Energetics and pollination ecology

Bumblebee thermoregulation at increasing temperatures is affected by behavioral state

Over the past decades, increasing environmental temperatures have been identified as one of the causes of major insect population declines and biodiversity loss. However, it is unclear how these rising temperatures affect endoheterothermic insects, like bumblebees, that have evolved thermoregulatory capacities to exploit cold and temperate habitats. To investigate this, we measured head, thoracic, and abdominal temperature of bumblebee (Bombus terrestris) workers across a range of temperatures (24 °C-32 °C) during three distinct behaviors. In resting bumblebees, the head, abdomen, and thorax conformed to the environmental temperature. In pre-flight bumblebees, the head and abdominal temperatures were elevated with respect to the environmental temperature, while the thoracic temperature was maintained, indicating a pre-flight muscle warming stage. In post-flight bumblebees, abdominal temperature increased at the same rate as environmental temperature, but the head and the thoracic temperature did not. By calculating the excess temperature ratio, we show that thermoregulation in bumblebees during flight is partially achieved by the active transfer of heat produced in the thorax to the abdomen, where it can more easily be dissipated. These results provide the first indication that the thermoregulatory abilities of bumblebees are plastic and behavior dependent. We also show that the flight speed and number of workers foraging increase with increasing temperature, suggesting that bees do not avoid flying at these temperatures despite its impact on behavioral performance.

The evolution of flower-pollinator trait matching, and why do some alpine gingers appear to be mismatched?

BACKGROUND AND AIMS

Morphological matching between flower and pollinator traits has been documented in diverse plant lineages. Indeed, the matching of corolla tube length and pollinator tongue length has been cited repeatedly as a classic case of coevolution. However, there are many possible evolutionary routes to trait matching. Our aim here is both to review the evolutionary mechanisms of plant-pollinator trait matching and to investigate a specific case of trait matching/mismatching in a genus of alpine gingers.

METHODS

Roscoea gingers with long corolla tubes in the western Himalayas have pollinators with correspondingly long tongues, but the match between corolla tube and pollinator tongue lengths is not seen in the eastern Himalayas. Six floral traits were measured, including corolla tube depth, an internal trait controlling pollinator access to nectar. We calculated coefficients of variation and phylogenetically controlled correlation patterns of these traits in six Roscoea species in order to gain possible insights into stabilizing selection and modularization of these traits.

KEY RESULTS

The distal (nectar-containing) portion of the corolla tube exhibited lower coefficients of variations than did the basal portion. This is consistent with the hypothesis that pollinators mediate stabilizing selection on the distal, but not basal, portion of the corolla tube. This result, combined with phylogenetic data, suggests that the elevated liquid level of nectar in the distal tube evolved subsequent to dispersal into the eastern Himalayan region and loss of long-tongue pollinators. After accounting for phylogeny, corolla tube length, anther length, style length and labellum width were all intercorrelated. Corolla-tube depth was not part of this covariational module, however, suggesting separate adaptation to short-tongued pollinators.

CONCLUSIONS

The reduction in functional corolla tube depth in the Roscoea appears to be related to the loss of long-tongued pollinators associated with dispersal to the eastern Himalayas and pollination by short-tongued pollinators. The apparent mismatch between floral tubes and pollinator tongues is a case of cryptic trait matching between flowers and pollinators, underscoring the importance of combining floral anatomy with pollination ecology in assessing plant-pollinator trait matching.

Post-secretory synthesis of a natural analog of iron-gall ink in the black nectar of Melianthus spp

The black nectar produced by Melianthus flowers is thought to serve as a visual attractant to bird pollinators, but the chemical identity and synthesis of the black pigment are unknown. A combination of analytical biochemistry, transcriptomics, proteomics, and enzyme assays was used to identify the pigment that gives Melianthus nectar its black color and how it is synthesized. Visual modeling of pollinators was also used to infer a potential function of the black coloration. High concentrations of ellagic acid and iron give the nectar its dark black color, which can be recapitulated through synthetic solutions containing only ellagic acid and iron(iii). The nectar also contains a peroxidase that oxidizes gallic acid to form ellagic acid. In vitro reactions containing the nectar peroxidase, gallic acid, hydrogen peroxide, and iron(iii) fully recreate the black color of the nectar. Visual modeling indicates that the black color is highly conspicuous to avian pollinators within the context of the flower. Melianthus nectar contains a natural analog of iron-gall ink, which humans have used since at least medieval times. This pigment is derived from an ellagic acid-Fe complex synthesized in the nectar and is likely involved in the attraction of passerine pollinators endemic to southern Africa.

