Effect of Apis mellifera on community composition of local pollinator bees and their pollination network in Qinling Mountains and surrounding areas

The Qinling Mountains, known for their rich vegetation and diverse pollinating insects, have seen a significant decline in bee species richness and abundance over recent decades, largely due to the introduction and spread of Apis mellifera. This decline has caused cascading effects on the region's community structure and ecosystem stability. To improve the protection of native bees in the natural and agricultural landscape of the Qinling Mountains and its surrounding areas, we investigated 33 sampling sites within three habitats: forest, forest-agriculture ecotones, and farmland. Using a generalized linear mixing model, t-test, and other data analysis methods, we explored the impact of Apis mellifera on local pollinator bee richness, abundance, and the pollination network in different habitats in these regional areas. The results show that(1)Apis mellifera significantly negatively affects the abundance and richness of wild pollinator bees,while Apis cerana abundance is also affected by beekeeping conditions.(2)There are significant negative effects of Apis mellifera on the community structure of pollinator bees in the Qinling Mountains and its surrounding areas: the Shannon-Wiener diversity index, Pielou evenness index, and Margalef richness index of bee communities at sites with Apis mellifera influence were significantly lower than those at sites without Apis mellifera influence.(3)The underlying driver of this effect is the monopolization of flowering resources by Apis mellifera. This species tends to visit flowering plants with large nectar sources, which constitute a significant portion of the local plant community. By maintaining a dominant role in the bee-plant pollination network, Apis mellifera competitively displaces native pollinator bees, reducing their access to floral resources. This ultimately leads to a reduction in local bee-plant interactions, decreasing the complexity and stability of the pollination network. These findings highlight the need for targeted conservation efforts to protect native pollinator species and maintain the ecological balance in the Qinling Mountains.

Twenty-Three Years of Insect Pollinator-Dependent Crop Studies in Agro-Ecological Zones of Cameroon (2011-2020)

Cultivation of pollinator-dependent crops has expanded globally, increasing our reliance on insect pollination. This essential ecosystem service is provided by a wide range of managed and wild pollinators whose abundance and diversity are thought to be in decline, threatening sustainable food production. In Cameroon, several studies on pollinator-dependent crops carried out in different agro-ecological zones (AEZ) have been published in national and international journals, in order to present the importance and impact of flowering insects on fruit and seed yields of plant species. We proposed to produce a review article highlighting the different flowering insects and their importance for different plants according to AEZ, without however focusing on the quality of the journal (predator or non-predator) and how the different insects were identified (scientific names given in the publications). Thus, from 1997 to 2020, we collected 116 published papers from which only 26 were kept for this review. The results show that Hymenoptera, including the Apidae, followed by Megachilidae, are the most excellent pollinators of plant species in Cameroon, and they are present in different agro-ecological zones. The majority of publications focused on bees, particularly the honeybee Apis mellifera.

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).

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

Reproduction of Hedysarum scoparium (Fabaceae) in patched habitat is pollen limited,but not just pollinator limited

Pollen limitation of plant reproduction occurs across Angiosperms, particularly those in patched habitats We investigated the, relationship between pollen limitation and patch variables （patch size, visitation frequency） in the desert plant Hedysarum scoparium （Fabaceae）, which is an important xerophyte in the arid and semi-arid regions of Northwest China and can grow well as a pioneer plant in shifting sand dunes. We observed insect visitation to H. scoparium over two flowering seasons and estimated pollen limitation using fruit set and seed production. Our results indicate that fruit set and seed production increased significantly with pollen supplementation compared with open pollination. Hedysarum scoparium was pollinated by over 8 species of bees, with 88.4% of visits made by introduced honeybees （Apis mellifera）. Bee visitation varied significantly among the patches of habitats, but not associated with patch size of habitat. In general, pollen limitation occurred more strongly during fruit set than during seed production. The patches that received higher rates of pollinator visits were less pollen limited for fruit set. Pollen limitation for seed production, however, was not associated with pollinator visitation frequency. We conclude that pollen limitation in H. scoparium was caused by more than one reason, not just pollinator visits.

