Potentials of Pesticidal Plants in Enhancing Diversity of Pollinators in Cropped Fields

Declines in populations of pollinators in agricultural based landscapes have raised a concern, which could be associated with various factors such as intensive farming systems like monocropping and the use of non-selective synthetic pesticides. Such practices are likely to remove beneficial non-crop plants around or nearby the cropped fields. This may in turn result into losses of pollinators due to loss of the natural habitats for insects therefore, interfering the interaction between beneficial insects and flowering crop plants. Initiatives to restore friendly habitats for pollinators require multidisciplinary approaches. One of these could be the use of pesticidal flowering plants as part of field margin plants with the aim of encouraging the population of pollinators whilst reducing the number of pests. Farmers should be fully engaged in the efforts of creating conducive environments to pollinators and be well equipped with the knowledge of proper habitats management strategies in agricultural fields. Developing appropriate conservation strategies to combat decline of pollinators is of high importance and thus there is a need to evaluate management practices, which potentially favour the populations of pollinators. Therefore, this review aims at unravelling available evidences on habitats manipulation options through provision of flowering plants along the field margins that have shown to increase plant biodiversity surrounding the cropped fields. It also summarizes the options for increasing plant biodiversity, which have improved habitats for the pollinating insects and beneficially boosting pollination services in agro-ecosystems.

Farmers’ perceptions of pollinators’ importance in coffee production in Uganda

Coffee (Coffea canephora) is the principal cash crop and the country’s largest agricultural foreign revenue earner in Uganda. Previous surveys confirmed that coffee grown in central Uganda was largely depending on bee pollination to set fruit set. Despite its high contribution to the economics of agricultural sector in Uganda and despite its great dependency to bees for fruit set, it is not clear if small-scale farmers are aware of the importance of managing farm-landscapes for pollination services conservation to increase coffee yield. The aim of this study was to assess farmers’ perceptions and knowledge of the importance of pollinators and pollination services conservation for coffee production enhancement. The main hypothesis was that small-scale coffee growers were not aware of the relevance of pollination services for coffee production. Farmers’ surveys were conducted in coffee-banana farming systems in central Uganda. It was found in this study that more than 90% of interviewed farmers were not aware of the role played by bees in coffee yield increase. Farmers were not willing to manage their lands to protect pollination services, particularly because they considered pollination service as an unsolicited “free service”, or as a “public good”. Farmers were not aware of the role of semi- natural habitats serving as reservoir (hiding points) for pollinators in the surrounding of coffee fields. However, they were aware of some ecosystem services delivered in the coffee- banana farming system such as planting shading trees. Only 3.3% of respondents believed that placing beehives in coffee farms could increase the yield. The study recommended the increase of the awareness of small-scale coffee growers on the importance of pollinators to increase coffee production. It is recommended that future management of pollination services are built on improving farmers’ indigenous knowledge and on adequate understanding of the ecology of the local pollinator species. There is a need to broadly scale-up best field, habitat and landscape management strategies and practices that are friendly to coffee pollinators in rural landscapes of

The Impact of Willow Flowering Time on Species Composition and the Number of <i>Apoidea</i>Pollinators

Pollinators are important to wild and cultivated plants, and the same plants are important to pollinators as well. A very important source of pollen and nectar to pollinators are willows (Salix spp.). The aim of this study was to demonstrate which Apoidea species are attracted by a species-diverse willow plantation (Poznań University of Life Sciences Willow Collection, Poland), the proportion of the number of honeybees to other species from the Apoidea superfamily visiting willow plantations, and whether the flowering date of male and female willow individuals affect the species composition and number of pollinators. Observations of willow phenology were carried out in the second year of willow growth, from March 9 to December 7, 2012. The insects were observed between April 6 and May 11, 2012. The results of this study showed 30 Apoidea species. Among 1591 Apoidea individuals, only 17 honeybee individuals were noted. The results show that the willow pollen production optimum occurred when the minimum air temperatures stopped dropping below zero. This parameter and this period are also related to the intensification of the occurrence of the noted insects. It can also be concluded that the pollen production season precedes the flowering optimum of female flowers and that the optimum flowering of female flowers is correlated with a significant increase in air temperature.

