“Adaptive foraging of pollinators can promote pollination of a rare plant species”

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Gita Benadi and Robert J. Gegear (Aug 2018)

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Contrary to previous knowledge, an IBM shows that adaptive foraging of pollinators could promote plant coexistence

Rare plant species can benefit from flexible foraging behavior of individual pollinators

A solitary bee visiting a flower of Ursinia cakilefolia (Asteraceae).
(Credit: Gita Benadi)

Most flowering plant species rely on animals for pollination and in exchange, animals obtain floral food resources such as nectar and pollen. Consequently, pollinator foraging decisions have a direct impact on plant reproductive success. Although the decisions of some animal pollinators are guided by innate preferences for a single type of flower, the vast majority of species have the flexibility to visit many flower types and are capable of rapidly and flexibly adjusting their flower selection strategy based on current floral conditions and past foraging experiences (memory). Yet, surprisingly few studies to date have considered the potential consequences of such flexible decision-making for pollinator-mediated ecological processes in plants. Previous studies suggested that adaptively foraging pollinators generally prefer abundant plant species over rarer ones and are less efficient in transferring pollen of rare plant species compared to more abundant species. This implies that the reproduction of rare plant species relying on animal pollination could be compromised, which could eventually lead to their extinction.

To better understand the role of adaptive foraging of pollinators for reproduction of rare plant species, Gita Benadi from the University of Freiburg (Germany) and Robert J. Gegear from Worcester Polytechnic Institute (USA) developed a computer simulation model of individual animals moving from flower to flower. Contrary to previous studies, their simulations suggest that under certain conditions, adaptive foraging of pollinators can favor pollination of a rare plant species. An important improvement of their model over previous approaches is that it accounts for limited information and memory of individual foragers. In the article, they show that foragers with realistically limited information about the distribution of floral resources forage in a way which favors pollination of the rarer plant species, while perfectly informed animals prefer the more abundant flowering plant. In addition, they demonstrate that even with perfectly informed pollinators, a rarer plant species benefits more from offering a high resource amount per flower than a more abundant one. These findings help to understand under which conditions rare plant species relying on animal pollination can persist, and when they are in danger of extinction.


Abstract

Most pollinators have the foraging flexibility to visit a wide variety of plant species. Yet, few studies of pollinator-mediated processes in plants have considered the effects of variation in individual foraging patterns on plant reproductive success. In this study, we use an individual-based model of pollinator foraging economics to predict how visitation rates and pollination success of two co-flowering plant species change with their frequency (relative abundance). Whereas previous studies suggested that adaptive foraging of pollinators always favors pollination of abundant plant species (positive frequency dependence), here we show that under certain conditions the per-capita pollination success of a rare plant species can exceed that of a more abundant species. Specifically, when the overall flower density is sufficiently high and pollinators’ perception ranges are sufficiently large, animals with limited memory of previously encountered rewards forage in a way which favors pollination of the rarer plant species. Moreover, even with perfectly informed foragers a rare plant species benefits more from offering a higher floral reward than a more abundant species. Our results show that adaptive foraging of individual pollinators can have important implications for plant community dynamics and the persistence of rare plant species.