Pollinator Activity Research Articles

Reconstruction of historical pollination rates reveals linked declines of pollinators and plants

Widespread reports of low pollination rates suggest a recent anthropogenic decline in pollination that could threaten natural and agricultural ecosystems. Nevertheless, unequivocal evidence for a decline in pollination over time has remained elusive because it was not possible to determine historical pollination rates. Here we demonstrate a widely applicable method for reconstructing historical pollination rates, thus allowing comparison with contemporary rates from the same sites. We focused on the relationship between the oil‐collecting bee Rediviva peringueyi (Melittidae) and the guild of oil‐secreting orchid species (Coryciinae) that depends on it for pollination. The guild is distributed across the highly transformed and fragmented lowlands of the Cape Region of South Africa. We show that rehydrated herbarium specimens of Pterygodium catholicum, the most abundant member of the guild, contain a record of past pollinator activity in the form of pollinarium removal rates. Analysis of a pollination time series showed a recent decline in pollination on Signal Hill, a small urban conservation area. The same herbaria contain historical species occurrence data. We analyzed this data and found that there has been a contemporaneous shift in orchid guild composition in urban areas due to the local extirpation of the non‐clonal species, consistent with their greater dependence on seeds and pollination for population persistence.

FLOWERING AND POLLINATION STUDIES WITH EUROPEAN PLUM (PRUNUS DOMESTICA L.) CULTIVARS

One of the most important factors affecting the financial outcome of commercial fruit growing is the success of pollination and fertilization, which in turn are dependent on weather conditions, activity of pollinators and the compatibility and overlap in flowering of the cultivars. Before introducing new cultivars, it is obviously important to know the compatibility and flowering characteristics of the genotypes. In order to find out these attributes of seven new and four established plum cultivars, pollen germination tests, hand pollinations and flowering phenology observations were carried out. 'Prosser 84' had 70% pollen germination. 'Opal' had just 3%, probably due to aged pollen. 'Anna Spath' flowered over a short period (13 days) and '1468' and 'DCA BO 46' over long (19 days) periods; the overlap of all cultivars was relatively good. With '1468', 'Victory', 'Anna Spath' and 'Prosser 84' flowering intensity varied between years, 'Jubileum', 'V70032', 'Tita' and 'DCA BO 46' flowered regularly, the others were intermediate. '1468' and 'WJ 65' flowered early, 'Prosser 84' and 'DCA BO 46' late and the rest fell in between. 'Victoria' proved to be self-fertile, 'Jubileum', 'V70032' and '1468' semi self-fertile. Fruit set percentages after June drop of all crosses were rather low; varying between 0 and 28%. With 'Tita', fruit drop occurred approximately two weeks later than with the other cultivars.

Biodiversité en forêt: n'oublions pas les insectes (essai) | Biodiversity in the forest: let's not forget the insects (essay)

In Europe, insects represent approximately ¾ of the forest animal species. Thanks to their appreciable numbers and their varied diets, they render numerous services to the forest. By accelerating the recycling of organic material they contribute to the fertility of the soil. A rich and diversified entomological fauna reduces the risk of a proliferation of pests, thanks to predation and competition. Last but not least, many forest insects are in addition active pollinators. Many very specialized forest insects lacking a great mobility have become exceedingly rare and survive only in a few isolated reservoirs. The forest entomological biodiversity must be preserved, quite as much for ethical reasons as for the services which it provides. In order to do this, it is necessary to conserve a structurally diversified forest with many old trees, hollow trunks and snags, clearings and multi-storeyed forest edges.

How to become a yucca moth: minimal trait evolution needed to establish the obligate pollination mutualism

The origins of obligate pollination mutualisms, such as the classic yucca-yucca moth association, appear to require extensive trait evolution and specialization. To understand the extent to which traits truly evolved as part of establishing the mutualistic relationship, rather than being preadaptations, we used an expanded phylogenetic estimate with improved sampling of deeply-diverged groups to perform the first formal reconstruction of trait evolution in pollinating yucca moths and their non-pollinating relatives. Our analysis demonstrates that key life history traits of yucca moths, including larval feeding in the floral ovary and the associated specialized cutting ovipositor, as well as colonization of woody monocots in xeric habitats, may have been established before the obligate mutualism with yuccas. Given these preexisting traits, novel traits in the mutualist moths are limited to the active pollination behaviors and the tentacular appendages that facilitate pollen collection and deposition. These results suggest that a highly specialized obligate mutualism was built on the foundation of preexisting interactions between early Prodoxidae and their host plants, and arose with minimal trait evolution.