Jasmonate signaling makes flowers attractive to pollinators and repellant to florivores in nature

Flowers are required for the Darwinian fitness of flowering plants, but flowers＇ advertisements for pollination services can attract florivores. Previous glasshouse work with Nicotiana attenuata revealed the role of jasmonate （JA） signaling in flower development, advertisement and defense. However, whether JA signaling mediates flowers＇ filtering of floral visitors in nature remained unknown. This field study revealed that silencing JA signaling resulted in flowers that produce less nectar and benzyl acetone, two pollinatorattractive traits. Meanwhile, flowers of defenseless plants were highly attacked by a suite of native herbivores, and damage to buds in native plants correlated negatively with their JA-lle levels.

The function of floral orientation in bluebells:interactions with pollinators and rain in two species of Mertensia(Boraginaceae)

Aims Pollinators are traditionally considered to be the primary agent of selection on floral traits.However,floral traits may also be under selection from abiotic agents(e.g.rain),which makes considering the relative importance of pollinators and abiotic selective agents on floral traits essential.The functional significance of floral orien-tation is often ascribed to pollinator attraction,but orientation can also protect reproductive structures from rain.Therefore,a study that incorporates both factors will enhance our understanding of the ecological roles of floral orientation in plant fitness.Mertensia brevistyla and M.fusiformis are herbaceous species that differ in their floral orientations.A series of field and laboratory experi-ments was used to investigate the adaptive function of floral orien-tation in these species,particularly with respect to pollinators and rain.Methods We measured and compared floral orientation and visitor assem-blages between M.brevistyla and M.fusiformis populations in west-ern Colorado,USA.We manipulated floral stems and conducted a choice experiment with floral visitors,and also compared orienta-tions of pollinator-visited stems with those of unvisited stems in a natural setting.We examined pollinator-and rain-mediated selec-tion on floral orientation by manipulating orientation,conducting supplemental pollinations,applying watering treatments and meas-uring subsequent seed set.We also experimentally tested the like-lihood of rain contact with anthers,and the effect of rainwater on pollen germinability.Important Findings Mertensia brevistyla had a significantly more upright floral orienta-tion than M.fusiformis,and seed set was highest in upright M.bre-vistyla and in horizontal/pendant M.fusiformis stems,supporting an adaptive function(via female fitness)of the interspecific difference in orientation.However,floral visitor assemblages did not differ significantly between the two species;visitors did not exhibit sig-nificant preference for either orientation;and pollinator-mediated selection on orientation was undetectable.Similarly,there was lit-tle effect of water on seed set in either species,regardless of floral orientation.However,pollen germinability was reduced in both species by immersion in water;and water was more likely to contact anthers in M.fusiformis than in M.brevistyla,due to interspecific differences in floral morphology.We conclude that pollinators are likely not the primary selective agent driving differences in orienta-tion in these Mertensia species.Instead,the negative effect of rain on pollen germinability helps explain the more pendant orientation of M.fusiformis,while short anthers in more upright M.brevistyla provide an alternative adaptation to rain.The selective agent driving effects of orientation on seed set remains unclear.This study illus-trates the necessity of considering male fitness and abiotic agents in interpreting the functional significance of inflorescence traits.

Patterns and drivers of plant sexual systems in the dry-hot valley region of southwestern China