Evaluation of Breeding Substrates for Cocoa Pollinator, <i>Forcipomyia</i>spp. and Subsequent Implications for Yield in a Tropical Cocoa Production System

A comparative study was carried out to determine the most suitable substrate for breeding of midges (Forcipomyia spp.) and the implications for pollination and yield in a typical cocoa production system in the forest ecological zone of Ghana. For the field experiment, the typically available substrates in cocoa farms which were used as the treatments under cocoa trees were: 1) rotten cocoa leaf litter;2) rotten cocoa pod husks;and 3) rotten banana pseudostem. The untreated cocoa trees served as control. The experiment was set up in a randomized complete block design with three replications. For the laboratory experiment, the design was completely randomized design with four replications. The objective was to determine which substrate best supported breeding of the midges. The rotten banana pseudostem substrate recorded the highest population (7680) of Forcipomyia spp. after 56 days of observation. The cocoa pod husk and cocoa leaf litter recorded populations of 5226 and 1920, respectively. Similar observations were recorded in the level of pollination of the cocoa trees treated with rotten banana pseudostem (95.78%), cocoa pod husks (89.05%) and cocoa leaf litter (68.42%). Application of all substrates to the cocoa tree resulted in a 77% mean reduction in flower abortion as compared to the control. Fruit abortion, on the other hand, was significantly greater in trees treated with rotten banana pseudostem (73.7%) and rotten cocoa pod husks (71.3%) than in trees treated with rotten cocoa leaf litter (54.3%). Application of banana substrate explained 88% of the variation in cherelle production (fruit set) whereas cocoa pod husks and cocoa leaf litter accounted for 71% and 94%, respectively, of the variation in cherelle production. The study concluded that although cocoa leaf litter resulted in average increases in midges population and subsequently not too high levels of pollination, there was a significantly higher number of set fruits retained which implied high cocoa pod yields. Consequently, in accordance with the observed trend cocoa leaf litter should be considered as the most appropriate substrate for midges activity in cocoa for high yields.

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.

Insect Pollinator Diversity and Their Influence on Yield and Quality of <i>Capsicum annuum</i>Linné(Solanaceae), Machakos, Kenya

Capsicum annuum (L.) yields have remained low due to poor quality fruits in developing countries such as Kenya, which could be attributed to inadequate insect pollination among other factors. The present study was conducted after the short and long rain seasons in 2018 to assess the diversity and abundance of insect pollinators of C. annuum and to determine their influence on yield. The experiment was laid out in a Randomized Complete Block Design with bagged and un-bagged pollination treatments. Insect pollinator assessment was conducted between 07:00 hours to 21:00 hours for one month during each season. Yield and quality were compared between the pollination treatments. During the entire study 13 insect pollinator species (3 orders, 7 families) were recorded onC. annuum flowers. Apis mellifera was the most abundant insect pollinator during the two seasons. The highest species diversity was recorded after the long rain season (H' = 1.85). With respect to time, species richness was the highest in the afternoon after the short rains and the highest in the morning after the long rains. The average yield parameters from both seasons showed that open pollination treatments had increased fruit weight (66.5%), seed weight (54.5%) fruit length (28%) and fruit diameter (30%) when compared to treatments bagged throughout. Findings from this study have shown that insect pollinator diversity varies seasonally and significantly influences the yield and quality of C. annuum. This calls for the need to practice sustainable agriculture so as to conserve insect pollinators of C. annuum for improved vegetable production in semiarid lands of Kenya.

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.

Pollen analysis reveals the effects of uncovered interactions,pollen-carrying structures,and pollinator sex on the structure of wild bee-plant networks

