Pollinator Assemblages Research Articles

Characterizing each step of pollination in Phlox drummondii reveals a single butterfly species predominates the pollinator assemblage.

A central goal of pollination biology is to connect plants with the identity of their pollinator(s). While predictions based on floral syndrome traits are extremely useful, direct observation can reveal further details of a species' pollination biology. The wildflower, Phlox drummondii, has a floral syndrome consistent with Lepidoptera pollination. We test this prediction using empirical data. We observe each step of pollination in P. drummondii. First, we observe 55.5 hours of floral visitation across the species range. We use temporal pollinator exclusion to determine the contribution of diurnal and nocturnal pollination to reproductive output. We then quantify P. drummondii pollen transfer by the dominant floral visitor, Battus philenor. Finally, we test the effect of B. philenor visitation on P. drummondii reproduction by quantifying fruit set following single pollinator visits. B. philenor is the primary pollinator of P. drummondii. Pollination is largely diurnal, and we observe a variety of lepidopteran visitors during this period. However, B. philenor is the most frequent visitor, representing 88.5% of all observed visits. We show that B. philenor is an extremely common visitor and also an effective pollinator by demonstrating that individuals transfer pollen between flowers and that a single visit can elicit fruit set. Our data are consistent with the prediction of lepidopteran pollination and further reveal a single butterfly species, B. philenor, as the primary pollinator. Our study demonstrates the importance of empirical pollinator observations, adds to our understanding of pollination mechanics, and offers a specific case study of butterfly pollination. This article is protected by copyright. All rights reserved.

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.

Ecological and Evolutionary Origin of Costus flammulus (Costaceae): A New Species from the Montane Cloud Forests of the Volcanic Cordilleras in Northern Costa Rica

Abstract— Costus flammulus is a new herbaceous species endemic to montane cloud forests of the volcanic cordilleras in northern Costa Rica. Costus flammulus has been mistaken for C. wilsonii, but phylogenetic evidence demonstrates that it is closely related to the widespread lowland species C. pulverulentus. Here, we use an integrated framework of species concepts to evaluate whether C. flammulus and C. pulverulentus are distinct species. First, we re-evaluate prior phylogenetic analyses to assess whether C. flammulus bifurcated from or budded off from within C. pulverulentus and whether C. flammulus is monophyletic. We then compare phenotypic traits to determine which diagnostic vegetative and inflorescence traits can be used to identify species in herbarium specimens and examine whether floral traits may confer floral isolation. We compare pollinator assemblages to examine whether pollinator specificity may contribute to reproductive isolation. Finally, we model species distributions and climatic niche overlap to assess ecogeographic isolation. We found that C. flammulus is a monophyletic species phenotypically, ecologically, and geographically distinct from C. pulverulentus and may have speciated as a peripheral isolate at the high elevation range edge of C. pulverulentus. Several lines of evidence, such as C. pulverulentus paraphyly, range size asymmetry, and C. flammulus’ nested distribution and vegetative traits, suggest that C. flammulus budded off from a C. pulverulentus‐like progenitor species, evolving to tolerate a colder and more seasonal montane environment.

Seasonality of pollinators in montane habitats: Cool‐blooded bees for early‐blooming plants

AbstractUnderstanding the factors that drive community‐wide assembly of plant‐pollinator systems along environmental gradients has considerable evolutionary, ecological, and applied significance. Variation in thermal environments combined with intrinsic differences among pollinators in thermal biology have been proposed as drivers of community‐wide pollinator gradients, but this suggestion remains largely speculative. We test the hypothesis that seasonality in bee pollinator composition in Mediterranean montane habitats of southeastern Spain, which largely reflects the prevalence during the early flowering season of mining bees (Andrena), is a consequence of the latter's thermal biology. Quantitative information on seasonality of Andrena bees in the whole plant community (275 plant species) and their thermal microenvironment was combined with field and laboratory data on key aspects of the thermal biology of 30 species of Andrena (endothermic ability, warming constant, relationships of body temperature with ambient and operative temperatures). Andrena bees were a conspicuous, albeit strongly seasonal component of the pollinator assemblage of the regional plant community, visiting flowers of 153 different plant species (57% of total). The proportion of Andrena relative to all bees reached a maximum among plant species which flowered in late winter and early spring, and declined precipitously from May onward. Andrena were recorded only during the cooler segment of the annual range of air temperatures experienced at flowers by the whole bee assemblage. These patterns can be explained by features of Andrena's thermal biology: null to weak endothermy; ability to forage at much lower body temperature than strongly endothermic bees (difference ~ 10°C); low upper tolerable limit of body temperature, beyond which thermal stress presumably precluded foraging at the warmest period of year; weak thermoregulatory capacity; and high warming constant enhancing ectothermic warming. Our results demonstrate the importance of lineage‐specific pollinator traits as drivers of seasonality in community‐wide pollinator composition; show that exploitation of cooler microclimates by bees does not require strong endothermy; and suggest that intense endothermy and precise thermoregulation probably apply to a minority of bees. Medium‐ and large‐sized bees with low upper thermal limits and weak thermoregulatory ability can actually be more adversely affected by climate warming than large, hot‐blooded, extremely endothermic species.