Early flowering changes robusta coffee yield responses to climate stress and management

A shift towards earlier flowering is a widely noted consequence of climate change for the world's plants. However, whether early flowering changes the way in which plants respond to climate stress, and in turn plant yield, remains largely unexplored. Using 10 years of flowering time and yield observations (Total N = 5580) from 558 robusta coffee (Coffea canephora) farms across Vietnam we used structural equation modelling (SEM) to examine the drivers of flowering day anomalies and the consequent effects of this on coffee climate stress sensitivity and management responses (i.e. irrigation and fertilization). SEM allowed us to model the cascading and interacting effects of differences in flowering time, growing season length and climate stress. Warm nights were the main driver of early flowering (i.e. flowering day anomalies <0), which in turn corresponded to longer growing seasons. Early flowering was linked to greater sensitivity of yield to temperature during flowering (i.e. early in the season). In contrast, when late flowering occurred yield was most sensitive to temperature and rainfall later in the growing season, after flowering and fruit development. The positive effects of tree age and fertilizer on yield, apparent under late flowering conditions, were absent when flowering occurred early. Late flowering models predicted yields under early flowering conditions poorly (a 50 % reduction in cross-validated R² of 0.54 to 0.27). Likewise, models based on early flowering were unable to predict yields well under late flowering conditions (a 75 % reduction in cross-validated R², from 0.58 to 0.14). Our results show that early flowering changes the sensitivity of coffee production to climate stress and management and in turn our ability to predict yield. Our results indicate that changes in plant phenology need to be taken into account in order to more accurately assess climate risk and management impacts on plant performance and crop yield.

An Odorant Receptor from the Proboscis of the Cotton Bollworm Helicoverpa armigera (Lepidoptera: Noctuidae) Narrowly Tuned to Indole

Simple Summary

Odorant receptors (ORs) are at the core of the high-efficiency and sensitive olfactory system in insects. The expression and specific function of ORs largely contribute to the habits and speciation of one species. Although being predominantly expressed in the antennae, ORs in non-olfactory organs are suggested to have particular roles in promoting the reproduction or host fitness of insects. Our previous work has identified four ORs in the mouthpart organs of Helicoverpa armigera. Here, we amplified the full-length sequences of HarmORs from the proboscis. Further functional characterization suggested that HarmOR30 narrowly tuned to indole, the vital nitrogen-containing compounds that mediate tritrophic interactions. Our study deepens the insight into the olfactory perception of H. armigera, and explored a candidate functional receptor target for studying the interaction between insects and their plant hosts.

Abstract

Helicoverpa armigera is a serious agricultural pest with polyphagous diets, widespread distribution, and causing severe damage. Among sixty-five candidate ORs in H. armigera, the co-receptor HarmOrco and three specific ORs with partial sequences were identified to be expressed in the proboscis by our previous work, whereas their exact function is not known yet. In this study, we first confirmed the expression of these ORs in the proboscis by full-length cloning, which obtained the complete coding region of HarmOrco, OR24, and OR30. We then performed functional identification of HarmOR24 and OR30 by co-expressing them respectively with HarmOrco in Xenopus oocytes eukaryotic expression system combined with two-electrode voltage-clamp physiology. By testing the response of HarmOR24/OR30-expressing oocytes against eighty structural-divergent compounds, respectively, HarmOR30 was characterized to narrowly tune to indole and showed a specific tuning spectrum compared to its ortholog in Spodoptera littoralis. As indole is a distinctive herbivore-induced plant volatile and floral scent component, HarmOR30 might play roles in foraging and mediating the interactions between H. armigera with its surrounding environment.