Pollination networks are increasingly used to model the complexity of interactions between pollinators and flowering plants in communities.Different methods exist to sample these interactions,with direct observations of plant-pollinator contacts in the field being by far the most common.Although the identification of pollen carried by pollinators allows uncovering interactions and increasing sample sizes,the methods used to build pollen-transport networks are variable and their effect on network structure remains unclear.To understand how interaction sampling influences the structure of networks,we analyzed the pollen found on wild bees from eight communities across Mallorca Island and investigated the differences in pollen loads between bee body parts(scopa vs.body)and sexes.We then assessed how these differences,as well as the uncovered interactions not detected in the field,influenced the structure of wild bee-plant networks.We identified a higher quantity and diversity of pollen in the scopa than in the rest of the female body,but these differences did not lead to differences in structure between plant-pollination(excluding scopa pollen)and bee-feeding interaction(including scopa pollen)networks.However,networks built with pollen data were richer in plant species and interactions and showed lower modularity and specialization(H2'),and higher nestedness than visitation networks based on field observations.Female interactions with plants were stronger compared to those of males,although not richer.Accordingly,females were more generalist(low d')and tended to be more central in interaction networks,indicating their more key role structuring pollination networks in comparison to males.Our study highlights the importance of palynological data to increase the resolution of networks,as well as to understand important ecological questions such as the differences between plant-pollination and bee-feeding interaction networks,and the role of sexes in pollination.

Non-associative learning underlies pollination interaction of pollinators and flowering plants

The behavioral response of pollinators is significantly influenced by the prior experience of flower visiting.Learning of pollinators,including non-associative learning,associative learning,and operant conditioning,is determined by the presence or absence of rewards during the flower visiting experience.Here,we indicate that process of non-rewarding flower(empty flower)visiting coincident well with the behavioral paradigm of non-associative learning.Habituation,one of non-associative learning,most likely modulates the pollinating behavior patterns of empty flower visitation.Moreover,we propose that the process of habituation recovery,including spontaneous recovery and dishabituation,may also modulate the behavior of pollinators,which leads to ecological consequences of long-distance pollen dispersal and high outcross pollination rate.We believe that utilizing the methodology of non-associative learning behavioral neurobiology paradigm to investigate pollinator behavior will establish novel insights into the sensory responses and neural activity of pollination behavior in the pollination systems.

Plant-pollinator metanetworks in fragmented landscapes:a simulation study

Background The topology of the plant-pollinator network can be explained by the species’abundance and their random interactions.Plant-pollinator networks can be studied in the context of a landscape,because each patch can accommodate a certain local network.Local populations of pollinators in the landscape can be connected through migration and then constitute a metanetwork that is known as a combination of spatial and ecological networks.In this regard,habitat fragmentation can affect the topology of plant-pollinator metanetworks through changes in the species abundance and limiting their interactions.However,it is not clear what pattern(fragmented or aggregated)of the landscape structure can accommodate networks with a higher degree of specialization.Methods we created simulated landscapes with different forest proportions scenarios(from 5%to 50%of the total landscape)and degrees of fragmentation.Then,for each landscape,we limited the proportion of pollinators to the forest patch.We assumed that plants and pollinators are randomly distributed around the landscape and interact randomly.We used landscape metrics to measure different aspects of landscape structure and bipartite metrics for calculating the degree of specialization in plant-pollinator networks.Results The statistical relationship between bipartite and landscape metrics showed that the relationship between the topology of plant-pollinator networks and the landscape structure is affected by the forest amount in the landscape and the degree of forest fragmentation.We also found that according to the nestedness and H2(a measure of specialization)metrics,fragmented landscapes contain more general plant-pollinator networks.Conclusions Our findings suggest that fragmented landscapes,characterized by scattered forest patches,can promote higher levels of interaction between limited pollinators and diverse flowers,leading to more general plant-pollinator networks.

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.

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.

Pollinator-mediated self-pollination and reproductive assurance in an isolated tree of Magnolia grandiflora L.