Effectiveness landscape of crop pollinator assemblages: Implications to pollination service management

There is a growing consensus that the world is facing a pollination crisis. To mitigate crop pollination deficits, some management strategies include the massive introduction of managed bee species, yet quite often they are applied blindly, as information on crop pollination effectiveness for each single pollinator species of assemblages is usually not available. Therefore, the introduction on managed species is not always the best option to improve crop yields. Here, by using the highly pollinator-dependent alfalfa crop (Medicago sativa L.) as a case study, we propose the use of the effectiveness landscape framework to identify key crop pollinator species. According to this framework, in a mutualistic interaction, each species´ effectiveness is represented by the product of a quantitative component and a qualitative one, these being measures of the outcomes of this interaction. We applied this framework for two managed and four wild bee species that visit alfalfa in fields southwest of Buenos Aires province, Argentina. We dissected the quantity components of the pollinator effectiveness landscape by estimating two quantitative subcomponents: visitation rate and flower tripping rate. Also, we estimate pod set as a qualitative component without dissecting it in subcomponents. Our results showed that the contribution of both components and the resulting pollinator effectiveness varied among pollinator species, indicating a contrasting effectiveness of different bee species on alfalfa pollination. For example, pollinator effectiveness was higher for managed than for wild bees, as consequence of their very high visitation rate, however, wild bee flower tripping rate and pod set were as high as managed ones. In fact, wild bees were more effective in promoting flower tripping than one of the managed bees (A. mellifera). This approach allowed us to assess which effectiveness components and subcomponents make pollinator species more or less effective, thus providing valuable information to identify key species to be enhanced to help in closing yield gaps. We suggest that the application of the effectiveness landscape framework would be useful to develop strategies to improve crop pollination service in pollinator-dependent crop systems.

Does Reproductive Success in Natural and Anthropogenic Populations of Generalist Epipactis helleborine Depend on Flower Morphology and Nectar Composition?

The purpose of our study was to determine the role of flower structure and nectar composition in shaping the reproductive success (RS) of the generalist orchid Epipactis helleborine in natural and anthropogenic populations. We supposed that the distinct character of two groups of habitats creates different conditions for plant-pollinator relationships, thus influencing reproductive success in E. helleborine populations. Both pollinaria removal (PR) and fruiting (FRS) were differentiated between the populations. On average, FRS was almost two times higher in the anthropogenic than in the natural populations. The difference between the two population groups in PR was smaller but still statistically significant. RS parameters were correlated with some floral display and flower traits. Floral display influenced RS only in three anthropogenic populations. Flower traits had a weak influence on RS (10 of the 192 cases analyzed). The more important trait in shaping RS was nectar chemistry. The nectar of E. helleborine is relatively diluted with a lower sugar concentration in the anthropogenic than in the natural populations. In the natural populations, domination of sucrose over hexoses was found, while in the anthropogenic populations, hexoses were more abundant and the participation of sugars was balanced. In some populations, sugars influenced RS. In E. helleborine nectar, 20 proteogenic and 7 non-proteogenic amino acids (AAs) were found with a clear domination of glutamic acid. We noted relationships between some AAs and RS, but distinct AAs shaped RS in different populations, and their impact was independent of their participation. Our results indicate that the flower structure and nectar composition of E. helleborine reflect its generalistic character and meet the requirements of a wide range of pollinators. Simultaneously, the differentiation of flower traits suggests a variation in pollinator assemblages in particular populations. Knowledge about the factors influencing RS in distinct habitats helps to understand the evolutionary potential of species and to understand mechanisms and processes crucial for shaping interactions between plants and pollinators.