Sexual systems play important roles in angiosperm evolution and exhibit substantial variations among different floras. Thus, studying their evolution in a whole flora is crucial for understanding the formation and maintenance of plant biodiversity and predicting its responses to environmental change. In this study, we determined the patterns of plant sexual systems and their associations with geographic elements and various life-history traits in dry-hot valley region of southwestern China, an extremely vulnerable ecosystem. Of the 3166 angiosperm species recorded in this area, 74.5% were hermaphroditic,13.5% were monoecious and 12% were dioecious, showing a high incidence of diclinous species. Diclinous species were strongly associated with tropical elements, whereas hermaphroditic species were strongly associated with temperate and cosmopolitan elements. We also found that hermaphroditism was strongly associated with showy floral displays, specialist entomophily, dry fruits and herbaceous plants.Dioecy was strongly associated with inconspicuous, pale-colored flowers, generalist entomophily, fleshy fruits, and woody plants, whereas monoecy was strongly associated with inconspicuous, pale-colored flowers, anemophily, dry fruits, and herbaceous plants. In addition, hermaphroditic species with generalist entomophily tended to flower in the dry season, whereas diclinous species with specialist entomophily tended to flower in the rainy season. However, independent of sexual systems, plants that produce dry fruits tended to flower in the rainy season and set fruits in the dry season, but the opposite pattern was found for fleshy fruit-producing plants. Our results suggest that in the dry-hot valleys, plant sexual systems are associated with geographic elements as well as various life-history traits that are sensitive to environmental change.

Enhanced and asymmetric signatures of hybridization at climatic margins: Evidence from closely related dioecious fig species

Hybridization plays a significant role in biological evolution. However, it is not clear whether ecological contingency differentially influences likelihood of hybridization, particularly at ecological margins where parental species may exhibit reduced fitnesses. Moreover, it is unknown whether future ecosystem change will increase the prevalence of hybridization. Ficus heterostyla and F. squamosa are closely related species co-distributed from southern Thailand to southwest China where hybridization, yielding viable seeds, has been documented. As a robust test of ecological factors driving hybridization, we investigated spatial hybridization signatures based on nuclear microsatellites from extensive population sampling across a widespread contact range. Both species showed high population differentiation and strong patterns of isolation by distance. Admixture estimates exposed asymmetric interspecific gene flow.Signatures of hybridization increase significantly towards higher latitude zones, peaking at the northern climatic margins. Geographic variation in reproductive phenology combined with ecologically challenging marginal habitats may promote this phenomenon. Our work is a first systematic evaluation of such patterns in a comprehensive, latitudinally-based clinal context, and indicates that tendency to hybridize appears strongly influenced by environmental conditions. Moreover, that future climate change scenarios will likely alter and possibly augment cases of hybridization at ecosystem scales.

Intraspecific floral colour variation in three Pedicularis species

Flower constancy describes the phenomenon that pollinators tend to successively visit flowers of a single species during foraging,reducing reproductive interference in natural communities.The extent of flower constancy is largely determined by the floral traits of co-flowering species.Both higher inter-specific and lower intraspecific differences of floral traits should contribute to a higher level of flower constancy.However,previous studies mainly focused on interspecific difference,and the intraspecific variation(consistency)of floral traits received much less attention.We hypothesise that selection may favour lower intraspecific floral trait variation in communities composed of multiple co-flowering congeners.We investigated the floral colour variation of three focal Pedicularis species that share pollinators in 19communities composed of either single or multiple Pedicularis species.Colour was quantified using image-based colour analysis as perceived by pollinators.We found that most of the intrapopulation floral colour variation was below the colour discrimination threshold of bumblebees,implying strongly constrained by the visual selection by pollinators.Contrary to the hypothesis,there is no significant difference in intraspecific floral colour variation between different community contexts.It may be due to the relatively large interspecific floral colour differences of most co-flowering species.The influence of community context on intraspecific variation may be reflected in floral traits other than colours.

Maximizing Resource Efficiency in Cloud Data Centers through Knowledge-Based Flower Pollination Algorithm (KB-FPA)

