Abstract
Extreme temperature events are increasing in frequency and intensity due to climate change. Such events threaten insects, including pollinators, pests and disease vectors. Insect critical ...thermal limits can be enhanced through acclimation, yet evidence that plasticity aids survival at extreme temperatures is limited. Here, using meta-analyses across 1374 effect sizes, 74 studies and 102 species, we show that thermal limit plasticity is pervasive but generally weak: per 1 °C rise in acclimation temperature, critical thermal maximum increases by 0.09 °C; and per 1 °C decline, critical thermal minimum decreases by 0.15 °C. Moreover, small but significant publication bias suggests that the magnitude of plasticity is marginally overestimated. We find juvenile insects are more plastic than adults, highlighting that physiological responses of insects vary through ontogeny. Overall, we show critical thermal limit plasticity is likely of limited benefit to insects during extreme climatic events, yet we need more studies in under-represented taxa and geographic regions.
1. We briefly review current understanding of wild pollinators and pollination services on farmlands. 2. We consider how concepts in plant ecology - community assembly and functional trait diversity ...- may be applied to create diverse, wild pollinator communities across scales in agroecosystems. 3. We also make recommendations for best practices to enhance pollination services and create more sustainable food production systems under changing environmental conditions, including creating greater landscape connectivity, embracing pollinator dynamics, and providing incentives and other motivations to support these practices. 4. Synthesis. We highlight the opportunity for agricultural lands to serve a dual role for both food production and pollinator conservation, and conclude by posing unanswered questions and top priorities for future studies.
•Almond trees are visited by a large number of wild pollinators.•Natural area around the fields increased pollinator richness and honeybee visits.•The local flower community increased, directly and ...indirectly, almond production.•Pollinator-species diversity directly increased almond production.•Preserving natural vegetation favors wild pollinators and almond production.
Wild pollinators are a valuable natural resource for crops, as they often increase their production and quality. For this reason, there is currently a great interest in the development of management and conservation tools that help to maintain a wide variety of wild pollinators in agro-systems. To achieve this, it becomes a priority to study the diversity of wild pollinators in relevant crops as well as the local and landscape characteristics that benefit them. The almond tree (Prunus dulcis) is a crop of high economic interest, with a large dependence on pollinators due to the self-incompatibility of most of its varieties and, thus, it is very vulnerable to pollinator losses. By using field data and habitat characterization of 18 almond fields in Mallorca Island (Spain), we assessed how the abundance and diversity of pollinators varied with local and landscape characteristics (at 1 and 2 km buffer zones) of the fields, and how those affected almond production (fruit set). Almond trees were mostly pollinated by honeybees, but they were also visited by a large number of wild pollinators. The percentage of natural area in the 2 km buffer zones increased both pollinator-species richness and honeybee visits. At the field level, the flower community in the ground positively influenced almond production, both directly and indirectly by increasing the diversity of wild pollinators. Pollinator-species diversity directly increased fruit production but was negatively affected by honeybee abundance, which suggests that a high density of honeybees might result in negative effects on almond production through competition with wild pollinators. Management strategies to improve almond production might include favoring wild pollinators through the maintenance of natural habitats surrounding crop fields, and preserving the flowering herb community that occurs spontaneously in the groundcover of almond fields in Mediterranean areas.
Although several insect orders have been deeply studied in plant–animal interactions (e.g. pollination) cockroaches have traditionally been ignored in taxonomic and ecological studies. However, they ...could be playing a role in the reproduction of several plants. To date, 8 plant species use cockroaches as a pollination agent. In our study, we have reviewed 2865 records from citizen science platforms and our own data from the Iberian Peninsula to find flower visits made by cockroaches. We have detected 51 interaction records involving at least 8 different cockroach species and 35 plant species. Furthermore, nearly half of the detected cockroaches carried pollen on various parts of their bodies. These insects were found to mainly visit white, yellow and pink flowers from Apiaceae, Asteraceae and Cistaceae plant families (among others) mainly in late spring and early summer. However, for the confirmation of effective pollination, new studies must be carried out. Additionally, although the existence of pollination syndrome is far from being understood, we provide new insights that could help shed some light on this unknown relationship. Here we provide the first approximation of cockroach floral perception and we have detected that white flowers show the best fit and higher conspicousness to cockroach colour vision, as suggested for other neglected pollinator insects.
