Drought stress alters floral volatiles and reduces floral rewards, pollinator activity, and seed set in a global plant

Rering, Caitlin C.; Franco, José G.; Yeater, Kathleen M.; Mallinger, Rachel E.

doi:10.1002/ecs2.3254

Cited by 86 publications

(96 citation statements)

References 58 publications

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“…Pollen number, nectar sugar concentration and content showed no consistent pattern which is in congruence with another study (Rering et al, 2020). Keeping sugar content and concentration relatively constant may be beneficial, as altered nectar amounts and viscosity may impair nectar intake by pollinators and lead to changes in visitation length and frequency (Harder, 1986;Kim et al, 2011;Thomson, 1988;Thomson & Plowright, 1980).…”

Section: Effects Of Water Deficit On Flower Resourcessupporting

confidence: 69%

A meta‐analysis of responses in floral traits and flower–visitor interactions to water deficit

Kuppler

Kotowska

2021

Global Change Biology

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Alterations in water availability and drought events as predicted by climate change scenarios will increasingly impact natural communities with effects already emerging at present. Water deficit leads to increasing physiological stress in plants, likely affecting floral development and causing changes in floral morphology, nectar and pollen production or scent. Understanding how these floral traits are altered by water deficit is necessary to predict changes in plant-pollinator interactions and how communities are impacted in the future. Here we employ a meta-analysis approach to synthesize the current evidence of experimental water deficit on floral traits and plant-pollinator interactions. Furthermore, we explore experimental factors potentially increasing heterogeneity between studies and provide ideas how to enhance comparability between studies. In the end, we highlight future directions and knowledge gaps for floral traits and plant-pollinator interactions under water deficit. Our analysis showed consistent decreases in floral size, number of flowers and nectar volume to reduced water availability. Other floral traits such as the start of flowering or herkogamy showed no consistent pattern. This indicates that effects of reduced water availability differ between specific traits that are potentially involved in different functions such as pollinator attraction or efficiency. We found no general decreasing visitation rates with water deficit for flower-visitor interactions. Furthermore, the comparison of available studies suggests that increased reporting of plant stress severity and including more hydraulic and physiological measurements will improve the comparability across experiments and aid a more mechanistic understanding of plant-pollinator interactions under altered environmental conditions. Overall, our results show that water deficit has the potential to strongly affect plant-pollinator interactions via changes in specific floral traits. Linking these changes to pollination services and pollinator performance is one crucial step for understanding how changing water availability and drought events under climate change will alter plant and pollinator communities.

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Section: Effects Of Water Deficit On Flower Resourcessupporting

confidence: 69%

A meta‐analysis of responses in floral traits and flower–visitor interactions to water deficit

Kuppler

Kotowska

2021

Global Change Biology

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“…This result suggests that the frequently observed impacts of water availability on floral traits might not always translate into substantial effects on pollinator visitation. In the few other systems that have investigated this question, drought reduced pollinator visitation in three of five species (Burkle and Runyon, 2016;Glenny et al, 2018;Rering et al, 2020). In M. ciliata the likelihood that a plant would receive a pollinator visit declined over the course of 4 weeks and was influenced by the July decline in the number of flowers per plant, as also seen in our previous work (Gallagher and Campbell, 2020).…”

Section: Comparative Impacts Of Phenology and Water Availability On Psupporting

confidence: 58%

Experimental Test of the Combined Effects of Water Availability and Flowering Time on Pollinator Visitation and Seed Set

Gallagher

Campbell

2021

Front. Ecol. Evol.

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Climate change is likely to alter both flowering phenology and water availability for plants. Either of these changes alone can affect pollinator visitation and plant reproductive success. The relative impacts of phenology and water, and whether they interact in their impacts on plant reproductive success remain, however, largely unexplored. We manipulated flowering phenology and soil moisture in a factorial experiment with the subalpine perennial Mertensia ciliata (Boraginaceae). We examined responses of floral traits, floral abundance, pollinator visitation, and composition of visits by bumblebees vs. other pollinators. To determine the net effects on plant reproductive success, we also measured seed production and seed mass. Reduced water led to shorter, narrower flowers that produced less nectar. Late flowering plants produced fewer and shorter flowers. Both flowering phenology and water availability influenced pollination and reproductive success. Differences in flowering phenology had greater effects on pollinator visitation than did changes in water availability, but the reverse was true for seed production and mass, which were enhanced by greater water availability. The probability of receiving a flower visit declined over the season, coinciding with a decline in floral abundance in the arrays. Among plants receiving visits, both the visitation rate and percent of non-bumblebee visitors declined after the first week and remained low until the final week. We detected interactions of phenology and water on pollinator visitor composition, in which plants subject to drought were the only group to experience a late-season resurgence in visits by solitary bees and flies. Despite that interaction, net reproductive success measured as seed production responded additively to the two manipulations of water and phenology. Commonly observed declines in flower size and reward due to drought or shifts in phenology may not necessarily result in reduced plant reproductive success, which in M. ciliata responded more directly to water availability. The results highlight the need to go beyond studying single responses to climate changes, such as either phenology of a single species or how it experiences an abiotic factor, in order to understand how climate change may affect plant reproductive success.