Pollination ecology in sympatric winter flowering Helleborus (Ranunculaceae)

We studied biotic and abiotic factors that influence pollination in two sympatric winter flowering species. Helleborus foetidus and Helleborus bocconei flower simultaneously in winter. Although climatic conditions are not favorable for biotic pollination both species rely mainly on large bees of the genus Bombus. At the beginning of flowering, harsh climatic conditions are restrictive for insect visits. As flowering continues and temperatures rise, pollinator activity increases. The two plant species share pollinators that visit them indiscriminately. The flowers of the two species differ in form and insects visit H. foetidus by inserting their heads and H. bocconei ventrally: pollen load on insects is highly specialized. With the arrival of spring, many other species start to bloom and in spite of the large number of flowers still on the plants insects abandon Helleborus species. At the end of spring increasing biotic interactions take away pollinators from the Helleborus species.

What We Think We Know vs. What We Need to Know About Orchid Pollination and Conservation: Cypripedium L. as a Model Lineage

While Darwin (1862, 1877) showed that reproductive success in orchid populations depended on adaptive floral morphology coupled with pollinator visitation a more recent review of the literature (Tremblay et al., 2005) confirmed that many out-breeding species are pollinator-limited because most orchid species showing low fecundity also lack rewards. The absence of rewards depresses both pollinator fidelity and the frequency of pollinator visits to an orchid population even though orchid flowers that lack rewards retain the same interlocking floral structures for precise pollinia removal and deposition found in related species that offer rewards. Using the genus, Cypripedium, as a model lineage of non-rewarding flowers this study also shows that the correlation between low fruit set in a Cypripedium sp. and its specific pollinator(s) is insufficient to predict specific frequencies of low fecundity. Annual rates of fruit set often vary broadly between populations of the same species and within the same population over several seasons. We speculate that fruit-set rates also decline when orchid demography and additional biotic and abiotic factors interrupt rates of pollinator activity (pre-zygotic) and fertilization/fruit maturation (post-zygotic). We suggest that that traditional field studies on pollination ecology and breeding systems be combined with data sets recording genetic variation and orchid flower demography in relation to seasonal variation in climate. We also propose that the same information be collected in regard to genetic variation, demography and phenology of populations of known orchid pollinators and co-blooming angiosperm species native to orchid habitats.

Effects of anthropogenic disturbance on the reproductive ecology and pollination service of Plymouth gentian (Sabatia kennedyana Fern.), a lakeshore plant species at risk

This study examines anthropogenic impacts on the pollination ecology of Sabatia kennedyana Fern. (Gentianaceae), a protandrous, insect-pollinated species at risk. Pollination processes were explored in disturbed and non-disturbed sites in both high and low density patches on each of three lakes in southwest Nova Scotia, Canada. The primary pollinators were Syrphid flies (Diptera: Syrphidae) and Halictid bees (Hymenoptera: Halictidae). Pollinator diversity was not significantly different among lakes or sites. High flowering density plots were visited significantly more frequently than low density plots in all site types; pollination rates and handling time were significantly lower in disturbed compared to non-disturbed sites, such that pollinators both visited and spent less time handling flowers in disturbed sites. The reproductive success of open-pollinated flowers was significantly different among lakes; there was also a disturbance by lake interaction with higher reproductive success on disturbed sites in two of the lakes. Thus, this study finds evidence of reduced pollination service together with a beneficial reproductive effect of disturbance. The significance of these results and the possibility that the spatial genetic structure of disturbed sites is reduced are discussed. We conclude that reduced pollination service and changes in the genetic structure of populations demonstrate the potentially negative impact of human associated activities on pollinator activity and plant reproductive strategy.

