Herbivory and dominance shifts among exotic and congeneric native plant species during plant community establishment.

Tim Engelkes,Annelein Meisner,Olga Kostenko,Wim H Van Der Putten,Mirka Macel,Elly Morriën

doi:10.1007/s00442-015-3472-6

Abstract

Invasive exotic plant species often have fewer natural enemies and suffer less damage from herbivores in their new range than genetically or functionally related species that are native to that area. Although we might expect that having fewer enemies would promote the invasiveness of the introduced exotic plant species due to reduced enemy exposure, few studies have actually analyzed the ecological consequences of this situation in the field. Here, we examined how exposure to aboveground herbivores influences shifts in dominance among exotic and phylogenetically related native plant species in a riparian ecosystem during early establishment of invaded communities. We planted ten plant communities each consisting of three individuals of each of six exotic plant species as well as six phylogenetically related natives. Exotic plant species were selected based on a rapid recent increase in regional abundance, the presence of a congeneric native species, and their co-occurrence in the riparian ecosystem. All plant communities were covered by tents with insect mesh. Five tents were open on the leeward side to allow herbivory. The other five tents were completely closed in order to exclude insects and vertebrates. Herbivory reduced aboveground biomass by half and influenced which of the plant species dominated the establishing communities. Exposure to herbivory did not reduce the total biomass of natives more than that of exotics, so aboveground herbivory did not selectively enhance exotics during this early stage of plant community development. Effects of herbivores on plant biomass depended on plant species or genus but not on plant status (i.e., exotic vs native). Thus, aboveground herbivory did not promote the dominance of exotic plant species during early establishment of the phylogenetically balanced plant communities.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-015-3472-6) contains supplementary material, which is available to authorized users.

Highlights

Present AddressKeywords Biological invasion · Phylogenetically controlled experiment · Community evenness · Biotic interactions · Enemy release
Exotic plant species can pose a major threat to the biodiversity and functioning of ecosystems worldwide, because some exotics change the cycling of carbon, nutrients, and water, as well as interactions with other plants and animals (Lodge 1993; Mack et al 2000; Richardson et al 2000).Oecologia (2016) 180:507–517During invasion, exotic plant species pass through several bottlenecks, including the introduction of propagules, colonization, establishment, and spread (Colautti et al 2004; Theoharides and Dukes 2007; Catford et al 2009)
In the work described in the present paper, we examined how aboveground herbivory can change the dominance of native and exotic plants in plant communities during plant community establishment in a riparian ecosystem