Cloud computing is a dynamic and rapidly evolving field,where the demand for resources fluctuates continuously.This paper delves into the imperative need for adaptability in the allocation of resources to applications and services within cloud computing environments.The motivation stems from the pressing issue of accommodating fluctuating levels of user demand efficiently.By adhering to the proposed resource allocation method,we aim to achieve a substantial reduction in energy consumption.This reduction hinges on the precise and efficient allocation of resources to the tasks that require those most,aligning with the broader goal of sustainable and eco-friendly cloud computing systems.To enhance the resource allocation process,we introduce a novel knowledge-based optimization algorithm.In this study,we rigorously evaluate its efficacy by comparing it to existing algorithms,including the Flower Pollination Algorithm(FPA),Spark Lion Whale Optimization(SLWO),and Firefly Algo-rithm.Our findings reveal that our proposed algorithm,Knowledge Based Flower Pollination Algorithm(KB-FPA),consistently outperforms these conventional methods in both resource allocation efficiency and energy consumption reduction.This paper underscores the profound significance of resource allocation in the realm of cloud computing.By addressing the critical issue of adaptability and energy efficiency,it lays the groundwork for a more sustainable future in cloud computing systems.Our contribution to the field lies in the introduction of a new resource allocation strategy,offering the potential for significantly improved efficiency and sustainability within cloud computing infrastructures.

Cognitive ecology of pollinators and the main determinants of foraging plasticity

Introduction The long-lasting coevolution between flowering plants and associate pollinators has made both partners intimately connected and reciprocally dependent on one another (Chittka and Thomson 2001;Harder and Barrett 2006;Waser and Oilerton 2006). The interaction between plants and pollinators rests mostly on a mutualistic exchange: plants invest in the production of nectar and pollen to reward pollinators who, in turn, sustain plant reproduction by vectoring their pollen to conspecific flowers (Harder and Barrett 2006;Waser and Oilerton 2006).

Dual ecological functions of scatter-hoarding rodents:pollinators and seed dispersers of Mucuna sempervirens(Fabaceae)

Double mutualism,that is,pollination and seed dispersal of the same plant species mediated by the same animal partners,is important but remains elusive in nature.Recently,rodent species were found as key pollinators(i.e.explosive openers)for some Mucuna species in(sub)tropical Asia,but no evidence has shown whether and how these rodents could also act as legitimate seed dispersers via scatter-hoarding for those producing large seeds.Here,my aim was to test the hypothesis that scatter-hoarding rodents could act as double mutualists for both pollination and seed dispersal of the same Mucuna species,that is,Mucuna sempervirens(Fabaceae).Based on camera-trapping survey at 2 locations with or without squirrel presence in the Dujiangyan subtropical forests,Southwest China,7 mammals and birds were identified as explosive openers for M.sempervirensflowers,but Leopoldamys edwardsi(rats)and Paguma larvata(civets)were the main pollinators at the squirrel-absent site,while Callosciurus erythraeus(squirrels)were the main pollinators at the squirrel-present site.By tracking the fate of individually-tagged seeds over 5 years at each site,I provide thefirst evidence for seed-eating rodents as legitimate seed dispersers via scatter-hoarding of seeds in this world-wide plant genus,although dispersal services were slightly reduced at squirrel-absent site.More importantly,the dual roles of scatter-hoarding rodents as key pollinators and seed dispersers for the same Mucuna species have shown a clear relationship of double mutualism,and their key services may be essential for population conservation of these Mucuna species in human-disturbed landscapes.

Effects of distinct pollinators on the mating system and reproductive success in Incarvillea sinensis,an annual with large floral displays

Aims Most flowering plants engage in mutualisms with animals to move pollen between individuals,and it is expected that pollinators play an essential role in the evolution of selfing,yet few studies have deter-mined how distinct pollinator types affect a plant’s mating system and reproductive success differentially.We investigated the effect of two different pollinators on the reproductive success of Incarvillea sinensis,an annual with showy,insect-pollinated,one-day flowers.Methods We marked flowers after a single visit from both pollinator species(Bombus patagiatus and Amegilla quadrifasciata)and calculated the number of pollen grains deposited on the stigma and pollen left in the anthers,the fruit and seed set,the outcrossing rate and the cor-relations of paternity.Important Findings There was no significant difference in the number of pollen grains deposited on the stigma,or in the seed and fruit set between the two pollinators in both years.The mean number of pollen grains removed by B.patagiatus was significantly higher than that removed by A.quadrifasciata.The outcrossing rate of flowers pollinated by B.patagiatus was significantly higher than that of flowers pollinated by A.quadrifasciata.The correlation of paternity of flowers pollinated by B.patagiatus was significantly lower than that of flowers polli-nated by A.quadrifasciata.For I.sinensis,B.patagiatus may exhibit larger pollen wastage,thus reducing the male reproductive success of the plant,but it causes higher female reproductive success because of its higher outcrossing rate and the lower correlation of paternity.Our findings highlighted that different animal pollinators could indeed cause differential mating systems and reproductive success.

