Foraging behavior of pollinating insects can directly influence plant–pollinator interactions in many aspects, thus studies on pollinator behavior are important for understanding plant diversity and ecological processes of plant reproduction. In this paper, we describe the characteristics of major pollinating insects and discuss the methods for studying foraging behavior of pollinating insects and factors potentially influencing pollinator behaviors. We also suggest some practical methods for studying the roles of nocturnal pollinators and how to conduct studies of insect foraging behaviors at community level. The purpose of this introduction is to provide some useful information for future studies on this multidisciplinary research in China, particularly for botanists and entomologists.

Mutualism is a relationship between individuals of different species that benefits all the partners. However, this interaction may also be described as mutual exploitation. The “host sanctions effect” predicts that the hosts punish partners that cheat by receiving benefits without paying for them. Fig trees (Ficus) and their fig-pollinating wasps (Agaonidae) constitute a mutualistic system with a mainly one-to-one relationship. In order to test if there exists the “host sanctions effect”, we carried out a study at Xishuangbanna Tropical Botanical Garden, Yunnan Province on the monoecious fig tree Ficus benjamina, which is actively pollinated by Eupristina koningsbergeri. We produced two groups of pollinating wasps, either carrying pollen or not, and introduced one or two foundress wasps from each group into single figs. Figs entered by no wasps aborted rapidly, but almost all figs entered by wasps completed their development normally, except a few entered by a single pollen-free wasp. However, pollen-loaded foundresses produced significantly larger broods than foundresses without pollen. This effect was particularly marked in figs containing two foundresses. Our results show that active pollination is not essential for the reproduction of the pollinator, but does improve its reproductive success. This suggests that a sanctions effect is operating.

Ficus are species-specifically pollinated by Chalcidoid wasps (Agaonidae). Each monoecious fig species shelters a wasp community of pollinator and nonpollinators. Ficus benjamina is a monoecious tree worldwide cultivated for ornamental purposes, but the fig wasp community inside the syconium of this spe-cies is still little known. In order to study the fig wasp community structure of F. benjamina in different habitats, we collected 180 syconia from three different study sites distinct in plant coverage and disturbance level in Xishuangbanna, Yunnan. In all syconia, 49,149 specimens were collected, consisting of 13 species of fig wasps from 8 genera of Chaleidoidae. Eupristina koningsbergeri was the pollinator, whereas the others were nonpollinators. The species diversity and abundance of the fig wasp community were significantly dif-ferent in the three study sites, and were significantly higher in the site with high plant coverage and relatively little disturbance. This result indicates that nonpollinators are inclined to oviposit in flowers of F. benjamina in habitats with high plant coverage and relatively little disturbance. The data also suggest that the correlation between pollinator and nonpollinators inside the syconium is significantly negative.

Self-incompatibility occurs widely in the Solanaceae, but a few species in this family, or a few intraspecific populations or a few individuals within the populations are highly self-compatible and their breeding systems have evolved from outcrossing to selfing. We studied pollination biology of Anisodus tanguticus from this family, a perennial endemic to the Qinghai-Tibetan Plateau. This species flowers in the early summer and probably suffers from the serious limitations of the outcrossing pollinator. We aimed to test whether the breeding systems of a few individuals in this species have shifted from outcrossing to selfing. Our experiments and observations were conducted in two populations with different altitudes. Most flowers of this species were incompletely protogynous, and the mean distance between the stigma and anthers decreased gradually with floral longevity. Both stigma and anthers did not come into touch when the corolla wilted in most of the monitored flowers and such herkogamy favours outcrossing. However, the complete contact of stigma and anthers in 4.9% of the measured flowers suggested potential occurrence of “autonomous selfing” in these flowers. Most of the examined individuals in both populations are self-incompatible and have to depend on insects for pollination. However, a few of them were found to be self-compatible. Flies were the effective outcrossing pollinators in the high altitude population and “autonomous selfing” was detected in a few individuals of this population. In contrast, the effective outcrossing pollinators were rarely observed in the low altitude population and the dominant visitors or pollinators, ants in this population, transferred pollen within the single flower, which finally resulted in “facilitated selfing”. Pollination limita-tions were obvious in both populations due to the lack of enough outcrossing pollinators. Two different self-ing mechanisms, uncovered here, may provide a partial compensation for the natural reproduction of this al-pine species in the arid alpine habitats when flowering at the early summer.

Investigation of intraspecific morphological variation is critical for the understanding of evolutionary and ecological processes, and may provide insights for uncovering the roles of natural selection, gene flow, and genetic drift in the distribution and abundance of species diversity. In the present study, we analyzed statistically the patterns of variation of 13 morphological traits among 12 populations in three localities of an endemic orchid, Changnienia amoena. The results showed that, among the three localities, the mean value of all measured morphological traits is the highest in the Lushan populations. There is abundant variation at both the species and population levels. Coefficient of variation (CV) varied between 0.02 and 0.30 at the species level, and the CV values of reproductive organs were lower than those of vegetative structures. ANOVA analysis showed that there was significant difference in most morphological traits among the three localities. UP-GMA analysis showed that the populations in three localities were clustered into three main clades, the populations from Xinning and Lushan formed one clade, while the Shennongjia populations formed another clade. It is noteworthy that the Shennongjia populations were separated into two subclades corresponding to the populations at Longmenhe and Guanmenshan, respectively. This morphological differentiation is most likely a result of pollinator-mediated selection because this species is pollinated by different bumblebee species at these two sites. Pearson correlation analysis showed that high correlation occurred within the vegetative organs, reproductive organs, and be-tween them. These results have important implications for our understanding of the evolutionary processes and mechanism of C. amoena and might provide useful information for the conservation and management of this endangered orchid.