The Tongue in Three Species of Lemurs: Flower and Nectar Feeding Adaptations

The mobility of the primate tongue allows for the manipulation of food, but, in addition, houses both general sensory afferents and special sensory end organs. Taste buds can be found across the tongue, but the ones found within the fungiform papillae on the anterior two thirds of the tongue are the first gustatory structures to come into contact with food, and are critical in making food ingestion decisions. Comparative studies of both the macro and micro anatomy in primates are sparse and incomplete, yet there is evidence that gustatory adaptation exists in several primate taxa. One is the distally feathered tongues observed in non-destructive nectar feeders, such as Eulemur rubriventer. We compare both the macro and micro anatomy of three lemurid species who died of natural causes in captivity. We included the following two non-destructive nectar feeders: Varecia variegata and Eulemur macaco, and the following destructive flower feeder: Lemur catta. Strepsirrhines and tarsiers are unique among primates, because they possess a sublingua, which is an anatomical structure that is located below the tongue. We include a microanatomical description of both the tongue and sublingua, which were accomplished using hematoxylin-eosin and Masson trichrome stains, and scanning electron microscopy. We found differences in the size, shape, and distribution of fungiform papillae, and differences in the morphology of conical papillae surrounding the circumvallate ones in all three species. Most notably, large distinct papillae were present at the tip of the tongue in nectar-feeding species. In addition, histological images of the ventro-apical portion of the tongue displayed that it houses an encapsulated structure, but only in Lemur catta case such structure presents cartilage inside. The presence of an encapsulated structure, coupled with the shared morphological traits associated with the sublingua and the tongue tip in Varecia variegata and Eulemur macaco, point to possible feeding adaptations that facilitate non-destructive flower feeding in these two lemurids.

The Evolution of Resource Provisioning in Pollination Mutualisms

AbstractResource dynamics influence the contemporary ecology of consumer-resource mutualisms. Suites of resource traits, such as floral nectar components, also evolve in response to different selective pressures, changing the ecological dynamics of the interacting species at the evolutionary equilibrium. Here we explore the evolution of resource-provisioning traits in a biotically pollinated plant that produces nectar as a resource for beneficial consumers. We develop a mathematical model describing natural selection on two quantitative nectar traits: maximum nectar production rate and maximum nectar reservoir volume. We use this model to examine how nectar production dynamics evolve under different ecological conditions that impose varying cost-benefit regimes on resource provisioning. The model results predict that natural selection favors higher nectar production when ecological factors limit the plant or pollinator's abundance (e.g., a lower productivity environment or a higher pollinator conversion efficiency). We also find that nectar traits evolve as a suite in which higher costs of producing one trait select for a compensatory increase in investment in the other trait. This empirically explicit approach to studying the evolution of consumer-resource mutualisms illustrates how natural selection acting via direct and indirect pathways of species interactions generates patterns of resource provisioning seen in natural systems.

The context dependency of pollinator interference: How environmental conditions and co-foraging species impact floral visitation

Animals often change their behaviour in the presence of other species and the environmental context they experience, and these changes can substantially modify the course their populations follow. In the case of animals involved in mutualistic interactions, it is still unclear how to incorporate the effects of these behavioural changes into population dynamics. We propose a framework for using pollinator functional responses to examine the roles of pollinator-pollinator interactions and abiotic conditions in altering the times between floral visits of a focal pollinator. We then apply this framework to a unique foraging experiment with different models that allow resource availability and sublethal exposure to a neonicotinoid pesticide to modify how pollinators forage alone and with co-foragers. We found that all co-foragers interfere with the focal pollinator under at least one set of abiotic conditions; for most species, interference was strongest at higher levels of resource availability and with pesticide exposure. Overall our results highlight that density-dependent responses are often context-dependent themselves.