Reproductive biology of Macleania rupestris (Ericaceae), a pollen-limited Neotropical cloud-forest species in Costa Rica

The reproductive success of hummingbird-pollinated plants often depends on complex interactions between environmental conditions and pollinator biology (Navarro 1999, Stiles 1985, Wolf et al. 1976). The effect of environment on reproductive success of hummingbird-pollinated plants is particularly pronounced at high altitudes, where large daily fluctuations in temperature, relative humidity and solar radiation limit the effective time for photosynthesis (Cavieres et al. 2000) and affect foraging activity (Navarro 1999) and abundance of pollinators (Rahbek 1997). At high altitudes in the tropical cloud forests of Costa Rica these factors may have serious impacts on fruit production.

Chemical ecology of obligate pollination mutualisms: testing the ‘private channel’ hypothesis in the Breynia–Epicephala association

*Obligate mutualisms involving actively pollinating seed predators are among the most remarkable insect-plant relationships known, yet almost nothing is known about the chemistry of pollinator attraction in these systems. The extreme species specificity observed in these mutualisms may be maintained by specific chemical compounds through 'private channels'. Here, we tested this hypothesis using the monoecious Breynia vitis-idaea and its host-specific Epicephala pollinator as a model. *Headspace samples were collected from both male and female flowers of the host. Gas chromatography with electroantennographic detection (GC-EAD), coupled gas chromatography-mass spectrometry, and olfactometer bioassays were used to identify the floral compounds acting as the pollinator attractant. *Male and female flowers of B. vitis-idaea produced similar sets of general floral compounds, but in different ratios, and male flowers emitted significantly more scent than female flowers. A mixture of 2-phenylethyl alcohol and 2-phenylacetonitrile, the two most abundant compounds in male flowers, was as attractive to female moths as the male flower sample, although the individual compounds were slightly less attractive when tested separately. *Data on the floral scent signals mediating obligate mutualisms involving active pollination are still very limited. We show that system-specific chemistry is not necessary for efficient host location by exclusive pollinators in these tightly coevolved mutualisms.

Evolution of obligate pollination mutualism in the tribe Phyllantheae (Phyllanthaceae)

AbstractThe landmark discovery of obligate pollination mutualism between Glochidion plants and Epicephala moths has sparked increased interest in the pollination systems of Phyllantheae plants. In this paper I review current information on the natural history and evolutionary history of obligate pollination mutualism in Phyllantheae. Currently, an estimated >500 species are mutualistic with Epicephala moths that actively pollinate flowers and whose progeny feed on the resulting seeds. The Phyllantheae also includes species that are not mutualistic with Epicephala moths and are instead pollinated by bees and/or flies or ants. Phylogenetic analyses indicate that the mutualism evolved independently five times within Phyllantheae, whereas active pollination behavior, a key innovation in this mutualism, evolved once in Epicephala. Reversal of mutualism has occurred at least once in both partner lineages, involving a Breynia species that evolved an alternative pollination system and a derived clade of Epicephala that colonized ant‐pollinated Phyllantheae hosts and thereby lost the pollinating habit. The plant–moth association is highly species specific, although a strict one‐to‐one assumption is not perfectly met. A comparison of plant and moth phylogenies suggests signs of parallel speciation, but partner switches have occurred repeatedly at a range of taxonomic levels. Overall, the remarkable species diversity and multiple originations of the mutualism provide excellent opportunities to address many important questions on mutualism and the coevolutionary process. Although research on the biology of the mutualism is still in its infancy, the Phyllantheae–Epicephala association holds promise as a new model system in ecology and evolutionary biology.

