Nectar alkaloids decrease pollination and female reproduction in a native plant

Adler, Lynn S.; Irwin, Rebecca E.

doi:10.1007/s00442-011-2153-3

Cited by 44 publications

(40 citation statements)

References 49 publications

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“…Moreover, our observation of uninfected bees having reduced probability of visiting a second flower on stems with high nectar iridoid glycosides accords with previous studies that have demonstrated pollinator deterrence by nectar secondary metabolites (Detzel and Wink , Kessler et al. , Adler and Irwin , Manson et al. ).…”

Section: Discussionsupporting

confidence: 92%

Nectar chemistry mediates the behavior of parasitized bees: consequences for plant fitness

Richardson

Bowers

Irwin

2016

Ecology

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Plants produce an array of secondary metabolites that play important ecological roles as anti‐herbivore and anti‐pathogen defenses. Many herbivores experience physiological costs when they consume secondary metabolites, yet some also benefit, for example when these chemicals confer resistance to parasites and predators. Secondary metabolites are often present in nectar and pollen, which is paradoxical given that floral rewards are important in the attraction of mutualists rather than deterrence of antagonists. Motivated by studies of interactions among plants, herbivores, and parasites, as well as research showing that secondary metabolites can reduce bee disease, we characterized the occurrence of two iridoid glycosides, aucubin and catalpol, in floral rewards and other tissues of the bee pollinated plant, Chelone glabra. We then experimentally investigated effects of nectar iridoid glycoside concentrations on the foraging behavior of bumble bee pollinators naturally afflicted by a parasitoid fly and a protozoan intestinal parasite, and subsequent effects on an estimate of plant reproduction. We found that floral nectar had lower iridoid glycoside concentrations than leaves, pollen, and corollas, and that, compared to those plant parts, the relative ratio of the two primary iridoid glycosides, aucubin and catalpol, was reversed in nectar. Whether bees carried parasitoid fly larvae did not affect their response to nectar chemistry; however, there was a significant interaction between protozoan parasite infection and nectar treatment, with infected bees foraging longer at flowers with high compared to low nectar iridoid glycoside concentrations. Parasitized bees were also more likely to return to inflorescences with high iridoid glycoside nectar. Consequently, flowers in the high iridoid glycoside nectar treatment donated significantly more pollen to conspecific stigmas than did flowers in the low iridoid glycoside treatment, suggesting an increase in male plant fitness. Taken together, these results demonstrate that nectar secondary metabolites can mediate the behavior of pollinators with subsequent benefits for estimates of plant reproduction.

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Section: Discussionsupporting

confidence: 92%

Nectar chemistry mediates the behavior of parasitized bees: consequences for plant fitness

Richardson

Bowers

Irwin

2016

Ecology

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“…; Hough et al . )], and is one of the highest known in plant species to date (London‐Shafir, Shafir & Eisikowitch ; Adler & Irwin , ; Boros et al . ; Manson et al .…”

Section: Discussionmentioning

confidence: 99%

Plant toxin levels in nectar vary spatially across native and introduced populations

et al. 2016

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Summary Secondary compounds in nectar can function as toxic chemical defences against floral antagonists, but may also mediate plant–pollinator interactions. Despite their ecological importance, few studies have investigated patterns of spatial variation in toxic nectar compounds in plant species, and none outside their native range. Grayanotoxin I (GTX I) occurs in nectar of invasive Rhododendron ponticum where it is toxic to honeybees and some solitary bee species. We examined (i) geographic variation in the composition of nectar GTX I, as well as GTX III (which is not toxic to these species), in the native and introduced range of R. ponticum, (ii) how their expression is structured at patch and landscape scales within ranges, and (iii) whether climatic and environmental factors underpin spatial patterns. While both GTXs varied within ranges, variation in GTX I, but not GTX III, was detected between ranges. GTX I expression was thus markedly lower or (in 18% of cases) absent from nectar in introduced plants. Spatial autocorrelation was apparent at both patch and landscape scales and in part related to heat load interception by plants (a function of latitude, aspect and slope). As expression of nectar GTXs was generally robust to environmental variation, and aggregated in space, this trait has the potential to be spatially discriminated by consumers. Given the specificity of change to GTX I, and its differential toxicity to some bee species, we conclude that its expression was likely to have been influenced during invasion by interaction with herbivores/consumers, either via pollinator‐mediated selection or enemy release from floral antagonists. Synthesis. As the first demonstration of large‐scale geographic variation and spatial structure in toxic nectar compounds, this work deepens our understanding of the chemical ecology of floral interactions in native and introduced species. Spatially explicit studies of nectar secondary compounds are thus required to show how the extent and structure of spatial variation may affect floral ecology. Future development of invasion theory should incorporate a holistic view of plant defence, beyond antagonistic interactions, which integrates the consequences of chemically defended mutualist rewards.

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“…Although no substantial pollinator richness declines were detected during these early time periods, local density declines or changes in their foraging behavior might have already occurred, preceding the richness declines detected later on (Fig. In addition, the time lag detected for insects could be a response to changes in resource quality (Adler and Irwin 2011, Hoover et al 2012, Nijssen et al 2017, as discussed below. This suggests a time-lag for pollinator richness changes in relation to plants.…”

Section: Effect Of Resource Preferences On Historical Patterns Of Biomentioning

confidence: 93%

Soil eutrophication shaped the composition of pollinator assemblages during the past century

et al. 2019

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Atmospheric nitrogen deposition and other sources of environmental eutrophication have increased substantially over the past century worldwide, notwithstanding the recent declining trends in Europe. Despite the recognized susceptibility of plants to eutrophication, few studies evaluated how impacts propagate to consumers, such as pollinators. Here we aim to test if soil eutrophication contributes to the temporal dynamics of pollinators and their larval resources.We used a temporally and spatially explicit historical dataset with information on species occurrences to test if soil eutrophication, and more specifically nitrogen deposition, contributes to the patterns of change of plant and pollinator richness in the Netherlands over an 80 yr period. We focus on bees and butterflies, two groups for which we have good knowledge of larval resources that allowed us to define groups of species with different nitrogen related diet preferences. For each group we estimated richness changes between different 20-yr periods at local, regional and national scale, using analytical methods developed for analyzing richness changes based on collection data.Our findings suggest that the impacts of soil eutrophication on plant communities propagate to higher trophic levels, but with a time-lag. Pollinators with nitrogenrelated diet preferences were particularly affected, in turn potentially impairing the performance of pollinator-dependent plants. Pollinator declines continued even after their focal plants started to recover. In addition, our results suggest that current levels Research 210 of nitrogen deposition still have a negative impact on most groups here analyzed, constraining richness recoveries and accentuating declines.Our results indicate that the global increase in nitrogen availability plays an important role in the ongoing pollinator decline. Consequently, species tolerances to soil nitrogen levels should be considered across all trophic levels in management plans that aim to halt biodiversity loss and enhance ecosystems services worldwide.

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Nectar alkaloids decrease pollination and female reproduction in a native plant

Cited by 44 publications

References 49 publications

Nectar chemistry mediates the behavior of parasitized bees: consequences for plant fitness

Nectar chemistry mediates the behavior of parasitized bees: consequences for plant fitness

Plant toxin levels in nectar vary spatially across native and introduced populations

Soil eutrophication shaped the composition of pollinator assemblages during the past century

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