During May to July, 2006 and April to May, 2007, we studied pollination biology in Ipomoea cairica, an invasive weed in Guangdong Province, China. Ipomoea cairica is a perennial creeping or climbing herbaceous vine, blooming all year round in Guangdong. The flowers gathered in cymes, with a purple or bluish purple bell-formed corolla. The petals unfolded at about 4:30–5:20 and closed at 17:40, lasting for about 12 hours. The proximity of the stigma and anthers during flowering period facilitated the transfer of self-pollen. The mean volume of nectar per flower was 5.82 ± 2.47 μL (n = 10), with a sugar concentration of 41.03 ± 6.52% and an amino acid concentration of ca. 0.042 mg/mL. During anthesis, both pollen viability and stigma receptivity remained at a high level (>90%). The mean P/O ratio was 4,778.18 ± 264.58 (n = 10). Carpenter Bees (Xylocopa sp.) were considered as effective pollinators, while flies and butterflies were occa-sional visitors. Ipomoea cairica is self-incompatible as determined by an absence of fruit set in the flowers following controlled hand self-pollination, producing fruits and viable seeds only after cross-pollination.

Figs (Ficus, Moraceae) constitute one of the greatest genera of flowering plants with ca. 750 species worldwide. Figs and fig wasps form an obligate specific mutualism, which is treated as the model system to study comparative biology of mutualism and co-evolution. This extraordinary system has received increasing attention because of its specificity and the development of the molecular technologies, although the phylogenetic reconstruction of both partners began in the 1990’s. In this paper, we summarized the research on phylogenetic relationships and fig-fig wasp co-evolution. We also analyzed interrelated researches in China and the future developing trends in research on this mutualism.

Crocus alatavicus, a geophytic-geocarpic plant, is an early spring ephemeral species that grows in subalpine areas of the western Tianshan Mountains. To understand the ecological significance of geocarpy in plants, we studied the breeding system and pollination biology of C. alatavicus, with special reference to its adaptive strategies for a subalpine existence. We found that C. alatavicus is hysteranthous and its flowering pattern was explosive at the population level. It began to flower in early- to mid-April, and the white flowers had neither nectar nor scent. The inferior ovary was below ground at anthesis, while the other floral parts were aboveground. The flowers were open during the day and closed at night, and individual flower duration was 6-9 days. Pollen viability was 75.39±5.69% at the end of anthesis, and stigma receptivity lasted eight days. Results of artificial pollination experiments suggested that the breeding system ofC. alatavicusis facultative xenogamy with the ability to self-pollinate spontaneously. Crocus alatavicushas a generalist pollination system, with Bombus lucorum, Anthophora senilis and Andrena capillosa being effective pollinators. These insects initiated pollination while foraging for pollen, and their visitation frequencies were 0.50±0.27, 0.18±0.08 and 0.13±0.05 per flower per hour, respectively. Thus,C. alatavicusnot only has evolved unique flowering pattern and generalist pollination system, but also utilizes an otherwise vacant niche in the early spring to improve the effectiveness of pollination. Furthermore, characteristics of its breeding system, such as self-compatibility and spontaneous self-pollination, ensure reproductive success even when pollinators are scarce and pollinator visitation frequencies are low in early spring.

The majority of flowering plants and crops rely in whole or part on animals for pollination. The mutualism between plants and pollinators has attracted ecologists and evolutionists to use this type of interspecific interaction as a model system to study species adaptation and diversification since Charles Darwin. Recent debate on the nature of pollination systems call for studies of this interaction at different levels, ranging from single species to entire communities in a given area. At the species level, detailed studies suggest that floral traits are under selection from mutualists and antagonists as well as the physical environment. In contrast, studies at community-level are rare, but recent analyses indicate considerable spatial and temporal variation in both generalized and specialized pollination systems. This special issue of Biodiversity Science focuses on plant-pollinator interaction, presenting current research status in this area from China. Papers include floral traits and pollinator behaviors addressed by phenotypic manipulation, estimates of pollen removal and receipt, anatomy of flowers, histochemistry analysis and spatial and temporal comparison. The taxa being investigated include wild orchid and cultivated legume, endemic, endangered and invasive species with diverse sexual systems. These thirteen experimental studies and three reviews show the development of pollination biology in China and expose how to facilitate our understanding of the critical ecological proc-esses underlying interspecific interaction in both natural and agricultural ecosystems.

Pollinator specificity has traditionally been considered as the main mechanism of reproductive isolation in orchids. Cypripedium smithii and C. tibeticum are two closely related species with similar characters and sympatric distributions. With the knowledge of reproductive biology of C. tibeticum, we studied the reproductive biology of C. smithii and compared the morphological characters between C. tibeticum and C. smithii. The results showed that a series of intermediate types occurred between typical C. smithiiand typical C. tibeticum, indicating that no distinct taxonomic boundary existed between C. tibeticum and C. smithii. Pollination experiment showed that both C. smithii and C. tibeticum were pollinated by bumble queens. The hand-pollination experiments indicated that C. tibeticum and C. smithii were cross-fertilized, so that they could hybridize in the natural conditions and produced transitional types. It is better to combine them as one identical species rather than separate them as two distinct species.

