Flower-strip agri-environment schemes provide diverse and valuable summer flower resources for pollinating insects

The diversity and abundance of insect pollinators are declining. This decline reduces the potential ecosystem services of pollination for wild and cultivated plants. Specific agri-environment schemes (AES) are subsidised to support and conserve biodiversity in farmlands. In Belgium, the pollinator flower-strips AES, strips of flower-rich hay meadows, has been promoted as a potential scheme to increase pollinator abundance and diversity, even if their effectiveness has not been locally evaluated. The main objective of this research is to assess the capacity of pollinator-strip AES to provide flower-resources to diverse pollinators. During 2 years, we monthly measured the availability of flower resources (pollen and nectar) produced on four flower-strips surrounded by intensive farming in Belgium. We counted and identified insects that visited these flowers, and we constructed the plant–insect interactions networks. The pollinator-strip AES presented a mix of both sown and spontaneous plant species. The ten sown plant species were all present, even after 8 years of strip settings. Three of them, Centaurea jacea, Lotus corniculatus, and Daucus carota were mainly visited for nectar collection, and a spontaneous non-sown species, Trifolium repens, had a key role in providing high-quality pollen to insects. Most of the observed flower-visiting insects belonged to common species of Hymenoptera and Diptera. All are considered highly efficient pollinators. The Belgian pollinator flower-strips are effective AES that provide flower resources to pollinators, mainly during summer and support pollination services. Nevertheless, spring and autumn flower resources remain poor and could reduce the strips’ effectiveness for supporting long-term insect diversity.     

Investigating a flower-insect forager network in a mountain grassland community using pollen DNA barcoding

Faced with the decline of pollinators, it is relevant to strengthen our understanding of the whole plant-pollinator web in semi-natural grasslands that serve as refuges for pollinator populations. The aim of this study was to explore the diversity of flower-foraging insects involved in pollen transfer in mountain semi-natural grasslands. Insects actively collecting pollen and/or nectar were caught in spring in six mountain semi-natural grasslands displaying a floristic richness gradient. Individual determinations of insects were made at the finest possible taxonomic scale and pollen loads were removed from the insect body. Using next-generation DNA sequencing, pollens were identified through the ribosomal DNA cistron using the ITS2 database and the ITS plant rDNA cistron sequences from Genbank. A total of 236 flower-foraging insects were collected. Diptera represented 82% of the total catches distantly followed by Hymenoptera (15%) and Apoidea (bees) (11%). Visual observations revealed that Diptera foraged on 16 of the 21 flower species visited by insects. DNA metabarcoding showed that 82% (191) of all of the collected insects were carrying pollen and 44% (104) were carrying two genera of plants or more. Our results demonstrate that Diptera are potential key-pollinators in mountain semi-natural grasslands that cannot be overlooked by the scientific community. However difficulties of taxonomic determination due to severe shortage of experts for Diptera have to be urgently overcome. Further studies on the link between pollen transfer and actual pollination in a global change context are also required. Moreover, our results support the idea that DNA metabarcoding provides accurate information about the plants-insects networks but it also pointed out sensitive issues, especially the necessity to build reliable national barcode databases.     

The structure of a high latitude plant-flower visitor system: the dominance of flies

The species richness of insect flower visitors to all angiosperms at a subarctic-alpine site in northern Sweden was described and the plant-flower visitor matrix was analysed and compared to other high latitude systems and with systems from lower latitudes. In the habitat, 23 plant species had a total of 242 interactions with 388 flower-visiting insects, belonging to 118 taxa. Connectance of the plant-flower visitor matrix was 8.9. Comparing our findings with other studies, we get that the proportion of dipteran species of the total pollinator fauna increases with latitude but that the proportions of species of Diptera, Hymenoptera and Lepidoptera do not vary significantly among high latitude systems. Muscidae and Empididae were more abundant and generalised than other dipteran families visiting flowers in the arctic, their proportions of the total Diptera fauna increase with latitude and they are the most widespread families of flower-visiting insects in the arctic. Several Muscidae species are typical to alpine habitats in the arctic-subarctic zone. These species have special pollen feeding behaviour and an elongated proboscis, which improves access to closed flowers.
Compared to other published pollination system studies, the connectance of low latitude systems ranges between 3.4 and 28.1, whereas high latitude and high altitude systems vary between 8.6 and 19 (-60).     