Unravelling host-mediated effects on hemiparasitic Mexican mistletoe Psittacanthus calyculatus(DC.)G.Don traits linked to mutualisms with pollinators and seed dispersers

Aims While the influence of mistletoe-host interactions on each other’s evolution is well-recognized,the role of interactions between mis-tletoes and its mutualistic pollinators and seed dispersers mediated by host species is relatively unexplored.Methods Here,we examine the effects of host species(Mexican hawthorn Crataegus mexicana DC,black cherry Prunus serotina Ehrh.,leather-leaf Mexican oak Quercus crassipes Bonpl.)on flower morphology,nectar production,pollinator visitation rate and female reproduct-ive fitness in hemiparasitic Mexican mistletoe Psittacanthus caly-culatus(DC.)G.Don(Loranthaceae)populations at three different locations.We first measured the lengths of corolla,style,stamen,exerted stamen and anther,the length and width of the ovary and nectar availability for mistletoe flowers in natural populations.Then,we evaluated flower visitation and measured(length and width)and weighed the fruits and its seeds of mistletoes growing on each of the three host species.Finally,we evaluated the effects of host species,location and flower traits on fruit or seed size variation(both as proxies of reproductive fitness).Important Findings We found mistletoes growing on natural hosts P.serotina and Q.crassipes produced larger flowers,fruits and seeds than mistle-toes on cultivated C.mexicana.However,these differences varied across space.The amount of available nectar and hummingbird vis-itation rates in flowers of mistletoes on C.mexicana was higher at the three sites than in flowers of mistletoes on P.serotina or Q.cras-sipes.The effects of host species,study site and floral trait covariates affected significantly all fitness measures,indicating that mistletoes’reproductive fitness is affected differently depending on the host species and their site of occurrence.These host-associated differ-ences in reproduction might have implications for interactions with mutualistic vectors.

Pollinators exert positive selection on flower size on urban,but not on rural Scotch broom(Cytisus scoparius L.Link)

Aims Adaptive evolution of invasive species is both particularly exciting for the evolutionary biologist and worrisome for those interested in controlling or halting spread.Invasive species often have a dis-tinct timeline and well-recorded population expansion.As invaders encounter new environments,they undergo rapid adaptive evolu-tion.Our aim in this study was to measure variation of floral size in the invasive shrub Cytisus scoparius(Scotch broom)and measure natural selection by pollinators on that trait.Past research has found that this invasive plant is pollinator limited in Washington State and that declines in pollinator populations can contribute to local extinction in another invaded range(New Zealand).This plant is pollinated by both native and introduced species of bees,represent-ing a broad range of pollinator sizes.Cytisus scoparius has a flower structure that is highly conducive to studies on pollinator choice,even in the absence of direct pollinator observations.Methods We surveyed urban and rural sites in and around the city of Olympia in Washington State.Measuring banner width,we were able to show that flower size varies substantially between plants but mini-mally within plants.By measuring the proportion of flowers that were‘tripped’,we could determine pollinator visitation rates and thus determine the level of selection due to pollinator choice alone.Important Findings We found that C.scoparius is under natural selection by pollinators for increased flower size.However,such positive natural selection was only seen in urban populations although it was consistent across two flowering seasons.Rural populations of Scotch broom do not appear to be under selection on flower size.The natural selection by pollinators on broom flowers could result in adaptive evolution into a new pollination niche by an invading species.A higher level of variation in broom flowers seen here than seen in previous works in native regions suggests that C.scoparius may be highly diverse and primed for adaptive evolution.