Floral symmetry is a classical feature of floral diversity. Actinomorphy and zygomorphy are two main types of floral symmetry in angiosperms. Zygomorphic flowers are thought to have evolved from ancestors whose flowers are actinomorphic. Transition from actinomorphy to zygomorphy has been recognized as a key innovation and is considered crucial in the rapid diversification of angiosperms. In recent years, great progress has been made towards understanding the mechanisms underlying changes in floral symmetry during the evolution of angiosperms in wide-ranging botanical disciplines. Evidence from floral development studies indicates that zygomorphy appears before organ initiation, and persists throughout floral development, or appears later at various stages of development. Reduction, suppression and differential elaboration of floral organs are the major determinants of zygomophy. Floral symmetry is strongly selected by pollinators during the different stages of pollination process. In addition, the tighter flower-pollinator interaction found in zygomorhpic flowers may contribute to increased reproductive success through increased precision in pollen placement on the pollinator’s body. The molecular base of flower symmetry has been explored in core eudicots, and available evidence indicates that CYC-like genes play an important role in the control of zygomorphy. Future prospects in the study of floral symmetry in development biology, pollination biology and molecular genetics are discussed.

Hymenoptera of the family Agaonidae (fig wasps) are the obligate pollinating insects of fig trees (Ficus spp.), and fig syconium is the only host of fig wasp. For the pollination of their flowers, fig trees are dependent upon fig wasps. For their reproduction and growth, fig wasps are dependent upon the gall (ovaries) of the figs, in which their larvae develop. Thus, the two groups share a symbiotic relationship. Species diversity and richness of fig and fig wasp are highest in Yunnan among all the provinces of China. Our study shows that the fig wasps collected from Yunnan include 50 species of 12 genera, which are mainly distributed in the tropics and south sub-tropics below an altitude of 1600 m. Both figs and fig wasps decrease in species number with increasing altitude. Above an altitude of 3700 m, no natural fig tress were found, except for cultivated species. Species diversity increased in the following order: northwestern Yunnan (H′= 0.6902), northeastern Yunnan (H′= 0.6976), central Yunnan (H′= 0.9211), southeastern Yunnan (H′=1.2164), western Yunnan (H′=1.5017), and southern Yunnan (H′=1.6441).

Mutualism, or a mutually beneficial interaction between two organisms, are ubiquitous in ecological systems. However, some “empty flowers”, which offer pollinators no any kinds of rewards, design different strategies to attract pollinators without providing rewards to the pollinators. These pollination mechanisms are called deceptive pollination. The family Orchidaceae, representing one of the largest groups in angiosperms, is distinguished by high floral diversity and intricate adaptations to pollinators. Darwin described and identified most of the functional floral morphology and biomechanics in orchid pollination. However, he never recognized that many of the flowers that he examined lacked food rewards for pollinators. Floral evolution in the Orchidaceae appears to be dominated by modes of deceptive pollination, and more than one third of orchid species are thought to be pollinated by deceit. Deceptive pollination is thought to be one of key roles which has lead to relatively high species diversity within the Orchidaceae. Deceptive orchids frequently exploit the food foraging, sexual, oviposition and sleep/warmth behaviors of insects. The most common deception mechanisms include generalized food deception, Batesian floral mimicry, sexual deception, brood-site imitation and shelter imitation. Additionally, floral color, morphology and fragrance play key roles to cheat target pollinators. Relationships between deceptive orchids and their pollinators possibly involve asynchronous evolution; therefore orchids track the diversification of their pollinators. However, deception has negative impacts on the pollinators, which may exert selection on the pollinators. Because duped pollinators tend to avoid rewardless flowers, deceptive orchids suffer low visitation rates and fruit set, various environment factors can affect the reproductive success of these orchids. Deceptive orchids depend largely on insect pollinators for reproduction, and the proclivity of these species to use deceptive pollination strategies puts many of these species at a relatively higher rate of extinction. Therefore, pollination biology studies are needed to provide a scientific basis for proper conservation of orchids. At the community level, co-occurring mimic, non-mimic, and mimic signal providing plant species affect the reproductive fitness of orchids. Therefore, it is necessary to further study the co-evolution webs of deceptive orchids and pollinators along with other related biological and ecological factors.

Natural hybridization mediated by pollen flow has been considered as an important factor to drive speciation in Rhododendron, one of the largest genera within alpine plants. The diversity of Rhododendron species is centered in southwestern China, yet the potential role of interspecific pollination in natural hybridization has not been empirically examined in this area. Here we investigated the flowering period and floral visitors, and conducted a series of pollination experiments to examine breeding systems and hybrid compatibility within four Rhododendron which are frequently sympatric in Yunnan Province. Rhododendron delavayi and R. decorum are clearly distinct by their morphological traits, but the putative hybrids R. agastum and R. irroratum are morphologically between the other two species. We observed that R. delavayi flowered from the beginning of March to the end of May, R. agastum and R. irroratum flowered from the beginning of March to the beginning of April, and after their flowering periods ended, R. decorum began to flower until the end of May. The anthesis of single flowers of the four Rhododendron species was almost one week. The floral visitors belong to the Hymenoptera and Diptera Orders, and Apis cerana cerana visited all of the four Rhododendron species. We found that R. delavayi, R. agastum and R. decorum are self-incompatible, but not R. irroratum. No breeding barrier between any of the four species was detected by artificial pollination, and the hybrid seeds were fertile. The hybrids between four species showed equivalent fitness to their par-ents. We suggest that the role of potential interspecific pollination is essential to hybrid speciation and evolu-tion of Rhododendron species.