Grassland Restoration on Landfill Sites in the East Midlands,United Kingdom: An Evaluation of Floral Resources and Pollinating Insects

Pollinators are declining in Europe due to intensification of agriculture, habitat loss and fragmentation. Restored landfill sites are a significant potential reserve of semi‐natural habitat, so their conservation value for supporting populations of pollinating insects was here examined by assessing whether the plant and pollinator assemblages of restored landfill sites are comparable to reference sites of existing wildlife value. Floral characteristics of the vegetation and the species richness and abundance of flower‐visiting insect assemblages were compared between nine pairs of restored landfill sites and reference sites in the East Midlands of the United Kingdom, using standardized methods over two field seasons. No differences were found between the restored landfill and reference sites in terms of species richness or abundance of plants in flower and both types of site had similar assemblages of pollinators. However, plant and insect assemblages differed across the season, with species richness and abundance being lower for the restored landfill sites in the spring and higher in the autumn compared to the reference sites. The results indicate that in this region, landfill sites are being restored to a state comparable to that of the reference sites with regards to their provision of floral resources and the associated insect pollinator assemblages. Since there are currently 2,200 working landfill sites in England and Wales, covering 28,000 ha, and closing at a rate of 100 per year, this is potentially a significant reserve of land that could be restored.     

Diversity, flower visitation frequency and generalism of pollinators in temperate rain forests of Chiloé Island, Chile

Species richness and taxonomic composition of pollinator assemblages are documented for 26 plant species from temperate rain forests of northern Chiloé Island, southern Chile (42°30'S). We investigated the patterns of generalism and specialization among plants and animal pollinators by comparing the flower visit frequency by different pollen vectors during the spring and summer months of three consecutive years (2000–2002). Species studied exhibited a range of floral morphologies (radial vs. zygomorphic, open vs. tubular) and rewards (nectar and/or pollen). Overall, we recorded 172 pollinator species, with an average of 6.6 species of pollen vectors/plant species. Pollinators visited an average of 15.2 plant species/pollen vector. Pollinator assemblages were dominated by Coleoptera (75 species), Diptera (56 species) and Hymenoptera (30 species), but passerine birds and hummingbirds were also important. The most specialized plants were vines, including the bee-pollinated genus Luzuriaga (Philesiaceae) and two endemic species of hummingbird-pollinated Gesneriaceae. Hymenoptera contributed 41.2% of all visits, with the bumblebee Bombus dalhbomii accounting for 22.5% of these. Plants with unspecialized flower morphology supported a higher species richness of pollinators, but visiting rates did not differ from specialized flowers.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 399–416.     

The impact of an alien plant on a native plant-pollinator network: an experimental approach

Studies of pairwise interactions have shown that an alien plant can affect the pollination of a native plant, this effect being mediated by shared pollinators. Here we use a manipulative field experiment, to investigate the impact of the alien plant Impatiens glandulifera on an entire community of coflowering native plants. Visitation and pollen transport networks were constructed to compare replicated I. glandulifera invaded and I. glandulifera removal plots. Invaded plots had significantly higher visitor species richness, visitor abundance and flower visitation. However, the pollen transport networks were dominated by alien pollen grains in the invaded plots and consequently higher visitation may not translate in facilitation for pollination. The more generalized insects were more likely to visit the alien plant, and Hymenoptera and Hemiptera were more likely to visit the alien than Coleoptera. Our data indicate that generalized native pollinators can provide a pathway of integration for alien plants into native visitation systems.     