By causing phenological shifts that vary among species, climate change is altering time envelopes for species interactions, often with unexpected demographic consequences. Indirect interactions, like ...apparent competition and apparent facilitation, are especially likely to change in duration because they involve multiple interactors, increasing the likelihood of asynchronous phenological shifts by at least one interactor. Thus, we might observe ecological surprises if intermediaries of indirectly interacting species change their mediating behaviour.
We explored this possibility in a plant–pollinator community that is likely to experience asynchronous phenological shifts. We advanced and delayed the flowering phenology of two ubiquitous exotic plants of western Washington prairies, Hypochaeris radicata and Cytisus scoparius, relative to seven native perennial forb species whose phenologies remained unmanipulated. These species interact indirectly through shared pollinators, whose foraging behaviour influences plant reproductive success. We quantified impacts of experimental phenological shifts on seedset, pollinator visitation rates and visiting pollinator composition relative to an unmanipulated control. We first verified that unmanipulated indirect interactions between native and exotic plants were strong, ranging from facilitative to competitive.
Seedset of native plants was strongly affected by changes in exotic flowering phenology, but the magnitude and direction of effects were not predicted by the nature of the original indirect interaction (facilitative vs. neutral vs. competitive) or the change in interaction duration. The relationship between pollinator visitation and seedset changed for most species, though changes in pollinator visitation rate and pollinator composition were not as widespread as effects on native seedset.
Synthesis. Changes in pollinator foraging behaviour in response to changes in available floral resources are probably responsible for the unexpected effects we observed. Asynchronous phenological shifts have the potential to produce large and unexpected effects on reproductive success via indirect interactions.
The time envelopes for indirect interactions (between two species mediated by a third species) are especially likely to be affected by phenological shifting, because interactors may not shift synchronously. Such shifts could change mediating behavior by the intermediary species, affecting the interaction outcome. We manipulated flowering phenology of exotic plants and found strong effects on seed production by neighboring native plants, probably due to changes in foraging behavior by shared pollinators.
Morphological trait‐matching and species abundance are thought to be the main factors affecting the frequency and strength of mutualistic interactions. However, the relative importance of ...trait‐matching and species abundance in shaping species interactions across environmental gradients remains poorly understood, especially for plant–insect mutualisms involving generalist species.
Here, we characterised variation in species and trait composition and the relative importance of trait‐matching and species abundance in shaping plant–Hymenoptera and plant–Diptera mutualisms in four meadows across an elevational gradient (2,725–3,910 m) in Yulong Snow Mountain, Southwest China. We also evaluated the effects of morphological traits of flower visitors and plant composition on their foraging specialisation (d' and normalised degree).
There was a high degree of dissimilarity in the composition of Hymenoptera and Diptera visitors and their visited plants between communities. This variation was mainly driven by the spatial replacement of species. Both for plant–Hymenoptera and plant–Diptera networks, trait‐matching between nectar tube depth and proboscis length was a stronger predictor of the interactions between temporally co‐occurring plants and flower visitors than species abundance. Fourth‐corner analyses revealed statistically significant trait‐matching between nectar tube depth and proboscis length in plant–Hymenoptera networks at all sites, suggesting that Hymenoptera consistently foraged on plant species with nectar tube depths matching their proboscis lengths. By contrast, significant trait‐matching in plant–Diptera networks was only observed at the two lower elevation sites. The species‐level specialisation d' of flower visitors increased significantly as the proboscis length and the difference in nectar tube depth between the plant community and the plants visited by flower visitors increased.
Our results highlight that the importance of trait‐matching in shaping pairwise interactions and niche partitioning depends on the specific features (e.g. species composition and trait availability) of the plant–pollinator system. For specialised plant–Hymenoptera systems, trait‐matching is an important determinant of species interactions, whereas for generalist plant–Diptera systems, trait‐matching is relatively unimportant.
Trait‐matching across environmental gradients remains poorly understood, particularly in plant–insect mutualisms involving generalist species. This study is one of the first to evaluate how elevational changes affect the degree of trait‐matching between insect visitors and plant hosts.