Complete understanding of floral function requires the recognition of floral traits at two aspects: floral design and floral display. Floral display, the fundamental unit of plant mating, refers to the number, type and arrangement of the open flowers on the plant in a certain period. Interactions between the flowers on a plant could influence pollinator behaviors on the plant and consequently may govern the mating outcomes. Pollinators prefer large floral displays, which often receive more visitations than smaller displays and thus could facilitate geitonogamous pollination. However, visitations for each flower do not increase with display size directly, suggesting that the variation of display size would balance the benefit of attractiveness against the cost of self-pollination. Flower morphs, such as unisexual or perfect flowers on one plant, may have dif-ferent gender function varying with pollinator preference and when or how much reward is available. Flow-ers on one plant also vary on size, color and reward to affect pollinator’s visitation behavior and minimize the potential self-pollination. Floral display often contains a three-dimensional floral arrangement that could in-fluence pollinator attraction and forage energy at a large scale, and is dynamic in response to the complex pollination and physical environments. Here we briefly review the progress of studies on floral display. It is clear that further studies on the interactions between floral traits and various pollination environments would provide insights into ecological functions of diverse floral displays in angiosperms.

Orchids are a flagship group in plant conservation. There are about 1,247 species and about 171 genera in China. The Chinese orchid flora is distinguished by having rich diversity in geographical types, especially by having a broad subtropical area lying between the Qinling Mountains and the Tropic of Cancer. This paper generally reviews the present situation of research and conservation of Chinese orchids. The publication of three volumes of flora of China (Orchidaceae), and some local flora of orchids, such as those for Hainan, Yunnan, Sichuan, and Guangxi Provinces, has laid down a profound foundation not only for correctly identifying and naming Chinese orchids but also for properly making conservation policy and strategies. Compared with relatively rich taxonomic knowledge, however, there is a wide gap in our knowledge of orchid ecology and many other aspects of orchid biology related to conservation. Five main priorities for education and scientific research for the long and short terms are suggested. First, strengthen and improve basic research such as ecology, biology and floristics. Second, identify and categorize Chinese orchid diversity hot spots at the country level. Third, promote study of ex situ conservation techniques, particularly developing artificial propagation methods for commercially important species, and starting reintroduction of selected endangered species. Fourth, develop public education programs through school lessons, the press, TV and radio. Finally, establish a scientific information pool at national level.

The floral nectaries of three species of Musaceae s. s. representing the genera Musa, Ensete and Musella were comparatively investigated. Our observations revealed that nectaries of these three genera belonged to the interlocular septal type. In female flowers, nectaries were limited to the upper part of the ovaries above the locules, while in male flowers (with aborted ovaries) nectaries entirely occupied the aborted ovaries. A transection of nectary ducts suggested a complex and highly proliferated labyrinthine structure. The three species shared a few common features in the palisade-like epithelial cells, vascular supplies, and nectary openings. However, they showed some differences in longitudinal section and transectinal outline. The nectaries of Ensete glaucum had the highest starch content, and those of Musa basjoo and E. glaucum had fibrillar material presented in nectar ducts. Pollination syndromes among the three species showed high diversity, while inflorescence and flower characters (such as pendant or erect inflorescences, bract color, nectar volume and production over time, etc.) and pollination patterns were highly correlated. There were no strong correlations between nectary structures and pollinator behavior, although gelatinous or watery nectar was associated with the foraging preference of pollinators.

Hedysarum laeve (Fabaceae) is an important legume for plant ecosystem restoration and reconstruction in Mu Us Sandland, Inner Mongolia. Fruit set is greatly enhanced when pollinators are available in the H. laeve system, since fruit set is stimulated less by spontaneous autogamy. This species is pollinated mainly by wild bees, but there is insufficient information to determine the overall effectiveness or importance of the pollinators. We investigated the composition of bee pollinator species of H. laeve and the pollination efficiency of the dominant ones. The species and numbers of pollinators of H. laeve were investigated in four 2 m×2 m plots in Mu Us Sandland during 2004–2006. We observed visitation frequency of the main pollinators and measured their pollen removal ratio from anthers after a single visit to virgin flowers, pollen deposition on stigmas by a single visit to virgin flowers, and the duration of each visit. The results showed that three bees Anthophora albifronella, Megachile maritima and Bombus sporsdicus were major pollinators, of which A. albifronella was dominant in number and visitation frequency. A. albifronella removed less pollen than M. maritima and B. sporsdicus, but the three bee species deposited similar amounts of pollen on stigmas. We suggest that A. albifronella was the most efficient pollinator for H. laeve according to comparison among the three bees of the amount of pollen removal, the pollen deposition on stigmas, and visitation frequency.

Flexistyly is a unique sexual dimorphic system found in Amomum and Alpinia species of the ginger family (Zingiberaceae). The populations of flexistylous species have two phenotypes, named an anaflexistylous morph and a cataflexistylous morph, and all individuals of both morphs separate their male and female functions spatio-temporally. We conducted manipulated pollinations and pollen tube growth experiments on Alpinia blepharocalyx and A. galanga to detect the manner of separation of male and female functions within the individual and its adaptive significance. The results showed that the outcrossing rates of manipulated and natural pollination in the cata-morph did not differ significantly (P>0.05). However, the number of seeds per fruit of manipulated cata-morphs was significantly lower (P<0.01) than that of control individuals, perhaps due to the inbreeding depression caused by ovule discounting. Pollen tube growth experiments showed that, when stigma were located at the receptive position (ana-morph in AM, cata-morph in PM), stigma provided appropriate conditions (had stigmatic secretion) for pollen grain germination, and pollen tubes penetrated into the style within 2 hours after pollination, regardless treatment of selfing or outcrossing. However, when stigma were beyond the anther (ana-morph in PM, cata-morph in AM, without stigmatic secretion), it usually took 6–10 hours for pollen germination and pollen tube penetration. Pollen tubes, however, could reach the ovary within 24 hours under both treatments. Hand-pollination also showed that pollen grains of anaflexistylous flowers have matured before the dehiscence of pollen sacs. Our research suggests that flexistyly is a floral dimorphism comprising reciprocal mobile herkogamy and heterodichog-amy. Heterodichogamy encourages outcrossing, meanwhile reciprocal curvatures of stigmas play a role of reducing interference between male and female functions.