Discrimination of small sugar concentration differences helps the nectar-feeding bat Leptonycteris yerbabuenae cover energetic demands

Every day nectar-feeding animals face an energetic challenge during foraging: they must locate and select flowers that provide nectar with adequate amounts of sugar to cover their very high energy needs. To understand this decision-making process, it is crucial to know how accurately sugar concentration differences can be discriminated. In a controlled laboratory setting, we offered the nectar-specialist bat Leptonycteris yerbabuenae the choice between different sugar solutions covering the entire concentration range of bat-pollinated plants (3-33%). When feeding on solutions below 10% sugar concentration, L. yerbabuenae were unable to cover their energetic demands because of physiological constraints. Their ability to discriminate sugar concentrations was better than that of any other nectar-feeding animal studied to date. At sugar concentrations below 15%, L. yerbabuenae can discriminate solutions differing by only 0.5%. The bats may utilize this fine-tuned ability to select nectar from flowers with reward qualities that provide them with the necessary amount of energy to survive.

Quantitative comparison of flowering phenology traits among trees, perennial herbs, and annuals in a temperate plant community

PREMISE

Flowering phenology may differ among life forms due to the costs and benefits to attract pollinators, dependence on outcross pollination, and resource availability in their habitats. However, few studies have compared flowering phenology among life forms within a community and described flowering phenology at the individual, species, and community levels.

METHODS

We recorded flowering events for individuals of insect-pollinated trees, perennial herbs, and annuals from spring to summer of 2016 and 2017 in a warm-temperate forest in Japan. To compare phenological variables including mean and variance of flowering length, we standardized the number of observed individuals for each species and tested differences in variables, considering the phylogenetic relationships among species.

RESULTS

Total flowering length in trees (9-50 d) was significantly shorter than perennial herbs (27-113 d) or annuals (22-89 d), but mean flowering length was not significantly different among them. Flowering length variance was significantly smaller and intraspecies synchrony significantly higher in trees than in perennial herbs and annuals. At the community level, flowering times largely overlapped among successively flowering species, but interspecies synchrony was positive for all life forms.

CONCLUSIONS

Shorter total flowering length and higher intraspecific synchrony in trees are explained by a modified pollinator attraction hypothesis suggesting that selection favors higher intraspecific synchrony because it promotes between-individual movement of pollinators. At the community level, positive interspecific synchrony for all life forms supports the hypothesis that flowering times tend to converge among species.

Floral display and habitat fragmentation: Effects on the reproductive success of the threatened mass-flowering Conospermum undulatum (Proteaceae)

Fragmentation of natural vegetation is currently one of the largest threats to plant populations and their interactions with pollinators. Plant reproductive susceptibility to habitat fragmentation has been investigated in many species; however, the response of wild mass-flowering species is poorly known, with research limited to mainly boreal plant species.Here, we studied twelve remnant populations of the threatened mass-flowering shrub Conospermum undulatum in the southwest Australian biodiversity hotspot, each presenting different population size, level of isolation, and floral display. We assessed the impact of fragmentation on (a) fruit and seed production; and (b) seed germination. To gain a deeper understanding of factors influencing the reproductive success of C. undulatum, we performed pollinator exclusion and self-pollination treatments to experimentally assess the mating system of this threatened shrub.We found C. undulatum to be strictly self-incompatible and totally reliant on pollinators visiting with an outcrossed pollen load to complete the reproductive cycle. Further, we found that fruit production dropped from 35% to <20% as a result of decreasing floral display. A reduction in population size from 880 to 5 plants and from ~700 to 0.21 in the floral display index led to a decrease in seed output, while a similar reduction in seed output, from 6% to 3%, was observed as a result of increasing isolation index from -21.41 to -0.04. Overall, seed germination was positively related to population size, and a negative relationship was found between germination and isolation. Synthesis and applications. Our results demonstrate the important relationship between pollinators and floral morphology in plants of southwest Australia that have coevolved with native pollinators and developed characteristic flower morphologies over long time frames. Indeed, due to its characteristic pollination mechanism, the self-incompatible C. undulatum can only rely on specialized native pollinators for pollen flow and cannot rely on its mass-flowering trait to attract generalist pollinators from coflowering species; neither can it compensate for the lack of visitors by promoting geitonogamy. Consequently, fragmentation has a significant effect on the reproductive output of C. undulatum, and size, isolation, and floral display of populations are important factors to be considered when planning conservation actions for the species.

