Pollinator Activity Research Articles

Reproducing under a warming climate: long winter flowering and extended flower longevity in the only Mediterranean and maritime Primula.

Under the pressure of global warming, general expectations of species migration and evolution of adaptive traits should always be confirmed with species-specific studies. Within this framework, some species can be used as study systems to predict possible consequences of global warming also on other relatives. Unlike its mountain congeneric, Primula palinuri Petagn. has endured all the climatic fluctuations since the Pleistocene, while surviving on Mediterranean coastal cliffs. The aim of this work was to investigate the possible evolution of reproductive biological and ecological traits in P.palinuri adaptation to a warmer environment. Data showed that flowering starts in mid-winter; single flowers remain open for over a month, changing from pendulous to erect. The number of insects visiting flowers of P.palinuri increases during the flowering season, and pollination reduces flower longevity. Overall, the best pollen performances, in terms of viability and germinability, occur at winter temperatures, while pollinator activity prolongs flowering until spring. Moreover, extended longevity of single flowers optimises reproductive success. Both phenotypic plasticity and selective processes might have occurred in P.palinuri. However, we found that reproductive traits of the only Mediterranean Primula remain more associated with cold mountain habitats than warm coastal cliffs. Given the rapid trend of climate warming, migration and new adaptive processes in P.palinuri are unlikely. Response to past climate warming of P.palinuri provides useful indications for future scenarios in other Primula species.

Balancing anti‐herbivore benefits and anti‐pollinator costs of defensive mutualists

Quantifying costs and benefits of ostensibly mutualistic interactions is an important step toward understanding their evolutionary trajectories. In food‐for‐protection interactions between ants and extrafloral nectar (EFN)‐bearing plants, tending by aggressive ants may deter herbivores, but it may also deter pollinators. The fitness costs of pollinator deterrence are not straightforward for long‐lived iteroparous plants, because reproductive vital rates often contribute weakly to fitness relative to growth and survival (vital rates that may be enhanced by ant defense). We used field manipulations of ant and pollinator activity and demographic modeling to examine how pollination costs of ant defense translate to plant fitness, given the benefits of ant defense elsewhere in the plant life cycle. We contrasted the net fitness effects of alternative ant partner species. Our work focused on the tree cholla cactus, Opuntia imbricata, an EFN‐bearing plant associated with two ant species (Crematogaster opuntiae and Liometopum apiculatum) that differ in quality of defense against insect herbivores. We found that ant defense imposed pollination costs, despite evidence for ant‐repellent floral volatiles and temporal partitioning of ant and pollinator activity. The two partner species similarly reduced pollinator visitation and seed mass, and one (C. opuntiae) additionally reduced seed number. We used the experimental data and other long‐term demographic data to parameterize an integral projection model that integrated costs and benefits of ant defense over the complete plant life cycle. Model results indicated that the pollination costs of L. apiculatum were balanced by beneficial effects on growth, leading to a net fitness effect that was neutral to positive. By contrast, pollination costs outweighed benefits for C. opuntiae, the weaker defender, rendering this species a reproductive parasite. Thus, we infer that pollination costs destabilize mutualism with one partner species, but are offset by strong defensive benefits provided by the other, leading to contrasting selective pressures imposed by alternative associations. Accounting for ontogenetic turnover in ant partner identity indicated that most plants avoid the parasitic effects of C. opuntiae by associating nonrandomly with L. apiculatum at reproductive life stages. Our results highlight the value of a demographic approach to quantifying the costs and benefits of mutualism.

Spatial and temporal distribution patterns of nectar-inhabiting yeasts: how different floral microenvironments arise in winter-blooming Helleborus foetidus