Range‐wide floral trait variation reflects shifts in pollinator assemblages, consistent with pollinator‐mediated divergence despite generalized visitation

Floral trait evolution mediated by pollinators is important in the diversification of flowering plants, yet few studies have demonstrated the range‐wide geographic variation in both floral traits and pollinators which represents a predicted precursor for pollinator‐mediated speciation. This study explores whether geographic variation in pollinator interactions underlies the observed patterns of floral divergence both 1) among species of theCastilleja purpureacomplex (C. purpurea,C. citrinaandC. lindheimeri) and the congenerC. sessiliflora, as well as 2) withinC. sessiliflora, across its wide geographic range. We sampled floral visitors and floral traits (morphology and color) at 23 populations across a 1900 km‐wide study area in 1–3 years, with reproductive fitness (fruit set) data for 18 of these populations. A wide diversity of pollinator functional groups visited the focal species, including bees, butterflies, hawkmoths and hummingbirds, and visitor assemblages varied among species and across geography. We identified relationships between floral traits and visitation by certain pollinator groups, which often aligned with predictions based on pollination syndromes. Despite visitor assemblages being largely generalized across most populations, we found that the observed changes in floral traits were associated with shifts in the relative frequencies of key pollinator functional groups. Hence this study demonstrates that variation in pollinator assemblages across the distributions of taxa may underlie divergence in floral traits and suggests that highly specialized relationships may not be required for early stages of pollinator‐mediated floral divergence. Our extensive sampling of 23 populations over multiple years across a large geographic area highlights the value of range‐wide studies for characterizing patterns of divergence mediated by ecological interactions.

Pollination of exotic fruit crops depends more on extant pollinators and landscape structure than on local management of domestic bees

Agricultural globalization has driven the expansion of exotic crops into new agricultural areas. Pollinator-dependent exotic crops not only have to face the abiotic constraints of the new cultivation regions but also deal with local pollinator assemblages, which may or may not fulfill pollination requirements. Here, we studied how three entomophilous exotic crops (kiwifruit, northern highbush blueberry and rabbiteye blueberry) adapt to a common pollination environment in new cultivation areas in Spain. For this, we assessed the pollination limitation of those crops, the contribution of insect assemblages to the pollination service, and the effect of landscape structure and the management of domestic pollinators on these assemblages. The three exotic crops showed large and diverse pollinator assemblages but differed in the assemblage composition and in the identity of the main pollinator species. Honeybee clearly dominated kiwifruit assemblages, representing almost 70 % of visits to flowers. Bumblebees and honeybee fairly equally dominated floral visits in highbush blueberry, and bumblebees accounted for more than 90% of visits in rabbiteye blueberry. Floral morphology partially explained interspecific differences in pollinator assemblages and led to the distinct contributions of the different insects to the different crops. Kiwifruit (but not blueberry) crops experienced pollination limitation that led to, on average, a 7.2 % reduction in fruit weight. This pollination limitation decreased when honeybee abundance rose. In all three crops, the local pollinator assemblages mostly depended on the landscape structure around orchards but were only affected by the management of domestic pollinators in rabbiteye blueberry crops. Our results highlight the importance of understanding the interspecific differences in the pollination ecology of new exotic crops before designing general management recommendations, and also question the use of managed pollinators before making an assessment of the contribution of extant insects to the pollination service.

Intercropping with Pigeonpea (Cajanus cajan L. Millsp.): An Assessment of Its Influence on the Assemblage of Pollinators and Yield of Neighbouring Non-Leguminous Crops.