Potential role of lava lizards as pollinators across the Galápagos Islands

Lizards have been reported as important pollinators on several oceanic islands.Here we evaluate the potential role of Galápagos lava lizards(Microlophus spp.)as pollinators across their radiation.Over 3 years,we sampled pollen transport by 9 lava lizard species on the 10 islands where they are present,including 7 single-island endemics.Overall,only 25 of 296 individuals sampled(8.4%)transported pollen of 10 plant species,the most common being Prosopis juliflora,Exodeconus miersii,Sesuvium sp.and Cordia leucophlyctis.At least 8 of these plant species were native,and none were confirmed as introduced to the archipelago.Despite the low overall proportion of individuals carrying pollen,this was observed in 7 of the nine lizard species,and on 8 of the ten main islands(Española,Fernandina,Floreana,Isabela,Marchena,Pinta,Santa Cruz and Santiago),suggesting that this is a widespread interaction.The results reported here support the potential role of lava lizards as pollinators across their radiation,although they may represent a relatively modest contribution when compared with birds and insects.However,we cannot discard that lizards may be ecologically significant for particular plant species and ecosystems given the specific climatic condition and functional diversity of each island.

Floral resources, pollinators and fruiting in a threatened tropical deciduous tree

Nothapodytes nimmoniana(Family Icacinaceae)is a deciduous tree species distributed in Asia facing severe population decline.Wood chips from the tree are a source of camptothecin,a globally soughtafter alkaloid with cancer-treating properties,and are harvested unsustainably in natural forests.We studied the pollination ecology of the species and asked if there are constraints in pollination and fruiting success in its natural populations.We also discuss the potential effects of wood extraction on pollinators and reproductive success in the population.Methods The study was carried out during the flowering season in two populations with varying exploitation levels,both located in the Protected Area Network in the Western Ghats of Karnataka State.We assessed floral resource availability and measured pollinator diversity and activity in the canopy from the perspective of the biology of the species.We quantified pollinator abundance and percent fruit set as a function of population density.Important Findings Flowers belong to the fly pollination syndrome and are open to visits by generalists such as Apis dorsata and Trigona iridipennis.Fruiting success did not vary between exploited and unexploited sites,but there was a significant difference in pollinator assemblage.In a lean male flowering year,fruit set was low,suggesting pollen limitation in the population.No fruiting was recorded in the second year at the site where trees were felled soon after the flowering period.We argue that when male floral resources are altered in exploited populations,pollinators of generalist nature may show a shift in foraging pattern.Also,generalist plants may be as susceptible to pollination loss as are specialist plants.The need for outcrossing in the species would probably exacerbate this vulnerability.

Shea Parklands Pollination in Burkina Faso, Some Techniques to Improve the Production

Shea tree is a major economic plant contributing to household income through the sale of edible fruits, kernels and shea butter. Shea butter is used industrially in the production of cosmetic products, chocolates and margarines. Fruits are used by human and also by birds. This study aimed to explore strategies for the improvement of shea yield through pollination. Two types of pollination (manual and natural pollination) were applied for the comparison of fruits set and their ripening. The fruits set and ripening index as well as average weight of ripe fruits and kernels were estimated. The results showed a significant difference between the fruits set Index of manual pollination and natural pollination (H(1) = 33.437, p = 7.361 × 10-9). Similarly, there was a significant difference between the ripening Index of manual pollination and natural pollination (H(1) = 4.5113, p = 0.03367). However, the mode of pollination did not influence the weight of ripe fruits and kernels. Therefore, the manual pollination enhances pollen supply to receptive stigmas for fertilization and improved fruit yield in Vitellaria paradoxa.