Interaction diversity within quantified insect food webs in restored and adjacent intensively managed meadows

1. We studied the community and food-web structure of trap-nesting insects in restored meadows and at increasing distances within intensively managed grassland at 13 sites in Switzerland to test if declining species diversity correlates with declining interaction diversity and changes in food-web structure. 2. We analysed 49 quantitative food webs consisting of a total of 1382 trophic interactions involving 39 host/prey insect species and 14 parasitoid/predator insect species. Species richness and abundance of three functional groups, bees and wasps as the lower trophic level and natural enemies as the higher trophic level, were significantly higher in restored than in adjacent intensively managed meadows. Diversity and abundance of specific trophic interactions also declined from restored to intensively managed meadows. 3. The proportion of attacked brood cells and the mortality of bees and wasps due to natural enemies were significantly higher in restored than in intensively managed meadows. Bee abundance and the rate of attacked brood cells of bees declined with increasing distance from restored meadows. These findings indicate that interaction diversity declines more rapidly than species diversity in our study system. 4. Quantitative measures of food-web structure (linkage density, interaction diversity, interaction evenness and compartment diversity) were higher in restored than in intensively managed meadows. This was reflected in a higher mean number of host/prey species per consumer species (degree of generalism) in restored than in intensively managed meadows. 5. The higher insect species and interaction diversity was related to higher plant species richness in restored than in intensively managed meadows. In particular, bees and natural enemies reacted positively to increased plant diversity. 6. Our findings provide empirical evidence for the theoretical prediction that decreasing species richness at lower trophic levels should reduce species richness at higher trophic levels, and in addition lead to even stronger reductions in interaction diversity at these higher levels. Species at higher trophic levels may thus benefit relatively more than species at lower trophic levels from habitat restoration in the grassland ecosystems studied. We also demonstrate enhanced compartment diversity and lower interaction evenness in restored than in intensively managed meadows, both of which are theoretically positively associated with increased ecosystem stability in restored meadows.     

The topological differences between visitation and pollen transport networks: a comparison in species rich communities of the Himalaya–Hengduan Mountains

Pollination networks are usually constructed and assessed by direct field observations which commonly assume that all flower visitors are true pollinators. However, this assumption is often invalid and the use of data based on mere visitors to flowers may lead to a misunderstanding of intrinsic pollination networks. Here, using a large dataset by both sampling floral visitors and analyzing their pollen loads, we constructed 32 networks pairs (visitation versus pollen transport) across one flowering season at four elevation sites in the Himalaya–Hengduan Mountains region. Pollen analysis was conducted to determine which flower visitors acted as potential pollinators (pollen vectors) or as cheaters (those not carrying pollen of the visited plants). We tested whether there were topological differences between visitation and pollen transport networks and whether different taxonomic groups of insect visitors differed in their ability to carry pollen of the visited plants. Our results indicated that there was a significantly higher degree of specialization at both the network and species levels in the pollen transport networks in contrast to the visitation networks. Modularity was lower but nestedness was higher in the visitation networks compared to the pollen transport networks. All the cheaters were identified as peripheral species and most of them contributed positively to the nested structure. This may explain in part the differences in modularity and nestedness between the two network types. Bees carried the highest proportion of pollen of the visited plants. This was followed by Coleoptera, other Hymenoptera and Diptera. Lepidoptera carried the lowest proportion of pollen of the visited plants. Our study shows that the construction of pollen transport networks could provide a more in‐depth understanding of plant–pollinator interactions. Moreover, it suggests that detecting and removing cheater interactions when studying the topology of other mutualistic networks might be also important.     

