Sexual reproduction of seed plants depends largely on pollen transfer. The pollination service provided by pollinators for wild plants and managed crops is one of the most crucial ecological processes on our planet, as it plays an essential role in sustaining biodiversity and crop production. Factors such as agricultural intensification, habitat fragmentation, and global climate change have increased the risk of pollinator decline and extinction, which would have detrimental effects on ecological function and agricultural production. To maintain the stability of ecological interactions between plants and pollinators, a series of pollinator monitoring schemes have been established, ranging from the regional to international scale. Participants including volunteer citizens and professional scientists have obtained the status and trends of pollination systems, thereby helping to provide early alerts and feedbacks for the risk of natural and agricultural ecological systems. In this view examining the methodologies of pollinator monitoring, we emphasize that it is necessary to distinguish pollinators from floral visitors. A diversity of direct and indirect methods for monitoring pollinators is summarized for seven types of animals (including Lepidoptera, Coleoptera, Hymenoptera, Diptera, Aves, Mammalia, and Lacertilia, respectively). A simple monitoring program that includes volunteer participation is also recommended. Commonly used field monitoring strategies for seven groups of pollinators would be useful as references for monitoring additional pollinator faunas. The pros and cons of these diverse methods for protecting and monitoring pollinators are discussed, which is useful for the long-term detection of pollinator dynamics.

Pollinators serve key ecological functions, ensuring stable ecosystems and high agricultural yields. Hence, assessing ecosystem health and effects of agricultural management would benefit from understanding and monitoring pollination networks, which involves identifications of pollinators and pollinated plants. Classic approaches of morphology-based identification of plants and pollinators can be time-consuming, labor-intensive and costly, and require highly specialized taxonomic expertise. In comparison, DNA barcoding and high-throughput sequencing technologies can provide efficient and accurate identifications of plants and their pollinators, which may facilitate construction of pollination networks. Here we propose using sequencing technologies with a PCR-free genome-skimming work frame, using "super DNA barcode" as a new method to assess plant-pollinator networks. We expect this technique to improve resolution and accuracy of taxonomic identification to help gain quantitative information for bulk samples of pollinators or pollens. Although there are technical challenges to be resolved, the robustness of the new methodology has been validated in relevant biodiversity studies, suggesting promise in constructing pollination networks.

Non-native plant invasion imposes great threats to global diversity and ecological safety, and now is a hot-spot of ecological studies. Understanding the reproductive strategies of invasive plants could provide insights into the invasion mechanisms and be helpful for proposing prevention and control strategies. Non-native invasive plants generally possess following reproductive traits: hermaphrodite-dominated sexual system, autonomous selfing-dominated breeding system, even asexual reproduction and apomixis, and high proportion of resources allocated to sexual reproduction, which may facilitate the success of some invasive plants. In turn, non-native plants could alter native plant-pollinator interactions, and in most cases decrease pollinator visitation and fitness of native plants. In addition, non-native plants may act as environmental stresses triggering rapid adaptation and evolution in reproductive strategies and phenotypes of resident native species in receipt communities. Studies in this field mostly have focused on rapid adaptation of invasive species to their new environments, while how native and non-native plants co-adapt and diverge remains largely unexplored, in particular from the perspective of plant reproduction. A better understanding of competition and cooperation between native and non-native plants will shed lights on rapid responses of native plants to non-native plant invasions. Such community studies of interspecific interactions with or without a competitor could provide evidence for displacement of reproductive traits and species coexistence, and improve our ability to predict and manage non-native invasive plants.

Clonal plants reproduce asexually via clonal growth and simultaneously reproduce sexually, and the consequences of clonal growth on pollination and mating have been one of the essential questions in ecology and evolution of plant reproduction. An increasing number of studies report the effects of clonal size, architecture, genetic diversity, and floral deployments on pollinator visit and behavior. The most common view is that clonal growth produces large floral displays and therefore increases attraction to pollinators. Consequently, clonal growth may help to maximize male reproductive success by dispersing more pollen. On the other hand, geitonogamy, pollination among flowers within one individual plant, is an inevitable byproduct with an increase in clone size. More frequent geitonogamous pollination has been expected in clonal plants with large floral displays and leads to a reduction in female fitness because of inbreeding depression or pollen clogging. However, some recent theoretical and empirical studies suggest new ideas on this issue. First, the number of flowers visited by individual pollinator within a clone did not increase proportionally with clone size in clumped clonal plants, and pollinator movements within a single bout mainly occurred within ramet. The selfing component analyses based on molecular markers further evidenced that within-ramet geitonogamy was the largest contributing factor to the total geitonogamy in two clonal species. Second, the experimental study of bumblebees foraging on artificial flowers showed that when the same amount of flowers was distributed among multiple ramets, geitonogamy was not higher but in fact, lower compared with one single inflorescence. The model-based simulation suggested clonal growth could promote pollination quality without increasing geitonogamy when flowers simultaneously received and donated pollen. These studies support a novel explanation of the evolution of clonality in plants. Future studies on the pollination ecology of clonal plants may focus on the effects of clonal growth on pollinator behavior and plant mating from multiple angles. Comparative studies between clonal and non-clonal taxa or between clonal and non-clonal populations of the same species are required to evaluate the ecological and evolutionary consequences of clonal growth.

