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1. Effects of experimental warming on floral scent, display and rewards in two subalpine herbs

   https://doi.org/10.1093/aob/mcad195  

   Wu, Carrie ; Powers, John M. ; Hopp, David Z. ; Campbell, Diane R. ( December 2023 , Annals of Botany)

   Floral volatiles, visual traits and rewards mediate attraction and defence in plant–pollinator and plant–herbivore interactions, but these floral traits might be altered by global warming through direct effects of temperature or longer-term impacts on plant resources. We examined the effect of warming on floral and leaf volatile emissions, floral morphology, plant height, nectar production, and oviposition by seed predators.

   We used open-top chambers that warmed plants in the field by +2–3 °C on average (+6–11 °C increase in daily maxima) for 2–4 weeks across 1–3 years at three sites in Colorado, USA. Volatiles were sampled from two closely related species of subalpine Ipomopsis with different pollinators: Ipomopsis aggregata ssp. aggregata, visited mainly by hummingbirds, and Ipomopsis tenuituba ssp. tenuituba, often visited by hawkmoths.

   Although warming had no detected effects on leaf volatiles, the daytime floral volatiles of both I. aggregata and I. tenuituba responded in subtle ways to warming, with impacts that depended on the species, site and year. In addition to the long-term effect of warming, temperature at the time of sampling independently affected the floral volatile emissions of I. aggregata during the day and I. tenuituba at night. Warming had little effect on floral morphology for either species and it had no effect on nectar concentration, maximum inflorescence height or flower redness in I. aggregata. However, warming increased nectar production in I. aggregata by 41 %, a response that would attract more hummingbird visits, and it reduced oviposition by fly seed predators by ≥72 %.

   Our results suggest that floral traits can show different levels of plasticity to temperature changes in subalpine environments, with potential effects on animal behaviours that help or hinder plant reproduction. They also illustrate the need for more long-term field warming studies, as shown by responses of floral volatiles in different ways to weeks of warming vs. temperature at the time of sampling.

    

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2. Plant volatiles induced by herbivore eggs prime defences and mediate shifts in the reproductive strategy of receiving plants

   https://doi.org/10.1111/ele.13509  

   Pashalidou, Foteini G. ; Eyman, Lisa ; Sims, James ; Buckley, James ; Fatouros, Nina E. ; De Moraes, Consuelo M. ; Mescher, Mark C. ; Turlings, ed., Ted ( April 2020 , Ecology Letters)

   Plants can detect cues associated with the risk of future herbivory and modify defence phenotypes accordingly; however, our current understanding is limited both with respect to the range of early warning cues to which plants respond and the nature of the responses. Here we report that exposure to volatile emissions from plant tissues infested with herbivore eggs promotes stronger defence responses to subsequent herbivory in twoBrassicaspecies. Furthermore, exposure to these volatile cues elicited an apparent shift from growth to reproduction inBrassica nigra, with exposed plants exhibiting increased flower and seed production, but reduced leaf production, relative to unexposed controls. Our results thus document plant defence priming in response to a novel environmental cue, oviposition‐induced plant volatiles, while also showing that plant responses to early warning cues can include changes in both defence and life‐history traits.

    

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3. Agricultural landscape simplification affects wild plant reproduction indirectly through herbivore-mediated changes in floral display

   https://doi.org/10.1038/s41598-024-65352-2  

   Schroeder, Hayley ; Salzberg, Annika ; Grab, Heather ; Crowther, Shea ; Hale, Casey ; Poveda, Katja ( June 2024 , Scientific Reports)

   As natural landscapes are modified and converted into simplified agricultural landscapes, the community composition and interactions of organisms persisting in these modified landscapes are altered. While many studies examine the consequences of these changing interactions for crops, few have evaluated the effects on wild plants. Here, we examine how pollinator and herbivore interactions affect reproductive success for wild resident and phytometer plants at sites along a landscape gradient ranging from natural to highly simplified. We tested the direct and indirect effects of landscape composition on plant traits and reproduction mediated by insect interactions. For phytometer plants exposed to herbivores, we found that greater landscape complexity corresponded with elevated herbivore damage, which reduced total flower production but increased individual flower size. Though larger flowers increased pollination, the reduction in flowers ultimately reduced plant reproductive success. Herbivory was also higher in complex landscapes for resident plants, but overall damage was low and therefore did not have a cascading effect on floral display and reproduction. This work highlights that landscape composition directly affects patterns of herbivory with cascading effects on pollination and wild plant reproduction. Further, the absence of an effect on reproduction for resident plants suggests that they may be adapted to their local insect community.

