Organic farming in isolated landscapes does not benefit flower-visiting insects and pollination

Organic farming has often been found to provide benefits for biodiversity, but the benefits can depend on the species considered and characteristics of the surrounding landscape. In an intensively farmed area of Northeast Italy we investigated whether isolated organic farms, in a conventionally farmed landscape, provided local benefits for insect pollinators and pollination services. We quantified the relative effects of local management (i.e. the farm system), landscape management (proportion of surrounding uncultivated land) and interactions between them. We compared six organic and six conventional vine fields. The proportion of surrounding uncultivated land was calculated for each site at radii of 200, 500, 1000 and 2000 m. The organic fields did not differ from the conventional in their floral resources or proportion of surrounding uncultivated land. Data were collected on pollinator abundance and species richness, visitation rates to, and pollination of experimental potted plants. None of these factors were significantly affected by the farming system. The abundance of visits to the potted plants in the conventional fields tended to be negatively affected by the proportion of surrounding uncultivated land. The proportion fruit set, weight of seeds per plant and seed weight in conventional and organic fields were all negatively affected by the proportion of surrounding uncultivated land. In vine fields the impact of the surrounding landscape was stronger than the local management. Enhancement of biodiversity through organic farming should not be assumed to be ubiquitous, as potential benefits may be offset by the crop type, organicmanagement practices and the specific habitat requirements in the surrounding landscape.

Where is the UK's pollinator biodiversity? The importance of urban areas for flower-visiting insects

Insect pollinators provide a crucial ecosystem service, but are under threat. Urban areas could be important for pollinators, though their value relative to other habitats is poorly known. We compared pollinator communities using quantified flower-visitation networks in 36 sites (each 1 km2) in three landscapes: urban, farmland and nature reserves. Overall, flower-visitor abundance and species richness did not differ significantly between the three landscape types. Bee abundance did not differ between landscapes, but bee species richness was higher in urban areas than farmland. Hoverfly abundance was higher in farmland and nature reserves than urban sites, but species richness did not differ significantly. While urban pollinator assemblages were more homogeneous across space than those in farmland or nature reserves, there was no significant difference in the numbers of rarer species between the three landscapes. Network-level specialization was higher in farmland than urban sites. Relative to other habitats, urban visitors foraged from a greater number of plant species (higher generality) but also visited a lower proportion of available plant species (higher specialization), both possibly driven by higher urban plant richness. Urban areas are growing, and improving their value for pollinators should be part of any national strategy to conserve and restore pollinators.

Social wasp-flower visiting guild interactions in less structurally complex habitats are more susceptible to local extinction

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Insect odour perception: recognition of odour components by flower foraging moths

Odours emitted by flowers are complex blends of volatile compounds. These odours are learnt by flower-visiting insect species, improving their recognition of rewarding flowers and thus foraging efficiency. We investigated the flexibility of floral odour learning by testing whether adult moths recognize single compounds common to flowers on which they forage. Dual choice preference tests on Helicoverpa armigera moths allowed free flying moths to forage on one of three flower species; Argyranthemum frutescens (federation daisy), Cajanus cajan (pigeonpea) or Nicotiana tabacum (tobacco). Results showed that, (i) a benzenoid (phenylacetaldehyde) and a monoterpene (linalool) were subsequently recognized after visits to flowers that emitted these volatile constituents, (ii) in a preference test, other monoterpenes in the flowers' odour did not affect the moths' ability to recognize the monoterpene linalool and (iii) relative preferences for two volatiles changed after foraging experience on a single flower species that emitted both volatiles. The importance of using free flying insects and real flowers to understand the mechanisms involved in floral odour learning in nature are discussed in the context of our findings.

