Different Groups Of Pollinators Research Articles

Butterflies, bumblebees and hoverflies are equally effective pollinators of Knautia arvensis (Caprifoliaceae), a generalist plant species with compound inflorescences

AbstractPlant‐pollinator interactions exist along a continuum from complete specialisation to highly generalised, that may vary in time and space. A long‐held assumption is that large bees are usually the most effective pollinators of generalist plants. We tested this by studying the relative importance of different groups of pollinators of Knautia arvensis (L.) Coult. (Caprifoliaceae: Dipsacoideae). This plant is suitable for such a study because it attracts a diversity of flower visitors, belonging to different functional groups. We asked whether all functional groups of pollinators are equally effective, or if one group is most effective, which has been documented in other species with apparently generalised pollination systems. We studied two subpopulations of K. arvensis, one at low and one at high density in Northampton, UK. To assess pollinator importance we exposed unvisited inflorescences to single visits by different groups of pollinators (butterflies, bumblebees, hoverflies and others) and assessed the proportion of pollinated stigmas. We then multiplied the effectiveness of each pollinator group with their proportional visitation frequency in five different years. For each group we also compared time spent on flowers and flight distance between visits. The relative importance of each pollinator group varied between years, as did their flight distances between flower visits. Butterflies were the best pollinators on a per visit basis (in terms of the proportion of stigmas pollinated) and flew further after visiting an inflorescence. Different measures and proxies of pollinator effectiveness varied between taxa, subpopulations, and years, and no one group of pollinators was consistently more effective than the others. Our results demonstrate the adaptive value of generalised pollination strategies when variation in relative abundance of different types of pollinators is considered. Such strategies may have buffered the ability of plants to reproduce during past periods of environmental change and may do so in the future.

Changes in Population Densities and Species Richness of Pollinators in the Carpathian Basin during the Last 50 Years (Hymenoptera, Diptera, Lepidoptera)

Temporal changes in population densities and species richness of three main pollinator groups—moths and butterflies (Lepidoptera); bees, wasps and sawflies (Hymenoptera); and hoverflies, horseflies, tachinids and bee flies (Diptera)—were investigated in the Carpathian Basin. Maintaining pollinator diversity is a crucial factor for preserving our biodiversity and ecosystems; furthermore, several pollinator species have a strong economic role in maintaining crop and fruit cultures. Our conclusions are based on our three and four decades of faunistic surveys in various regions of the Carpathian Basin. Analyzing and comparing our data with the historical data of the last 50 years, we concluded that densities of some pollinators declined during the past decade and a half (Symphyta, hoverflies), although populations of several species of Mediterranean origin grew (Aculeata) and new species even migrated from the warmer regions. In numerous cases, this decrease was dramatic: more than 90% decline of certain butterfly species were detected. On the other hand, the composition of pollinator fauna significantly changed due to the disappearance of some mountainous or mesophile species. The main reason for the decrease in pollinator communities is due partly to climatic change and partly to anthropogenic factors. Different groups of pollinators react differently: some groups like Syrphidae, Tachinidae, most of the butterfly families and bumblebees suffered a strong decline in the last two decades; other warm-loving groups like most of Aculeata and horseflies and bee flies showed a significant increase in population densities. Our conclusion: in our region, the pollinator crisis is present but moderate; however, there is a clear sign of the gradual transition of our pollinator fauna towards the Mediterranean type.

High floral trait diversity of aquatic plants in the Pantanal reveals different pollination strategies

This research brings novel information regarding the floral traits and pollinator groups of aquatic macrophytes. Classifying functional traits and pollinator groups contributes to understanding reproductive processes, community structuring, and ecosystem functioning. Based on an extensive survey of information on 524 species of aquatic macrophyte angiosperms from the Pantanal wetland, we classified the floral traits of these species to identify their potential group of pollinators and how these traits are distributed throughout the botanical families of aquatic plants. We classified their life forms, floral traits (flower type, color, and resource), and main pollinator groups. We also investigated trends, plotting the occurrence of species throughout the phylogeny of angiosperm families, and using a network of interactions, we verified how interactions with different groups of pollinators are distributed within species traits. As a result, the species of aquatic macrophytes in the Pantanal are well distributed within the phylogeny, indicating that they may be more related to ecological than phylogenetic factors. We found a high diversity of floral traits and pollinator groups, predominating white flowers, providing nectar as a resource, and bees as their primary pollinators. Although bees were the main group of pollinators, we also found abiotic interactions linked to the species richness in Poaceae and Cyperaceae, with pollination system mainly performed by wind. Our research represents a first step towards identifying key information gaps. Future studies should focus on understanding in loco traits to fill this gap, besides information on ecological interactions with potential pollinators and species phenology.