Reproductive Ecology of Trillium recurvatum (Trilliaceae) in Wisconsin

Abstract Trillium recurvatum Beck is a long lived perennial with its northernmost distributional range in southern Wisconsin and is listed as Special Concern. The breeding system and reproductive ecology of this purple sessile flowered Trillium have not been previously studied. To test the hypothesis that pollen limitation is a primary contributing factor to the rarity of T. recurvatum, its breeding system and reproductive ecology were studied. Pollinator activities, pollen to ovule ratios, fruit and seed set and breeding system dynamics via field crossing studies were assessed. Observations of insect visitations revealed a single effective pollinator Coleomegilla maculata De Greer. The estimated pollen to ovule ratio was 3255 to 1 suggesting strongly obligate outcrossing. Seeds were small weighing less than any species in the genus. Fruit set in hand pollinated, outcrossed flowers was significantly greater than in open pollinated controls, demonstrating pollen limitation. Autogamous crosses yielded less ...

Pollination behaviour of Linum aretioides Boiss. (Linaceae) and its relations with air temperature and humidity

Linum aretioides Boiss., a local endemic, is distributed only on 2 mountains (İzmir: Bozdağ; Denizli: Babadağ) at the western part of Turkey between 1630 and 2300 m altitudes, above the tree line. The studies were conducted on Mount Bozdağ above the ski complex between 1750 and 2150 m, and on Mount Babadağ between 1630-2300 m both located at subalpine zones. Four 8 × 8 m quadrats on Bozdağ and 5 on Babadağ were used for the experiments. The development of reproductive structures of plants and frequency of insect visits were observed from early May to late June in 2006 and 2007. Blooming and pollination periods terminated by the last week in May on Babadağ and by the second week in June on Bozdağ. Temperatures below 10 °C before these periods appear to affect the activities of main pollinators, such as bees and butterflies, resulting in a decline in pollination, and eventually in seed formation. In Bozdağ, the average relative humidity values at 1000 hours, when the insect activities were the highest, were 65.22 ± 2.79% in June 2006, 61.6 ± 4.44% in May 2007, and 59.6 ± 3.53% in June 2007. The corresponding values on Babadağ were 52.8 ± 3.1%, 59.58 ± 3.52%, and 53.28 ± 3.41%, respectively. The most effective species in pollination process were butterflies, in particular Pieris brassicae.

Floral Resources and Nesting Requirements of the Ground-Nesting Social Bee,Lasioglossum malachurum(Hymenoptera: Halictidae), in a Mediterranean Semiagricultural Landscape

In order to adopt correct conservation strike plans to maintain bee pollination activity it is necessary to know the species' resource utilisation and requirements. We investigated the floral resources and the nesting requirements of the eusocial beeLasioglossum malachurumKirby at various sites in a Mediterranean landscape. Analysis of bees' pollen loads showed that Compositae was the more exploited family, although interpopulations differences appeared in the pollen types used. From 5 to 7 pollen types were used by bees, but only as few as 1–1.9 per load. Variations of the pollen spectrum through the annual nesting cycle were conspicuous. At all sites, bees nested in horizontal ground areas with high soil hardness, low acidity, and rare superficial stones. On the other side, the exploited soil was variable in soil granulometry (although always high in % of silt or sand) and it was moderately variable in content of organic matter and highly variable in vegetation cover. Creation of ground patches with these characteristics in proximity of both cultivated and natural flowering fields may successfully promote colonization of new areas by this bee.

Reproduction of Byrsonima sericea (Malpighiaceae) in Restinga Fragmented Habitats in Southeastern Brazil

ABSTRACTHabitat fragmentation may affect the reproductive success of plant populations in many different ways. Thus, negative, neutral, or positive plant responses can be observed, according to the balance of the different interactions. Variables related to mutualistic and antagonistic interactions (pollinator activity and gall occurrence, respectively) were measured on Byrsonima sericea populations of a fragmented seashore area (restinga) in southeastern Brazil. Pollinator visits to the oil‐bearing flowers, insect gall occurrence on stems and inflorescences, and fruit set of B. sericea were compared between three small (up to 0.3 ha) and three large (14.0–99.0 ha) fragments. MANOVA showed differences between fragment classes. Nevertheless, a posteriori univariate ANOVA showed that the pollinator visit frequency was more than twofold higher in small fragments, and that gall occurrence and fruit set did not show significant differences between small and large fragments. These results suggest that the habitat fragmentation does not affect the female reproductive success of B. sericea in the studied restinga areas because resource availability seems to be a more important factor for fruit set than pollen limitation due to pollination failure. This is the first work assessing the effects of habitat fragmentation in restinga areas, which are intensely impacted by urbanization, so that no generalization about the fragmentation consequences can still be made for this ecosystem.