南京地区外来植物一年蓬上访花昆虫的多样性及其访花选择性的影响因素分析

为揭示外来植物一年蓬Erigeron annuus上的本土访花昆虫多样性和影响访花行为的因素, 本研究在南京郊区进行了连续2年的野外调查, 采用跨栏模型分析了环境因素如何影响昆虫的访花选择性, 即接受概率（测度是否接受一年蓬花）和访问频数（测度接受一年蓬花的程度）。调查发现, 访问一年蓬花的昆虫共计9目54科145种, 其中, 科丰富度占优势的是膜翅目、 鳞翅目和鞘翅目（均占总科数的20.75%）, 其次是双翅目（18.87%）和半翅目（13.21%）; 物种丰富度占优势的是双翅目（26.39%）, 其次是膜翅目（18.75%）、 半翅目（18.75%）、 鞘翅目（17.36%）和鳞翅目（15.38%）。多数目的物种丰富度在6-7月最高, 9月最低, 仅双翅目（食蚜蝇为主）在5月最高。运用跨栏模型对物种优势度最大的半翅目、 膜翅目和双翅目等的访花个体数量及其影响因素的分析结果表明： 影响半翅目和膜翅目对一年蓬花访问倾向（接受概率）的因素多于影响其访问频数的因素, 由此预测这些访花昆虫可能参考较多因素做出是否接受一年蓬花, 而依据较少线索做出访问程度的访花行为决策; 一年蓬植株密度影响半翅目和膜翅目昆虫的接受概率, 而花密度影响半翅目和双翅目昆虫的接受概率和访问频数, 说明靶标植物花的特性可能对访花昆虫的访花行为决策起主要作用。     

Flower-visiting insect communities on two closely related Rhododendron species flowering in different seasons

To determine the effects of flowering season on the community structure and dynamics of flower visitors, I examined annual and hourly variation in flower-visiting insects on two Rhododendron species in a deciduous secondary forest in central Japan. Rhododendron reticulatum flowers from late March to mid-April, whereas R. macrosepalum flowers from late April to late May. Bagged and hand-pollination experiments indicated that outcrossing by flower visitors was important for the pollination of both R. reticulatum and R. macrosepalum. Pollinator and pollen limitation were detected in both Rhododendron species, although the extent of both differed between the two species. The flowers of both Rhododendron species were visited by insects of diverse taxa, including Hymenoptera, Diptera and Lepidoptera. The composition of flower visitors differed between R. reticulatum and R. macrosepalum, although a few species visited both of them. The beefly Bombylius major (Diptera: Bombyliidae) most frequently visited R. reticulatum, whereas the bumblebee Bombus ardens ardens (Hymenoptera: Apidae) most frequently visited R. macrosepalum. Hourly changes in the number of flower visitors also differed between R. reticulatum and R. macrosepalum; insects visited R. reticulatum flowers less frequently in the morning than in the afternoon, whereas insect visitations to R. macrosepalum flowers did not differ between morning and afternoon. Differences in both insect community structure and hourly changes of visitations between the two Rhododendron species occurred annually and may be related to the life history of the abundant visitor species as well as flowering phenology.     

Flowering and seasonal changes in flower sex ratio and frequency of flower visitors in a population of Saxifraga hirculus

The open, dish-shaped flowers of Saxifraga hirculus reflected ultraviolet and yellow light, contained very small amounts of nectar, and contained an average of about 75300 pollen grains per flower. Almost 11% of the pollen was inviable. Stigmatic pollen loads and seed set decreased during the course of the season. The plant appeared to be fully between-ramet compatible and partially within-ramet compatible. Seed set for the population was 30.3%. The protandrous flower opened during the day and had male and female phases of nine and three days, respectively. The protandrous system reduced the number of pollination days by a third.
At least 26 species of insects, 16 of which were syrphids, visited the flowers. Based on the number of flower visits, four species were the dominant visitors of S. hirculus: Eurimyia lineata and Neoascia tenur (Diptera: Syrphidae); Asindulum nigrum (Diptera: Mycetophilidae), and Zygaena trlfolii (Lepidoptera: Zygaenidae). Eurimyia lineata was the most frequent visitor (51% of all visits). As the season advanced, the visits by E. lineata decreased, whereas the visits by A. nigrum increased. Z. trifolli disappeared completely towards the end of the season. Only two thirds of the pollination days were "good" foraging days for these visitor species. The four major visitor species spent an average of 11.7, 27.4, 30.7 and 22.6 s per flower, respectively. Estimates suggest that about 6.5 visits (which is equal to 2.6 min of flower-visiting) and 2100 grains of pollen were required to produce one seed.     

