Divvying up an incubator: How parasitic and mutualistic fig wasps use space within their nursery microcosm
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Differential occupancy of space can lead to species coexistence. The fig–fig wasp pollination system hosts species-specific pollinating and parasitic wasps that develop within galls in a nursery comprising a closed inflorescence, the syconium. This microcosm affords excellent opportunities for investigating spatial partitioning since it harbours a closed community in which all wasp species are dependent on securing safe sites inside the syconium for their developing offspring while differing in life history, egg deposition strategies and oviposition times relative to nursery development. We determined ontogenetic changes in oviposition sites available to the seven-member fig wasp community of Ficus racemosa comprising pollinators, gallers and parasitoids. We used species distribution models (SDMs) for the first time at a microcosm scale to predict patterns of spatial occurrence of nursery occupants. SDMs gave high true-positive and low false-positive site occupancy rates for most occupants indicating species specificity in oviposition sites. The nursery microcosm itself changed with syconium development and sequential egg-laying by different wasp species. The number of sites occupied by offspring of the different wasp species was negatively related to the risk of syconium abortion by the plant host following oviposition. Since unpollinated syconia are usually aborted, parasitic wasps ovipositing into nurseries at the same time as the pollinator targeted many sites, suggesting response to lower risk of syconium abortion owing to reduced risk of pollination failure compared to those species ovipositing before pollination. Wasp life history and oviposition time relative to nursery development contributed to the co-existence of nursery occupants.
KeywordsEnemy-free space Life history Nursery pollination Resource partitioning Species distribution models
We thank the Ministry of Environment and Forests, Government of India, for supporting this research. We also thank Gautam Pramanik, Kanchan Jogdev, Santhosh Revadi, and Yathiraj Ganesh for help with collecting the samples. For assistance with data analysis we thank Meera Mane and Meghana Kulkarni. We are grateful to Takeshi Osawa for help with the bagging GLM analysis and for sending us the relevant R code, and to three anonymous reviewers and Alexander Bradley Duthie for insightful comments on the manuscript. We are especially thankful to Lakshy Katariya, Karpagam Chelliah, Venkatappa and Mary Sunitha for technical support.
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