ABSTRACT
The aculeate wasps are one of the most diverse and speciose insect taxa; they are omnipresent across ecosystems and exhibit diverse co‐evolutionary and exploitative associations with other ...organisms. There is widespread conjecture that aculeate wasps are likely to perform essential ecological and economic services of importance to the health, well‐being and nutritional needs of our planet. However, the scope and nature of the ecosystem services they provide are not well understood relative to other insect groups (e.g. bees, butterflies, beetles); an appreciation of their value is further tarnished by their public reputation as pointless pests. Here, we conduct the first comprehensive review of how aculeate wasps contribute to the four main areas of ecosystem services: regulatory, provisioning, supporting and cultural services. Uniting data from a large but previously disconnected literature on solitary and social aculeate wasps, we provide a synthesis on how these insects perform important ecosystem services as parasites, predators, biological indicators, pollinators, decomposers and seed dispersers; and their additional services as a sustainable alternative to meat for human consumption, and medicinal potential as sources of research leads for anti‐microbials and cancer treatments. We highlight how aculeate wasps offer substantial, but largely overlooked, economic benefits through their roles in natural pest management and biological control programs. Accordingly, we provide data‐driven arguments for reasons to consider the ecosystem service value of aculeate wasps on a par with other ‘useful’ insects (e.g. bees). Finally, we provide a research roadmap identifying the key areas of research required to capitalise better on the services provided by these important insects.
The interactions of plants with environment and insects are bi-directional and dynamic. Consequently, a myriad of mechanisms has evolved to engage organisms in different types of interactions. These ...interactions can be mediated by allelochemicals known as volatile organic compounds (VOCs) which include volatile terpenes (VTs). The emission of VTs provides a way for plants to communicate with the environment, including neighboring plants, beneficiaries (e.g., pollinators, seed dispersers), predators, parasitoids, and herbivores, by sending enticing or deterring signals. Understanding terpenoid distribution, biogenesis, and function provides an opportunity for the design and implementation of effective and efficient environmental calamity and pest management strategies. This review provides an overview of plant-environment and plant-insect interactions in the context of terpenes and terpenoids as important chemical mediators of these abiotic and biotic interactions.
Some pollination systems, such as buzz‐pollination, are associated with floral morphologies that require a close physical interaction between floral sexual organs and insect visitors. In these ...systems, a pollinator's size relative to the flower may be an important feature determining whether the visitor touches both male and female sexual organs and thus transfers pollen between plants efficiently. To date, few studies have addressed whether in fact the “fit” between flower and pollinator influences pollen transfer, particularly among buzz‐pollinated species. Here we use Solanum rostratum, a buzz‐pollinated plant with dimorphic anthers and mirror‐image flowers, to investigate whether the morphological fit between the pollinator's body and floral morphology influences pollen deposition. We hypothesized that when the size of the pollinator matches the separation between the sexual organs in a flower, more pollen should be transferred to the stigma than when the visitor is either too small or too big relative to the flower. To test this hypothesis, we exposed flowers of S. rostratum with varying levels of separation between sexual organs, to bumblebees (Bombus terrestris) of different sizes. We recorded the number of visits received, pollen deposition, and fruit and seed production. We found higher pollen deposition when bees were the same size or bigger than the separation between anther and stigma within a flower. We found a similar, but not statistically significant pattern for fruit set. In contrast, seed set was more likely to occur when the size of the flower exceeded the size of the bee, suggesting that other postpollination processes may be important in translating pollen receipt to seed set. Our results suggest that the fit between flower and pollinator significantly influences pollen deposition in this buzz‐pollinated species. We speculate that in buzz‐pollinated species where floral morphology and pollinators interact closely, variation in the visitor's size may determine whether it acts mainly as a pollinator or as a pollen thief (i.e., removing pollen rewards but contributing little to pollen deposition and fertilization).
We conducted an experimental test with Solanum rostratum, a buzz‐pollinated plant with dimorphic anthers and mirror‐image flowers, to investigate whether the morphological fit between the pollinator's body and floral morphology influences pollen deposition. We exposed flowers of S. rostratum with varying levels of separation between sexual organs, to bumblebees (Bombus terrestris) of different sizes. Our results suggest that the fit between flower and pollinator significantly influences pollen deposition in this buzz‐pollinated species and determines whether floral visitor acts mainly as a pollinator or as a pollen thief.
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