Yeasts frequently colonise floral nectar, where they can reach high densities. Recent investigations have further shown that yeast metabolism alters nectar properties by decreasing its total sugar content, modifying sugar composition, or raising nectar local temperature. However, the distribution patterns of nectar yeasts remain poorly investigated at multiple spatial and temporal scales. Here, we study natural variation of the nectar yeasts in a single host plant, Helleborus foetidus , in a mountainous region. We quantified spatio-temporal variation in the frequency and abundance of yeast species across six populations located along an altitudinal gradient. Variance partitioning techniques were used to estimate the relative magnitude of variation in yeast abundance between individual plants, flowers within plants, and nectaries within flowers. Although yeast frequency and abundance varied widely across sites and dates, the largest part of total variance occurred at the sub-individual level (i.e., flowers on the same plant). Pollinator composition and activity seemed the main factors explaining the observed patterns of yeast frequency and abundance across floral nectar samples. • Nectar yeast incidence varied widely across sites and dates for a single host plant. • However, the largest part of total variance occurred at the sub-individual level. • Pollinator features were the main factors explaining yeast abundance patterns. • Nectar yeast patchy distribution may affect pollinator choice and plant fitness. • Sub-individual variation may disfavour plant selective forces against nectar yeasts.

Unpaved roads disrupt the effect of herbivores and pollinators on the reproduction of a dominant shrub

Anthropogenic linear developments, such as trails and firebreaks, also called soft linear developments (SLD), can influence animal behavior, altering the ecological interactions in which animals are involved. For example, SLD can affect the behavior of pollinators and herbivores, but little is known about the combined effect of these three elements on plant reproduction.We evaluated the combined effect of SLD, insect pollinators and herbivores (ungulates) on three reproductive output variables (fruit set, seed set, and seed mass) of a Mediterranean shrub (Halimium halimifolium). We considered two different habitats (SLD verges vs. adjacent scrublands), two scenarios of herbivory (with and without ungulates), and three scenarios of pollinator activity (without pollinators, with manual pollination and with natural pollination).SLD had contrasting effects on H. halimifolium reproduction. In the absence of herbivores, overall fruit set was lower in the verges of SLD than in adjacent scrublands, probably due to lower flower pollination rates. Where herbivores were present, overall fruit set was similar between habitats, because ungulate browsing was lower in SLD verges than in adjacent scrublands. The quantity and weight of seeds per fruit was similar in both habitats, probably because all fertilized flowers received similar amounts of pollen.SLD can alter the interaction among pollinators, herbivores and plants, leading to changes in the reproductive performance of the latter. These changes can have strong negative impacts on endangered plants that rely on fruit and seed production to persist. However, SLD verges could be safe places for plants particularly sensitive to herbivory by ungulates.

Daily rhythm of mutualistic pollinator activity and scent emission in Ficus septica: ecological differentiation between co-occurring pollinators and potential consequences for chemical communication and facilitation of host speciation.

The mutualistic interaction between Ficus and their pollinating agaonid wasps constitutes an extreme example of plant-insect co-diversification. Most Ficus species are locally associated with a single specific agaonid wasp species. Specificity is ensured by each fig species emitting a distinctive attractive scent. However, cases of widespread coexistence of two agaonid wasp species on the same Ficus species are documented. Here we document the coexistence of two agaonid wasp species in Ficus septica: one yellow-colored and one black-colored. Our results suggest that their coexistence is facilitated by divergent ecological traits. The black species is longer-lived (a few more hours) and is hence active until later in the afternoon. Some traits of the yellow species must compensate for this advantage for their coexistence to be stable. In addition, we show that the composition of the scent emitted by receptive figs changes between sunrise and noon. The two species may therefore be exposed to somewhat different ranges of receptive fig scent composition and may consequently diverge in the way they perceive and/or respond to scents. Whether such situations may lead to host plant speciation is an open question.

Humans, bees, and pollination services in the city: the case of Chicago, IL (USA)

Despite the global trend in urbanization, little is known about patterns of biodiversity or provisioning of ecosystem services in urban areas. Bee communities and the pollination services they provide are important in cities, both for small-scale urban agriculture and native gardens. To better understand this important ecological issue, we examined bee communities, their response to novel floral resources, and their potential to provide pollination services in 25 neighborhoods across Chicago, IL (USA). In these neighborhoods, we evaluated how local floral resources, socioeconomic factors, and surrounding land cover affected abundance, richness, and community composition of bees active in summer. We also quantified species-specific body pollen loads and visitation frequencies to potted flowering purple coneflower plants (Echinacea purpurea) to estimate potential pollination services in each neighborhood. We documented 37 bee species and 79 flowering plant genera across all neighborhoods, with 8 bee species and 14 flowering plant genera observed on average along each neighborhood block. We found that both bee abundance and richness increased in neighborhoods with higher human population density, as did visitation to purple coneflower flower heads. In more densely populated neighborhoods, bee communities shifted to a suite of species that carry more pollen and are more active pollinators in this system, including the European honey bee (Apis mellifera) and native species such as Agapostemon virescens. More densely populated neighborhoods also had a greater diversity of flowering plants, suggesting that the positive relationship between people and bees was mediated by the effect of people on floral resources. Other environmental variables that were important for bee communities included the amount of grass/herbaceous cover and solar radiation in the surrounding area. Our results indicate that bee communities and pollination services can be maintained in dense urban neighborhoods with single-family and multi-family homes, as long as those neighborhoods contain diverse and abundant floral resources.

