The effects of leaf toughness on feeding preference by two Tasmanian shredders
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The effect of leaf toughness on the diet preference of two shredding invertebrates, Caenota plicata (Trichoptera: Calocidae) and Antipodeus wellingtoni (Amphipoda) using native leaves, Eucalyptus globulus, Eucalyptus obliqua and Pomaderris apetala, and one exotic species, Alnus glutinosa (Alder) were tested in the laboratory. We hypothesised that the softer textured leaves of P. apetala and A. glutinosa would be preferred over the tougher eucalypt leaves. Leaf toughness was measured using a penetrometer and preference was calculated based on Chesson–Manly selection index. E. globulus, E. obliqua and A. glutinosa were all consumed to some extent; however, there was a clear avoidance of P. apetala by both shredder species. Only A. wellingtoni showed a clear preference for E. globulus. This study demonstrates that the toughness of leaves does not affect the consumption of leaves by A. wellingtoni and C. plicata. Hence there is no reason to assume a priori that the tougher Australian leaves would be avoided by local shredders as have been observed in northern hemisphere studies.
KeywordsMultichoice feeding trials Eucalyptus Pomaderris apetala Alnus glutinosa Shredders
This work was supported by the School of Zoology, University of Tasmania, Honours programme and in collaboration with Dr. Luz Boyero of James Cook University with support from the National Geographic Society (USA). We are grateful to Professor B.J.F Manly (formerly of University of Otago) for making available his software for computing the selectivity index and its confidence interval. We are thankful to all the volunteers who assisted in the field and to Daryl, Susanne, Adam and Sally. This research was carried out under permits granted by the Wellington Park Management Trust (07-84-46) and the Inland Fisheries Service of Tasmania.
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