A Closer Look into the Competition and Coexistence between Fig Wasp Species.

Abstract

<p>Figs and their pollinating wasps are a textbook case of mutualism in which each fig species depends on its host-specific wasp species for pollination services and, in turn, the wasp larvae develop within a subset of the fig’s seeds. In addition, the fig-pollinator mutualism is parasitized by a diversity of non-pollinating fig wasps that compete with pollinators by also galling and developing within fig seeds. Given than many co-occurring fig wasp species utilize precisely the same resource – fig seeds – the ecological theory of competitive exclusion predicts that they should not stably coexist over time. To investigate how they do in fact coexist, we asked if wasp species minimize inter-specific competition by utilizing spatially segregated subsets of seeds within fig fruit. Focusing on 5 co-occurring, seed-galling wasps associated with the Sonoran Desert rock fig, Ficus petiolaris, we dissected seeds from nearly mature fig fruit and tested whether the different wasps differentially develop with seeds located more deeply or shallowly within fig fruit. Our results indicate significant differences between wasp species with respect to depth of seeds they utilize, which promotes coexistence. Further, consistent with theory, we show that species utilizing different seeds experience reduced inter-specific competition.</p>