DOI: 10.5061/dryad.s14s1
title: Data from: Stronger effect of gastropods than rodents on seedling establishment, irrespective of exotic or native plant species origin

description: 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.
description: Seedling and species
 recruitment of sown plant speciesSeedling and species
 recruitment data for exotic ("EXO") and native ("NAT")
 sown species were recorded in the field on 0.5 x 0.5 square meter subplots
 in seed addition and control subplots (separate column
 "Control") on 18 experimental sites in two regions (8 Central
 California ("CA"), 10 Central Germany ("GE")). Data
 were recorded in 2012 (census 1 and 2) and 2013 (census 3). Subplots were
 either located in rodent exclosure (Rod), gastropod exclosure (Gas) or
 control plots (Con). The number of added seeds per species ranged from 50
 to 175 (column "Number"), depending on the seed size. The number
 of sown species ranged from 17 (California) to 20 (Germany). Acronyms for
 the species can be derived by taking the first 3 letters of the genus and
 species names (see Table A 4).Seedling and Species
 recruitment.xlsx