Design/implementation of a novel insect exclosure and addressing issues regarding methodology in pollination ecology

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Troy Tetreault and Ken Aho, Department of Biological Sciences, Idaho State University, Pocatello, ID

Background/Question/Methods
Exclosures are a common method for quantifying the effects of pollinators on plant species. Many terms have alluded to devices preventing pollinator access to flowering plants, including: “cage”, “mesh”, “netting”, and “exclosure”. Use of these terms is generally unaccompanied by explicit descriptions of basic exclosure design. This lack of standardized language, design, and description of exclosures decreases replicability and reduces scientific rigor. A goal of this study was to develop an exclosure that could withstand the harsh conditions of the alpine zone. Exclosures built for this ecosystem are likely to be tolerant of the climatic extremes from most ecosystems, and research in the alpine has also been necessitated given the negative effects of global warming on alpine plant species. We summarized descriptions of pollination exclosures in the literature and developed/tested an exclosure suitable for alpine conditions that was 1) effective as an exclosure mechanism, including the exclusion of pollinators of particular size ranges, 2) lightweight, 3) easy to produce and 4) cost-effective.
A cylindrical internal structure of wire-fencing with an integrated anchoring system was designed. Two types of mesh materials were attached to the structures to exclose all insects and insects of larger size classes. 120 of these exclosures were set up and monitored for 39 days. Once fruiting was complete, we counted fruit set, which was used as a proxy for plant fitness.
Results/Conclusions
Exclosures had a >95% field success rate, with 114 of 120 remaining in place throughout the field season. Mesh exclosures showed high efficacy in inhibiting insects from reaching flowering plants, with plants fruiting at a low level while in non-control exclosures. A mixed-effect ANOVA identified significant (α = 0.05) differences in fruit set based on exclosure type (p = 0.02314). No blocking (elevational) effect was detected. An ANOVA of fruits per flower by treatment showed strong treatment effects.
Our novel exclosure design builds off a breadcrumb trail of design mentions by researchers within pollination ecology. We provide ecologists with an exclosure that is inexpensive, easy to produce and set-up, durable, has a high efficacy at exclosing insects, and is transferable to other ecosystems and subdisciplines of ecology. While the exclosure design is important, we also highlight the need for researchers to report their methods in a responsible way. Through this study, we give the community both an efficacious tool for research and show a spotlight on broad issues regarding repeatable methodology.