Flower morphology evolution in Jaborosa (Solanaceae): shape and size variation associated with contrasting pollination modes.

Flower morphology is considered an important factor in species diversification because it may influence the efficiency of pollination in different ways (e.g. attraction and mechanical fit with different groups of pollinators). In the present study, we quantified the variation in flower morphology (i.e. shape and size) of the diverse South American genus Jaborosa Juss. (Solanaceae) in relation to contrasting pollination modes: rewarding pollination either by moths or by generalist small insects versus brood-site deceptive pollination by saprophilous flies. We examined variations of flower morphology in frontal (pollinator attraction) and sagittal (functional fit with pollinators) views in 12 Jaborosa species using geometric morphometric methods and comparative approaches to infer whether flower shape evolution, not attributable to flower allometry or phylogenetic relationship, is associated with shifts in pollination modes. We found remarkable variation in flower morphology among both Jaborosa species and pollination modes, largely in sagittal view. Evolutionary trends in shape of fly-pollinated flowers were mainly attributable to changes in developmental trajectories. Variation in flower architecture facilitated differential pollen placement - on the proboscis of moths, and either on the back or ventral region of saprophilous flies - promoting diversification of the genus. Diversification of shape, independent of size, in most of the studied Jaborosa species would indicate adaptation to contrasting pollination modes.

Pollination of urban meadows – Plant reproductive success and urban-related factors influencing frequency of pollinators visits

Pollination is a key ecological service for human food security and the reproduction of the majority of flowering plants. This plant-animal interaction is crucial in both wild and urban habitats, however, increasing urbanization and change in land use alter these interactions. The concerns regarding pollination have led to numerous efforts aimed at improving the quality of wildlife in cities, however, understanding the importance of these activities warrants further research. In Warsaw, the Polish capital, we analyzed the influence of urban-related factors such as floral resource richness, the proportion of green areas in the proximity of foraging sites, air pollution or temperature on plant-pollinator interaction in 14 meadows. We also analyzed the reproductive success and the heterospecific pollen transfer in the case of plants growing in the meadows. Our study revealed that the frequency of visits to flowers was related to city-related factors, but the reaction varied among different groups of pollinators. For example, bumblebees were negatively influenced by higher air pollution, while the rest of the flower visitors were not, Syrphidae flies were more frequent flower visitors when the proportion of green area was higher in the buffer of 150 m, while we did not observe this tendency in other groups of flower visitors. Plants growing in Warsaw meadows were frequently visited and effectively pollinated - urban pollinator assemblages seem to provide sufficient pollination services to plants growing in the city. Species-rich communities were not a threat to pollination; we found mostly conspecific pollen grains on the stigmas of the studied plant species. The results of our study show that species-rich communities make a valuable contribution to pollinator conservation. The conservation activities, however, should be adjusted to the target group of pollinators, since different groups of flower visitors respond differently to urban-related factors studied.

Spatiotemporal availability of pollinator attractive trees in a tropical streetscape: unequal distribution for pollinators and people

Street trees integrate the urban green infrastructure and are important elements for the maintenance of biodiversity, including pollinators. Thus, assessments of the spatiotemporal distribution and composition of these trees can subsidize strategies of conservation for different groups of pollinators in the cities. Here, we evaluated the spatiotemporal distribution of trees attractive to pollinators across the streetscape of a large Brazilian metropolis with more than 2.5 million inhabitants. We used the georeferenced data of ca. 300,000 woody plant individuals cataloged across the streetscape. These plants were characterized according to their geographical origin, flowering season, and the floral visitor groups that are attracted based on a literature survey. We also tested the “luxury effect” hypothesis on the resource availability to pollinators by evaluating the relationship between the average family income of the population and the richness and abundance of trees. We found that the streetscape was characterized by the dominance of a few tree species, with a balanced representation of both native and non-native species. Bees were the most favored group (94.86%) while bats (1.43%) and moths (1.73%) were the least. The potential supply of resources was homogeneous across dry and wet seasons, but the density of trees was reduced in most of the landscape. We found a strong luxury effect since tree richness and abundance were positively related to regions with higher average family income. Our study highlights the need for better planning and management practices of urban green areas to support pollinators more uniformly across streetscapes. This will allow the benefits provided by pollinators to be more evenly shared among residents of urban landscapes.

