title: Mutualists or parasites? Context-dependent influence of symbiotic fly larvae on carnivorous investment in the Albany pitcher plant.
abstract: Carnivorous plants allocate more resources to carnivorous structures under nutrient-limited conditions, and relative investment can also be influenced by animals (infauna) that live in association with these plants and feed on their prey. We investigated these effects within a population of the pitcher plantCephalotus folliculariscontaining varying densities of larvae of the flyBadisis ambulans. For plants with a relatively high proportion of adult pitchers, increasing larval density was associated with lower relative leaf allocation to new pitcher buds. For plants with relatively few adult pitchers, however, there was greater relative leaf allocation to pitcher buds with increasing larval density. In a field experiment, there was no significant effect of experimental larval presence or absence on the change in carbon-to-nitrogen (C/N) ratio of plants. Although the direction of the correlation betweenB. ambulanslarvae and relative investment in carnivorous and non-carnivorous structures depends on the relative number of mature structures, whether the larvae enhance or reduce nutrient stress under different conditions remains unclear. The change in C/N was, however, less variable for pitchers that contained larvae, suggesting a stabilizing effect. Eighteen of 52 experimental pitchers were damaged by an unknown species, causing the pitcher fluid to drain. These pitchers were significantly more likely to survive if they contained larvae. These results suggest that the relationship between infauna and host varies with the initial resource status and environmental context of the host plant.
authors.affiliation: Centre for Evolutionary Biology, School of Animal Biology , The University of Western Australia , 35 Stirling Highway, Crawley, Western Australia 6009 , Australia.
authors.forename: Samuel J
authors.identifier: 0000-0002-8801-7880
authors.initials: SJ
authors.lastname: Lymbery
authors.affiliation: School of Animal Biology, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia; Centre for Environment and Life Sciences, CSIRO Land and Water, Underwood Avenue, Floreat, Western Australia 6014, Australia.
authors.forename: Raphael K
authors.initials: RK
authors.lastname: Didham
authors.affiliation: Centre of Excellence in Natural Resource Management, and School of Plant Biology , The University of Western Australia , Albany, Western Australia 6330 , Australia.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Hopper
authors.affiliation: Centre for Evolutionary Biology, School of Animal Biology , The University of Western Australia , 35 Stirling Highway, Crawley, Western Australia 6009 , Australia.
authors.forename: Leigh W
authors.identifier: 0000-0003-0562-1474
authors.initials: LW
authors.lastname: Simmons
keywords: carnivorous plants; infauna; insect–plant interaction; nutrient limitation; phenotypic plasticity; resource allocation