Linking pollinator efficiency to patterns of pollen limitation: small bees exploit the plant-pollinator mutualism

Seemingly mutualistic relationships can be exploited, in some cases reducing fitness of the exploited species. In plants, the insufficient receipt of pollen limits reproduction. While infrequent pollination commonly underlies pollen limitation (PL), frequent interactions with low-efficiency, exploit...

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Bibliographic Details
Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2018-06, Vol.285 (1880), p.20180635-20180635
Main Authors: Koski, Matthew H, Ison, Jennifer L, Padilla, Ashley, Pham, Angela Q, Galloway, Laura F
Format: Article
Language:English
Subjects:
Animal reproduction
Animals
Bees
Bees - physiology
Body Size
Bombus
Breeding success
Bumblebees
Campanulaceae - physiology
Ecology
Efficiency
Fitness
Flowers
Flowers - physiology
Megachile campanulae
Mutualism
Parasites
Plant reproduction
Pollen
Pollination
Pollinators
Populations
Reproduction
Reproduction (biology)
Reproductive failure
Reproductive fitness
Scaling
Seed set
Species Specificity
Symbiosis
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Summary:Seemingly mutualistic relationships can be exploited, in some cases reducing fitness of the exploited species. In plants, the insufficient receipt of pollen limits reproduction. While infrequent pollination commonly underlies pollen limitation (PL), frequent interactions with low-efficiency, exploitative pollinators may also cause PL. In the widespread protandrous herb , visitation by three pollinators explained 63% of the variation in PL among populations spanning the range. Bumblebees and the medium-sized enhanced reproductive success, but small solitary bees exacerbated PL. To dissect mechanisms behind these relationships, we scored sex-specific floral visitation, and the contributions of each pollinator to plant fitness using single flower visits. Small bees and overvisited male-phase flowers, but bumblebees frequently visited female-phase flowers. Fewer bumblebee visits were required to saturate seed set compared to other bees. Scaling pollinator efficiency metrics to populations, small bees deplete large amounts of pollen due to highly male-biased flower visitation and infrequent pollen deposition. Thus, small bees reduce plant reproduction by limiting pollen available for transfer by efficient pollinators, and appear to exploit the plant-pollinator mutualism, acting as functional parasites to It is therefore unlikely that small bees will compensate for reproductive failure in when bumblebees are scarce.
ISSN:0962-8452
1471-2954
DOI:10.1098/rspb.2018.0635