title: Host sanctions in Panamanian Ficus are likely based on selective resource allocation.
abstract: OBJECTIVE
  Fig trees and their pollinators, fig wasps, present a powerful model system for studying mutualism stability: both partners depend on each other for reproduction, cooperation levels can be manipulated, and the resulting field-based fitness quantified. Previous work has shown that fig trees can severely reduce the fitness of wasps that do not pollinate by aborting unpollinated figs or reducing the number and size of wasp offspring. Here we evaluated four hypotheses regarding the mechanism of sanctions in four Panamanian fig species.
  
  
  METHODS
  We examined wasp and fig samples from field experiments with manipulated levels of pollination.
  
  
  RESULTS
  In unpollinated figs, the fig wall and the wasp offspring had a lower dry mass. Unpollinated figs had as many initiated wasp galls as pollinated figs but fewer galls that successfully produced live wasp offspring. Across three experimentally increasing levels of pollination, we found nonlinear increases in fig wall mass, the proportion of wasp galls that develop, and wasp mass.
  
  
  CONCLUSIONS
  Our data did not support the hypotheses that lack of pollination prevents gall formation or that fertilized endosperm is required for wasp development. While our data are potentially consistent with the hypothesis that trees produce a wasp-specific toxin in response to lack of pollination, we found the hypothesis that sanctions are a consequence of trees allocating more resources to better-pollinated figs more parsimonious with the aggregate data. Our findings are completely analogous to the selective resource allocation to more beneficial tissues documented in other mutualistic systems.
authors: Department of Organismic and Evolutionary Biology, Level 4 MCZ Labs, 26 Oxford Street, Harvard University, Cambridge, Massachusetts 02138, USA cjander@oeb.harvard.edu.|Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut USA.|Smithsonian Tropical Research Institute, Unit 9100 Box 0948, DPO, AA 34002-9998 USA.
authors: K Charlotte
authors: KC
authors: Jandér
authors: Smithsonian Tropical Research Institute, Unit 9100 Box 0948, DPO, AA 34002-9998 USA.
authors: Edward Allen
authors: EA
authors: Herre
mesh_terms: D000818:Animals; D030681:Ficus / Q000502:physiology*; D007814:Larva / Q000254:growth & development / Q000502:physiology; D010176:Panama; D054817:Pollination; D012098:Reproduction; D013559:Symbiosis; D014863:Wasps / Q000254:growth & development / Q000502:physiology*
keywords: Ficus; Moraceae; coevolution; cooperation; fig wasp; mutualism; partner choice; pollination; resource allocation; sanctions; species interaction