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Linking parasitic plant-induced host morphology to tritrophic interactions

Mooney, Kailen A.; Geils, Brian W.; Linhart, Yan B. 2006. Linking parasitic plant-induced host morphology to tritrophic interactions. Annals of the Entomological Society of America. 99(6): 1133-1138.

We investigated the tritrophic interactions among southwestern dwarf mistletoe [Arceuthobium vaginatum (Willd.) Presl subsp. cryptopodum], mistletoe herbivores, and host pine (Pinus ponderosa Dougl. ex Laws. and C. Laws. variety scopulorum Engelm.) associated predators. In an observational study, we characterized differences in pine-associated arthropods and pine branch morphology between branches either parasitized by mistletoe (brooms) or not visibly infected. Compared with noninfected branches, brooms had a more reticulate branching structure, collected 36 times more dead needles and supported 1.7 times more arthropod predators. In a manipulative field experiment, we investigated whether pine-associated predators fed upon lepidopteran herbivores of mistletoe and thereby reduced herbivore damage to the parasite. Over a 30-d trial, herbivores fed upon approximately two-thirds of available mistletoe shoots. Predator removal increased herbivore survival by 56% but had no detectable effect on the level of herbivory damage. We speculate that herbivores compete for mistletoe shoots and that increased per-capita feeding compensated for predator reduction of herbivore abundance. In summary, our results demonstrate that mistletoe parasitism altered the pine arthropod community, including an increase in the density of predators that likely feed upon mistletoe herbivores.

Keywords: community ecology, detritus, indirect effect, plant morphology, tritrophic

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Title: RMRS Other Publications: Linking parasitic plant-induced host morphology to tritrophic interactions
Electronic Publish Date: September 8, 2007
Last Update:
September 8, 2007

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