Plants and pollinators: Will natural selection cause an imbalance between nectar supply and demand?

• Published in: Ecology letters 2021-09, Vol.24 (9), p.1741-1749
• Main Authors: Ratnieks, Francis L. W., Balfour, Nicholas J., Irwin, Rebecca
• Format: Article
• Language: English
• Subjects: Feedback; Hypotheses; Natural selection; Nectar; networks; phenology; Plant nectar; Plant reproduction; plants; Pollen; pollen limitation; Pollination; Pollinators; Positive feedback; Seasonal variations; seasonality; Seed set; Supply & demand
• ISSN: 1461-023X; 1461-0248
• DOI: 10.1111/ele.13823

Pollination is an important ecological process. However, plant and pollinator needs are not always met. Commonly, pollen limitation reduces seed set or bees experience nectar dearth. Using a cost‐benefit approach, we show that natural selection will lead to lower nectar production when pollinators are abundant, and vice‐versa. At the community level, competition among plants for pollinators causes positive feedback that exacerbates pre‐existing seasonal imbalances between nectar supply and demand. When pollinators are scarce, plants will be selected to produce more nectar to outcompete other plants in attracting pollinators, and when pollinators are abundant, plants will be selected to produce less nectar. We suggest ways to test this positive feedback hypothesis and note that evidence for seasonal variation in nectar availability provides preliminary empirical support. If correct, our hypothesis indicates that pollination faces a particular challenge in balancing nectar supply with pollinator demand and is a further example of the underappreciated role of positive feedback in ecology and evolution. Pollination is an important ecological process. However, the needs of plants and pollinators are not always met ‐ pollen limitation commonly reduces seed set and bees often experience nectar dearth. Using a theoretical cost‐benefit optimization model we show that natural selection acting at the level of individual plants and pollinators will result in positive feedback that exacerbates pre‐existing imbalances between nectar supply and demand.