Characterization of the social wasp guild (Hymenoptera: Vespidae) visiting flowers in the Caatinga (Itatim, Bahia, Brazil)

Thirteen species of flower-visiting social wasps were collected from 41 plant species. The number of wasp species did not vary significantly. On the other hand, the number of individuals varied significantly during the data collection period. Four of the wasp species (Mischocyttarus lanei, Polybia ignobilis, Polybia occidentalis, and Polybia sericea) showed changes in body size over the year. The total wasp biomass and the number of plants monthly visited by wasps had a positive significant correlation. The structure of this social wasp community is characterized by a small number of dominant species, a large number species that are not frequently present and several plant species visited by few wasps. Social wasp species are differently affected by seasonal changes in the 'caatinga'.

Food for Pollinators: Quantifying the Nectar and Pollen Resources of Urban Flower Meadows

Planted meadows are increasingly used to improve the biodiversity and aesthetic amenity value of urban areas. Although many ‘pollinator-friendly’ seed mixes are available, the floral resources these provide to flower-visiting insects, and how these change through time, are largely unknown. Such data are necessary to compare the resources provided by alternative meadow seed mixes to each other and to other flowering habitats. We used quantitative surveys of over 2 million flowers to estimate the nectar and pollen resources offered by two exemplar commercial seed mixes (one annual, one perennial) and associated weeds grown as 300m2 meadows across four UK cities, sampled at six time points between May and September 2013. Nectar sugar and pollen rewards per flower varied widely across 65 species surveyed, with native British weed species (including dandelion, Taraxacum agg.) contributing the top five nectar producers and two of the top ten pollen producers. Seed mix species yielding the highest rewards per flower included Leontodon hispidus, Centaurea cyanus and C. nigra for nectar, and Papaver rhoeas, Eschscholzia californica and Malva moschata for pollen. Perennial meadows produced up to 20x more nectar and up to 6x more pollen than annual meadows, which in turn produced far more than amenity grassland controls. Perennial meadows produced resources earlier in the year than annual meadows, but both seed mixes delivered very low resource levels early in the year and these were provided almost entirely by native weeds. Pollen volume per flower is well predicted statistically by floral morphology, and nectar sugar mass and pollen volume per unit area are correlated with flower counts, raising the possibility that resource levels can be estimated for species or habitats where they cannot be measured directly. Our approach does not incorporate resource quality information (for example, pollen protein or essential amino acid content), but can easily do so when suitable data exist. Our approach should inform the design of new seed mixes to ensure continuity in floral resource availability throughout the year, and to identify suitable species to fill resource gaps in established mixes.

Mehiläisten (Apis mellifera) kukkavierailut mansikalla (Fragaria x ananassa) ja vadelmalla (Rubus idaeus) sekä kukkavierailuihin vaikuttavat tekijät

Hyönteispölytys lisää monien ristipölytteisten viljelykasvien siemensatoa sekä parantaa sadon laatua. Marjakasveilla, kuten mansikalla ja vadelmalla marjojen koko suurenee sekä niiden laatu paranee onnistuneen pölytyksen seurauksena. Aiempien havaintojen mukaan mansikan kukat eivät pääsääntöisesti houkuttele mehiläisiä, kun taas vadelma on yksi mehiläisten pääsatokasveista. Tutkimuksen tarkoituksena oli selvittää, miten tehokkaasti mehiläiset vierailevat mansikalla sekä vadelmalla, keskittyen kukkakohtaisiin käynteihin tuntia kohti. Mehiläisiä voidaan käyttää Gliocladium catenulatum-vektoreina torjuttaessa mansikan ja vadelman harmaahometta (Botrytis cinerea). Kukkavierailujen perusteella arvioidaan, onko vektorilevitys riittävän tehokas torjumaan harmaahometta ja miten hyvin mehiläisiä voidaan käyttää pölytyspalveluihin, etenkin mansikalla. Havainnot kerättiin kuudelta eri tilalta Sisä-Savosta kesällä 2007. Kukkavierailuja laskettiin mansikan ja vadelman kukinnan aikana erilaisissa sääolosuhteissa, eri kellonaikoina ja eri etäisyyksillä mehiläispesistä. Kukat valittiin satunnaisesti, ja valintaperusteena oli kukan avonaisuus. Tarkkailuaika riippui mehiläisten lentoaktiivisuudesta. Mansikan koko havaintojakson keskiarvoksi tuli 1,75 käyntiä kukkaa kohti tunnissa. Vadelmalla vastaava luku oli 4,27, joten keskiarvojen perusteella vadelma oli houkuttelevampi kuin mansikka. Kasvukauden vaiheella ei ollut eroja vierailuihin kummallakaan kasvilla, mutta vuorokaudenajan suhteen vierailuja oli enemmän aamupäivällä kuin iltapäivällä. Lämpötila korreloi positiivisesti vierailutiheyden kanssa kummallakin kasvilla. Sääolosuhteet rajoittivat havaintojen keräämistä ja kesä oli erittäin sateinen. Mehiläiset vierailivat kukissa riittävästi haastavissakin sääolosuhteissa niin, että harmaahometorjunta onnistui. Vektorilevitystä suunnitellessa, etenkin mansikalla, tulee ottaa huomioon pesien sijoittelu sekä riittävä lukumäärä. Pesien ravinnontarpeen tulee olla suuri, jotta mehiläiset keräisivät ravintoa kukista mahdollisimman tehokkaasti. Pesiin voidaan lisätä tarvittaessa avosikiöitä tai poistaa siitepölyvarastoja ravinnonkeruuaktiivisuuden lisäämiseksi. Lisätutkimusta tarvitaan pesien sijoittelun, kilpailevien kasvien sekä mansikkalajikkeiden houkuttelevuuden vaikutuksesta vierailutiheyteen. Suomalaisten mansikkalajikkeiden meden sekä siitepölyneritystä olisi myös hyvä selvittää.

