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Title: A new look at factors influencing intraguild predation and cannibalism between native and invasive species
Author: Bunke, Mandy
ISNI:       0000 0004 7431 1055
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2018
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Biological invasions are a major ecological problem with freshwater environments particularly susceptible to their impacts. Invasive species interact with their native analogues and have direct and indirect impacts on their population dynamics. These interactions between natives and invasives are also influenced by parasitism. Cannibalism and intraguild predation are important interaction between individuals, because they can affect the dynamics of the prey population. They may offer the predator the advantage associated with the removal of potential competitors. In this thesis I use the predatory functional response approach to investigate the cannibalism and intraguild predation interactions between native and invasive amphipods and the influence of parasitism on these interactions. I explored cannibalism in the native Gammarus duebeni celticus and the invasive Gammarus pulex in Northern Ireland. The rate of cannibalism of juveniles by adults did not differ between the species. However, I found that in G. d. celticus this maximum consumption rate is doubled by an infection with microsporidian parasite Pleistophora mulleri. Investigation of cannibalism in G. pulex revealed that the effect of the acanthocephalan parasite Echinorhynchus truttae was influenced by other environmental factors: in the presence of habitat structure and of higher order predator cures, the cannibalistic maximum consumption rate of infected G. pulex to be double that of their uninfected counter parts. This means that parasite infection can have a negative impact on the population dynamics of its host and might even cause population collapse if too many juveniles are consumed. I also used the comparative functional response approach to compare intraguild predation between the native and the invasive species. Overall I found the IGP maximum consumption to be higher than the cannibalistic maximum consumption rate. This means that the invader can affect the population dynamics of the native and the native can affect on the population dynamics of the invader. No difference was found in the maximum consumption rate by adults of heterospecific juveniles. I found that parasitism causes the maximum consumption rate of G. d. celticus to increase while it does not impact on the maximum consumption rate of G. pulex. This may indicate that parasitism facilitates the coexistence between the native and invasive. I also investigated the IGP between the native Gammarus pulex and the recently arrived invader Dikerogammarus villosus in England. I used the comparative functional response approach to investigate how an increase in temperature, as might be caused by climate change, affects the interaction between the two species. Overall the maximum consumption rate of heterospecific juveniles was five times higher in the invader than in the native. An increase in water temperature caused the maximum consumption rate in the invader to increase while it showed a deceasing trend in the native's maximum consumption rate. This may mean that climate change might speed up the invasion process in this case. I also investigated how an parasitic infection in the native impacts IGP interactions in adults and found that increases the occurrence of IGP. In this case parasitism may facilitate the invasion process and the replacement of the native by the invader.
Supervisor: Dunn, Alison Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available