Explore the vast range of titles available.

Climate change can alter species interactions essential for maintaining biodiversity and ecosystem function, such as pollination. Understanding the interactive effects of multiple abiotic conditions on floral traits and pollinator visitation are important to anticipate the implications of climate change on pollinator services. Floral visual and olfactory traits were measured from individuals of four forb species subjected to drought or normal water availability, and elevated or ambient concentrations of CO2 in a factorial design. Pollinator visitation rates and community composition were observed in single-species and multi-species forb assemblages. Drought decreased floral visual traits and pollinator visitation rates but increased volatile organic compound (VOC) emissions, whereas elevated CO2 positively affected floral visual traits, VOC emissions and pollinator visitation rates. There was little evidence of interactive effects of drought and CO2 on floral traits and pollinator visitation. Interestingly, the effects of climate treatments on pollinator visitation depended on whether plants were in single- or multi-species assemblages. Components of climate change altered floral traits and pollinator visitation, but effects were modulated by plant community context. Investigating the response of floral traits, including VOCs, and context-dependency of pollinator attraction provides additional insights and may aid in understanding the overall effects of climate change on plant–pollinator interactions.

Volatile organic compounds (VOCs) play important roles in the environmental adaptation and fitness of plants. Comparison of the qualitative and quantitative differences in VOCs among closely related taxa and assessing the effects of environment on their emissions are important steps to deducing VOC function and evolutionary importance. Headspace VOCs from five taxa of sagebrush (Artemisia, subgenus Tridentatae) growing in two common gardens were collected and analyzed using GC-MS. Of the 74 total VOCs emitted, only 15 were needed to segregate sagebrush taxa using Random Forest analysis with a low error of 4%. All but one of these 15 VOCs showed qualitative differences among taxa. Ordination of results showed strong clustering that reflects taxonomic classification. Random Forest identified five VOCs that classify based on environment (2% error), which do not overlap with the 15 VOCs that segregated taxa. We show that VOCs can discriminate closely related species and subspecies of Artemisia, which are difficult to define using molecular markers or morphology. Thus, it appears that changes in VOCs either lead the way or follow closely behind speciation in this group. Future research should explore the functions of VOCs, which could provide further insights into the evolution of sagebrushes.

The importance of plant volatiles in mediating interactions between plant species is much debated. Here, we demonstrate that the parasitic plant Cuscuta pentagona (dodder) uses volatile cues for host location. Cuscuta pentagona seedlings exhibit directed growth toward nearby tomato plants (Lycopersicon esculentum) and toward extracted tomato-plant volatiles presented in the absence of other cues. Impatiens (Impatiens wallerana) and wheat plants (Triticum aestivum) also elicit directed growth. Moreover, seedlings can distinguish tomato and wheat volatiles and preferentially grow toward the former. Several individual compounds from tomato and wheat elicit directed growth by C. pentagona, whereas one compound from wheat is repellent. These findings provide compelling evidence that volatiles mediate important ecological interactions among plant species.

The tree-killing mountain pine beetle (Dendroctonus ponderosae Hopkins) is an important disturbance agent of western North American forests and recent outbreaks have affected tens of millions of hectares of trees. Most western North American pines (Pinus spp.) are hosts and are successfully attacked by mountain pine beetles whereas a handful of pine species are not suitable hosts and are rarely attacked. How pioneering females locate host trees is not well understood, with prevailing theory involving random landings and/or visual cues. Here we show that female mountain pine beetles orient toward volatile organic compounds (VOCs) from host limber pine (Pinus flexilis James) and away from VOCs of non-host Great Basin bristlecone pine (Pinus longaeva Bailey) in a Y-tube olfactometer. When presented with VOCs of both trees, females overwhelmingly choose limber pine over Great Basin bristlecone pine. Analysis of VOCs collected from co-occurring limber and Great Basin bristlecone pine trees revealed only a few quantitative differences. Noticeable differences included the monoterpenes 3-carene and D-limonene which were produced in greater amounts by host limber pine. We found no evidence that 3-carene is important for beetles when selecting trees, it was not attractive alone and its addition to Great Basin bristlecone pine VOCs did not alter female selection. However, addition of D-limonene to Great Basin bristlecone pine VOCs disrupted the ability of beetles to distinguish between tree species. When presented alone, D-limonene did not affect behavior, suggesting that the response is mediated by multiple compounds. A better understanding of host selection by mountain pine beetles could improve strategies for managing this important forest insect. Moreover, elucidating how Great Basin bristlecone pine escapes attack by mountain pine beetles could provide insight into mechanisms underlying the incredible longevity of this tree species.