Background:The ability to produce seeds when pollinators or potential mates are scarce is one of the principal advantages of self-pollination in flowering plants.However,the role of pollinators mediating self-pollination to ensure seed set when pollen or potential mates are limited has received less attention.This study examined the reproductive consequences and involvement of pollinators in assuring seed set in an isolated tree of Magnolia grandiflora,a predominantly outcrossing species.Methods:We tested various aspects of reproduction such as flower density,floral rewards,stigma receptivity,pollinator abundance and behaviour,fruit set and seed set,in two successive reproductive years(2015-2016).Results:Flowers of M.grandiflora possess a suite of traits facilitating pollinator-mediated self-pollination(PMS),although the chances of autonomous self-pollination are reduced due to herkogamy,spatial separation of anther and stigma.The mean pollen production/flower was 5,152,289±285,094 with a pollen-to-ovule ratio of 39430±164.We found a significant positive correlation between number of visits and seed production for bees(r=0.5099,p=0.0007)and beetles(r=0.7159,p=0.00001),indicating these are effective at PMS.There was a significant negative correlation for thrips(r=-0.3206,p=0.044)and no correlation for flies or spiders.The percent fruit set was 100%and the seed set per ovule ranged between 19 and 20%.Conclusions:PMS will guarantee reproductive assurance and mitigate the effect of reduced mates or pollen limitation which is expected to increase the fecundity and establishment of individual trees in geographically isolated locations.

Physiological effects of climate warming on flowering plants and insect pollinators and potential consequences for their interactions

Growing concern about the influence of climate change on flowering plants, pollinators, and the mutualistic interac- tions between them has led to a recent surge in research. Much of this research has addressed the consequences of warming for phenological and distributional shifts. In contrast, relatively little is known about the physiological responses of plants and insect pollinators to climate warming and, in particular, how these responses might affect plant-pollinator interactions. Here, we summa- rize the direct physiological effects of temperature on flowering plants and pollinating insects to highlight ways in which plant and pollinator responses could affect floral resources for pollinators, and pollination success for plants, respectively. We also con- sider the overall effects of these responses on plant-pollinator interaction networks. Plant responses to wanning, which include altered flower, nectar, and pollen production, could modify floral resource availability and reproductive output of pollinating in- sects. Similarly, pollinator responses, such as altered foraging activity, body size, and life span, could affect patterns of pollen flow and pollination success of flowering plants. As a result, network structure could be altered as interactions are gained and lost, weakened and strengthened, even without the gain or loss of species or temporal overlap. Future research that addresses not only how plant and pollinator physiology are affected by warming but also how responses scale up to affect interactions and networks should allow us to better understand and predict the effects of climate change on this important ecosystem service .

Does persistence of showy calyces in Limonium leptolobum enhance pollinator attraction?

Aims The calyx,the outermost whorl of a flower(usually green),has been considered to function to protect flowers.in some species,how-ever,calyces are colorful and retained during seed development.Limonium species have been exploited as cut flower crops because the calyces persist for several months after the corolla has closed.To explore the adaptive significance of the persistent calyx in a desert plant Limonium leptolobum,we ask whether persistence of caly-ces can enhance pollinator attraction by enlarging floral displays,increasing reproductive success in this self-incompatible species.Methods The yellow flower of L.leptolobum lasted 1-2 days but its white,membranous calyx extended fully after the corolla closed,and per-sisted for over 2 months in the field,making hundreds of‘showy flowers’on one individual.To examine the ecological function of calyces,we test the pollinator attraction hypothesis.in an experi-mental population,we compared the difference in visit frequency and visitor behavior between intact inflorescences and inflores-cences with their calyces removed on the same individual plants.Important findingsin four experimental plots four types of floral visitors were observed including bees,butterflies,syrphid flies and day-flying moths.No significant preference was observed between calyx-free and intact inflorescences for both first arrivals and total visit frequency of all types of floral visitors,indicating that the persistence of calyces did not make plants more attractive to potential pollinators.The pollina-tor attraction hypothesis for the showy calyces was not supported by the current data.Whether the calyx in this desert plant helps seed development or has other functions needs further study.

Stigmatic exudate in the Annonaceae:Pollinator reward,pollen germination medium or extragynoecial compitum?