Nectar traits differ between pollination syndromes in Balsaminaceae

BACKGROUND AND AIMS

The attractiveness of nectar rewards depends both on the quantity of nectar produced and on its chemical composition. It is known that nectar quantity and chemical composition can differ in plant species depending on the main pollinator associated with the species. The main aims of this study were to test formally whether nectar traits are adapted to pollination syndromes in the speciose Balsaminaceae and, if so, whether a combination of nectar traits mirrors pollination syndromes.

METHODS

Comparative methods based on Ornstein-Uhlenbeck models were used to test whether nectar volume, nectar sucrose proportion, sugar and amino acid concentration and amino acid composition had evolved as a function of pollination syndromes in 57 species of Balsaminaceae. Cluster analysis and ordination were performed to derive clusters of species resembling each other in nectar composition.

KEY RESULTS

Evolutionary models for nectar volume and nectar sucrose proportion performed best when including information on pollination syndrome, while including such information improve model fit neither for sugar and amino acid concentration nor for amino acid composition. A significant relationship emerged between pollination syndrome and the combined nectar traits.

CONCLUSIONS

Our results show that nectar volume and nectar sucrose proportion evolve rapidly towards optimal values associated with different pollination syndromes. The detection of a signal indicating that nectar traits in combination are to a certain extent able to predict pollination syndromes in Balsaminaceae suggests that a holistic approach including the whole set of nectar traits helps us to better understand evolution of nectar composition in response to pollinators.

Effect of Corolla Slitting and Nectar Robbery by the Eastern Carpenter Bee (Hymenoptera: Apidae) on Fruit Quality of Vaccinium corymbosum L. (Ericales: Ericaceae)

Eastern carpenter bees, Xylocopa virginica (L.) (Hymenoptera: Apidae), are among the most abundant native bee visitors to highbush blueberry, Vaccinium corymbosum L., flowers in the northeastern United States, and they sometimes display corolla-slitting behavior to rob nectar. We studied foraging behavior of X. virginica on 14 blueberry cultivars in an experimental planting in Rhode Island, and assessed factors related to slitting frequency, and the effects of slitting on fruit set and blueberry quality. Among 14 cultivars in bloom, an average of 35% (range 16-67%) of flowers were slit in 2017, and 39% (range 20-62%) in 2018. Factors that affected the proportion of corollas slit included cultivar, anther length, flower volume, and number of days in bloom at or above 15°C. Corolla slitting did not affect fruit set. Average weight and percent soluble solids of fruit resulting from slit and non-slit corollas did not differ significantly in two early- ('Bluehaven', 'Earliblue'), two mid- ('Collins', 'Bluecrop'), and two late-season ('Herbert', 'Lateblue') ripening cultivars in 2017. In 2018, average fruit weight and percent soluble solids resulting from slit and non-slit flowers did not differ significantly in most cultivars, but slit corollas resulted in berries with greater mass in two cultivars, 'Bluehaven' and 'Collins'. 'Collins' fruit from non-slit corollas had a significantly higher percentage of soluble solids at maturity than fruit from slit corollas in 2018. Corolla slitting and nectar robbery by X. virginica did not have a significant negative effect on fruit quality under the described growing conditions and pollinator community.

Random search with resetting as a strategy for optimal pollination

The problem of pollination is unique among a wide scope of search problems, since it requires optimization of benefits for both the searcher (pollinator) and its targets (plants). To address this challenge, we propose a pollination model which is based on a framework of first passage under stochastic restart. We derive equations for the search time and number of visited plants as functions of the distribution of nectar in the plant population and of the probability that a pollinator will leave the plant after examining a flower, thus effectively restarting the search. We demonstrate that nectar variation in plants serves as a driving force for pollination and establish conditions required for optimal pollination, which provides an efficient pollinator search strategy and the maximum number of plants visited by the pollinator.

