Please use this identifier to cite or link to this item: https://hdl.handle.net/1959.11/15655
Title: Invasive ants compete with and modify the trophic ecology of hermit crabs on tropical islands
Contributor(s): McNatty, Alice (author); Abbott, Kirsten (author); Lester, Philip J (author)
Publication Date: 2009
DOI: 10.1007/s00442-009-1279-z
Handle Link: https://hdl.handle.net/1959.11/15655
Abstract: Invasive species can dramatically alter trophic interactions. Predation is the predominant trophic interaction generally considered to be responsible for ecological change after invasion. In contrast, how frequently competition from invasive species contributes to the decline of native species remains controversial. Here, we demonstrate how the trophic ecology of the remote atoll nation of Tokelau is changing due to competition between invasive ants (Anoplolepis gracilipes) and native terrestrial hermit crabs (Coenobita spp.) for carrion. A significant negative correlation was observed between A. gracilipes and hermit crab abundance. On islands with A. gracilipes, crabs were generally restricted to the periphery of invaded islands. Very few hermit crabs were found in central areas of these islands where A. gracilipes abundances were highest. Ant exclusion experiments demonstrated that changes in the abundance and distribution of hermit crabs on Tokelau are a result of competition. The ants did not kill the hermit crabs. Rather, when highly abundant A. gracilipes attacked crabs by spraying acid and drove crabs away from carrion resources. Analysis of naturally occurring N and C isotopes suggests that the ants are effectively lowering the trophic level of crabs. According to δ¹⁵ N values, hermit crabs have a relatively high trophic level on islands where A. gracilipes have not invaded. In contrast, where these ants have invaded we observed a significant decrease in δ¹⁵ N for all crab species. This result concurs with our experiment in suggesting long-term exclusion from carrion resources, driving co-occurring crabs towards a more herbivorous diet. Changes in hermit crab abundance or distribution may have major ramifications for the stability of plant communities. Because A. gracilipes have invaded many tropical islands where the predominant scavengers are hermit crabs, we consider that their competitive effects are likely to be more prominent in structuring communities than predation.
Publication Type: Journal Article
Source of Publication: Oecologia, 160(1), p. 187-194
Publisher: Springer
Place of Publication: Germany
ISSN: 1432-1939
0029-8549
Field of Research (FOR): 050103 Invasive Species Ecology
060202 Community Ecology (excl Invasive Species Ecology)
060808 Invertebrate Biology
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
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