Primula merrilliana, a rare and endangered National Grade Ⅲ protected plant, is endemic to Anhui Province, China. We studied its reproductive characteristics from the aspects of phenology, breeding system structure and pollination. Our observations showed that: (1) P. merrilliana is typically distylous in both mor-phology and function, and it is a biennial plant that grows from September in the first year and lasts until late June or early July of the next year. In addition, the long-styled plants tend to flower 3 to 5 days earlier than the short-styled morphs in each population; (2) The pantoporate pollen of P. merrilliana shows that the spe-cies has vital taxonomical and evolutionary significance in Primula. The short-styled pollen diameter is 1.78 times as wide as the long-styled, but the pollen production of a short-styled flower is less than that of a long-styled flower; (3) The long-styled pistil is about 1.64 times as long as that of the short-styled morph with shorter and more frequent papillae; (4) The pollen-ovule ratio (P/O) is different in the three studied populations, and we noted larger variation in pollen than ovule production, which may be related to habitats; (5) P. merrilliana is an outcrossing plant pollinated by thrips, and the seed-set of legitimate pollination is higher than that of illegitimate; and (6) The seed morphology of P. merrilliana usually appears like a non-equilateral heptahedron, a few seeds resembles an irregular polyhedron, but there is no obvious difference between the two morphs, the long-styled and the short-styled. Based on this study, biased morph frequencies in small populations of P. merrilliana, destruction of habitats and disappearance of accompanying species are possibly the main reasons for the endangerment of this species.

Pollination has been recognized to be an important ecological process to maintain and promote biodiversity on earth. The order Hymenoptera, especially the superfamily Apoidea, is one of the most abundant and diverse groups among natural pollinators. However, studies on the ecological functions of wild bee pollinators have been underappreciated in China. More professional taxonomists are urgently needed to sur-vey fauna, to provide accurate identifications and to do comprehensive studies. Our understanding of nesting biology or pollination biology is not comprehensive for most wild bees. On the other side, much more atten-tion should be paid to the associations between bees and plants for their application to various projects on pollination biology, biodiversity or conservation biology in the future. We review current research on the status of wild bees, and we anticipate further applications to practices in agriculture and forestry with infor-mation from taxonomy, nesting biology and pollination biology of wild bees.

In the fig-fig wasp reciprocal mutualism, understanding mechanisms of coexistence between pollinating wasps and non-pollinating wasps is an important and relevant topic. Niche partitioning has widely been considered as the most important mechanism in the coexistence of pollinating and non-pollinating wasps. In this study, we experimentally examined the diet of five species of non-pollinators and the relationship among fig wasps in Ficus racemosain Xishuangbanna, southern China, from Dec. 2006 to Jun. 2007. Platyneura testacea and P. mayri are gall-makers, but oviposit sequentially, utilizing different female flowers at different developmental stages; Apocryptasp., A. westwoodi and P. agraensis are parasitoids of P. testacea, P. mayri and Ceratosolen fusciceps respectively, presenting species-specific relationships with the hosted species. Species correlation coefficients differed greatly among seasons and conditions, suggesting that the use of correlation analysis to deduce or identify relationships between species in previous studies may be of limited value. Pollinators were the dominant species at our study sites. In these conditions, non-pollinating wasps exist at relatively low population density, and therefore may have a weak impact on the stability of the mutualism, potentially enabling the non-pollinating wasps coexist with the mutualism between figs and fig wasps.

Mutualism is one of the most important ecological interactions, with strong influences on almost all levels of biological systems. Their long-term persistence raises many challenging evolutionary questions, especially those involving high-level coevolution and coadaptation. Figs and their pollinating wasps are among the most tightly integrated mutualisms known, and provide a model system for developing and testing theories of coevolution. Initial studies suggested specific coevolution between them, described as the famous rule of one fig one wasp. However, more and more exceptions have been revealed by recent studies, and cryptic species in pollinating wasps and host switching were found common in some regions and within some Ficus groups, inducing debates on the levels of species specificity and coevolution. A broad-sense coevolution model to describe the relationship of the related groups of figs and their pollinating wasps was proposed recently. The diverse relationships between figs and their pollinating wasps indicated coexistence of both specific and diffuse coevolution in this mutualism system, producing different species-specificity level. However, which model is the dominant one in this system is still keeping open. The species specificity could be tight or loose in different regions and fig groups involved. Consequently, the frequencies and mechanisms of breakdowns of the one-to-one rule within different fig groups as well as in different regions are essential for the understanding of the relative importance of the competing finer-scale cospeciation or broad-sense coevolution models.