A new long-legged fly species, Chrysotus soya sp. nov. (Diptera: Dolichopodidae), is described and illustrated from specimens collected in soybean fields near Brookings, South Dakota, USA. The abundance of this species in soybeans suggests it plays an important role as a beneficial predator.

While the importance of floral odours for pollinator attraction relative to visual cues is increasingly appreciated, how they structure community‐level plant–pollinator interactions is poorly understood. Elucidating the functional roles of flowering plant species with respect to their floral volatile organic compounds (VOCs) and how those roles vary over the growing season is an initial step towards understanding the contribution of floral VOCs to plant–pollinator interaction structure. We sampled the floral VOCs, phenologies and bee visitors of naturally growing plants in a montane meadow in the Northern Rocky Mountains of USA in order to acquire a base understanding of how floral VOCs and other plant traits may structure plant–pollinator interactions across the growing season. We expected forb species with floral VOCs that were original (far from the community mean) and unique (far from the nearest neighbour) would have few pollinating partners (i.e. specialists), while forbs with non‐original or highly variable floral VOCs would form the generalist core of interactors, thereby contributing to network nestedness (specialists interacting with nested subsets of generalists). Network modularity (patterns of distinct, highly connected subnetworks) could be influenced by groups of pollinators that are attracted to or repelled by certain floral bouquets. Species blooming in early spring emitted similar floral VOC blends containing generalist attractants, whereas floral VOC complexity was highest in mid to late summer. Forb species varied in the originality, uniqueness, and intraspecific variation (i.e. dispersion) of their floral VOCs, indicating the potential for different functional roles in plant–pollinator networks. Specifically, the originality, uniqueness and dispersion of forb species’ floral VOCs increased across the growing season. Floral VOCs influenced forb interactions with pollinators. Floral VOCs contributed to the nested structure, but not modular structure, of community‐level plant–pollinator network structure. Forb species with more original floral VOCs were less connected, while forb species emitting more compounds and with higher intraspecific variation in floral VOCs were more connected to pollinators. These findings show that floral scent plays important roles in structuring bee–forb interactions and guiding seasonal patterns in complex communities. Understanding seasonal patterns in floral VOCs may have important implications for plant–pollinator interactions among communities differing in species composition, or as shifts occur in suites of co‐flowering species due to climate change. A free Plain Language Summary can be found within the Supporting Information of this article. A free Plain Language Summary can be found within the Supporting Information of this article.

Public lands face growing demands to provide ecosystem services, while protecting species of conservation concern, like insect pollinators. Insect pollinators are critical for the maintenance of biodiversity and ecosystem function, but it is unclear how management of public lands influence pollinator conservation. We found 63 studies investigating the effects of prescribed burning, logging, grazing, invasive species removal, revegetation with wildflower mixes, and hosting commercial pollinators, on native insect pollinators on natural and semi-natural ecosystems in the US and summarized the results across taxa and habitat types. Manual removal of invasive shrubs and revegetation with wildflower mixes had consistently positive effects on pollinators. Grazing had neutral effects on pollinators in the Great Plains, but negative effects elsewhere. Prescribed burning had neutral or positive effects for bees depending on the habitat type, with occasional negative effects on butterflies. Logging had neutral to positive effects that were more uniform across ecosystems and taxa than burning. Burning combined with logging benefited pollinators, even when burning or logging alone had no effects. Although poorly studied, hosting commercial pollinators may negatively affect wild bees through pathogen transmission and competition for floral resources. Despite the rapid accumulation of information on factors contributing to pollinator declines, the effects of management actions on pollinators remain understudied for many taxa and habitat types in the US. Improving our understanding of the effects of public land management on pollinators is essential to conserve ecosystem health and services required by society.