Investigating Lag Phase and Invasion Potential of Vitex rotundifolia: A Coastal Dune Exotic

Murren, C.J.; Purvis, K.G.; Glasgow, D.; Messervy, J.; Penrod, M., and Strand, A.E., 2014. Investigating lag phase and invasion potential of Vitex rotundifolia: a coastal dune exotic. After initial establishment in nonnative environments, exotic species are often found in low numbers for long periods of time. After a lag phase, a transition to an exponential growth phase is characteristic. A broad question remains: Can we identify factors that contribute to the lag phase or assess the potential for additional invasion? Our approach employed a case study of V. rotundifolia (beach vitex), a nonnative dune plant introduced in the late 1980s to North and South Carolina. We performed manipulative and observational experiments on the sexual and asexual reproductive ecology, mating system, seed ecology, and pollination ecology to assess the possibility of additional invasion potential and to gain an understanding of potential among population variation and among site ecological variation that could contribute to a transition from lag to exponential spread phases. We found that vegetative reproduction, sexual reproduction, and viable seed set rates are high, and there is future potential for spread through vegetative reproduction as not all the ovules set seed. Pollinator activity varied by year and was consistent with increased fruit and seed set, indicating a likely mechanism contributing to current sexual reproductive success. Germination rate was low, but given the high numbers of seeds produced per square meter, we estimate an average of 13 new germinants m−2 y−1. On the basis of our observations, we found the potential for increased reproductive success and increased invasion potential. Management practices that minimize vegetative expansion from nearby sites and through seed dispersal are the highest priority.

Contextualising pollination benefits: effect of insecticide and fungicide use on fruit set and weight from bee pollination in lowbush blueberry

AbstractCurrent approaches to determining the value of insect pollinators to crop yield assume that plants are primarily pollen limited. This is particularly relevant in a crop such as lowbush blueberry, Vaccinium angustifolium, where no fruit will set without insect‐mediated cross‐pollination. However, such valuations usually ignore other factors that are necessary to maximise crop yields. We conducted an experiment to test whether yields of lowbush blueberry attributed to pollinator activity increased independently of pest management. The experiment was a 2 × 2 factorial design, incorporating two intensities of pollination (25% or 100% of flowers), and two levels of insect and disease management with recommended fungicide and insecticide sprays (‘full inputs’ or ‘no inputs’). We demonstrated an interaction between these two factors, such that increased fruit set at harvest was only possible if 100% pollination was combined with the ‘full input’ treatment. Furthermore, increases in fruit weight among the remaining treatments were only realised in the ‘full input’ plots. These results suggest that the value accorded to pollinator activity in blueberries is strongly dependent upon pest and disease management of the crop.

Are there contrasted impacts of urbanization and land uses on population persistence? The case of Teucrium pseudochamaepitys, an endangered species in Southern France

Among the endangered flora of the Mediterranean basin, Teucrium pseudochamaepitys, endemic Lamiaceae, is threatened by human activities. The threats are even more important that its distribution in Mediterranean France is very limited. This study was based on the comparison of nine sites urbanized or impacted by other human activities. Particularly, the associated plant community, the density and reproductive parameters of the study species, and pollinator activities were compared to asset the effect of urbanization and land use changes on the local population persistence. Interestingly, in urban sites, the result shows more ruderal species and a higher density of T. pseudochamaepitys due to clonal growth. Surprisingly, reproductive success is low in each site despite an effective insect pollination. However, diversity of pollinators is lower in urban sites. Effects are thus contrasted considering urbanization and land use changes. Changes in land uses lead to closing landscape which threaten short term persistence of populations due to competition while the loss of pollinator diversity may impact urban populations over the long term only.