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“…Further, the reduced number of flowers visited per plant suggest that not all flowers will be efficiently pollinated. In Fagopyrum esculentum (Polygonaceae), Rering et al (2020) have shown that drought stress leads to reduced visits, decreased pollination success, and consequently lower seed set (see also Gallagher and Campbell, 2017 ). Therefore, increasing drought events and longer drought periods will influence bumblebee foraging behavior leading to fewer and shorter visits on drought-stressed plants and hence to reduced pollination success ( Chagnon et al, 1989 ).…”

Section: Discussionmentioning

confidence: 99%

“…Drought stress increases floral scent emission and causes a shift in the composition of floral VOCs as some compound pathways might be up- or down-regulated. Studies showed an increase under drought for some compounds such as: (Z)-3-hexenol, 6-methyl-5-hepten-2-one, benzaldehyde, α- and β-pinene, and (E)-β-ocimene, (E,E)-α-farnesene ( Burkle and Runyon, 2016 ; Glenny et al, 2018 ; Campbell et al, 2019 ; Rering et al, 2020 ).…”

Section: Introductionmentioning

confidence: 99%

Bumblebee Behavior on Flowers, but Not Initial Attraction, Is Altered by Short-Term Drought Stress

2021

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Climate change is leading to increasing drought and higher temperatures, both of which reduce soil water levels and consequently water availability for plants. This reduction often induces physiological stress in plants, which in turn can affect floral development and production inducing phenotypic alterations in flowers. Because flower visitors notice and respond to small differences in floral phenotypes, changes in trait expression can alter trait-mediated flower visitor behavior. Temperature is also known to affect floral scent emission and foraging behavior and, therefore, might modulate trait-mediated flower visitor behavior. However, the link between changes in flower visitor behavior and floral traits in the context of increasing drought and temperature is still not fully understood. In a wind-tunnel experiment, we tested the behavior of 66 Bombus terrestris individuals in response to watered and drought-stressed Sinapis arvensis plants and determined whether these responses were modulated by air temperature. Further, we explored whether floral traits and drought treatment were correlated with bumblebee behavior. The initial attractiveness of drought and watered plants did not differ, as the time to first visit was similar. However, bumblebees visited watered plants more often, their visitation rate to flowers was higher on watered plants, and bumblebees stayed for longer, indicating that watered plants were more attractive for foraging. Bumblebee behavior differed between floral trait expressions, mostly independently of treatment, with larger inflorescences and flowers leading to a decrease in the time until the first flower visit and an increase in the number of visits and the flower visitation rate. Temperature modulated bumblebee activity, which was highest at 25°C; the interaction of drought/water treatment and temperature led to higher visitation rate on watered plants at 20°C, possibly as a result of higher nectar production. Thus, bumblebee behavior is influenced by the watered status of plants, and bumblebees can recognize differences in intraspecific phenotypes involving morphological traits and scent emission, despite overall morphological traits and scent emission not being clearly separated between treatments. Our results indicate that plants are able to buffer floral trait expressions against short-term drought events, potentially to maintain pollinator attraction.

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Drought stress alters floral volatiles and reduces floral rewards, pollinator activity, and seed set in a global plant

Cited by 86 publications

References 58 publications

A meta‐analysis of responses in floral traits and flower–visitor interactions to water deficit

A meta‐analysis of responses in floral traits and flower–visitor interactions to water deficit

Experimental Test of the Combined Effects of Water Availability and Flowering Time on Pollinator Visitation and Seed Set

Bumblebee Behavior on Flowers, but Not Initial Attraction, Is Altered by Short-Term Drought Stress

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