Orchid bees are abundant and widespread in the Neotropics, where males are important pollinators of orchids they visit to collect fragrant chemicals later used to court females. Assemblages of orchid bees have been intensively surveyed in parts of Central America, but less so in Belize, where we studied them during the late-wet and early-dry seasons of 2015-2020. Using bottle-traps baited with chemicals known to attract a variety of orchid bee species, we conducted surveys at sites varying in latitude, historical annual precipitation, elevation, and the presence of nearby agricultural activities. Each sample during each survey period consisted of the same number of traps and the same set of chemical baits, their positions randomized along transects. In 86 samples, we collected 24 species in four genera: (16 species), (3), (3), and (2). During our most extensive sampling (December 2016-February 2017), species diversity was not correlated with latitude, precipitation, or elevation; species richness was correlated only with precipitation (positively). However, a canonical correspondence analysis indicated that species composition of assemblages varied across all three environmental gradients, with species like , and most common in the drier north, and , and more so in the wetter southeast. Other species, such as and , were common throughout the area sampled. Mean species diversity was higher at sites with agricultural activities than at sites separated from agricultural areas. A Chao1 analysis suggests that other species should yet be found at our sites, a conclusion supported by records from adjacent countries, as well as the fact that we often added new species with repeated surveys of the same sites up through early 2020, and with the use of alternative baits. Additional species may be especially likely if sampling occurs outside of the months/seasons that we have sampled so far.

Trade‐offs between plant defense investment and fitness traits, including growth, are often invoked to explain evolutionary strategies targeted at resisting herbivores. Many Pinus species have specialized herbivores, including the mountain pine beetle (MPB), Dendroctonus ponderosae, and have historically been a focus of defense investigations. We compared defense traits of two high‐elevation Pinus species, P. aristata and P. flexilis, that are hosts to MPB and hypothesized to have different growth and defense traits and potential trade‐offs. Interspecific differences were assessed by sampling trees within the same stands, and intraspecific differences were assessed by sampling stands at sites across latitudes where both species co‐occurred. Constitutive defenses were measured at Day 0, and the timing, concentration, and composition of an induced resin defense response were assessed by sampling at 1, 4, and 30 days following either mechanical wounding only or a simulated MPB attack using its primary fungal symbiont Grosmannia clavigera. At Day 4, induced resin concentrations did not differ between mechanical wounding and simulated MPB attack in either species. By Day 30, resin defense concentrations in response to simulated MPB attack were greater than those in response to mechanical wounding and were >19‐fold greater than constitutive levels. Results suggest that initial induced resin defense responses in the two species are likely generalized, with a delayed response that is targeted specifically at MPB and G. clavigera. At all sites, P. aristata had higher concentrations of constitutive and Day‐30 induced resin defenses than P. flexilis, although P. flexilis induced proportionately more. Trade‐offs in growth and defense between the species were only found at the two most climatically favorable sites where P. aristata grew slower than P. flexilis. No trade‐offs were found between the two defense types at either biological scale. Overall, our findings highlight that the two pine species growing in the same stands (1) have a delayed response to a specialized native herbivore and fungal symbiont, (2) only exhibited interspecific defense–growth trade‐offs at two climatically favorable sites, and showed no intraspecific defense–growth trade‐offs, (3) showed no trade‐offs between constitutive and induced defenses at either biological scale, and (4) have evolved different defense strategies.

Patterns of abundance across space and time, and intraspecific variation in body size, are two species attributes known to influence diet breadth and the structure of interaction networks. Yet, the relative influence of these attributes on diet breadth is often assumed to be equal among taxonomic groups, and the relationship between intraspecific variation in body size on interaction patterns is frequently neglected. We observed bee–flower interactions in multiple locations across Montana, USA, for two growing seasons and measured spatial and temporal patterns of abundance, along with interspecific and intraspecific variation in body size for prevalent species. We predicted that the association between spatial and temporal patterns of abundance and intraspecific variation in body size, and diet breadth, would be stronger for bumble bee compared to non-bumble bee species, because species with flexible diets and long activity periods can interact with more food items. Bumble bees had higher local abundance, occurred in many local communities, more intraspecific variation in body size, and longer phenophases compared to non-bumble bee species, but only local abundance and phenophase duration had a stronger positive association with the diet breadth of bumble bee compared to non-bumble bee species. Communities with a higher proportion of bumble bees also had higher intraspecific variation in body size at the network-level, and network-level intraspecific variation in body size was positively correlated with diet generalization. Our findings highlight that the association between species attributes and diet breadth changes depending on the taxonomic group, with implications for the structure of interaction networks.