Intercropping is practiced in modern intensive agriculture considering many benefits, including additive crop yield. However, it may have competitive or facilitative interactions between pollinator-dependant crops. Here, we investigated the reproductive aspects of pigeonpea (Cajanus cajan). We assessed the influence of blooming pigeonpea on pollinator's assemblage and the yield of neighbouring non-leguminous crops (e.g., coriander, mustard). For these, we recorded floral visitors and the yield of the targeted crops from two types of fields-closely situated and distantly situated concerning pigeonpea plantation. Pigeonpea is autogamous, but pollinator's visits enhance fruit and seed sets. Bright, nectariferous flowers emitted several volatile organic compounds and were visited by numerous insect species. The prime pollinators of pigeonpea are carpenter bees and leafcutter bees. In contrast, halictidae, honeybees and stingless bees mainly pollinate the co-blooming non-leguminous crops (coriander and mustard). The richness and abundance of pollinators on these co-blooming crops remain similar in closely situated and distantly situated fields. As a result, the yield of the neighbouring crops is not significantly influenced by the blooming pigeonpea. Therefore, it can be concluded that planting pigeonpea in ridges of agricultural fields will be an additional agricultural output without affecting the assemblage of pollinators and yields of neighbouring co-blooming crops.

Distribution Patterns of Insect Pollinator Assemblages at Deva Vatala National Park, Bhimber, Azad Jammu and Kashmir

Distribution Patterns of Insect Pollinator Assemblages at Deva Vatala National Park, Bhimber, Azad Jammu and Kashmir

The nonlinear change in pollinator assemblages and self-mating syndromes ofPrimula atrodentataalong elevation gradients

AbstractThe reproductive strategies of alpine plants are often altered by environmental changes caused by changes in the spatial distribution of the gradient. However, few studies have investigated whether reproductive patterns of the same species vary with elevation. Three natural populations of Primula atrodentata, which are distributed in the eastern Himalayas and have a long flowering period, were selected along the elevation gradients in Shergyla Mountain, Tibet, China. Morph ratio investigation, floral trait measurement, pollinator observation and manipulated pollination experiments were conducted to explore the changes in self-compatibility and floral traits associated with the selfing syndrome along elevation gradients. We found that the breeding system of the S-morph is facultative outcrossing, and that of the L-morph is obligatory outcrossing. We further found that with increasing elevation, the number of pollen and ovules, anther–stigma distance, and inbreeding depression index first increased and then decreased, whereas the seeds per fruit and seed-setting rate under hand self-pollination, pollen limitation and self-incompatibility index tended to decrease first, but then increased. In addition, pollinator diversity and visiting frequency were the highest at the middle elevation (4050 population), which can better explain the nonlinear change in self-fertility with elevation. Our findings provide insights into the evolutionary pattern of self-compatibility in alpine plants along elevational gradients.

Experimental insecticide applications change tomato pollinator assemblages and do not increase fruit production

One of the main threats to pollinators is insecticide application, many products widely used have lethal and sub-lethal (affects behavior, health, and fitness) effects on pollinators, and hence pollination. As sensitivity to such effects varies across species, insecticide application also changes the pollinator community composition within agricultural landscapes and hence affects the assemblages of crop pollinators. However, studies on the effects on native bees and their consequences on pollination services are lacking for many pesticides. Here, we use an experimental setup placed in four study regions (each with three blocks, with 15 experimental per block) to evaluate the effect of lambda-cyhalothrin pulverization on pollination and production of tomato (Solanum lycopersicum L.). Lambda-cyhalothrin is a pyrethroid insecticide highly toxic to the environment and commonly used in the tomato crops of Brazil, a crop that is pollinated by a diverse community of native bees. The effect of an alternative insecticide, classified as biological, on pollinators and pollination of tomatoes was also evaluated. For each experimental individual under each treatment, we collected data on the pollinator visitation before and after starting pulverization up to 23 days after the last application of pesticides. We also evaluated the effect of the three treatments on stigma pollen load, fruit, and seed production. We found that in all treatments (even control) visitation rate was higher before than after pulverization. During the spraying period, the plants sprayed with pyrethroid insecticide showed lower pollinator visitation compared to other treatments, these plants also ended with lower pollen deposition on the stigma. Paratrigona lineata was more susceptible to insecticide pulverization than other bee species. Recovery of visitation rates was detected after 23 days for all treatments. Despite the effect on visitation and pollen deposition, fruit and seed sets were similar among treatments. Overall, our results show that pyrethroid insecticide pulverization causes changes in the behavior of native flower-visiting bees. The mechanisms that explain these changes deserve further investigation, and further studies are needed to understand the large-scale effects of the use of pyrethroid insecticide on insect biodiversity and agricultural landscapes. As the biological insecticide had lower negative effects on bees, future studies that take into account both the effects on pest damage and pollination are needed to define more sustainable management approaches, minimizing negative impacts on biodiversity.