    

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4. Transgenerational impacts of herbivory and inbreeding on reproductive output in Solanum carolinense

   https://doi.org/10.1002/ajb2.1402  

   Nihranz, Chad T. ; Walker, William S. ; Brown, Steven J. ; Mescher, Mark C. ; De Moraes, Consuelo M. ; Stephenson, Andrew G. ( January 2020 , American Journal of Botany)

   Plant maternal effects on offspring phenotypes are well documented. However, little is known about how herbivory on maternal plants affects offspring fitness. Furthermore, while inbreeding is known to reduce plant reproductive output, previous studies have not explored whether and how such effects may extend across generations. Here, we addressed the transgenerational consequences of herbivory and maternal plant inbreeding on the reproduction of Solanum carolinenseoffspring.

   Manduca sextacaterpillars were used to inflict weekly damage on inbred and outbredS. carolinensematernal plants. Cross‐pollinations were performed by hand to produce seed from herbivore‐damaged outbred plants, herbivore‐damaged inbred plants, undamaged outbred plants, and undamaged inbred plants. The resulting seeds were grown in the greenhouse to assess emergence rate and flower production in the absence of herbivores. We also grew offspring in the field to examine reproductive output under natural conditions.

   We found transgenerational effects of herbivory and maternal plant inbreeding on seedling emergence and reproductive output. Offspring of herbivore‐damaged plants had greater emergence, flowered earlier, and produced more flowers and seeds than offspring of undamaged plants. Offspring of outbred maternal plants also had greater seedling emergence and reproductive output than offspring of inbred maternal plants, even though all offspring were outbred. Moreover, the effects of maternal plant inbreeding were more severe when plant offspring were grown in field conditions.

   This study demonstrates that both herbivory and inbreeding have fitness consequences that extend across generations even in outbred progeny.

    

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5. A key floral scent component (β‐trans‐bergamotene) drives pollinator preferences independently of pollen rewards in seep monkeyflower

   https://doi.org/10.1111/1365-2435.13246  

   Haber, Ariela_I ; Sims, James_W ; Mescher, Mark_C ; De_Moraes, Consuelo_M ; Carr, David_E ; Brody, ed., Alison ( December 2018 , Functional Ecology)

   Floral odours play an important role in attracting insect pollinators. Because pollinators visit flowers to obtain pollen and nectar rewards, they should prefer floral odour profiles associated with the highest‐rewarding flowers (honest signals). In previous work, bumblebees exhibited a preference for flowers from outbred over inbredMimulus guttatusplants. Pollen is the only floral reward inM. guttatus, and pollen viability (a reliable indicator of protein content) is reduced in inbred plants. Yet, differences in pollen viability did not explain the observed preferences.

   In this study, we examined the floral volatile profiles of inbred and outbredM. guttatusto identify inbreeding effects and associations between volatile compounds and the number of viable pollen grains per flower, designated “PRQ” (pollen reward quality). We also conducted pairwise choice tests withBombus impatiensto evaluate the ability of bees to discriminate between odours of rewarding and non‐rewarding flowers and to determine whether bumblebee preferences are explained by differences in the floral odours of inbred and outbred plants.

   Inbred plants exhibited reduced emission of β‐trans‐bergamotene, the second‐most abundant compound in the volatile blend of outbred plants. Furthermore, pollen and fertile anthers emitted nonadecane. Six other compounds in the floral blend were positively correlated withPRQ. There was no overlap between compounds affected by inbreeding and compounds associated withPRQ.

   Even when given prior experience foraging onM. guttatus, bumblebees did not distinguish between the floral odours of rewarding and non‐rewarding outbred plants. However, they preferred floral odours from non‐rewarding outbred plants over rewarding inbred plants. Bumblebees without prior experience of flowers preferred volatile blends with higher versus lower amounts of β‐trans‐bergamotene.

   Taken together, these results suggest that the volatile emissions ofM. guttatusprovide reliable indicators of pollen rewards (potential honest signals), but that the preference of bumblebees for outbred plants is not driven by these cues but rather by a sensory bias for β‐trans‐bergamotene. This may represent a subtle form of deceit‐pollination that allows plants to attract pollinators while minimizing investment in costly rewards.

   Aplain language summaryis available for this article.

    

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