Although ＂dry-type＂ stigmas are widely re- garded as ancestral in angiosperms, the early-divergent family Annonaceae has copious stigmatic exudate. We evaluate three putative functions for this exudate： as a nutritive reward for pollinators; as a pollen germination medium; and as an extragynoecial compitum that enables pollen tube growth between carpels. Stigmatic exudate is fructose dominated （72.2%）, but with high levels of glucose and sucrose; the dominance of hexose sugars and the diversity of amino acids observed, including many that are essential for insects, support a nutritive role for pollinators. Sugar concentration in pre-receptive flowers is high （28.2%）, falling during the peak period of stigmatic receptivity （17.4%）, and then rising again toward the end of the pistillate phase （32.9%）. Pollen germination was highest in sugar concentrations 〈2%. Sugar concentrations during the peak pistillate phase therefore provide optimal osmolarity for pollen hydration and germination; subsequent changes in sugar concentration during anthesis reinforce protogyny （in which carpels mature before stamens）, enabling the retention of concentrated exudate into the staminate phase as a pollinator food reward without the possibility of pollen germination. Intercarpellary growth of pollen tubes was confirmed： the exudate therefore also functions as a suprastylar extragynoecial compitum, overcoming the limitations of apocarpy.

How do belowground organisms influence plant-pollinator interactions?

Aims The majority of angiosperms are pollinated by animals,and this interaction is of enormous importance in both agricultural and natural systems.Pollinator behavior is influenced by plants’floral traits,and these traits may be modified by interactions with other community members.In recent years,knowledge of ecological linkages between above-and belowground organ-isms has grown tremendously.Soil communities are extremely diverse,and when their interactions with plants influence floral characteristics,they have the potential to alter pollinator attrac-tion and visitation,but plant-pollinator interactions have been neglected in studies of the direct and indirect effects of soil organism-root interactions.Here,we review these belowground interactions,focusing on the effects of nitrogen-fixing bacteria,arbuscular mycorrhizal fungi and root-feeding herbivores,and their effects on floral traits and pollinators.Further,we identify gaps in our knowledge of these indirect effects and recommend promising directions and topics that should be addressed by future research.Important Findings Belowground organisms can influence a wide variety of floral traits that are important mediators of pollinator attraction,including the number and size of flowers and nectar and pollen production.Other traits that are known to influence pollinators in some plant species,such as floral volatiles,color and nectar composition,have rarely or never been examined in the context of belowground plant interac-tions.Despite clear effects on flowers,relatively few studies have measured pollinator responses to belowground interactions.When these indirect effects have been studied,both arbuscular mycorrhi-zal fungi and root herbivores were found to shift pollinator visitation patterns.Depending on the interaction,these changes may either increase or decrease pollinator attraction.Finally,we discuss future directions for ecological studies that will more fully integrate below-ground ecology with pollination biology.We advocate a multilevel approach to these questions to not only document indirect effect pathways between soil interactions and pollination but also iden-tify the mechanisms driving changes in pollinator impacts and the resultant effects on plant fitness.A more thorough understanding of these indirect interactions will advance ecological theory and may inform management strategies in agriculture and conservation biology.

Urbanization affects plant flowering phenology and pollinator community:effects of water availability and land cover

Introduction:Climate change and urbanization have been shown to alter plant phenology.However,a mechanistic understanding of these changes in flowering phenology and associated pollinator communities is lacking.Thus,this study was designed to examine finer scale flowering phenological patterns and driving processes in an arid urban ecosystem.Specifically,we tested the effect of water availability and land cover type on the flowering phenology of brittlebush(Encelia farinosa)and investigated the arthropod pollinator community associated with brittlebush.Methods:The fieldwork was carried out as part of a larger community ecology experiment following a factorial nested design.We chose three land cover types,each of which had three replicates,resulting in a total of nine sites.For water availability manipulations,60 genetically different 5-gallon potted plants were placed on the ground within each site.Pan-trapping was used to collect potential pollinators.Results:Our results showed that water availability did not produce significant differences in flowering phenology.However,brittlebush planted in mesiscaped urban sites bloomed later,longer,and at a higher percentage than those planted in desert remnant sites and desert fringe sites.Furthermore,desert remnant sites were significantly lower in pollinator abundance than desert fringe sites.Pollinator richness varied over time in all land cover types.Conclusions:This study provides empirical evidence that land cover type,which is strongly correlated to temperature,is the primary cause for altered flowering phenology of brittlebush in the Phoenix area,although water availability may also be important.Moreover,land cover affects total abundance of bee pollinators.