双翅目昆虫传粉研究进展

昆虫传粉不仅在自然生态系统中发挥着十分重要的作用,也和农业生态系统中产量密切相关。众所周知,膜翅目昆虫是最重要的传粉昆虫。双翅目昆虫分布广,物种多,数量大,也是一类十分重要的传粉昆虫,但其传粉作用未受到足够的重视。本文主要综述了双翅目传粉昆虫的主要种类、传粉效力、传粉特征、与植物的协同进化以及双翅目昆虫传粉的生态学意义。据记载双翅目昆虫中至少有71个科涉及虫媒种类,目前有资料显示访花昆虫类群中双翅目约有54 417种,按涉及的种数排序居于昆虫纲传粉昆虫目中第4位。尽管双翅目昆虫单次访问可携带花粉量相对较少(相比于膜翅目),但是较高访问速率及庞大的个体数量,保证了其作为有效传粉者的地位。传粉综合征能够有效揭示植物与传粉者的协同进化关系,尤其是对一些专化传粉现象(如五味子科-瘿蚊系统)和泛化传粉的深入研究,更加深了我们对协同进化的理解。就生态学意义而言,一方面双翅目传粉昆虫是膜翅目传粉昆虫的有益补充,另一方面在一些特殊环境中,双翅目昆虫具有不可替代的作用。当前传粉昆虫(包括双翅目)数量急剧下降,而且双翅目昆虫的传粉价值还利用较少。结合我国当前的研究现状提出了以下未来研究重点:1)加深双翅目传粉效力和适应意义的案例研究以明确双翅目昆虫在传粉体系中的地位;2)加强栖息地格局变化与昆虫多样性的研究以明确栖息地改变对昆虫的影响程度;3)梳理访花和传粉、专化传粉和泛化传粉等关系以更加明确双翅目昆虫在与植物协同进化中的作用;4)逐步深入探讨花粉浪费和花粉竞争以探究传粉策略和植物繁殖策略。这些努力将为双翅目传粉昆虫的知识普及、资源保护与利用研究等方面提供参考。     

Pollination ecology of Silene acutifolia (Caryophyllaceae): floral traits variation and pollinator attraction

BACKGROUND AND AIMS: The floral display influences the composition of pollinators interacting with a plant species. Geographic and temporal variation in pollinator composition complicates the understanding of the evolutionary consequences of floral display variation. This paper analyses the relationships between Silene acutifolia, a hermaphroditic perennial herb, and its pollinators, based on field studies in the north-west of Spain. METHODS: Studies were conducted over three years (1997-1999). Firstly, the main pollinators of this species were determined for two years in one population. Secondly, pollen limitation in fruit and seed production was analysed by supplementary hand pollinations, and counting the pollen grains and tubes growing in styles for two different-sized populations. Finally, the effect of flower size and number on the rate of visitation and total seed number was examined for 15 marked plants. RESULTS AND CONCLUSIONS: The primary pollinators were long-tongued insects, including Hymenoptera, Lepidoptera and Diptera, but the composition and visitation frequencies differed between years. Pollen limitation occurred in one of the years of study. There was between-population variation in the number of pollen grains and pollen tubes found in styles, suggesting pollen limitation in one population. Overall, pollinators visited plants with more open flowers more frequently, and pollinated more flowers within these plants. Conversely, petal and calyx sizes had no effect on insect visitation. Plants with higher rates of visits produced higher number of seeds, suggesting that pollinator-mediated limitation of seed and fruit production may be important in some years.     