Potential role of pollinators in microhabitat structure within a large population of Echinacea laevigata (Asteraceae)1

Understanding the linkages among population spatial, demographic, and genetic structure is a priority for threatened or endangered species, particularly when the physical or biotic landscape influences key processes such as pollinator behavior or plant establishment, growth, and flowering. We investigated spatial, demographic, and genetic structure, and followed activity of insect visitors within a large population of a federally endangered herb, Echinacea laevigata (C.L.Boynton & Beadle) S.F.Blake, distributed among microhabitats from an open powerline right-of-way across a narrow dirt road and into adjacent forest. Population and genetic structure differed among the microhabitats, but these differences were not due to clonal growth. Most genetic variation was within rather than among microhabitats. Plants differed in size (number of leaves) and the percentage of flowering plants among microhabitats, with smaller plants and lower flowering in the edge, larger plants and intermediate flowering in the forest and powerline, and smaller plants, but higher flowering, along the open road. Observations of insect visitors suggest activity of potential pollinators can interact with demographic structure contribute to, or reinforce, genetic structure in the population. Collectively, results of this research indicate that microhabitat effects on population structure and pollinator activity should be considered in species management plans for E. laevigata.

Correlations Between Environmental Factors and Wild Bee Behavior on Alfalfa (Medicago sativa) in Northwestern China

To discover the effect of environmental factors on pollinator visitation to flowering Medicago sativa, several field experiments were designed to examine the diurnal movement patterns of wild bee species in the Hexi Corridor of northwestern China. Our study results showed that Megachile abluta, M. spissula, and Xylocopa valga showed unimodal diurnal foraging behavior, whereas Andrena parvula and Anthophora melanognatha showed bimodal diurnal foraging behavior. Correlation analysis indicated that diurnal foraging activities of pollinators were significantly correlated with environmental factors. Correlations of foraging activities versus environmental factors for M. abluta, M. spissula, and X. valga best fit a linear model, whereas those of A. parvula and A. melanognatha best fit a parallel quadratic model. Results of this study indicated that solitary wild bees such as M. abluta, M. spissula, X. valga, A. parvula, and A. melanognatha are potential alfalfa pollinators in the Hexi Corridor. An understanding of the environmental factors that affect the behaviors of different wild bees foraging in alfalfa are basic to the utilization of solitary wild bees in a practical way for increased, or more consistent, pollination of alfalfa for seed production.

완숙토마토 품종별 서양뒤영벌(Bombus terrestris) 방사시 추가 화분공급에 의한 봉군수명 연장과 경제적 효과

토마토 및 경제작물의 수분용으로 50,000봉군 정도 이용되고 있는 서양뒤영벌을 시설완숙 토마토하우스에 방사하여 품종별로 효율적인 사용과 경제적 효과를 알아보기 위하여 2008년 2월부터 8월까지 춘천시 에서 추가화분공급효과를 조사하였다. 슈퍼도태랑, 제우스42, 그리고 슈퍼선로드 품종에서 서양뒤영벌 봉군내 추가화분공급(<TEX>$5{\sim}6g$</TEX>/3일)으로 화분매개활동과 방화흔 비율 그리고 봉군수명이 뚜렷하게 나타났다. 특히 슈퍼도태랑과 슈퍼선로드품종에서 추가화분공급효과가 더 크게 나타났다. About 50,000 hives of Bombus terrestris are used for pollination of tomato and other economical crops (fruit vegetables and fruit trees) in Korea. Therefore this study was conducted to find out the effective use of B. terrestris and its economic effect in the major beefsteak-tomato cultivation areas from February to August in 2008. The pollinating activities, rate of bite-mark and lifespan of B. terrestris's hive according to all beefsteak-tomato varieties (Super Momotaro, Zeus42, Mascara and Super Sunroad, 500 <TEX>$m^2$</TEX>, <TEX>$9,600{\sim}12,000$</TEX>plants) were apparent by regular supplement of pollen (<TEX>$5{\sim}6g$</TEX>/3 days) to the hive of B. terrestris. Especially, Super Momotaro and Super Sunroad variety were most distinctive in the effects by regular pollen supplement.

