Changes from historic weather patterns have affected the phenology of many organisms world‐wide. Altered phenology can introduce organisms to novel abiotic conditions during growth and modify species interactions, both of which could drive changes in reproduction. We explored how climate change can alter plant reproduction using an experiment in which we manipulated the individual and combined effects of snowmelt timing and frost exposure, and measured subsequent effects on flowering phenology, peak flower density, frost damage, pollinator visitation and reproduction of four subalpine wildflowers. Additionally, we conducted a pollen‐supplementation experiment to test whether the plants in our snowmelt and frost treatments were pollen limited for reproduction. The four plants included species flowering in early spring to mid‐summer. The phenology of all four species was significantly advanced, and the bloom duration was longer in the plots from which we removed snow, but with species‐specific responses to snow removal and frost exposure in terms of frost damage, flower production, pollinator visitation and reproduction. The two early blooming species showed significant signs of frost damage in both early snowmelt and frost treatments, which negatively impacted reproduction for one of the species. Further, we recorded fewer pollinators during flowering for the earliest‐blooming species in the snow removal plots. We also found lower fruit and seed set for the early blooming species in the snow removal treatment, which could be attributed to the plants growing under unfavourable abiotic conditions. However, the later‐blooming species escaped frost damage even in the plots where snow was removed, and experienced increased pollinator visitation and reproduction.
Changes to flowering time caused by climate change could affects plant fecundity, but studies that compare the individual‐level responses of phenologically distinct, co‐occurring species are lacking. We assessed how variation in floral phenology affects the fecundity of individuals from three montane species with different seasonal flowering times, including in snowmelt acceleration treatments to increase variability in phenology.
We collected floral phenology and seed set data for individuals of three montane plant species (
Differences in individual phenology relative to the rest of the population affected fecundity in our focal species, but effects were species‐specific. For our early‐season species, individuals that bloomed later than the population peak bloom had increased fecundity, while for our midseason species, simply blooming before or after the population peak increased individual fecundity. For our late‐season species, blooming earlier than the population peak increased fecundity. The early and midseason species were pollen‐limited, and conspecific density affected seed set only for our early‐season species.
Our study shows that variation in individual phenology affects fecundity in three phenologically distinct montane species, and that pollen limitation may be more influential than conspecific density. Our results suggest that individual‐level changes in phenology are important to consider for understanding plant reproductive success.
- Award ID(s):
- 2129759
- NSF-PAR ID:
- 10496928
- Publisher / Repository:
- American Journal of Botany
- Date Published:
- Journal Name:
- American Journal of Botany
- Volume:
- 110
- Issue:
- 3
- ISSN:
- 0002-9122
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Synthesis. This study provides insight into how plant communities could become altered due to changes in abiotic conditions, and some of the mechanisms involved. While early blooming species may be at a disadvantage under climate change, species that bloom later in the season may benefit from early snowmelt, suggesting that climate change has the potential to reshape flowering communities. -
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Premise Flowering time may influence pollination success and seed set through a variety of mechanisms, including seasonal changes in total pollinator visitation or the composition and effectiveness of pollinator visitors.
Methods We investigated mechanisms by which changes in flowering phenology influence pollination and reproductive success of
Mertensia ciliata (Boraginaceae). We manipulated flowering onset of potted plants and assessed the frequency and composition of pollinator visitors, as well as seed set. We tested whether floral visitors differed in their effectiveness as pollinators by measuring pollen receipt and seed set resulting from single visits to virgin flowers.Results Despite a five‐fold decrease in pollinator visitation over four weeks, we detected no significant difference in seed set among plants blooming at different times. On a per‐visit basis, each bumblebee transferred more conspecific pollen than did a solitary bee or a fly. The proportion of visits by bumblebees increased over the season, countering the decrease in visitation rate so that flowering time had little net effect on seed set.
Conclusions This work illustrates the need to consider pollinator effectiveness, along with changes in pollinator visitation and species composition to understand the mechanisms by which phenology affects levels of pollination.
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How climate change influences the dynamics of plant populations is not well understood, as few plant studies have measured responses of vital rates to climatic variables and modeled the impact on population growth. The present study used 25 y of demographic data to analyze how survival, growth, and fecundity respond to date of spring snowmelt for a subalpine plant. Fecundity was estimated by seed production (over 15 y) and also divided into flower number, fruit set, seeds per fruit, and escape from seed predation. Despite no apparent effects on flower number, plants produced more seeds in years with later snowmelt. Survival and probability of flowering were reduced by early snowmelt in the previous year. Based on demographic models, earlier snowmelt with warming is expected to lead to negative population growth, driven especially by changes in seedling establishment and seed production. These results provide a rare example of how climate change is expected to influence the dynamics of a plant population. They furthermore illustrate the potential for strong population impacts even in the absence of more commonly reported visual signs, such as earlier blooming or reduced floral display in early melting years.more » « less
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Abstract In habitats where resource availability declines during the growing season
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1002/ajb2.16123