Intraspecific variation in morphology of spiny pollen grains along an altitudinal gradient in an insect-pollinated shrub.

Intraspecific variations in pollen morphological traits are poorly studied. Interspecific variations are often associated with pollination systems and pollinator types. Altitudinal environmental changes, which can influence local pollinator assemblages, provide opportunities to explore differentiation in pollen traits of a single species over short distances. The aim of this study is to examine intraspecific variations in pollen traits ofan insect-pollinated shrub, Weigela hortensis (Caprifoliaceae), along an altitudinal gradient. Pollen spine phenotypes (length, number and density), pollen diameter, lipid mass (pollenkitt) around pollen grains, pollen production per flower and pollinator assemblages were compared at four sites at different altitudes. Spine length and the spine length/diameter ratio of pollen grains were greater at higher altitudes but not correlated with flower or plant size. Spine number and density increased as flower size increased, and pollen lipid mass decreased as plant size increased. Bees were the predominant pollinators at low-altitude sites whereas flies, specifically Oligoneura spp. (Acroceridae), increased in relative abundance with increasing altitude. The results of this study suggest that the increase in spine length with altitude was the result of selection favouring longer spines at higher-altitude sites and/or shorter spines at lower-altitude sites. The altitudinal variation in selection pressure on spine length could reflect changes in local pollinator assemblages with altitude.

Linalool: A ubiquitous floral volatile mediating the communication between plants and insects

AbstractTerpenoids, one of the most important plant volatiles, mediate the communication between plants and pollinators, herbivores as well as pathogens. Recently, researchers have shown intensive interest in the complicated interactions. Linalool, an acyclic monoterpene, is one of the common flavor‐related volatiles across the plant kingdom. In this review, we summarized the biosynthesis and transcriptional regulation of terpenoids, and then focused on the biological function of linalool in plant–insect interactions. We found that flowers emitting linalool as the dominant volatile appeal to broad assemblages of pollinators, while some pollinators typically have strong preferences for these flowers as well. Hereinto, moths and bees are the main pollinators of linalool‐dominant flowers. Additionally, linalool produced by plants could defend against insect pests and pathogens. It is noteworthy that the two enantiomers of linalool have distinct functions. (S)‐(+)‐linalool mainly attracts pollinators, while (R)‐(−)‐linalool seems to act as insect repellents. Further research on the biofunctional diversity and genetic mechanisms of linalool enantiomers will reveal the complexity of plant survival strategies, and the increasing understanding of the molecular mechanisms underlying their biosynthesis and transcriptional regulation will provide theoretical foundation and practical basis for directional transformation of plants.

Flower-Visiting Insect Assemblages on Fall-Blooming Native California Sage Scrub Shrubs

Pollinator studies in the endangered California sage scrub ecosystem have focused on spring insect assemblages, when most plant species bloom. Consequently, the insect assemblages using common fall-blooming sage scrub shrubs Lepidospartum squamatum, Ericameria pinifolia, and Baccharis pilularis remain undescribed. Our study aimed to: (1) document flower-visiting insect assemblages on fall-blooming shrubs, (2) assess the efficacy of three sampling techniques in inventorying insect assemblages, and (3) explore, using DNA metabarcoding, which plants are utilized and the extent to which surrounding suburban habitats’ plants are also used. While elevated sampling is required to inventory flower-visiting insects, we describe a diverse assemblage consisting of 123 species. Insect assemblages differed between L. squamatum and B. pilularis, as well as, E. pinifolia and B. pilularis, but not between L. squamatum and E. pinifolia. Direct sampling approaches (netting and photo documentation) collected 115 species not collected by passive malaise traps, highlighting that active observations are required to describe flower-visiting insect assemblages. Sequencing the ITS2 region of pollen from abundant visitors revealed that a majority of pollen is from the sage scrub ecosystem, highlighting its value. Our results indicate that the presence of fall-blooming shrubs may be critical for maintaining diverse sage scrub insect and pollinator assemblages.