Pollinator distribution in patches of suitable habitat depends more on patch isolation than on floral abundance

Intrinsic complexity of real-world systems makes particularly difficult to decipher which factors influence the dispersal of pollinators in the landscape matrix and their distribution amongst patches of suitable habitat. Saltmarshes are an ideal and naturally simplified landscape to study the ability of different groups of pollinators to disperse across a landscape matrix, as they consist of a matrix of flooded areas surrounding patches of suitable habitat with different degrees of isolation from the mainland and different levels of floral abundance. We hypothesise that pollinator distribution to flowering plants depends more on patch isolation than on floral abundance, with pollinator richness and visitation rates to flowering plants decreasing with increasing distance from the mainland. To this end, we established 60 permanent plots at varying distances from the mainland and monitored pollinator visitation to entomophilous plants. We also quantified the reproductive success of entomophilous species in the surveyed plots by calculating fruit set. We found that the pollinator community of saltmarshes consisted only of flying pollinators with good dispersal abilities, while we recorded no flightless pollinator species. Both pollinator richness and visitation rate decreased with increasing distance of patches of suitable habitat from the mainland, affecting reproductive success of a non-autogamous entomophilous species. Interestingly, floral abundance did not affect pollinator richness and visitation rate to flowering plants, nor did it affect reproductive success of target plant species. In saltmarshes, the pollinator distribution depends more on patch distance from the mainland than on floral abundance. Our results suggest that the presence of patches of suitable habitat in a landscape matrix does not necessarily ensure the maintenance of pollinators. Rather, our results suggest that suitable habitat isolation is the critical factor in pollinator dispersal and distribution that should be considered to improve landscape matrix permeability to pollinators.

Artificial Intelligence-Aided Meta-Analysis of Toxicological Assessment of Agrochemicals in Bees

The lack of consensus regarding pollinator decline in various parts of the planet has generated intense debates in different spheres. Consequently, much research has attempted to identify the leading causes of this decline, and a multifactorial synergism (i.e., different stressors acting together and mutually potentiating the harmful effects) seems to be the emerging consensus explaining this phenomenon. The emphasis on some stressor groups such as agrochemicals, and pollinators such as the honey beeApis mellifera, can hide the real risk of anthropogenic stressors on pollinating insects. In the present study, we conducted a systematic review of the literature to identify general and temporal trends in publications, considering the different groups of pollinators and their exposure to agrochemicals over the last 76 years. Through an artificial intelligence (AI)-aided meta-analysis, we quantitatively assessed trends in publications on bee groups and agrochemicals. Using AI tools through machine learning enabled efficient evaluation of a large volume of published articles. Toxicological assessment of the impact of agrochemicals on insect pollinators is dominated by the order Hymenoptera, which includes honey bees. Although honey bees are well-explored, there is a lack of published articles exploring the toxicological assessment of agrochemicals for bumble bees, solitary bees, and stingless bees. The data gathered provide insights into the current scenario of the risk of pollinator decline imposed by agrochemicals and serve to guide further research in this area.Systematic Review Registrationhttps://asreview.nl/.

The Effects of Flower Patch Density on Pollinator Visitation.

