely driven by context‐specific differences in the rodent assemblages. Across both study regions, exotics had higher seedling recruitment than natives, indicating that higher recruitment success constitutes an inherent feature of exotic species. After two years, more exotic than native species established at grassland sites in California while the opposite was true for the German grassland sites. Consistently across regions, native and exotic species did, however, not differ in their response to herbivory, suggesting that generalist consumers suppress recruitment and colonization of plant species irrespective of their origin. Our results demonstrate the importance of a multi‐species, multi‐site approach to separate general responses of exotic and native plants to generalist herbivory from local, regional or species‐specific peculiarities. |
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