Kin discrimination allows plants to modify investment towards pollinator attraction

Pollinators tend to be preferentially attracted to large floral displays that may comprise more than one plant in a patch. Attracting pollinators thus not only benefits individuals investing in advertising, but also other plants in a patch through a ‘magnet’ effect. Accordingly, there could be an indirect fitness advantage to greater investment in costly floral displays by plants in kin-structured groups than when in groups of unrelated individuals. Here, we seek evidence for this strategy by manipulating relatedness in groups of the plant Moricandia moricandioides, an insect-pollinated herb that typically grows in patches. As predicted, individuals growing with kin, particularly at high density, produced larger floral displays than those growing with non-kin. Investment in attracting pollinators was thus moulded by the presence and relatedness of neighbours, exemplifying the importance of kin recognition in the evolution of plant reproductive strategies.

Plants can recognize nearby kin and alter their growth in response. Here, Torices et al. demonstrate that flower production can also be sensitive to social context, with plants producing larger floral displays in the presence of relatives, which may increase attraction of pollinators to the group.

Phylogenomics resolves evolutionary relationships and provides insights into floral evolution in the tribe Shoreeae (Dipterocarpaceae)

A supra-annual, community-level synchronous flowering prevails in several parts of the tropical forests of Southeast Asia and its evolution has been hypothesized to be linked to pollinator shifts. The aseasonal Southeast Asian lowland rainforests are dominated by Dipterocarpaceae, which exhibit great floral diversity, a range of pollination syndromes and include species with annual and supra-annual gregarious flowering. Phylogenetic relationships within this family are still unclear, especially in the tribe Shoreeae. Here, we develop a pipeline to maximize recovery of genome-wide SNPs from restriction-site associated DNA sequencing (RADseq) in non-model organisms across wide phylogenetic scales. We then infer phylogenomic relationships in the tribe Shoreeae using both traditional and coalescent analyses. The phylogenetic trees obtained with these methods are congruent to each other and highly resolved. They allow reconstructing the evolutionary patterns of floral traits (number of stamens, anther structure and anther/appendage size) in the group. Our inferences indicate that species with many stamens, but smaller, globose anthers and longer appendages and have evolved multiple times from species with fewer stamens, but larger, oblong anthers and shorter appendages. This could have happened in parallel to iterative shifts in pollinators across the uncovered phylogeny from larger, longer generation to smaller, shorter-generation insects that can quickly build up the necessary population sizes during mass flowering episodes.

Asymmetric competition for nectar between a large nectar thief and a small pollinator: an energetic point of view

There are two alternative hypotheses related to body size and competition for restricted food sources. The first one supposes that larger animals are superior competitors because of their increased feeding abilities, whereas the second one assumes superiority of smaller animals because of their lower food requirements. We examined the relationship between two unrelated species of different size, drinking technique, energy requirements and roles in plant pollination system, to reveal the features of their competitive interaction and mechanisms enabling their co-existence while utilising the same nectar source. We observed diurnal feeding behaviour of the main pollinator, the carpenter bee Xylocopa caffra and a nectar thief, the northern double-collared sunbird Cinnyris reichenowi on 19 clumps of Hypoestes aristata (Acanthaceae) in Bamenda Highlands, Cameroon. For comparative purpose, we established a simplistic model of daily energy expenditure and daily energy intake by both visitor species assuming that they spend all available daytime feeding on H. aristata. We revealed the energetic gain-expenditure balance of the studied visitor species in relation to diurnal changes in nectar quality and quantity. In general, smaller energy requirements and related ability to utilise smaller resources made the main pollinator X. caffra competitively superior to the larger nectar thief C. reichenowi. Nevertheless, sunbirds are endowed with several mechanisms to reduce asymmetry in exploitative competition, such as the use of nectar resources in times of the day when rivals are inactive, aggressive attacks on carpenter bees while defending the nectar plants, and higher speed of nectar consumption.