There is conflicting research regarding how conspecific plant density can affect pollinator visitation, with some studies indicating dense flower patches will receive more visitors and other studies demonstrating the opposite. This study investigated the effects of conspecific density on pollinator visitation in a restored prairie. Three plant species, Penstemon digitalis (Nutt. ex Sims) (Lamiales: Plantaginaceae), Monarda fistulosa (L.) (Lamiales: Lamiaceae), and Eryngium yuccifolium (Michx.) (Apiales: Apiaceae), were observed, with visiting pollinators recorded. Conspecific density did not have an effect on total pollinator visitation rates for any of the focal plant species. However, different groups of pollinators varied in their responses to flower density, notably with larger Bombus spp. tending to visit dense flowering patches more than did other groups of bees. This suggests that plant density may impact certain pollinators differently than others. These results also indicate a possible mechanism through which multiple pollinator species can coexist while only one flowering resource is available, with the foraging behavior of smaller bees potentially allowing them to avoid competition with larger, social bees. Furthermore, a comparison of seed weight demonstrated that E. yuccifolium plants tended to have larger seed sets in isolated individuals, suggesting that flowers in large patches may be pollinated less effectively and are competing for, rather than facilitating, pollinator visits.

Broader phenology of pollinator activity and higher plant reproductive success in an urban habitat compared to a rural one.

Urban habitat characteristics create environmental filtering of pollinator communities. They also impact pollinating insect phenology through the presence of an urban heat island and the year‐round availability of floral resources provided by ornamental plants.Here, we monitored the phenology and composition of pollinating insect communities visiting replicates of an experimental plant assemblage comprising two species, with contrasting floral traits: Sinapis alba and Lotus corniculatus, whose flowering periods were artificially extended. Plant assemblage replicates were set up over two consecutive years in two different habitats: rural and densely urbanized, within the same biogeographical region (Ile‐de‐France region, France).The phenology of pollination activity, recorded from the beginning (early March) to the end (early November) of the season, differed between these two habitats. Several pollinator morphogroups (small wild bees, bumblebees, honeybees) were significantly more active on our plant sets in the urban habitat compared to the rural one, especially in early spring and autumn. This resulted in different overall reproductive success of the plant assemblage between the two habitats. Over the course of the season, reproductive success of S. alba was always significantly higher in the urban habitat, while reproductive success of L. corniculatus was significantly higher in the urban habitat only during early flowering.These findings suggest different phenological adaptations to the urban habitat for different groups of pollinators. Overall, results indicate that the broadened activity period of pollinating insects recorded in the urban environment could enhance the pollination function and the reproductive success of plant communities in cities.

Pronounced differences in visitation by potential pollinators to co-occurring species of Fabaceae in the Southwest Australian biodiversity hotspot

AbstractDespite their diversity and the potential for specialized pollination systems, Australian Fabaceae have received little attention in pollination studies. In the Southwest Australian Floristic Region (SWAFR), a recognized biodiversity hotspot, co-occurring and abundant species of Faboideae exhibit a range of floral colours and forms, suggestive of adaptation to different groups of pollinators. For four communities of Fabaceae in the SWAFR we investigated whether co-occurring species overlap in pollinator genera, whether these pollinators show differences in behaviour on the pea flower and whether variations in stamen length and nectar composition among species are associated with different pollinator types. Species of Fabaceae were visited by one to four genera of native bees, suggesting varying levels of ecological specialisation. In Fabaceae with more specialized interactions, co-occurring species showed marked differences in the bee genera attracted. Unexpectedly, some Fabaceae frequently attracted beetles, which may play an important role in their pollination. There was no evidence for an association between stamen length or nectar composition and the type of pollinator. The introduced honeybee, visited all studied species of Fabaceae, suggesting that they may act both as a pollinator and a potential competitor with native pollinators.

A "plan bee" for cities: Pollinator diversity and plant-pollinator interactions in urban green spaces.

