Exotic vertebrate and invertebrate herbivores differ in their impacts on native and exotic plants: a meta-analysis

Abstract

Herbivores modify various ecological processes including interactions between native and exotic plants that may affect invasion success by the exotic plants. It is unknown whether different types of exotic herbivores have similar effects on native and exotic plants. Using two distinct data sets, we ran meta-analyses to compare exotic vertebrate and invertebrate herbivore preferences for, and effects on performance and population sizes of native and exotic plants. We found that exotic vertebrate herbivores have positive effects on exotic plant performance and population sizes, and no significant effects on native plants. Exotic invertebrates have significant negative effects on performance and population sizes of both exotic and native plants. Vertebrates prefer to feed on native plants relative to exotic plants, while invertebrates prefer the exotic plants to native plants. Thus the exotic vertebrate herbivores may aid invasiveness of exotic plants, in accordance with the invasional meltdown hypothesis, while exotic invertebrate herbivores probably have no net effect on invasion process of the exotic plants. Invertebrate herbivore preferences for exotic plants support the biotic resistance hypothesis, as the native plants probably resist the invertebrate herbivory. We also tested an evolutionary logic that posits that herbivores with similar evolutionary history as plants will affect the plants less negatively than plants with which they have not co-evolved. Our results indicate that there is no consistent pattern in effects of exotic vertebrate and invertebrate herbivores on exotic plants with or without which they have co-evolved.

Trait-based plant mortality and preference for native versus non-native seedlings by invasive slug and snail herbivores in Hawaii

“…For example, native D. sandwicensis and M. polymorpha seedlings suffered very little damage and no mortality, whereas non-native P. cattleianum and A. elliptica seedlings suffered up to 30-50 % mortality from A. fulica and V. cubensis herbivory. There are many factors that can affect herbivory (e.g., plant characteristics, phylogenetic relatedness, herbivore behavior, plant species composition) and contribute to the lack of differences in levels of herbivory between native and non-native species observed in our study and in previous studies (Buschmann et al 2006;Funk and Throop 2010;Oduor et al 2010). For the seedling characteristics that we included in our analysis, leaf thickness and seedling height showed the greatest promise for predicting species mortality caused by V. cubensis and A. fulica.…”

“…Native floras on oceanic islands are highly susceptible to displacement and extinction following the introduction of non-native species (Kueffer et al 2010;Oduor et al 2010). Successful invasion of nonnative plant species in island ecosystems is commonly explained by the enemy release hypothesis, which states that non-native species experience higher survival, growth, abundance, or reproduction in their introduced range relative to their native range because they have escaped enemies (e.g.…”

Impacts of marine invaders on biodiversity depend on trophic position and functional similarity

“…1), a common metric in ecological meta-ana lyses (e.g. Salo et al 2007, Kaplan et al 2008, Gaertner et al 2009, Morales & Traveset 2009, Oduor et al 2010:…”

A conceptual framework for understanding arthropod predator and parasitoid invasions

“…Moreover, they recorded five times more direct trophic interactions among IAS for phytophagous insects on plants (131) than for predators on prey (23), suggesting that the likelihood of invasive alien plants facilitating invasion by phytophagous arthropods is greater than for invasive alien phytophagous arthropods facilitating invasion by arthropod predators and parasitoids. However, from a meta-analysis of the impact of alien herbivores on native and alien plants, Oduor et al (2010) found that alien invertebrate herbivores do not facilitate alien plant invasions, suggesting that facilitation of invasion via trophic interactions may be unidirectional. In contrast, invasive ants can both facilitate the invasion of alien sap feeding insects (e.g., Helms and Vinson (2003) and O'Dowd et al (2003)), or be facilitated in their own invasion by alien sap feeding insects (Helms et al 2011).…”