Mouthpart conduit sizes of fluid-feeding insects determine the ability to feed from pores

Fluid-feeding insects, such as butterflies, moths and flies (20% of all animal species), are faced with the common selection pressure of having to remove and feed on trace amounts of fluids from porous surfaces. Insects able to acquire fluids that are confined to pores during drought conditions would have an adaptive advantage and increased fitness over other individuals. Here, we performed feeding trials using solutions with magnetic nanoparticles to show that butterflies and flies have mouthparts adapted to pull liquids from porous surfaces using capillary action as the governing principle. In addition, the ability to feed on the liquids collected from pores depends on a relationship between the diameter of the mouthpart conduits and substrate pore size diameter; insects with mouthpart conduit diameters larger than the pores cannot successfully feed, thus there is a limiting substrate pore size from which each species can acquire liquids for fluid uptake. Given that natural selection independently favoured mouthpart architectures that support these methods of fluid uptake (Diptera and Lepidoptera share a common ancestor 280 Ma that had chewing mouthparts), we suggest that the convergence of this mechanism advocates this as an optimal strategy for pulling trace amounts of fluids from porous surfaces.

Tropical Forest Fragmentation Limits Movements, but Not Occurrence of a Generalist Pollinator Species

Habitat loss and fragmentation influence species distributions and therefore ecological processes that depend upon them. Pollination may be particularly susceptible to fragmentation, as it depends on frequent pollinator movement. Unfortunately, most pollinators are too small to track efficiently which has precluded testing the hypothesis that habitat fragmentation reduces or eliminates pollen flow by disrupting pollinator movement. We used radio-telemetry to examine space use of the green hermit hummingbird (Phaethornis guy), an important ‘hub’ pollinator of understory flowering plants across substantial portions of the neotropics and the primary pollinator of a keystone plant which shows reduced pollination success in fragmented landscapes. We found that green hermits strongly avoided crossing large stretches of non-forested matrix and preferred to move along stream corridors. Forest gaps as small as 50 m diminished the odds of movement by 50%. Green hermits occurred almost exclusively inside the forest, with the odds of occurrence being 8 times higher at points with >95% canopy cover compared with points having <5% canopy cover. Nevertheless, surprisingly. the species occurred in fragmented landscapes with low amounts of forest (~30% within a 2 km radius). Our results indicate that although green hermits are present even in landscapes with low amounts of tropical forest, movement within these landscapes ends up strongly constrained by forest gaps. Restricted movement of pollinators may be an underappreciated mechanism for widespread declines in pollination and plant fitness in fragmented landscapes, even when in the presence of appropriate pollinators.

Innate olfactory preferences for flowers matching proboscis length ensure optimal energy gain in a hawkmoth

Cost efficient foraging is of especial importance for animals like hawkmoths or hummingbirds that are feeding 'on the wing', making their foraging energetically demanding. The economic decisions made by these animals have a strong influence on the plants they pollinate and floral volatiles are often guiding these decisions. Here we show that the hawkmoth Manduca sexta exhibits an innate preference for volatiles of those Nicotiana flowers, which match the length of the moth's proboscis. This preference becomes apparent already at the initial inflight encounter, with the odour plume. Free-flight respiration analyses combined with nectar calorimetry revealed a significant caloric gain per invested flight energy only for preferred-matching-flowers. Our data therefore support Darwin's initial hypothesis on the coevolution of flower length and moth proboscis. We demonstrate that this interaction is mediated by an adaptive and hardwired olfactory preference of the moth for flowers offering the highest net-energy reward.

Hawkmoths evaluate scenting flowers with the tip of their proboscis

Pollination by insects is essential to many ecosystems. Previously, we have shown that floral scent is important to mediate pollen transfer between plants (Kessler et al., 2015). Yet, the mechanisms by which pollinators evaluate volatiles of single flowers remained unclear. Here, Nicotiana attenuata plants, in which floral volatiles have been genetically silenced and its hawkmoth pollinator, Manduca sexta, were used in semi-natural tent and wind-tunnel assays to explore the function of floral scent. We found that floral scent functions to increase the fitness of individual flowers not only by increasing detectability but also by enhancing the pollinator's foraging efforts. Combining proboscis choice tests with neurophysiological, anatomical and molecular analyses we show that this effect is governed by newly discovered olfactory neurons on the tip of the moth's proboscis. With the tip of their tongue, pollinators assess the advertisement of individual flowers, an ability essential for maintaining this important ecosystem service.