Sources of parthenocarpy for Zucchini breeding: relationship with ethylene production and sensitivity

Parthenocarpy is becoming an essential trait for off-season greenhouse production of Zucchini squash. Given that winter conditions promote a reduction in the number of male flowers and in the activity of pollinators, the application of synthetic auxins is currently the most widespread method to induce fruit set. We have evaluated the parthenocarpic tendency of 48 long-fruited accessions of Cucurbita pepo spp. pepo, from morphotypes Zucchini, Vegetable marrow and Cocozelle, including 45 traditional cultivars and 3 commercial hybrids, with the goal of identifying new sources of parthenocarpy for breeding programs. After the first screening, 20 selected accessions were evaluated for the growth rate of unpollinated fruit. Twelve of the selected accessions identified as either strongly parthenocarpic or non-parthenocarpic, were compared for fruit rate growth, ethylene production and ethylene sensitivity. Apart from the three control hybrids, the fastest parthenocarpic fruit growth was observed in ‘CpCAL112’, ‘CM-37’, ‘E-27’, ‘PI261610’, and ‘V-185’. The source of the parthenocarpy of some of these accessions differs from that of the hybrids as it was not associated with the conversion of female into bisexual flowers or with the so-called “fruits with attached flowers” syndrome, which is an undesirable trait in current parthenocarpic hybrids. The alternative sources of parthenocarpy may be of great importance in current Zucchini breeding programs. We also demonstrate that the parthenocarpy of these accessions is associated with downregulation of ethylene production in unpollinated fruits during the first days post anthesis (DPA). In non-parthenocarpic accessions, unpollinated fruits boosted ethylene production at 3 DPA, concomitantly with fruit abortion and senescence, while in parthenocarpic accessions, fruits produced little ethylene at 3 DPA. Therefore, ethylene production in ovaries/fruits at 3 DPA can be used as a marker to identify and select parthenocarpy in Zucchini squash. However, in the cultivars tested here, ethylene production and sensitivity in vegetative organs and in male flowers earlier than 3 PDA do not appear well associated with parthenocarpy.

Is the timing of scent emission correlated with insect visitor activity and pollination in long-spurred Satyrium species?

Plants are expected to emit floral scent when their pollinators are most active. In the case of long-tubed flowers specialised for pollination by crepuscular or nocturnal moths, scent emissions would be expected to peak during dawn. Although this classic idea has existed for decades, it has rarely been tested quantitatively. We investigated the timing of flower visitation, pollination and floral scent emissions in six long-spurred Satyrium species (Orchidaceae). We observed multiple evening visits by pollinaria-bearing moths on flowers of all study species, but rarely any diurnal visits. The assemblages of moth pollinators differed among Satyrium species, even those that co-flowered, and the lengths of moth tongues and floral nectar spurs were strongly correlated, suggesting that the available moth pollinator fauna is partitioned by floral traits. Pollinarium removal occurred more frequently during the night than during the day in four of the six species. Scent emission, however, was only significantly higher at dusk than midday in two species. Analysis of floral volatiles using gas chromatography coupled with mass spectrometry yielded 168 scent compounds, of which 112 were species-specific. The scent blends emitted by each species occupy discrete clusters in two-dimensional phenotype space, based on multivariate analysis. We conclude that these long-spurred Satyrium species are ecologically specialised for moth pollination, yet the timing of their scent emission is not closely correlated with moth pollination activity. Scent composition was also more variable than expected from a group of closely related plants sharing the same pollinator functional group. These findings reveal a need for greater understanding of mechanisms of scent production and their constraints, as well as the underlying reasons for divergent scent chemistry among closely related plants.