The impact of Pleistocene glaciations and environmental gradients on the genetic structure of Embothrium coccineum.

The South American temperate forests were subjected to drastic topographic and climatic changes during the Pliocene-Pleistocene as a consequence of the Andean orogeny and glacial cycles. Such changes are common drivers of genetic structure and adaptation. Embothrium coccineum (Proteaceae) is an emblematic tree of the South American temperate forest (around 20°S of latitude) that has strongly been affected by topographic and climatic events. Previous studies have shown a marked genetic structure in this species, and distinct ecotypes have been described. Yet, little is known about their adaptive genetic responses. The main goal of this study was to investigate the effects of historical and contemporary landscape features affecting the genetic diversity and connectivity of E.coccineum throughout its current natural distribution. Using over 2000 single nucleotide polymorphisms (SNPs), we identified two genetic groups (a Northern and a Central-Southern group) that diverged around 2.8 million years ago. The level of genetic structure was higher among populations within the Northern genetic group than within the Central-Southern group. We propose that these differences in genetic structure may be due to differences in the assemblages of pollinators and in the evolutionary histories of the two genetic groups. Moreover, the data displayed a strong pattern of isolation by the environment in E.coccineum, suggesting that selection could have led to adaptive divergence among localities. We propose that in the Chilean temperate forest, the patterns of genetic variation in E.coccineum reflect both a Quaternary phylogenetic imprint and signatures of selection as a consequence of a strong environmental gradient.

Pollinator sharing between reproductively isolated genetic lineages of Silene nutans.

High reciprocal pollination specialization leading to pollinator isolation can prevent interspecific pollen transfer and competition for pollinators. Sharing pollinators may induce mating costs, but it may also increase pollination services and pollen dispersal and offer more resources to pollinators, which may be important in case of habitat fragmentation leading to pollination disruption. We estimated pollen dispersal and pollinator isolation or sharing between two reproductively isolated genetic lineages of Silene nutans (Caryophyllaceae), which are rare and occur in parapatry in southern Belgium, forming two edaphic ecotypes. As inter-ecotypic crosses may lead to pollen wastage and inviable progeny, pollinator isolation might have evolved between ecotypes. Silene nutans is mainly pollinated by nocturnal moths, including nursery pollinators, which pollinate and lay their eggs in flowers, and whose caterpillars feed on flowers and seeds. Pollinator assemblages of the two ecotypes are largely unknown and inter-ecotypic pollen flows have never been investigated. Fluorescent powdered dyes were used as pollen analogues to quantify intra- and inter-ecotypic pollen transfers and seeds were germinated to detect chlorotic seedlings resulting from inter-ecotypic pollination. Nocturnal pollinators were observed using infrared cameras on the field, and seed-eating caterpillars were collected and reared to identify nursery pollinator species. No pollinator isolation was found: we detected long-distance (up to 5km) inter-ecotypic dye transfers and chlorotic seedlings, indicating inter-ecotypic fertilization events. The rare moth Hadena albimacula, a nursery pollinator specialized on S. nutans, was found on both ecotypes, as well as adults visiting flowers (cameras recordings) as seed-eating caterpillars. However, S. nutans populations harbor different abundance and diversity of seed predator communities, including other rare nursery pollinators, suggesting a need for distinct conservation strategies. Our findings demonstrate the efficiency of moths, especially of nursery pollinators, to disperse pollen over long distances in natural landscapes, so to ensure gene flow and population sustainability of the host plant. Seed-predator specificities between the two reproductively isolated genetic lineages of S. nutans, and pollinator sharing instead of pollinator isolation when plants occur in parapatry, suggest that conservation of the host plant is also essential for sustaining (rare) pollinator and seed predator communities.