Variable insect behaviors may result in different flower visiting frequencies, which may result in diverse impacts on plant pollination. Although flies, hoverflies, and Italian bees (Apis mellifera ligustica) were the most common visitors of Chimonanthus praecox, these insect groups had disparate visiting behaviors. Flies traveled quickly, and crawled or jumped between flowers. Italian bees also flew quickly or occasionally crawled between flowers. In contrast, hoverflies generally spent a majority of time foraging on a given flower. Based on the average foraging time and inter-floral flight time, one Italian bee could visit 4.57 flowers per minute, whereas individual bees and hoverflies could visit 2.65 and 0.53 flowers on average, respectively. After incorporating the total number of individuals for each insect group, we extrapolated the visiting rates of Italian bees, flies and hoverflies as 498.19, 1,089.74 and 99.78 flowers per minute, respectively. Flies and Italian bees had higher pollination effectiveness (number of pollinated flowers by the same number of visitors in a given time interval under the same condition), with estimates of 93% and 100% (n = 30), respectively, while only 13% (n = 30) for hoverflies. If we consider the pollen load ability and pollination effectiveness for Italian bees and flies, visiting rate may be the main limiting factor for their potential in pollinating flowers. Thus following these conclusions, flies are the major pollinators of C. praecox, followed by Italian bees (pollination role was limited by their low number) and hoverflies (limited by their foraging and hovering behaviors and lower pollination effectiveness).

The orchid family is renowned for its enormous diversity of pollination mechanisms and unusually high occurrence of non-rewarding flowers compared to other plant families. We investigated the pollination biol-ogy of Cymbidium lancifolium during 2005 and 2006 in the Yachang Nature Reserve, Guangxi Province, SW China. Our observations showed that Apis cerana cerana (Hymenopterous, Apidae) was the only pollinator. The bee directly landed on the mid-lobe, then adjusted its direction and entered into the flower. When it found no rewards in the flower, it would exit from the flower with the hind legs forcibly grasping the mid-lobe. The pollinaria together with the anther cap adhered to the thorax by the viscidium during the re-treating process of the bees. The pollinator stayed for 8–71 s in the flower with an average of 18.3 s (N = 11). It is likely that C. lancifolium attracted the bee by the purplish chestnut spots on the labellum (false nectar guides) exploiting the foraging preference of bees. The anther cap that remained on the back of the pollinator blocked the pollinaria from being received by the subsequently visited flower. The height of the anther cap (0.154 ± 0.032 cm) (N = 10) together with thorax of the pollinator (2005: 0.37 ± 0.03 cm (N = 10), 2006: 0.35 ± 0.04 cm (N = 7)) was higher than the entrance of the flower (0.29 ± 0.04 cm) (N = 21), suggesting a possi-bility of anther cap retention for geitonogamy. The reproductive success in the population was respectively 21.13% and 21.28% in 2005 and 2006. Breeding experiments showed that C. lancifolium was self-compatible and there was no significant difference in reproductive success between self-pollination and cross-pollination. There was neither apomixes nor spontaneous autogamy. The pollination success of this species was depend-ent on pollinators. The viability of seed by TTC was estimated as 85.78% (N = 11), and it was not considered to be the key limiting factor for seed germination. Therefore, it is suggested that other factors, such as the density of the pollinators and their pollination frequency, influence the fruit set and maintenance of the popu-lation of C. lancifolium.

Insect visitation was preliminarily monitored in some typical herbaceous plant communities at different altitudes (1,000–2,600 m) in the Shennongjia Mountains, Hubei Province, China. In the nine quadrats studied, insects in eleven families of Hymenoptera, Lepidoptera and Diptera were observed to be floral visitors. The taxa of insect visitors were visibly associated with the community composition. Observing the behavior of floral visitors, we found that the total visitation frequency and the frequency of visits of each kind of insect both differed in communities with different plant species, and that more insect species ap-peared in communities with more plant species in bloom. Visitation frequencies to some plant species were significantly different when they occurred in different communities. For example, no insects were observed to visit Rumex acetosa flowers, with an indistinctive perianth, in some communities, but high visitation fre-quencies were observed in others. Geranium henryi, featuring an obvious perianth, was visited by insects in every community. On the other hand, some plants, such as Vicia cracca, were always visited by insects, but the taxa of visitors were different in each community. Our results suggest that different plants contributed to various roles in attracting pollinators within communities, and one should consider the community back-ground of the plant populations in studies of plant–pollinator interactions.

Wutong Mountain in Shenzhen City is one of the several remaining natural habitats of the endangered species Paphiopedilum purpuratum. From October 1, 1998 to February 28, 2002, we observed altogether 407 ramets at nine sites. The climate, vegetation, soil and other environmental factors of this place were described and their relation to the observed plants was analyzed. The species was found to be growing very well in the secondary broad-leaved forests. Its flowers were effectively pollinated by Ischiodon scutellaris and most of the flowering plants of this orchid could bear fruits. We conclude that the main threat this species is facing is the destruction of its forest habitat and not limitations of the plants themselves.

The nutritive reserves in angiosperm pollen grains and the pollen and ovule numbers of single flowers are considered to be correlated with the pollinating vectors. In this paper, we studied the relationships between pollen histochemistry, pollen grain number, ovule number and pollinators in Phyllanthaceae. Hymenoptera- and Diptera-pollinated species tend to have starchless, lipid-rich pollen while most Lepidopteran-pollinated species have starchy pollen grains. No correlation was found between pollinator-types and pollen number of single flowers. Flowers of fly-pollinated species have much fewer ovules than flowers of moth-pollinated species. It is suggested that the decrease in ovule number may be an adaptation to the pollinating flies, which have relatively poorer pollen-transferring ability and which transfer pollen less precisely in comparison with other pollinating insects such as moths or butterflies. Pollen grains in single flowers of shrub species were found to be almost ten times as many as that of herbs, while the tree species also have higher pollen grain numbers than congeneric shrub species. This may be due to the different flower size in plants with different life forms. Significant differences were found in the pollen ornamentation patterns under SEM between fly-pollinated and moth-pollinated species.