Mating patterns and pollinator mobility are critical traits in forest fragmentation genetics

Most woody plants are animal-pollinated, but the global problem of habitat fragmentation is changing the pollination dynamics. Consequently, the genetic diversity and fitness of the progeny of animal-pollinated woody plants sired in fragmented landscapes tend to decline due to shifts in plant-mating patterns (for example, reduced outcrossing rate, pollen diversity). However, the magnitude of this mating-pattern shift should theoretically be a function of pollinator mobility. We first test this hypothesis by exploring the mating patterns of three ecologically divergent eucalypts sampled across a habitat fragmentation gradient in southern Australia. We demonstrate increased selfing and decreased pollen diversity with increased fragmentation for two small-insect-pollinated eucalypts, but no such relationship for the mobile-bird-pollinated eucalypt. In a meta-analysis, we then show that fragmentation generally does increase selfing rates and decrease pollen diversity, and that more mobile pollinators tended to dampen these mating-pattern shifts. Together, our findings support the premise that variation in pollinator form contributes to the diversity of mating-pattern responses to habitat fragmentation.

ORCHID BEES (APIDAE: EUGLOSSINI) IN A FOREST FRAGMENT IN THE ECOTONE CERRADO-AMAZONIAN FOREST, BRAZIL

<p>This paper presents information about the species richness and abundance of orchid bees in the transitional area between the Cerrado and the Amazon Forest in the Xingu river basin. The males were collected in a forest fragment in the municipality of Ribeirão Cascalheira, northeast Mato Grosso state, Brazil, between 1 and 5 November 2011. Benzyl benzoate, 1.8 cineole, eugenol and vanillin were used as baits, to attract the bees using insect nets and methyl salicylate was used only in the bottle traps. A total of 168 males belonged to four<em> </em>of five Euglossini genera distributed among 16 species were recorded. The greatest species richness was registered in the genus <em>Euglossa</em>, however <em>Eulaema nigrita</em>,<em> </em>was<em> </em>the most abundant Euglossine species in the community. The species richness varied between the edge and the first point within the fragment. The males were more active between 10:00 and 11:00 h, and the 1.8 cineole was the most attractive substance. The fragment studied contained representative species richness of orchid bees in a region of widespread environmental heterogeneity, which is still largely unknown as regards its pollinators and deserves attention for the compilation of new inventories.</p><p><strong>Abejas de orquídeas (Apidae: Euglossini) en un fragmento de bosque en el ecotono Cerrado-Selva Amazónica, Brasil</strong></p><p>En este trabajo se presenta información sobre la riqueza de especies y abundancia de Euglossini en la zona de transición entre el Cerrado y la selva amazónica, en la cuenca del río Xingu. Las muestras se recogieron en un fragmento de bosque en el municipio de Ribeirão Cascalheira, nordeste de Mato Grosso, Brasil, entre el 1 y 5 de noviembre de 2011. Las sustancias puras de benzoato de bencilo, 1,8 cineol, eugenol y la vainillina fueron utilizadas como cebos para atraer los machos usando red de insectos aunque el salicilato de metilo se utilizó en trampas pasivas. Un total de 168 machos pertenecientes a cuatro géneros fueron registrados, distribuidos en 16 especies. La mayor riqueza de especies se registró en el género <em>Euglossa</em>, aunque <em>Eulaema nigrita </em>fue<em> </em>la especie más abundante en la comunidad. La riqueza de especies varió entre el borde y el primer punto dentro del fragmento. Los machos de abejas de orquídeas<em> </em>eran más activos entre 10:00-11:00 h, y el 1.8 cineol fue la sustancia pura más atractiva. El fragmento estudiado contenía un alto grado de riqueza de especies de abejas de orquídeas en una región de heterogeneidad ambiental extensa, que sigue siendo en gran parte desconocido con relación a su fauna de insectos polinizadores y merece la atención para la elaboración de nuevos inventarios.</p>