Pollination efficiency of Xylocopa olivacea (Hymenoptera: Apidae) on Cajanus cajan (Fabaceae) flowers at Yaoundé, Cameroon

To assess the impact of the carpenter bee, Xylocopa olivacea Fabricius 1787, on the pod and seed yields of Cajanus cajan (L.) Millsp. 1900, in this study, its foraging and pollinating activities were examined in Nkolbisson during two seasons (July 2008-January 2009 and June-December 2009). Observations were made on 180 inflorescences per treatment. The treatments included unlimited floral access to all visitors, bagging of flowers to prevent access to all visitors, and floral access to limited visits by X. olivacea only, fn addition, information on all floral visitors was recorded. The carpenter bee’s seasonal rhythm of activity, its foraging behaviour on flowers, its pollination efficiency, the fruiting rate (Fr) and the number of seeds per pod were recorded. Nineteen species of insects were recorded visiting the flowers of C. cajan. Chalicodoma cincta cincta was the most prominent one, followed by X. olivacea, Apis mellifera adansonii, Megachile bituberculata and Xylocopa albiceps, and the bees were the most frequent floral visitors. Xylocopa olivacea mainly foraged for nectar and pollen and its foraging speed was 11.75 flowers/min. The Fr, the number of seeds/pod and the percentage of normal seeds of unprotected inflorescences were significantly higher than those of inflorescences protected from insects. The foraging activity of X. olivacea resulted in a significant increase in the Fr by 22.26%, as well as the number of seeds/pod by 34.98% and the percentage of normal seeds by 12.09% in the two study years. Placing X. olivacea nests close to C. cajan fields is recommended to increase pod and seed production in Cameroon.

Foraging and pollination behaviour of Xylocopa olivacea (Hymenoptera: Apidae) on Phaseolus coccineus (Fabaceae) flowers at Ngaoundéré (Cameroon)

To evaluate the effect of the carpenter bee, Xylocopa olivacea Lepeletier 1841, on the pod and seed yields of Phaseolus coccineus L., in this study, its foraging and pollination activities were examined in Ngaoundere during the June-July 2010 and July-August 2011 cropping seasons. Treatments included open floral access to all visitors, bagging of flowers to avoid all visits and floral access to limited visits of X. olivacea. Observations were made on 120 flowers per treatment. In addition, all flower visitors were recorded. The seasonal rhythm of the activity of the carpenter bee, its foraging behaviour on flowers and its pollination efficiency (fruiting rate, number of seeds/pod and percentage of normal or well-developed seeds) were recorded. Phaseolus coccineus flowers were visited by 13 insect species in 2010 and by 14 insect species in 2011. Xylocopa olivacea was the most frequent visitor and intensely and exclusively foraged the flowers for nectar. The mean foraging speed was 9.28 flowers/min. In 2010, the foraging activity of X. olivacea resulted in a significant increase in the fruiting rate (27.49%), number of seeds/pod (45.43%) and percentage of normal seeds (89.38%). In 2011, the corresponding values were 56.14% (fruiting rate), 74.44% (number of seeds/pod) and 66.44% (percentage of normal seeds). These results reveal that this crop experiences a pollination deficit, considering that flowers visited by X. olivacea had higher yields than those under unlimited access to all visitors. Hence, the conservation of X. olivacea nests close to P. coccineus crop fields is recommended for improving pod and seed production.

Self-compatibility and floral traits adapted for self-pollination allow homostylous Nymphoides geminata (Menyanthaceae) to persist in marginal habitats

Many stylar polymorphic plants are equipped with reciprocal herkogamy and incompatibility systems so that each floral morph within a population can only mate with the compatible reciprocal morph. In the ecological or geographical margins of the range of stylar polymorphic taxa, homostyly may evolve in response to a lack of mate and/or poor pollinator visitation. This prediction is tested here by comparing floral traits, seed production without pollinators (i.e. autonomously), pollinator activity and ploidy level between the homostylous Nymphoides geminata that colonise geographically marginal habitats and its stylar polymorphic and self-incompatible closely related species N. montana that typically occur in natural water bodies in south-eastern Australia. Autonomous self-fertilisation is detected in glasshouse. Homostyly in N. geminata is also associated with floral adaptation to autonomous self-pollen deposition. There is a reduction in size and attractiveness of homostylous floral organs: over 80 % shorter stigma–anther separations and lower pollen:ovule ratio than the polymorphic flowers. The SEM images reveal that homostylous flowers possess similar pollen and stigma papillae morphology to those of short styles and long styles of the polymorphic flowers, respectively. Nymphoides geminata may be an example of recombinant homostyly: combining the pollen compatibility features of one morph with the stylar compatibility features of the reciprocal morph. Results of floral visitor observations and open pollinations indicate the ability of homostylous plants to reproduce successfully despite pollinator scarcity. Somatic chromosome counts indicate a possible lack of relationship between ploidy level and sexual system. Homostylous condition should provide an opportunity for reproductive assurance in environments with unreliable pollinators.

