In habitats where resource availability declines during the growing season
The evolution of flowering time is often attributed to variations in pollinator rates over time. This study proposes that flowering time can evolve through siring success variation among individuals caused by differential pollen dispersal timing (a result of flowering time variation). By building quantitative genetic models, I show that flowering time evolves to be earlier when the pollen removal rate is low and pollen deposition rate is high, and the fertilization ability of removed pollen declines slowly. Using evolutionary game theory, I show that the evolutionarily stable variance of flowering time is large when the pollen removal rate is either low or high, the pollen deposition rate is moderate, and the fertilization ability of removed pollen declines rapidly. Investigation of the coevolution of flower longevity and flowering time shows that under constant pollination rates, late flowering will be correlated with long-lived flowers due to nonrandom mating, which suggests that the observed correlation between late flowering and short-lived flowers is caused by other factors, such as declining pollination rates during late-stage flowering. I discuss how altered pollination rates under climate change will influence flowering time evolution and the importance of distinguishing between pollen removal and deposition rates.
more » « less- PAR ID:
- 10484868
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Evolution
- ISSN:
- 0014-3820
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Pollination requires a flower to remain open for long enough to allow for the arrival of pollinators. However, maintaining flowers costs energy and resources. Therefore, flower longevity, the length of time a flower remains viable, is critical for the outcome of plant reproduction. Although previous studies showed that the evolution of flower longevity depends on the rates of pollen deposition and removal, whether plants should increase or decrease flower life span when the pollination environment is unpredictable has not been explored. Moreover, the common hypothesis that an unpredictable pollination environment should select for increased flower longevity may be too simplistic since there is no distinction drawn between the effects of spatial and temporal variation. Adopting evolutionary game theory, we investigate the evolution of flower longevity under three types of variation: spatial heterogeneity, daily fluctuations within a flowering season and yearly fluctuations between flowering seasons. We find that spatial heterogeneity often selects for a shorter flower lifespan, while temporal fluctuations of fitness accrual rates at both daily and yearly time scales tends to favour greater longevity, although daily and yearly fluctuations have somewhat different effects. However, the presence of correlation between female and male fitness accrual rates seems to have no effect on flower longevity. Our work suggests that explicit measurements of spatial and temporal variation in both female and male functions may provide a better understanding of the evolution of flower longevity and reproduction.
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Abstract Climate change has had numerous ecological effects, including species range shifts and altered phenology. Altering flowering phenology often affects plant reproduction, but the mechanisms behind these changes are not well‐understood. To investigate why altering flowering phenology affects plant reproduction, we manipulated flowering phenology of the spring herb
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Understanding how pollen moves between species is critical to understanding speciation, diversification, and evolution of flowering plants. For co-flowering species that share pollinators, competition through interspecific pollen transfer (IPT) can profoundly impact floral evolution, decreasing female fitness via heterospecific pollen deposition on stigmas and male fitness via pollen misplacement during visits to heterospecific flowers. The pollination literature demonstrates that such reproductive interference frequently selects for reproductive character displacement in floral traits linked to pollinator attraction, pollen placement, and mating systems and has also revealed that IPT between given pairs of species is typically asymmetric. More recent work is starting to elucidate its importance to the speciation process, clarifying the link between IPT and current and historical patterns of hybridization, the evolution of phenotypic novelty through adaptive introgression, and the rise of reproductive isolation. Our review aims to stimulate further research on IPT as a ubiquitous mechanism that plays a central role in angiosperm diversification.more » « less
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Abstract Despite widespread recognition of the need for long‐term monitoring of pollinator abundances and pollination service provision, such studies are exceedingly rare.
In this study, we assess changes in bee visitation and net capture rates for 73 species visiting watermelon crop flowers at 19 farms in the mid‐Atlantic region of the United States from 2005 to 2012.
Over the 8 years, we found a 58% decline in wild bee visitation to crop flowers, but no significant change in honey bee visitation rate. Most types of wild bees showed similar declines in both the visitation and the net capture data; bumble bees, however, declined by 56% in the visitation data but showed no change in net capture rates. Trends in pollination services, that is, estimated pollen deposition, largely followed the trends in visitation and net capture rates.
While we detected large and significant declines in wild bees when using generalised linear mixed models (GLMMs), permutation analyses that account for non‐directional variation in abundance were non‐significant, demonstrating the challenge of identifying and describing trends in highly variable populations.
As far as we are aware, this article represents one of fewer than 10 published time‐series (defined as >5 years of data) studies of changes in bee abundance, and one of only two such studies conducted in an agricultural setting. More such studies are needed in order to understand the magnitude of bee decline and its ramifications for crop pollination.