Green infrastructure in cities is considered to serve as a refuge for insect pollinators, especially in the light of an ongoing global decline of insects in agricultural landscapes. The design and maintenance of urban green spaces as key components of green infrastructure play a crucial role in case of nesting opportunities and for foraging insects. However, only few research has explored the impact of urban green space design on flower visitor communities, plant-pollinator interaction and the provision of the ecosystem service of pollination in cities. We investigated the abundance and diversity of pollinator communities in different urban park types in designed, standardized vegetation units, linked the visitation rates to the structural composition of the park types and derived indices for implemented pollination performances. The study was performed in two different structural park elements, flower beds and insect-pollinating trees. To gain a comprehensive understanding of the interaction between plants and pollinators, we calculated a plant-pollinator network of the recorded community in the investigation area. Visitation rates at different park types clearly showed, that the urban community gardens in comparison to other urban park types had a significantly higher abundance of pollinator groups, comparable to results found on a rural reference site. Tilia trees contributed significantly to the ecosystem service of pollination in investigated green spaces with a high supply of nectar and pollen during their flowering period. Calculations of pollination performances showed that recreational parks had comparably low visitation rates of pollinators and a high potential to improve conditions for the ecosystem service of pollination. The results indicated the strong potential of cities to provide a habitat for different groups of pollinators. In order to access this refuge, it is necessary to rely on near-natural concepts in design and maintenance, to create a wide range of flower diversity and to use even small green patches. Based on the findings, we encourage an integrated management of urban free spaces to consider parks as key habitats for pollinators in anthropogenic dominated, urban environments.

Nectar sugars and amino acids in day- and night-flowering Nicotiana species are more strongly shaped by pollinators' preferences than organic acids and inorganic ions.

Floral nectar contains mainly sugars but also amino acids, organic acids, inorganic ions and secondary compounds to attract pollinators. The genus Nicotiana exhibits great diversity among species in floral morphology, flowering time, nectar compositions, and predominant pollinators. We studied nectar samples of 20 Nicotiana species, composed equally of day- and night-flowering plants and attracting different groups of pollinators (e.g. hummingbirds, moths or bats) to investigate whether sugars, amino acids, organic acids and inorganic ions are influenced by pollinator preferences. Glucose, fructose and sucrose were the only sugars found in the nectar of all examined species. Sugar concentration of the nectar of day-flowering species was 20% higher and amino acid concentration was 2-3-fold higher compared to the nectar of night-flowering species. The sucrose-to-hexose ratio was significantly higher in night-flowering species and the relative share of sucrose based on the total sugar correlated with the flower tube length in the nocturnal species. Flowers of different tobacco species contained varying volumes of nectar which led to about 150-fold higher amounts of total sugar per flower in bat- or sunbird-pollinated species than in bee-pollinated or autogamous species. This difference was even higher for total amino acids per flower (up to 1000-fold). As a consequence, some Nicotiana species invest large amounts of organic nitrogen for certain pollinators. Higher concentrations of inorganic ions, predominantly anions, were found in nectar of night-flowering species. Therefore, higher anion concentrations were also associated with pollinator types active at night. Malate, the main organic acid, was present in all nectar samples but the concentration was not correlated with pollinator type. In conclusion, statistical analyses revealed that pollinator types have a stronger effect on nectar composition than phylogenetic relations. In this context, nectar sugars and amino acids are more strongly correlated with the preferences of predominant pollinators than organic acids and inorganic ions.

Pollinators and crossability as reproductive isolation barriers in two sympatric oil-rewarding Calceolaria (Calceolariaceae) species

Pollinator species are widely accepted as an important factor in plant reproductive isolation. Although mostly investigated in plants visited by different groups of pollinators (e.g., hummingbirds vs bees), few studies have examined the role of pollinators belonging to the same taxonomic group (e.g., only bees) on plant reproductive isolation. In this study, we investigate this question by evaluating pre- and post-zygotic mechanisms putatively involved in the reproductive isolation of two oil-rewarding sympatric Calceolaria species (i.e., Calceolaria filicaulis and C. arachnoidea) in an Andean ecosystem of Chile. We estimated reproductive isolation values using a combination of field (pollinator visitation rates) and experimental (intra and interspecific manual cross-pollination and seed germination of parents and hybrids) evidence. The two Calceolaria species were preferentially visited by different oil-collecting bee species. Results from hand cross-pollination experiments indicate that intraspecific crossings produced significantly more seeds than interspecific ones. Notwithstanding, seed germination essays did not reveal differences between parental and hybrids. Taken together, these results suggest that pollinator species are responsible for most of the reproductive isolation in the two Calceolaria species studied here. This study is the first assessment of pollinator-mediated reproductive isolation in Calceolaria species and the first to document reproductive barriers in oil-rewarding plants.