A vegetation-based indicator to assess the pollination value of field margin flora

Conservation of pollinator abundance and diversity is an important issue because it contributes to maintaining a diverse community of plant species in agroecosystems. The presence of semi-natural areas favorable to pollination is a key factor for achieving this objective of sustainability. Sowing mixtures of dicotyledonous plants that are rich in pollen and nectar as flower strips along field margins is an efficient solution to attract pollinators and to support their foraging activity on arable land. The enhancement of agroecosystems requires operational methods that make it possible to assess the impact of existing and sown semi-natural areas on pollination. We developed here a new predictive indicator that can be used at the field margin and floral levels, which predicts the pollination value of floral diversity and abundance of field margins on arable land.We based the predictive indicator on decision trees using “if-then” linguistic rules because of the lack of sufficient quantitative knowledge about the relationships between floral traits and pollination. This approach makes it possible to use quantitative and qualitative information. We associated fuzzy subsets to the decision trees and the classes of variables in order to avoid the knife-edge effect of class limits. At the species level, the indicator depends on three criteria: (i) visual attractiveness in terms of flower size, color and UV reflection; (ii) flower accessibility according to the botanical family, the symmetry and the shape of the flower; and (iii) the reward linked to pollen and nectar quantity and quality. An aggregation procedure allows us to obtain a value at the field margin level for each month as a function of the flowering period and pollination activity. Examples of calculations for honeybees, wild bees, bumblebees and hoverflies are shown.The evaluation of the predictive quality yielded significant correlations between pollinator abundance and the indicator value. The level of correlation is satisfying for this type of indicator, which might be further improved with additional data on plant traits. Coupling this indicator with a model that assesses the impact of management on plant diversity and abundance will be a further step to help agronomists who work on the improvement of arable farming management in order to lower its negative impact on pollination.

Invasive bees promote high reproductive success in Andean orchids

Most non-autogamous orchids rely on either a single, or on a small number of pollinators to set fruit. The nectar-rewarding orchid Brachystele unilateralis and the nectarless and deceit-pollinated Chloraea virescens are restricted to the Southern Andes, where a single native and endemic bumblebee (Bombus dahlbomii) occured until the introduction of honeybees and highly invasive European bumblebees. Here, we describe the floral features, breeding system, pollinator activity and fruiting success of these orchid species. Both are self-compatible but pollinator-dependent, i.e., unable to set fruit and seed in the absence of pollinators. Field observations revealed that most of their current reproductive success is due to the introduced Bombus terrestris, Bombus ruderatus and Apis mellifera bees. The only native pollinator recorded was B. dahlbomii, but this bee was rarely observed due to its steady decline since the introduction of the alien Bombus species. The observed natural fruiting success per inflorescence in both studied species proved to be remarkably high by orchid standards: 83% and 66%, respectively. These results suggest that sexual reproduction in these orchids is not necessarily threatened by the decline of their native pollinator since pollination is successfully achieved by introduced bees. This provides a plausible better outlook for these and other regional, bumblebee-pollinated orchids and raises caution on eventual conservation policies involving the management of these introduced bee species. To our knowledge, this is the first report of native orchid pollinators being effectively replaced by invasive bumblebees and, furthermore, the first description of the pollination biology of a species of Brachystele.

La polinización natural en el maracuyá (Passiflora edulis f. flavicarpa Degener) como un servicio reproductivo y ecosistémico.

