413 publications from this institution
Abstract In contrast to expectations of the enemy release hypothesis, but consistent with the notion of biotic resistance, we found that native generalist crayfishes preferred exotic over native freshwater plants by a 3 : 1 ratio when plants were paired by taxonomic relatedness. Native crayfishes also preferred exotic over native plants when tested across 57 native and 15 exotic plants found growing sympatrically at 11 sites throughout the southeastern USA. Exotic grass carp that share little evolutionary history with most of these plants exhibited no preference for native vs. exotic species. Analyses of three terrestrial data sets showed similar patterns, with native herbivores generally preferring exotic plants, while exotic herbivores rarely exhibited a preference. Thus, exotic plants may escape their coevolved herbivores only to be preferentially consumed by the native generalist herbivores in their new ranges, suggesting that native herbivores may provide biotic resistance to plant invasions.
Exotic species are widely assumed to thrive because they lack natural enemies in their new ranges. However, a meta-analysis of 63 manipulative field studies including more than 100 exotic plant species revealed that native herbivores suppressed exotic plants, whereas exotic herbivores facilitated both the abundance and species richness of exotic plants. Both outcomes suggest that plants are especially susceptible to novel, generalist herbivores that they have not been selected to resist. Thus, native herbivores provide biotic resistance to plant invasions, but the widespread replacement of native with exotic herbivores eliminates this ecosystem service, facilitates plant invasions, and triggers an invasional “meltdown.”
Seaweeds with free-living diploid and haploid stages might express recessive traits during haploid stages, or exhibit other differences, that would allow those stages to differ in fitness under different environmental conditions. Heteromorphic seaweeds are well known to have variable ecological traits associated with their morphological differences, but ecological differences among isomorphic stages have rarely been investigated. The chemically defended brown alga Diclyola ciliolala has a life history with isomorphic alternation of generations, allowing us to assess how chemical traits and susceptibility to herbivory differ among stages. Herbivorous amphipods and sea urchins consumed similar amounts of diploid sporophytes and haploid female and male gametophytes. Concomitant with similar palatability, the different life stages had similar concentrations of soluble protein and levels of chemical defenses. Thus, in addition to morphological similari-ties, the life stages of D. cilio/(/ta appear to share these ecological similarities.
Results of regression analyses testing for relationships between mean effect size and experimental plot size.
GPS location coordinates of Acanthaster individuals used in a tagging study in Viti Levu, Fiji