Defining honeybee subspecies in an evolutionary context warrants strategized conservation

Despite the urgent need for conservation consideration,strategic action plans for the preservation of the Asian honeybee,Apis cerana Fabricius,1793,remain lacking.Both the convergent and divergent adaptations of this widespread insect have led to confusing phenotypical traits and inconsistent infraspecific taxonomy.Unclear subspecies boundaries pose a significant challenge to honeybee conservation efforts,as it is difficult to effectively prioritize conservation targets without a clear understanding of subspecies identities.Here,we investigated genome variations in 362 worker bees representing almost all populations of mainland A.cerana to understand how evolution has shaped its population structure.Whole-genome single nucleotide polymorphisms(SNPs)based on nuclear sequences revealed eight putative subspecies,with all seven peripheral subspecies exhibiting mutually exclusive monophyly and distinct genetic divergence from the widespread central subspecies.Our results demonstrated that most classic morphological traits,including body size,were related to the climatic variables of the local habitats and did not reflect the true evolutionary history of the organism.Thus,such morphological traits were not suitable for subspecific delineation.Conversely,wing vein characters showed relative independence to the environment and supported the subspecies boundaries inferred from nuclear genomes.Mitochondrial phylogeny further indicated that the present subspecies structure was a result of multiple waves of population divergence from a common ancestor.Based on our findings,we propose that criteria for subspecies delineation should be based on evolutionary independence,trait distinction,and geographic isolation.We formally defined and described eight subspecies of mainland A.cerana.Elucidation of the evolutionary history and subspecies boundaries enables a customized conservation strategy for both widespread and endemic honeybee conservation units,guiding colony introduction and breeding.

Does pollinator dependence decrease along elevational gradients?

Plants have long been thought to be less dependent on pollinators for seed production at higher elevations due to adverse pollination environments.However,recent research has yet to consistently support the generality of this expectation.In this study,we asked whether pollinator dependence decreases along an elevational gradient and how it varies with various reproductive traits.To answer these questions,we quantified pollinator-plant associations and various reproductive traits for 112 flowering plants spanning a large elevational gradient(990-4260 m a.s.l.)in the Qinghai-Tibet Plateau.We found that flowering plants in the Qinghai-Tibet Plateau region are highly dependent on pollinators for seed production(76.2%of seed production was contributed by animal pollinators and 44.6%of plants would produce no seed without pollinator visitation).Contrary to our expectation,there was no significant elevational gradient in pollinator dependence index.Although the pollinator dependence index was not significantly correlated with pollen limitation,flower size,floral longevity,or reward type,it was correlated with compatibility status and flowering time.These findings indicate that pollinator dependence does not decrease along an elevational gradient in the Qinghai-Tibet Plateau.Our study also highlights the severe vulnerability of flowering plant seed production to pollinator declines under global change in the Qinghai-Tibet Plateau region,particularly for early-flowering or self-incompatible plants growing at higher elevations(e.g.,subnival belt).

Floral trait variation across individual plants within a population enhances defense capability to nectar robbing

Floral trait variation may help pollinators and nectar robbers identify their target plants and,thus,lead to differential selection pressure for defense capability against floral antagonists.However,the effect of floral trait variation among individuals within a population on multi-dimensional plant-animal interactions has been little explored.We investigated floral trait variation,pollination,and nectar robbing among individual plants in a population of the bumble bee-pollinated plant,Caryopteris divaricata,from which flowers are also robbed by bumble bees with varying intensity across individuals.We measured the variation in corolla tube length,nectar volume and sugar concentration among individual plants,and evaluated whether the variation were recognized by pollinators and robbers.We investigated the in-fluence of nectar robbing on legitimate visitation and seed production per fruit.We found that the primary nectar robber(Bombus nobilis)preferred to forage on plants with long-tubed flowers,which produced less nectar and had lower sugar concentration compared to those with shorter corolla tubes.Individuals with shorter corolla tubes had comparatively lower nectar robbing intensity but higher visitation by legitimate visitors(mainly B.picipes)and higher seed production.Nectar robbing signifi-cantly reduced seed production because it decreased pollinator visits.However,neither pollination nor seed production differed between plants with long and short corolla tubes when nectar robbers were excluded.This finding suggests that floral trait variation might not be driven by pollinators.Such variation among individual plants thus allows legitimate visitors and nectar robbers to segregate niches and enhances population defense against nectar robbing in unpredictable conditions.