Food for insect pollinators on farmland: insect visits to flowers of annual seed mixtures

Intensification of agriculture in recent decades has impoverished farmland for insect pollinators by removing their food plants. Arable farmland can be enhanced as a habitat for these insects by growing annual nectar- and pollen-producing herbaceous plants for them in non-cropped areas such as set-aside and field margins. In 1996 and 1997, observations were made in Hertfordshire, UK, on the flowering phenology and flower-attractiveness to visiting Hymenoptera, Diptera and Lepidoptera of plots sown to mixtures of six annual flowering plant species: borage (Borago officinalis), buckwheat (Fagopyrum esculentum), cornflower (Centaurea cyanus), mallow (Malva sylvestris), marigold (Calendula officinalis) and phacelia (Phacelia tanacetifolia) in different proportions. The mixtures had good agronomic and biological properties. They established and flowered well from a range of seed rates and sowing-dates. They attracted a diversity of flower-visiting insects, including the honey bee and eightspecies of bumble bee amongst 16 species of aculeate Hymenoptera, 17 species of Diptera, mostly syrphids, and six species of Lepidoptera. Sequential sowings provided nectar and pollen from early summer to late autumn during the period after arable crops had finished flowering and food for pollinators was scarce. Different insect species were favoured by different sowing-dates and plant species     

多伞阿魏的繁育系统及其生态适应性

多伞阿魏（Ferula ferulaeoides）是新疆特有的类短命植物,具有巨大的生态作用和潜在的经济价值。实验通过研究多伞阿魏的花部形态特征、繁殖系统及传粉昆虫,来阐明其对生态环境的响应。结果表明：（1）多伞阿魏花序花期一般持续10~15 d,单花花期为7~10 d,两性花呈现雌雄异位和雌雄异熟的现象;（2）其繁育系统类型为兼性异交,存在自交部分亲和,自然结果率较高,为72.24%;（3）传粉昆虫多种多样,其中以双翅目和膜翅目昆虫居多;（4）开花当天的花粉活力呈单峰曲线,在12：00时活力最高,柱头可授性在花药完全散粉后第2天最强。     

Pollinator diversity and specialization in relation to flower diversity

In the face of global decline in biodiversity, the relationship between diversity and species interactions deserves particular attention. If pollinators are strongly dependent on floral diversity due to mutual specialization, declines in plant diversity, e.g. caused by land use intensification, may be associated with linked extinctions of pollinators. However, the general extent of pollinator specialization is still poorly known. To explore the dependence of local bee and hoverfly communities on flower diversity, we recorded flower supply and flower‐visiting insects on 27 meadows with varying flower diversity in southern Germany and analyzed (a) whether the diversity of flower visitors is correlated with flower diversity, (b) whether the degree of dietary specialization of flower visitors changes with flower diversity and (c) whether flower preferences of individual flower visitor species are constant or variable between different communities. Flower–visitor interaction webs were compiled during a single day on each meadow. This approach prevents relating pollinator species to flowers they never encounter because of non‐overlapping phenology or spatial segregation. (a) Flower diversity and flower visitor diversity were positively correlated. (b) Flower visitor assemblies were significantly specialized at a relatively high level, contrasting to the opinion that plant–pollinator webs are highly generalized, and providing a possible explanation for the positive diversity correlation. However, the level of specialization did not change significantly across the gradient of flower diversity, suggesting that pollinators are partitioned to a similar extent in each meadow. (c) In the analysis of ten common flower visitor species previously categorized as generalists, strong evidence was found for both, consistent preferences and preferences that differ between sites. These results indicate a flexibility in flower preferences and a dynamic resource partitioning among pollinators. Generally, our findings highlight the complexity of plant–pollinator interactions and confirm the importance of flower diversity for bee and hoverfly communities.     

Arbuscular mycorrhizal fungi influence visitation rates of pollinating insects

Abstract.  1. Arbuscular mycorrhizal (AM) fungi can increase a number of plant traits to which pollinating insects are known to respond. These include total plant size, flower number, flower size, and amount of pollen produced.
2. It was hypothesised that these effects would lead to a different visitation rate of pollinating insects on mycorrhizal and non-mycorrhizal plants. To test this idea, three species of annual plants ( Centaurea cyanus , Tagetes erecta , and Tagetes patula ) were grown with and without AM fungi and the visits by pollinating insects were recorded over a 2-month period.
3. In all three species, mycorrhizal plants experienced a greater number of pollinator visits per flower per unit time. Diptera and Hymenoptera were the predominant insects and the latter order showed the strongest response.
4. Here, it is suggested that mycorrhizal fungi increase floral visitation rates by insects, but that the mechanism varies from one plant species to another. In C. cyanus , it appears to be due to flower number per plant, in T. patula it is individual inflorescence size, and in T. patula it is nectar standing crop per inflorescence.     