Acanthaceae da Marambaia, Estado do Rio de Janeiro, Brasil

RESUMO Este trabalho consiste do tratamento taxonômico das Acanthaceae Juss. na Marambaia, Estado do Rio de Janeiro, e sua distribuição nas diferentes formações vegetais locais. Foram constatados cinco gêneros e nove espécies encontradas nos manguezais, na restinga e na floresta ombrófila, além de áreas urbanizadas. Thunbergia alata é introduzida e amplamente naturalizada no Brasil inteiro e Ruellia blechum é uma espécie neotropical também naturalizada; as demais espécies (Avicennia schaueriana, Aphelandra longiflora, Justicia brasiliana, J. cydoniifolia, J. plumbaginifolia, Ruellia solitaria e Schaueria litoralis) são nativas. São apresentadas chave de identificação, descrições, ilustrações, comentários taxonômicos e a ocorrência nas formações vegetais locais, em outras restingas fluminenses e no Brasil. As espécies de Acanthaceae da Marambaia são recursos importantes para diferentes grupos de polinizadores e reúnem espécies típicas (Justicia brasiliana, J. cydoniifolia) e exclusivas (Schaueria litoralis) das restingas; essas espécies, juntamente com Avicennia schaueriana, são ameaçadas de extinção na flora fluminense.

Tackling pollination of tubular flowers in Rutaceae and a case study of Conchocarpus rubrus (Galipeinae, Rutaceae)

Tubular flowers are only found in two distantly related groups in Rutaceae: the mainly Australian tribe Boronieae and the Neotropical subtribe Galipeinae. It is assumed that these nectar-rewarded, tubular flowers arose from convergent evolution driven by pollinator pressures. However, there are few empirical studies on pollen vectors of Neotropical Rutaceae. We explored the floral biology and pollination of Conchocarpus rubrus (A.St.-Hil.) Bruniera and Groppo (Galipeinae), including details about its nectar-secreting floral structures. We also compared the available records on floral biology and pollination of Boronieae and Galipeinae, aiming to provide a better understanding of the factors that influenced their floral evolution. Conchocarpus rubrus was pollinated by a single species of hermit hummingbird (Phaethornis idaliae Bourcier and Mulsant 1856) and by butterflies (Pyrginae and Pierinae), which take nectar accumulated at the bottom of the tube. Floral features and pollination data indicate that the convergent evolution of floral tubes in Rutaceae resulted from phenotypic specialization toward a subset of nectar-foraging pollinators with long mouth parts. Specifically, while in the Australian Boronieae the evolutive pathway toward sympetaly was likely influenced by Meliphagidae birds, in the Galipeinae, it was influenced by hummingbirds, butterflies, and settling moths. Besides a floral tube, floral features also linked to phenotypic specialization toward Meliphagidae pollination in Boronieae were related not only to birds’ attraction (nectar features, attractive colors, etc.), but also to insect impediments (sensory exclusion, absence of landing platforms, etc.), occurring together with other ornithophilous features. In Galipeinae, floral features are more diverse, and functionally linked to the different groups of pollinators herein found.

Diurnal versus nocturnal pollination success in Billbergia horrida Regel (Bromeliaceae) and the first record of chiropterophily for the genus.

Billbergia horrida is endemic of the Atlantic Forest fragments in southeastern Brazil and characterized by flowers with typical traits for pollination by nocturnal animals. Although the majority of Billbergia species rely on diurnal pollination by hummingbirds, B. horrida is also visited by bats and this study evidences for the first time the occurrence of chiropterophily within the genus. The role of different groups of pollinators on the reproductive success of B. horrida was evaluated, as well as the correlation of nectar features in sustaining these animals during different periods of the day. Bats contributed to 82.1% of fruit set of B. horrida. Hummingbirds, in turn, contributed to only 10% of fruit set, and were poorly related to the reproductive success of this species. Amounts of nectar production and sugar concentration were similar to those of other chiropterophilous bromeliads and only the nectar volume changed significantly throughout the period of flower availability. Recurring visits by hummingbirds were probably because the flowers of B. horrida were open for 24h, offering energetic rewards for daytime visitors and due to the presence of other attractive bromeliad species growing at the same phorophyte and flowering at the same time.

Phenotypic integration in style dimorphic daffodils (Narcissus, Amaryllidaceae) with different pollinators.

