In Northern Ireland, the amphipods Gammarus duebeni celticus (native) and G. pulex (invasive) coexist in some places, whilst in others the native species has been replaced by the invader. We explored the role of parasites in mediating interactions between these amphipods, which demonstrate mutual intraguild predation (IGP: predation between animals that also compete for prey). IGP and cannibalism can be important factors in structuring populations and communities. We investigated the effects of parasitism on rates of IGP between G. d. celticus and G. pulex and on cannibalism within each species by comparing functional responses (FRs: relationships between the use of a prey resource and its availability). Infection with the microsporidian Pleistophora mulleri caused an increase in IGP and cannibalism by G. d. celticus, which showed increased attack rates and reduced prey handling times. In contrast, infection with the acanthocephalan parasite Echinorhynchus truttae did not alter IGP or cannibalism by G. pulex. A prey preference experiment revealed that both amphipods were more likely to feed on heterospecific rather than conspecific prey, and this was also corroborated by the fact that overall IGP FRs were higher than cannibalism FRs. This may be selectively advantageous, as feeding on heterospecific prey removes possible competitors without the risk of consuming juvenile kin or acquiring parasites from infected conspecifics. Infection of the native G. d. celticus with P. mulleri enhanced IGP on the invasive G. pulex, which is likely to facilitate the coexistence of the 2 species.
Bibliographical noteFunding Information:
Acknowledgements. This work was funded by NERC studentship 200565413. All authors conceived and de signed the experiment, M.B. collected and analysed the data. M.B. and A.M.D. wrote the manuscript. All authors critically revised the manuscript. We thank Dan Warren for statistical advice.
© Inter-Research 2019
Copyright 2019 Elsevier B.V., All rights reserved.
- Biological invasion · Intraguild predation · Cannibalism · Microsporidia · Acanthocephala · Gammarus pulex · Gammarus duebeni celticus
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Aquatic Science