Native flowering shrubs promote beneficial insects in avocado orchards

1. Flower strips can promote and conserve beneficial insects in agroecosystems. Knowing which groups are favoured and which plant traits affect visitation rates by beneficial insects is important for the design of plant strips.
2. We established 21 Native Flower Strips (NFS) in avocado orchards in Central Chile. NFS contained 7–11 plant species, with variable corolla length and flowering period, to promote beneficial insects. We assessed flight activity of ladybirds (Coccinellidae) and bees (Apiformes) in sites adjacent to and far from NFS within avocado orchards. Additionally, we evaluated flower visitation for the main flower visitor groups (Apiformes, Lepidoptera, Diptera, and Coleoptera) to the plant species in NFS according to season and corolla length.
3. We found almost six times greater flight activity of coccinellids and bees in NFS than sites far from NFS within avocado orchards. Visitation rates of pollinator groups varied according to corolla length and season. Diptera, Coleoptera, and Lepidoptera consistently visited short corolla flowers. NFS were highly visited in summer and autumn, when avocados were not in bloom.
4. NFS in orchards should be encouraged by policymakers because they support beneficial insects that could deliver ecosystem services and contribute to local biological conservation.

     

神农架地区典型草本群落中的昆虫访花行为比较

对神农架地区不同海拔高度(1,000–2,600 m)的典型草本群落中的昆虫访花行为进行了初步的监测和统计。在9个样地中共观察到鳞翅目、膜翅目、双翅目11科昆虫访花, 访花者的类群在不同海拔高度的群落中有所不同, 但明显与植物群落的物种组成有关。对昆虫访花频率的监测发现, 不同物种组成的草本群落中, 所有昆虫访花的总频率和不同类群的昆虫访花频率都有差异, 正在开花的物种较多的群落中通常能吸引相对较多的访花者。同一种植物在不同的群落背景中受访频率差异显著, 如花被不甚显著的酸模(Rumex acetosa)在某些群落中未观察到访花者, 在另一些群落中却有昆虫频繁访问。而花被显著的血见愁老鹳草(Geranium henryi)在各群落中都有频繁的昆虫访问。一些植物(如广布野豌豆Vicia cracca)虽然在不同群落中都有昆虫访问, 但访花者类群却有较大差异。作者认为, 在植物群落中, 不同植物的花在吸引昆虫传粉方面存在着一定的相互作用, 在研究特定植物的虫媒传粉时应重视该植物种群所处的群落背景所起的作用。     

Stigmatic pollen delivery by flies and bees: Methods comparing multiple species within a pollinator community

A wide variety of insect species provide pollination services in natural and agricultural ecosystems, but in order to quantify their contribution it is necessary to evaluate their effectiveness. An important component of this is to determine their ability to transfer pollen to stigmas which typically requires observers to wait for insects to visit focal flowers (static approach); a time-consuming process not amenable to obtaining measures for pollinating species of low local abundance. An alternative method (active approach) is to detach test flowers and present them to the targeted flower visitor. This offers a number of advantages (e.g. increased speed and flexibility), but may alter insect behaviour. We compared pollen deposition within flowering onion crops using three bee (Apoidea) and three fly (Diptera) species. The two approaches resulted in similar numbers of pollen grains being deposited onto stigmas for each insect species, thereby supporting the validity of the active as an alternative to the static approach in our test crop. The ability to rapidly assess stigmatic pollen deposition of a broad range of insects using the active approach can greatly assist assessments of pollinator contribution within plant pollinator assemblages.