Insect pollinators play a vital role in plant sexual reproduction. Pollinators facilitate cross-pollination that in turn promotes genetic diversity, mediates plant speciation, and contributes to ecosystem stability. However, the abundance, diversity and health of wild pollinators are threatened by human activities such as anthropogenic climate impacts, habitat destruction and environmental pollutants, and the impact of these human activities on ecosystems is likely to increase. Despite recognizing the importance of wild pollinators and the implementation of targeted conservation programs, the contemporary threats of wild insect pollinators remain poorly understood. For the giant honey bee (Apis dorsata), an important wild pollinator and honey producer in tropical rainforests and agricultural areas across Asia, here we describe nest characteristics, colony migration and pollination role and review threats to their conservation. We found that A. dorsata nests featured a single honeycomb hanging from the branches of large trees. The bees undertook long distance migrations to locate seasonally ephemeral forage sources but regularly returned to previous nesting sites. We identified several anthropogenic activities that posed significant threats to A. dorsata conservation: harvesting entire colonies, deforestation, pesticide and herbicide utilization, parastioids, mites, pathogens and climate change. Based on our study, we recommend several conservation initiatives to promote wild A. dorsata populations, which include artificial domestication, developing ecological agriculture, establishing of ecological corridors, inspection and quarantine controls on domesticated colonies, and sustainable utilization of the floral resources used by A. dorsata. We hope that this review will stimulate future research on giant honey bees whilst playing a significant role in their conservation and sustainable utilization.

Bumblebees are important pollinators of many wild flowers and crops and play a significant role in maintaining natural and agricultural ecosystems. The varied geomorphology and vegetation of China makes it the greatest hotspot of bumblebee diversity in the world. However, the bumblebee fauna of China has been insufficiently studied. Here, we report the results of systematic field surveys and the application of bumblebees to pollination over the last two decades in China. The results showed the following: (1) More than 50,000 bumblebee specimens were collected during 2002-2017. The taxonomic status of some difficult taxa was revealed by integrating morphology with DNA barcoding. A total of 125 bumblebee species have been identified, which represents 50% of the total number of bumblebee species worldwide. (2) We report the first compiled list of the bumblebee species of China, which includes 22 species that are endemic to China. The transitional zone from the eastern Qinghai-Tibetan Plateau to the Loess Plateau, the Qinling Mountains, and the Sichuan Basin is the centre of bumblebee diversity worldwide. (3) Six native bumblebee species, including Bombus lucorum, B. patagiatus, B. ignitus, B. pyrosoma, B. picipes and B. lantschouensis from Northern China, were selected for rearing between 1998-2017. Furthermore, B. patagiatus and B. lantschouensis, which had traits that favoured domestication, are now used as pollinators of crops in greenhouses within China. We propose a multi-pronged strategy to conserve the native bumblebees of China, which includes protecting their habitats and food resources and controlling invasive alien species and pesticide use. We hope that this study will help inform the conservation and the sustainable use of wild pollinators across the globe, but especially bumblebees of China.

Heteracia szovitsii (Asteraceae) is a common ephemeral annual species occurring only in desert regions of northern Xinjiang in China, with short-lived florets and achenes within a single infructescence (capitulum) having three different morphs. To explore the relationship between morphological differences in florets and the polymorphic fruits and reproductive characteristics, we compared floral traits, flowering pattern, and flower visitors to the three floral morphs in H. szovitsii, and reproductive efforts by hand pollination treatments. The results showed that: Peripheral and intermediate florets did not have pappus, while central florets did. Number of florets and length and width of ligules were significantly different among the three floral morphs in a single capitulum. Further, the length of stigma lobes of peripheral florets was significantly greater than that of central florets, the length of ovary beaks of central florets was significantly greater than that of peripheral and intermediate florets. Differences in morphology with or without pappus, width of ovaries, length of ovary beaks among three morphs of florets were consistent with those of three morphs of achenes. These results indicated that the numbers of three morphs of achenes and their morphology had differentiated during the development period of three kinds of florets. The concentrated flowering pattern of blooming in the morning of three kinds of florets within capitulum, made the capitulum act as functional units, i.e. like a flower, thereby increasing flower display and attracting pollinators. Pollinator visits may facilitate outcrossing during the short flower longevity. Pollen grains of the three floral morphs could germinate and produce pollen tubes on their stigma lobes, indicating that this species is self-compatible. The three kinds of florets bagged without emasculation all can produce achenes, but fruit-set was all significantly lower than that of natural pollination, suggesting that this species could be autogamous and cross-pollination could increase fruit set. Due to the protandrous and the pump/bush mechanism of secondary pollen presentation, pollen of three floral morphs was present at the apex of the stigma and on the brush of hairs of both the upper part of style and outside lateral of the closed stigma lobes. This character prolonged the duration of pollen presentation (male stage), and reduced the interference between male and female functions within flower, promoted cross pollination, thereby improving male/female fitness. Meanwhile, it could allow the pollen deposition on the lobes when the stigma lobes expanded to complete self-pollination autonomously. Halictus sexnotatulus was the most frequent floral visitor, and the duration time among insects visiting, inflorescence opening, highest pollen viability and the highest stigma receptivity had a high degree of synchronicity. This strategy facilitated the output of pollen at the male stage and receipt of pollen on the stigma at the female stage, thus ensuring that pollination was completed quickly and effectively in a short time after flowering and that outcrossing was successful. In the desert spring environment of the northern Xinjiang, H. szovitsii with short-lived florets can not only provide reproductive assurance via autonomous self-pollination quickly under the condition of the lack of pollinators and/or limited activity due to low temperatures and windy conditions, but also can provide the opportunities for outcrossing, through concentrated flowering, protandry and secondary pollen presentation when environmental conditions became favorable for pollinator activities.