Gene flow is an important factor influencing the genetic structure of plant populations and plays role in the conservation of endangered plants. This paper introduced different methods for measurement of gene flow in plants, analyzed the patterns of gene flow within and among populations. Relation between gene flow and population differentiation was also discussed. At last, implications of gene flow in the conservation of endangered plants were introduced.

Heteranthery in flowers has often been explained by Darwin’s ‘division-of-labor’ hypothesis. In order to test the hypothesis, we examined pollination pattern and the roles of two dimorphism stamens in pollination in Melastoma malabathricum; this species contains two sets of stamens differing markedly in shape, size and color. We found differences in morphological characters, numbers of pollen grains, seed sets following experimental treatments, with stamens removed and pollinator behaviour between the two types of stamen. The anther of purple stamens contained more pollen grains than that of yellow stamens. Carpenter bees (genus species) alighted only on the yellow stamens, and grasped their five anthers. Flowers that had their yellow stamens removed set significantly fewer seeds than intact flowers. There was no difference in the seed set of flowers with purple stamens removed and intact flowers. These results suggest that the yellow anthers function to attract pollinators and satisfy the insects’ demand for pollen, and the purple anthers satisfy plant’s need for safe gamete dispersal. However, there were no differences in pollen viability, histochemistry, or fruit set between anther type, suggesting the lack of physiological differentiation. Our experimental manipulations also demonstrate the absence of self-pollination and agamospermy in Melastoma malabathricum, and that the breeding system is facultative xenogamy.

One of the main purposes of scientific research is to form questions and collect data to find patterns that best explain a particular process. In plant reproductive ecology, scientists have found important patterns including overwhelming occurrence of co-sexual flowers, separate flowering and fruiting periods, low seed-set ratio, simultaneous mass blooming, high occurrence of outcrossing in harsh habitats, interactions of mating systems and life-history, flower differentiations on the same inflorescence, and heteranthery (stamen differentiations in same flower). The underlying mechanisms of these patterns are in debate and are still in need of further examination. In this paper, we emphasize resource allocation at different levels, i.e. individual, inflorescence, and flower, and try to explain above patterns to reconcile some contradictory results obtained in studies based on different foci. Resource and sexual allocations directly determine the sexual role of a flower and floral traits, and as a consequence, plant mating systems are determined. In the future, studies considering both ecological factors and hierarchical levels will become more important and it is essential to focus more effort to study resource allocation to gain greater understanding and accurate predictions of floral adaptations and evolution.

The alpine regions are regarded as one of the most extreme land environments due mainly to of harsh environmental conditions. However, these regions have very distinctive and diverse alpine plants, and the reproductive strategies of these species are an area of concern for many researchers. In this paper, we summarize previous research on reproductive strategies of alpine plants, including resource allocation, the responses of the flower morphology to abiotic factors, animal pollination and the adaptive mechanism of alpine plants, fruits and seeds, and clonal reproduction. For example, some special floral structures adapt to low temperature and inadequate water in the alpine belt by flower heliotropism, floral closure, pubescence and semi-translucent bracts. Additionally, harsh and stochastic climate conditions lead to a paucity of pollinators. Selfing mechanisms such as delayed selfing, autonomous selfing, and clonal reproduction and abiotic pollination (anemophily) adaptions to the lack of pollinators. As for insect pollinated plants, resource allocations of reproduction structure have increased, with enlarged “advertisement” investments. These advertisements can increase pollination rates through bigger floral displays or elongation of flower longevity. Additionally, plant species possessing a generalized floral structure and the ability to flower in different seasons can also improve the probability of reproduction success. Furthermore, dry fruits and a persistent seed bank aid in alpine plant seed dispersal and germination. Combined with our previous research, we highlight four subjects for future study: (1) selection on the flower morphology of alpine plants by abiotic factors; (2) seasonal variation and reproductive strategy; (3) the interaction of pollinators and plants at the community level; and (4) response of alpine ecosystems to global warming.

To understand patterns of species diversity distribution and speciation mechanisms for Salvia (Lamiaceae) plants, we queried species names and specimen collection information from the Global Biodiversity Information Facility (GBIF), The Plant List, Chinese Virtual Herbarium (CVH), Specimen Resources Sharing Platform for Education, Specimen Resources Sharing Platform of Chinese Nature Reserves as well as collection information for Salvia spp. specimens preserved in 32 Chinese herbaria. Based on these collection data, we analyzed the distributional patterns and plotted distribution maps at the country and geographic regional level (e.g. the Hengduan Mountains, Qinling Mountains, Wuling Mountains, Nanling Mountains, Dabie Mountains, and Tianmu-Huangshan Mountains), respectively. Additionally, the records from Yunnan and Sichuan provinces of China were obtained at the county level. In total our sample consisted of 57,674 global distributional records and 11,596 Chinese records, and 952 accepted names of Salvia were confirmed. Globally, Central and South America (510 species) support the largest number of species, followed by West Asia (270 species), Europe (117 species), East Asia (97 species) and North America (94 species). At the national level, Mexico supports the largest number of species (322), followed by Russia (109), Turkey (88), the United States (85) and China (82). Within China, Yunnan and Sichuan provinces support a substantially larger number of species than other provinces, accounting for 63% of the total number of Salvia species in China. The three counties within Yunnan and Sichuan provinces that contain the largest number of species are Yulong (23), Shangri-la (20), Dali (13), and Muli (17), Baoxing (13) and Mabian (13). The Hengduan Mountains, with 52.8% of all Salvia species in China, contain more Salvia species than any other region in China; 23 species are endemic to this area with narrow distributions. Native Chinese Salvia species were divided into four abundance ranks based on the number of county-level records: S. plebeia ranked the highest (395 distribution counties), followed by S. japonica (199 counties), S. miltiorrhiza (192 counties), S. cavaleriei (173 counties), S. chinensis (153 counties), and S. roborowskii (100 counties). Our results indicate that Salvia is mainly distributed in temperate and subtropical high-altitude countries of the northern hemisphere; China is the center of diversity in East Asia, containing representative and narrow-range endemic species. Within China, the Hengduan Mountains have the highest species diversity and percentage of endemic species.

