Maintenance of specificity in sympatric host-specific fig/wasp pollination mutualisms.

Background: Fig/wasp pollination mutualisms are extreme examples of species-specific plant-insect symbioses, but incomplete specificity occurs, with potentially important evolutionary consequences. Why pollinators enter alternative hosts, and the fates of pollinators and the figs they enter, are unknown.

Methods: We studied the pollinating fig wasp, , which concurrently interacts with its typical host and the locally sympatric alternative host , recording frequencies of the wasp in figs of the alternative hosts. We measured ovipositor lengths of pollinators and style lengths in female and male figs in the two host species. Volatile organic compounds (VOCs) emitted by receptive figs of each species were identified using GC-MS. We tested the attraction of wasps to floral scents in choice experiments, and detected electrophysiologically active compounds by GC-EAD. We introduced foundresses into figs of both species to reveal the consequences of entry into the alternative host.

Results: entered a low proportion of figs of the alternative host, and produced offspring in a small proportion of them. Despite differences in the VOC profiles of the two fig species, they included shared semiochemicals. Although females prefer receptive figs of , they are also attracted to those of . that entered male figs of produced offspring, as their ovipositors were long enough to reach the bottom of the style; however, broods were larger and offspring smaller than in the typical host. Female figs of failed to produce seeds when visited by . These findings advance our current understanding of how these species-specific mutualisms usually remain stable and the conditions that allow their diversification.