Floral longevity, the length of time that a flower remains open and functional, varies greatly among species. The high plasticity of floral longevity can reflect an adaptation to variable pollination environments. In the alpine meadows of Qinghai-Tibetan Plateau (2,900 m vs. 3,600 m), we assessed how potential floral longevity, the shortest floral longevity and the actual floral longevity of 11 species varied under treatments of different pollination contexts. We modeled the response of floral longevity to pollinator exclusion (potential floral longevity minus actual floral longevity) and supplemental pollination (actual longevity minus shortest longevity), and the plasticity of floral longevity (potential longevity minus shortest longevity) at high and low altitude habitats. We found that the plants at the high-altitude community had longer potential floral longevity compared to the low-altitude community, while the shortest floral longevity was not significantly different. Furthermore, pollinator exclusion significantly increased flower longevity, while supplemental pollination significantly decreased floral longevity (i.e. the potential floral longevity > the actual floral longevity > the shortest floral longevity) in both high and low-altitude habitats. In comparison with the low-altitude community, high-altitude plants exhibited higher plasticity of floral longevity. Overall, our results suggest that greater plasticity of floral longevity may increase the opportunity for pollination and thus aid fitness at higher altitudes where pollinators are scarce and unpredictable.

Understanding the variation in plant sexual strategies provides insights into the evolution of plant sexual systems. In hermaphrodite plants, floral gender is thought to be a plastic response that allows individuals to vary resource allocation to both female and male function under variable environmental conditions. Tulipa sinkiangensis is known to be hermaphroditic, early spring ephemeral plant, but our preliminary investigation showed that some populations had perfect flowers whereas other populations had staminate flowers. To understand correlates of occurrence and temporal variation of staminate flowers in T. sinkiangensis, we examined flower sex and its variation among individuals in a population of nearly 1,000 plants in Xinjiang, northwestern China from 2011 to 2017. (1) In the study population one-flower and two-flower plants comprised 74.5% (4,373) and 23.0% (1,358) of all flowering individuals (5,863), respectively. Sex differentiation was seen primarily in drier areas with shallow soils. Perfect and staminate flowers randomly occurred on different plants, constituting a hermaphroditic based population with some male and andromonoecious individuals. (2) Compared to perfect flowers, staminate flowers appeared later within individual plants and in the whole population during flowering. Staminate flowers were smaller and had aborted ovaries without visible ovules. However, pollen number and size, pollen morphology and fertility were not significantly different from perfect flowers when the two floral morphs were the same size. (3) During 2011 to 2014 of the study period, percentage of staminate flowers in the population declined from 23.4% to 3.1% but remained at stable (1.5% to 1.0%) from 2015 to 2017. The number of one-flower plants and two-flower plants fluctuated with time. (4) Our observations suggest that the production of staminate flowers in this endemic tulip flower was likely a plastic response to plant resource status, environmental conditions and other ecological factors.

As a comprehensive and interdisciplinary platform on biodiversity assessments, it is foreseeable that the assessment reports and policy recommendations of Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) will exert key effects on global biodiversity conservation. Based on the analysis of the pollinators protection policy formulation and implementation process in USA, this research gained the process and mode on establishment of the biological diversity related protection policy, scientific evaluation-government attention-the introduction of restrictive policies and measures. Considering the first thematic assessment report delivered in 2016 by IPBES, The Assessment Report on Pollinators, Pollination and Food Production, we speculated that the deliverable may facilitate a restrictive policy on the new neonicotinoid pesticide industry and bee products trade, especially wild bee products. We further analyze possible impact of IPBES deliverables on biodiversity and related protection policy in the world and China, in terms of promoting scientific research and evaluation on biodiversity and ecosystem service, mainstreaming biodiversity conservation and bring it to be an important political issue and so on. In addition, our research will provide support for establishing adaptation policies for biodiversity conservation in China.