Species richness declines and biotic homogenization have slowed down for NW-European pollinators and plants

Concern about biodiversity loss has led to increased public investment in conservation. Whereas there is a widespread perception that such initiatives have been unsuccessful, there are few quantitative tests of this perception. Here, we evaluate whether rates of biodiversity change have altered in recent decades in three European countries (Great Britain, Netherlands and Belgium) for plants and flower visiting insects. We compared four 20-year periods, comparing periods of rapid land-use intensification and natural habitat loss (1930–1990) with a period of increased conservation investment (post-1990). We found that extensive species richness loss and biotic homogenisation occurred before 1990, whereas these negative trends became substantially less accentuated during recent decades, being partially reversed for certain taxa (e.g. bees in Great Britain and Netherlands). These results highlight the potential to maintain or even restore current species assemblages (which despite past extinctions are still of great conservation value), at least in regions where large-scale land-use intensification and natural habitat loss has ceased.

The identity of crop pollinators helps target conservation for improved ecosystem services

Insect pollinated mass flowering crops are becoming more widespread and there is a need to understand which insects are primarily responsible for the pollination of these crops so conservation measures can be appropriately targeted in the face of pollinator declines. This study used field surveys in conjunction with cage manipulations to identify the relative contributions of different pollinator taxa to the pollination of two widespread flowering crops, field beans and oilseed rape. Flower visiting pollinator communities observed in the field were distinct for each crop; while field beans were visited primarily by a few bumblebee species, multiple pollinator taxa visited oilseed, and the composition of this pollinator community was highly variable spatially and temporally. Neither pollinator community, however, appears to be meeting the demands of crops in our study regions. Cage manipulations showed that multiple taxa can effectively pollinate both oilseed and field beans, but bumblebees are particularly effective bean pollinators. Combining field observations and cage manipulations demonstrated that the pollination demands of these two mass flowering crops are highly contrasting, one would benefit from management to increase the abundance of some key taxa, whilst for the other, boosting overall pollinator abundance and diversity would be more appropriate. Our findings highlight the need for crop specific mitigation strategies that are targeted at conserving specific pollinator taxa (or group of taxa) that are both active and capable of crop pollination in order to reduce pollination deficits and meet the demands of future crop production.