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.

Interaction between animal-pollinated plants and their pollinators is thought to be an important selecting force shaping the evolution of flowers. Successful pollination of a plant relies on its attractiveness to pollinators and the ability of the pollinators to deposit enough compatible pollen on the flower’s stigma. To assess the attractiveness, we manipulated the flower of Aconitum kusnezoffii by removing the sepals and pet-als, respectively. We then evaluated the mating system based on pollinator behavior and flower biology of A. kusnezoffii. The bumblebee, Bombus ignites, was the effective pollinator of A. kusnezoffii. Bumblebee be-havior differed on the manipulated flowers. The visiting frequency was significantly reduced by se-pal-removal treatment, but remained unchanged by nectar-removal treatment. Bumblebees were attracted by the flower exterior morphology formed by five sepals, not by the nectary formed by the two petals. The two lower sepals provided a landing platform, and the uppermost sepal functioned as a nectar guide, ensuring bumblebee find the nectar precisely and rapidly. The two lateral sepals restricted the direction in which a bumblebee can enter the flower, ensuring pollination efficiency in zygomorphic flowers. Nectar was the main reward for bumblebees, with a sugar concentration of 39.23% and histidine concentration of 0.25 μg/μL. The flower of A. kusnezoffii was large, protandrous and herkogamous, suggesting an outcrossing mating system based on the outcrossing index. In Aconitum inflorescences the oldest flowers were functionally female at the bottom of acropetal racemes, while younger flowers were functionally male at the upper positions. Bombus ignites generally flew from a younger functionally male flower near the top of an A. kusnezoffii inflorescence to an older functionally female flower near the bottom of another inflorescence, and then moved progres-sively upward. This behavior promoted the outcrossing of A. kusnezoffii. Aconitum kusnezoffii flowers were strongly protandrous, with the male phase lasting 2–4 days, during which the anthers gradually dehisced. Aconitum packaged pollen within each flower as individual anthers dehisced over a protracted period. Such pollen packaging necessarily limited pollen removal during single visits and increased male fitness by pro-moting pollen dispersal.

Scented nectar secreted by flowers is an interesting natural phenomenon in angiosperms that is often overlooked by most researchers. Scented nectar is an evolutionary feature coupling the behavior between flower-visitors and their rewards. The effect of scented nectar on pollinator or nectar-thief is a scientific problem which deserves further exploration. We evaluated Mucuna sempervirens flowering dynamics, floral nectar volatiles, behaviors of Dremomys pernyi and Callosciurus erythraeus to inflorescence opening, nectar’s attraction effect to Apis cerana cerana, and the toxic effect of M. sempervirens nectar to Tapinoma sp. Aliphatic compounds (87.2%) were the main volatiles in nectar of M. sempervirens, whereas ketones accounted for 56.1% of the total volatiles. Lastly, volatile components with sulfur elements were absent from nectar samples. Previous studies of bat pollinated plant species have found that plants in the genus Mucuna always release sulfur compounds. Additionally, we found that the nectar of M. sempervirens was poisonous to Tapinoma sp. ant species, whereas it attracted A. cerana cerana using the Y olfactory bioassay. Squirrel species (D. pernyi and C. erythraeus) were effective pollinators of M. sempervirens, so we suspected that M. sempervirens might not be pollinated by bats only. This study provides data of pollination mechanisms in Mucuna and provides a new perspective of composition and function study of nectar in other plant groups in future.

The 750 species of Ficus (Moraceae) constitute the most distinctive and widespread genus of tropical plants. There are species-specific mutualisms between fig trees and their pollinating insects ( Agaonidae ) and perplexing relationships within the ecosystem. Valuable research results in the areas of the systematics of Ficus and fig wasps, the origin and maintenance of dioecy, biodiversity, co-evolution and ethology are provided by the approaches of systematics, biogeography, ecology, and conservation biology. China′s ancient biogeographic realm, its unique geographic traits and the diversity of its fig flora (71 dioecious species) make it an ideal location to study these questions. Up to now, we have determined less than 20 species of pollinators ( Agaonidae ) of the 98 fig/pollinator mutualisms in China, and our knowledge of these fig trees and related animals is still very limited. In utilizing the resourceful advantages of Chinese biota and geography, well-organized programs will advance smoothly and stimulate further research into fig trees and associated animals.

The species diversity status of important pollination insects , Bombus (Hymenoptera) was investigated at three sites , Mengla County at low elevations , Nanjian County at intermediate elevations , and Deqin County at high elevations , in Lancang River Basin in Yunnan , China. The species diversity of Bombus at present (1996～1980) and 20 years ago (1976～1980) was compared. The reduction of vegetation induced by human activities has led to great changes in the habitats , number of species and population size of bumble bees over 20 years. The changing tendency among pollination insect species and populations obviously varied due to different biological and ecological characteristics. The decreasing rate of endemic bumble bee species and populations is more rapid than that of common and euryecic ones. The results showed that changes of habitats induced by human activities significantly influenced species diversity of pollination insects in Lancang River Basin. To conserve and restore the population of bumble bees , the priority is to conserve and restore local ecosystems.