Variación interespecífica de ensambles de polinizadores en Nierembergia (Solanaceae) en relación con la localización geográfica y la variación fenotípica de las flores

Understanding how the interactions of related plant species with pollinators vary on a spatial scale provides the opportunity to establish links between macroevolutionary patterns and microevolutionary processes, as well as to approach the mechanisms underlying plant diversification. In this work, we explore the variation in pollinator assemblages of 15 species and varieties of Nierembergia (Solanaceae) across the distribution range of the genus in Argentina, in relation to variation in floral phenotype and geographic location. By field observations, morphometric measurements of flowers and comparative phylogenetic methods, pollinator assemblages and flowers of Nierembergia taxa were characterized and compared, and the association between pollinator assemblage composition, geographic location, floral morphology and phylogenetic relationships was evaluated. 13 species of oil-collecting bees were recorded as pollinators. The assemblage composition was strongly associated with geographic location, that is, Nierembergia taxa in nearby areas had greater similarity in their pollinator assemblages than geographically distant taxa. This pattern was not associated with phylogenetic relationships among taxa, except for a group of high mountain species in northwestern Argentina. On the other hand, interspecific variation was found in the floral phenotype, mainly in the corolla and the oil-producing gland size. However, Nierembergia taxa with similar floral phenotypes did not share the composition of the pollinator assemblage, as expected. In conclusion, we found a mixed macroevolutionary pattern in which some phylogenetically distant Nierembergia taxa converge geographically in the composition of pollinator assemblages, while this attribute is conserved in a phylogenetic clade. This pattern suggests that the role of pollinators in Nierembergia diversification is more complex than previously thought.

Pollination ecology and breeding system of the tropical tree Guaiacum sanctum on two Caribbean islands with contrasting pollinator assemblages

Insular pollination systems are more extinction-prone and vulnerable to invasive species than mainland ones. They often have plants with reproductive mechanisms allowing for self-compatibility and low species-rich communities of pollinators. Here, we document different reproductive traits of the tropical tree Guaiacum sanctum on two insular populations with contrasting pollinator assemblages: Guánica in Puerto Rico with alien honeybees and Mona Island where honeybees do not occur. Using field observations and pollination experiments, we evaluated pollinator species richness, visitation rates, breeding system, and the fitness of selfed- vs. crossed-progenies. We found that flowers are pollinated by insects on both islands, but while the species richness of pollinators was higher on Mona, the visitation rates were considerably higher in Guánica where trees are almost exclusively visited by the introduced Apis mellifera. Flowers are not apomictic, and autogamy is negligible indicating that pollinators are required to set fruits. Outcrossing yielded nearly twice the number of fruits and seeds than selfing and these differences were consistent between populations, which might reflect early acting inbreeding depression, partial self-incompatibility, or differences in resource allocation between selfed and outcrossed fruits. Our combined results suggest that the substantial reduction in pollinator visitors in areas dominated by A. mellifera may add an additional level of vulnerability to these threatened populations. Although reproductive fitness is higher in Guánica, mostly due to the pollination services provided by A. mellifera, this population may be more susceptible to environmental changes and large-scale disturbances affecting pollinator abundance given the reduced diversity of flower visitors.

Evaluating the effects of observation period, floral density, and weather conditions on the consistency and accuracy of timed pollinator counts

Insect pollinators are experiencing substantial declines as a result of habitat loss, agricultural intensification, invasive pests, and climate change. To investigate factors causing pollinator declines, evaluate the success of conservation measures, and institute long-term monitoring schemes, it is essential to validate and standardize pollinator sampling techniques. This study investigated how sampling duration, weather conditions, and abundance of floral resources influenced the results of timed pollinator counts by repeatedly sampling the same pollinator assemblage in an Irish meadow. The likelihood of detection of Apis mellifera, Bombus spp, solitary bees, and Syrphidae was strongly associated with the density of floral units or floral cover in the observation plot. Also, even though protocol criteria restricted pollinator counts to the middle of the day and benevolent weather, pollinator counts were strongly influenced by factors such as cloud cover, light levels, wind speed and relative humidity. Increasing the duration of the timed counts from 5-minutes to 30-minutes considerably increased the probability of detection of each pollinator group. Additionally, the perceived diversity of the pollinator assemblage at the meadow was markedly affected by sampling duration and floral abundance. To improve the consistency or comparability of studies using timed pollinator counts, we recommend that criteria are set restricting surveys to narrow ranges of weather conditions and floral density when possible. Additionally, pollinator field investigations or monitoring programs would benefit from a systematic evaluation of how erroneous non-detection of target taxa can be reduced to acceptable levels by modifying sampling duration.