Contribution of insect pollinators to crop yield and quality varies with agricultural intensification

Background: Up to 75% of crop species benefit at least to some degree from animal pollination for fruit or seed set and yield. However, basic information on the level of pollinator dependence and pollinator contribution to yield is lacking for many crops. Even less is known about how insect pollination affects crop quality. Given that habitat loss and agricultural intensification are known to decrease pollinator richness and abundance, there is a need to assess the consequences for different components of crop production. Methods: We used pollination exclusion on flowers or inflorescences on a whole plant basis to assess the contribution of insect pollination to crop yield and quality in four flowering crops (spring oilseed rape, field bean, strawberry, and buckwheat) located in four regions of Europe. For each crop, we recorded abundance and species richness of flower visiting insects in ten fields located along a gradient fromsimple to heterogeneous landscapes. Results: Insect pollination enhanced average crop yield between 18 and 71% depending on the crop. Yield quality was also enhanced in most crops. For instance, oilseed rape had higher oil and lower chlorophyll contents when adequately pollinated, the proportion of empty seeds decreased in buckwheat, and strawberries’ commercial grade improved; however, we did not find higher nitrogen content in open pollinated field beans. Complex landscapes had a higher overall species richness of wild pollinators across crops, but visitation rates were only higher in complex landscapes for some crops. On the contrary, the overall yield was consistently enhanced by higher visitation rates, but not by higher pollinator richness. Discussion. For the four crops in this study, there is clear benefit delivered by pollinators on yield quantity and/or quality, but it is not maximized under current agricultural intensification. Honeybees, the most abundant pollinator, might partially compensate the loss of wild pollinators in some areas, but our results suggest the need of landscape-scale actions to enhance wild pollinator populations.

Entomofauna visitante de Stenolobium stans (Juss.) Seem (Bignoniaceae), durante seu período de floração

Realizaram-se estudos sobre as formas de reprodução de Stenolobium stans (Juss.) Seem e determinou-se a diversidade, freqüência e constância dos insetos visitantes nas flores em diferentes horas, durante quatro anos. As flores de S. stans começam a se abrir nas primeiras horas do dia entre 5 e 6h, com duração de 3 a 8h. Quando o estigma está receptivo, o pólen tem 90% de viabilidade. Além do pólen, a flor possui outros atrativos para os insetos visitantes, ou seja, os osmóforos responsáveis pelo odor adocicado, luz ultravioleta refletida e néctar com 25% de açúcar. A planta é autocompatível, reproduzindo-se por autogamia, geitonogamia ou xenogamia o que determina a necessidade de polinizadores externos e justifica ser a espécie vegetal em estudo uma séria invasora de campos e pastagens. Grande diversidade de insetos foi verificada visitando as flores, com predominância das abelhas. Os polinizadores foram Centris collaris Lepeletier, Bombus morio (Swederus), Eulaema nigrita Lepeletier e Epicharis sp. No meio rural houve menor incidência das espécies nativas do que no ambiente urbano, com predominância da abelha introduzida Apis mellifera L. Fatores ambientais, principalmente a temperatura, luminosidade, umidade relativa do ar e velocidade do vento, influenciaram a atividade forrageadora dos insetos.

Trait-mediated effects on flowers: Artificial spiders deceive pollinators and decrease plant fitness

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A Meta-Analysis of Predation Risk Effects on Pollinator Behaviour

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Impacto humano afeta negativamente a dispersão de sementes de frutos ornitocóricos: Uma perspectiva global

Ornithochorous fruits make up an important part of the diet of birds and many studies have related the different morphological types of fruits with the choice by birds. We analyzed the intrinsic characteristics of plants and how human impact can affect this choice. Through analyses of covariance we related the degree of human pressure in each study site (high or low) and the morphological characteristics of 57 ornithochorous species with visiting rates and consumption of fruits by birds. We did not find any intrinsic plant characteristic (life form, size and type of diaspore) that explains the rates of consumption and visit by birds. On the other hand, the degree of human impact affected directly the mutualism between plants and birds. Plant species located in areas that suffer high human pressure had number of visits and consumption rates 3,3 and 3,5 lower than plants located in pristine areas, respectively. The negative consequences of the reduction of consumption of fruits in areas with high human pressures may directly affects the interactions between birds and plants and the regeneration of the ornithochorous species.