Transmission of Tomato chlorotic dwarf viroid by bumblebees (Bombus ignitus) in tomato plants

Quantitative PCR revealed that Tomato chlorotic dwarf viroid (TCDVd) was present in substantial amounts in viroid-infected tomato flowers. Healthy tomato plants were arranged in two different glasshouses, and plants were mechanically inoculated with TCDVd. Bumblebees (Bombus ignitus) were then introduced into the glasshouses to reveal whether the viroid was transmitted from infected source plants to neighbouring healthy plants. TCDVd infection was found in neighbouring tomato plants more than 1 month after the introduction of the bees, some of which expressed symptoms, in both glasshouses. Thus, bumblebees transmitted TCDVd from tomato to tomato by pollination activities.

Pollination and yield responses of cowpea ( Vigna unguiculata L. Walp .) to the foraging activity of Apis mellifera adansonii (Hymenoptera: Apidae) at Ngaoundéré (Cameroon)

To determine the apicultural value of Vigna unguiculata (L.) Walp. (Fabaceae) and evaluate the Apis mellifera adansonii Latreille (Hymenoptera: Apidae) activity on its pod and seed yields, the bee foraging and pollinating activities were studied in Ngaoundere. The experiment was carried out within the University of Ngaoundere Campus on 210 flowers differentiated in two lots, based on the protection/or not of plant inflorescences against insect visits. The bee’s seasonal rhythm of activity, its foraging behaviour on flowers, the fructification rate, the number and dry weight of seeds/pod, the percentage of normal seeds/pod, and the pod length were evaluated. Results show that A. m. adansonii foraged on plants throughout the whole blooming period. Worker bees intensively and preferably harvested nectar. The greatest mean number of workers foraging simultaneously was 500 per 1000 flowers. The mean foraging speed was 8.67 flowers/min. These findings allow the classification of V. unguiculata as a highly nectariferous bee plant. The number and dry weight of seed/pod, the pod length and the percentage of normal seeds/pod from unprotected flowers were significantly higher than those of flowers protected from insects. The fructification rates were 62 and 48%, while the percentages of healthly seeds were 97.61 and 76.17%, respectively in unprotected and protected inflorescences. The installation of A. m. adansonii colonies close to V. unguiculata field could be recommended to improve its pods and seeds production in the region.

Pollination and reproduction of a self-incompatible forest herb in hedgerow corridors and forest patches

Habitat-corridors are assumed to counteract the negative impacts of habitat loss and fragmentation, but their efficiency in doing so depends on the maintenance of ecological processes in corridor conditions. For plants dispersing in linear habitats, one of these critical processes is the maintenance of adequate pollen transfer to insure seed production within the corridor. This study focuses on a common, self-incompatible forest herb, Trillium grandiflorum, to assess plant-pollinator interactions and the influence of spatial processes on plant reproduction in hedgerow corridors compared to forests. First, using pollen supplementation experiments over 2 years, we quantified the extent of pollen limitation in both habitats, testing the prediction of greater limitation in small hedgerow populations than in forests. While pollen limitation of fruit and seed set was common, its magnitude did not differ between habitats. Variations among sites, however, suggested an influence of landscape context on pollination services. Second, we examined the effect of isolation on plant reproduction by monitoring fruit and seed production, as well as pollinator activity and assemblage, in small flower arrays transplanted in hedgerows at increasing distances from forest and from each other. We detected no difference in the proportion of flowers setting fruit or in pollinator activity with isolation, but we observed some differences in pollinator assemblages. Seed set, on the other hand, declined significantly with increasing isolation in the second year of the study, but not in the first year, suggesting altered pollen transfer with distance. Overall, plants in hedgerow corridors and forests benefited from similar pollination services. In this system, plant-pollinator interactions and reproduction seem to be influenced more by variations in resource distribution over years and landscapes than by local habitat conditions.