The reliance of each fig species on its specific pollinator wasp, and vice versa, is the archetype of both obligatory mutualism and coevolution. Pollinator sharing between host fig species is only known to occur among closely related sympatric species. On the Hawaiian island of Kauai, we gathered syconia from 23 non-native fig species, three of which contained the wasp Pleistodontes imperialis. Of the three fig species, one is the wasp’s natural host, Ficus rubiginosa, and another is its sister species, Ficus watkinsiana, which overlaps in native ranges, although researchers have not previously documented pollinator sharing. The third fig species, Ficus rubra, is distant to the others both in terms of phylogenetic relationship and native range. We found viable seeds for all three fig species, whereas species without wasps did not produce seeds. To investigate similarity between these pollinator-sharing fig species, we collected morphometric data for syconia of our study fig species. We found that fig species with and without P. imperialis significantly differ based on the orientation of their inner ostiolar bracts. These findings suggest that pollinator sharing among these three fig species may normally be impeded by pollinator competition in the case of F. watkinsiana, and by geographic distance in the case of F. rubra. This work therefore demonstrates that coevolution depends on interactions within native species assemblages, and that mutualisms can be disrupted in new non-native communities.
Bibliographical noteFunding Information:
Contributions from KB were supported in part by funds acquired by the Kauai Invasive Species Committee.
We are grateful to Timothy Flynn from the National Tropical Botanical Garden for guiding us into the Lihue-Koloa Forest Reserve. For their assistance with germination assays, we thank Margaret Clark, Shyla Kaninauali?i Villanueva, Jeffrey Frelinger, Leilani Naki, Sherry Hines, and Phyllis Albert. We furthermore appreciate Alex Lau with SWCA? Environmental Consultants for knowledge about the first viable seeds of F. religiosa L. recorded on Oahu Island. For informing KB about a volunteer F. religiosa specimen in Lihue, Kauai, we also thank Adam Williams with the Hawaii Department of Land and Natural Resources. Funding. Contributions from KB were supported in part by funds acquired by the Kauai Invasive Species Committee.
© Copyright © 2020 Bernard, Brock, Tonnell, Walsh, Wenger, Wolkis and Weiblen.
- convergent evolution
- fig wasps
- fundamental niche
- geographic mosaic theory
- host breadth expansion