title: Plant reproductive traits mediate tritrophic feedback effects within an obligate brood-site pollination mutualism.
abstract: Plants, herbivores and parasitoids affect each other directly and indirectly; however, feedback effects mediated by host plant traits have rarely been demonstrated in these tritrophic interactions. Brood-site pollination mutualisms (e.g. those involving figs and fig wasps) represent specialised tritrophic communities where the progeny of mutualistic pollinators and of non-mutualistic gallers (both herbivores) together with that of their parasitoids develop within enclosed inflorescences called syconia (hence termed brood-sites or microcosms). Plant reproductive phenology (which affects temporal brood-site availability) and inflorescence size (representing brood-site size) are plant traits that could affect reproductive resources, and hence relationships between trees, pollinators and non-pollinating wasps. Analysing wasp and seed contents of syconia, we examined direct, indirect, trophic and non-trophic relationships within the interaction web of the fig-fig wasp community of Ficus racemosa in the context of brood site size and availability. We demonstrate that in addition to direct resource competition and predator-prey (host-parasitoid) interactions, these communities display exploitative or apparent competition and trait-mediated indirect interactions. Inflorescence size and plant reproductive phenology impacted plant-herbivore and plant-parasitoid associations. These plant traits also influenced herbivore-herbivore and herbivore-parasitoid relationships via indirect effects. Most importantly, we found a reciprocal effect between within-tree reproductive asynchrony and fig wasp progeny abundances per syconium that drives a positive feedback cycle within the system. The impact of a multitrophic feedback cycle within a community built around a mutualistic core highlights the need for a holistic view of plant-herbivore-parasitoid interactions in the community ecology of mutualisms.
authors.affiliation: Centre for Ecological Sciences, Indian Institute of Science, Bangalore, 560 012, India.
authors.forename: Anusha
authors.initials: A
authors.lastname: Krishnan
authors.affiliation: Centre for Ecological Sciences, Indian Institute of Science, Bangalore, 560 012, India.|Botanical Garden, Department of Molecular Biology and Ecology of Plants, George Wise Faculty of Life Science, Tel Aviv University, 69978, Tel Aviv, Israel.
authors.forename: Mahua
authors.initials: M
authors.lastname: Ghara
authors.affiliation: Centre for Ecological Sciences, Indian Institute of Science, Bangalore, 560 012, India.
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Kasinathan
authors.affiliation: Centre for Ecological Sciences, Indian Institute of Science, Bangalore, 560 012, India.|Institute of Microscopy, Anatomy and Neurobiology, Johannes Gutenberg-University Medicine Mainz, Hanns-Dieter-Hüsch-Weg 19, 55128, Mainz, Germany.
authors.forename: Gautam Kumar
authors.initials: GK
authors.lastname: Pramanik
authors.affiliation: Centre for Ecological Sciences, Indian Institute of Science, Bangalore, 560 012, India.|Unit of Chemical Ecology, Department of Plant Protection and Biology, Swedish University of Agricultural Sciences, 23053, Alnarp, Sweden.
authors.forename: Santosh
authors.initials: S
authors.lastname: Revadi
authors.affiliation: Centre for Ecological Sciences, Indian Institute of Science, Bangalore, 560 012, India. renee@ces.iisc.ernet.in.
authors.forename: Renee M
authors.initials: RM
authors.lastname: Borges
mesh_terms: D000818:Animals; D030681:Ficus / Q000254:growth & development / Q000469:parasitology / Q000502:physiology*; D060434:Herbivory; D006790:Host-Parasite Interactions; D056626:Inflorescence / Q000254:growth & development / Q000502:physiology; D010641:Phenotype; D054817:Pollination; D012098:Reproduction / Q000235:genetics; D012639:Seeds / Q000235:genetics; D013559:Symbiosis; D014863:Wasps / Q000502:physiology*
keywords: Feedback cycle; Inflorescence size; Interaction web; Plant–herbivore–parasitoid interactions; Trait-mediated indirect effect