El objetivo de esta investigacion fue estudiar los mecanismos de la polinizacion en el cultivo del maracuya y la importancia de los polinizadores naturales. El estudio se realizo en los anos 2010–2011, en el municipio de Palestina, Caldas, Colombia a 1050 msnm. Se emplearon cinco tratamientos de polinizacion: natural (P.N), manual dirigida (P.M.D), autopolinizacion manual y espontanea (A.P, A.P.E) y geitonogamia (G), en 48 accesiones de maracuya. Los resultados mostraron diferencias significativas entre tratamientos, la P.N realizada por abejorros del genero Xylocopa spp. obtuvo el mayor porcentaje de frutos formados (88%), seguido por P.M.D (60%), y solo un 3% en los tratamientos de autopolinizacion (A.P.E, A.P, G). De igual manera, la P.N presento mayor peso promedio del fruto (203 g) y porcentaje de pulpa mas semilla (47%) en comparacion a P.M.D (187,5 g y 44,7%). La actividad y efectividad de los polinizadores estuvo correlacionada con la temperatura maxima diurna (r=0,69), brillo solar (r=0,56) y humedad relativa (r=0,64). Cuando las dos primeras variables descendieron simultaneamente por debajo de 26°C y menos de tres horas por dia, se alcanzaron los mayores porcentajes de fructificacion.

Both biotic and abiotic factors influence floral longevity in three species of Epidendrum (Orchidaceae)

AbstractExtended flower longevity has been widely defended to occur as a consequence of low pollination activity. To test this hypothesis in Neotropical rainforests, we selected three species of Epidendrum that flower during rainy conditions and commonly exhibit low levels of insect visits. Experimental studies carried out in 15 populations distributed along a wide spatial gradient detected the presence of pollinator limitation in all populations. Pollinia removal without pollen deposition increased longevity, and thus extended longevity could apparently be considered as an ecological advantage for these orchids. Nevertheless, flower longevity was severely shortened by abiotic factors like precipitation and humidity. Comparison with other tropical orchids showed that flower longevity was higher even in species that flower during periods of more pollinator activity than the ones studied here, which is contrary to the hypothesis that pollinators are the only driving force for long‐lived flowers in Epidendrum. Thus, although long floral longevities are apparently favorable for the reproductive success of these species, the high maintenance costs experienced during rainy conditions are also an important factor constraining the selection of long‐lived flowers in Epidendrum.

Can ants equal honeybees as effective pollinators of the energy crop Jatropha curcas L. under Mediterranean conditions?

AbstractJatropha curcas L. is the subject of many research and breeding programs concerned with its potential as an oil crop for biodiesel production. Despite an increasing amount of information regarding this relatively new crop, pollination requirements of this plant are largely neglected. The aim of the study was to evaluate the relative significance of ants and honeybees as potential pollinators of J. curcas grown under Mediterranean conditions. Jatropha curcas plants bloomed throughout the summer and fall, peaking twice, in early summer and late fall. During this period, the plants were visited by 70 species of insects representing 45 families from seven orders, with most species rarely being observed. Ants and Honeybees were the most common species, accounting for >95% of all flower visits. The foraging behavior of the honeybees followed the pattern of bloom phenology, especially during the summer, and mostly promoted cross‐pollination. Ants on the other hand, mostly promoted self pollination showing no such correlative behavior, reacting often too late to nectar availability, and were highly susceptible to climatic changes. Pollinator exclusion treatments revealed that during summer, fruit and seed sets, as well as seed size and oil and protein contents, were relatively similar for ant and bee‐pollinated flowers. During fall, however, reproductive success of bee‐pollinated flowers was relatively high (66%), while fruit set of ant‐pollinated flowers was significantly reduced from 71 to 11%. In conclusion, while both groups are equal in their pollination effectiveness in the summer, during the fall the honeybees are almost the sole pollinators of the plant. Based on bloom phenology and pollination activity data, the honeybees are responsible for the pollination of more than 80% of the annual reproductive potential of J. curcas, under Mediterranean conditions.

Development of polymorphic microsatellite loci for Eupristina altissima, the pollinating wasp of Ficus altissima (Moraceae)

Fig trees are keystone resources of tropical forests, which are suffering from a rapid decline. Fig trees are pollinated by species-specific fig wasps. We developed 16 polymorphic microsatellites from Eupristina altissima, the only active pollinator of Ficus altissima. Numbers of alleles per locus ranged from 4 to 11. No significant linkage disequilibrium between pairs of loci was found. Four loci were significantly deviated from Hardy–Weinberg equilibrium in a population sampled from Hainan of China. These polymorphic microsatellite markers would be a useful tool for population genetic studies of E. altissima and coevolution with its host F. altissima.