Different pollinators can exert different selective pressures on floral traits, depending on how they fit with flowers, which should be reflected in the patterns of variation and covariation of traits. Surprisingly, empirical evidence in support of this view is scarce. Here, we have studied whether the variation observed in floral phenotypic integration and covariation of traits in Narcissus species is associated with different groups of pollinators. Phenotypic integration was studied in two style dimorphic species, both with dimorphic populations mostly visited by long-tongued pollinators (close fit with flowers), and monomorphic populations visited by short-tongued insects (loose fit). For N. papyraceus, the patterns of variation and correlation among traits involved in different functions (attraction and fit with pollinators, transfer of pollen) were compared within and between population types. The genetic diversity of populations was also studied to control for possible effects on phenotypic variation. In both species, populations with long-tongued pollinators displayed greater phenotypic integration than those with short-tongued pollinators. Also, the correlations among traits involved in the same function were stronger than across functions. Furthermore, traits involved in the transfer of pollen were consistently more correlated and less variable than traits involved in the attraction of insects, and these differences were larger in dimorphic than monomorphic populations. In addition, population genetic parameters did not correlate with phenotypic integration or variation. Altogether, our results support current views of the role of pollinators in the evolution of floral integration.

Generalized pollination system: Are floral traits adapted to different pollinators?

Flowers that are pollinated both during the day and at night could exhibit two different groups of pollinators and produce two different sets of attractants and rewards. We explored the patterns of emission of flower scents and production of nectar in the cactus Echinopsis chiloensis ssp. chiloensis, in relation to the patterns of activity of its diurnal and nocturnal pollinators. We measured frequency of flower visitors, analyzed floral scents, measured nectar production and sugar concentration, and performed pollination exclusion experiments. Bees were the main visitors at daytime and hawkmoths at nighttime. Diurnal scents were dominated by several compounds that can attract a wide range of pollinators, whereas nocturnal scents were less diverse and were dominated by (E)-nerolidol, a compound eliciting antennal responses in hawkmoths. Nectar volume and sugar concentration at night were similar to those recorded in hawkmoth-pollinated flowers. Daytime nectar volume was higher than those commonly found in bee-pollinated flowers, but similar to those found in flowers pollinated by several pollinators. Daytime sugar concentration was similar to those recorded in bee-pollinated flowers. Flowers of E. chiloensis ssp. chiloensis seem morphologically adapted to hawkmoth pollination, but diurnal and nocturnal pollinators contribute to similar extents to reproductive success. Additionally, diurnal and nocturnal pollinators showed a synergic effect on the product of fruit set and seed set. The results are discussed in terms of the linkage between floral traits and perception abilities and requirements of pollinators.

Pollinator community responses to the spatial population structure of wild plants: A pan-European approach

Land-use changes can alter the spatial population structure of plant species, which may in turn affect the attractiveness of flower aggregations to different groups of pollinators at different spatial scales. To assess how pollinators respond to spatial heterogeneity of plant distributions and whether honeybees affect visitation by other pollinators we used an extensive data set comprising ten plant species and their flower visitors from five European countries. In particular we tested the hypothesis that the composition of the flower visitor community in terms of visitation frequencies by different pollinator groups were affected by the spatial plant population structure, viz. area and density measures, at a within-population (‘patch’) and among-population (‘population’) scale. We found that patch area and population density were the spatial variables that best explained the variation in visitation frequencies within the pollinator community. Honeybees had higher visitation frequencies in larger patches, while bumblebees and hoverflies had higher visitation frequencies in sparser populations. Solitary bees had higher visitation frequencies in sparser populations and smaller patches. We also tested the hypothesis that honeybees affect the composition of the pollinator community by altering the visitation frequencies of other groups of pollinators. There was a positive relationship between visitation frequencies of honeybees and bumblebees, while the relationship with hoverflies and solitary bees varied (positive, negative and no relationship) depending on the plant species under study. The overall conclusion is that the spatial structure of plant populations affects different groups of pollinators in contrasting ways at both the local (‘patch’) and the larger (‘population’) scales and, that honeybees affect the flower visitation by other pollinator groups in various ways, depending on the plant species under study. These contrasting responses emphasize the need to investigate the entire pollinator community when the effects of landscape change on plant–pollinator interactions are studied.