Bumblebee flight distances in relation to the forage landscape

1. Foraging range is a key aspect of the ecology of 'central place foragers'. Estimating how far bees fly under different circumstances is essential for predicting colony success, and for estimating bee-mediated gene flow between plant populations. It is likely to be strongly influenced by forage distribution, something that is hard to quantify in all but the simplest landscapes; and theories of foraging distance tend to assume a homogeneous forage distribution. 2. We quantified the distribution of bumblebee Bombus terrestris L. foragers away from experimentally positioned colonies, in an agricultural landscape, using two methods. We mass-marked foragers as they left the colony, and analysed pollen from foragers returning to the colonies. The data were set within the context of the 'forage landscape': a map of the spatial distribution of forage as determined from remote-sensed data. To our knowledge, this is the first time that empirical data on foraging distances and forage availability, at this resolution and scale, have been collected and combined for bumblebees. 3. The bees foraged at least 1.5 km from their colonies, and the proportion of foragers flying to one field declined, approximately linearly, with radial distance. In this landscape there was great variation in forage availability within 500 m of colonies but little variation beyond 1 km, regardless of colony location. 4. The scale of B. terrestris foraging was large enough to buffer against effects of forage patch and flowering crop heterogeneity, but bee species with shorter foraging ranges may experience highly variable colony success according to location.     

Consistent mixing of near and distant resources in foraging bouts by the solitary mason bee Osmia lignaria

Female bees are usually confronted with a choice among severalflower species that differ in their location and abundance withinthe community, and in the efficiency with which their pollenand nectar can be harvested. We investigated the effects ofdistance and flower density of two flower species on pollencollection by providing nest locations for the mason bee Osmialignaria in natural settings. Distance weakly affected pollenuse; on average, bees nesting near a flower species tended tocollect more of its pollen than did bees nesting at a greaterdistance. Flower density did not predictably impact pollen use,and use did not track changes in density during the season.Bees consistently mixed pollen from more distant species, despitesubstantial added foraging costs, and also mixed when one specieswas an order of magnitude less abundant than the other. Beesrequire nectar as well as pollen to feed their offspring, andour preliminary data suggest that the efficiencies of pollenand nectar collection are inversely related between the twoflower species, which would favor visitation to both species.Bees appear to collect some pollen from the low-pollen, high-nectarplant while visiting it for nectar. Thus, a nectar-collectingconstraint may favor collecting pollen from mixtures of species.     

角额壁蜂在苹果梨园生活力下降的原因分析

采用测定苹果梨和苹果的花粉量以及对其主要营养成分进行定量分析的方法,探椭角额壁蜂Osmia cornifrons(Radoszkowski)在苹果梨园生活力下降的主要原因。结果表明,苹果梨花粉的花粉量约为苹果花粉的1/3,是角额壁蜂在苹果梨园的繁殖比明显低于苹果园的主要原因;苹果梨花粉与红富士等苹果花粉相比,在主要营养物质方面具有高糖、高纤维,低蛋白、低水分的特点,在矿质营养方面,苹果梨花粉具有高Ca和Mg,低Fe和Zn的特点。这些差异是引起连续使用苹果梨园的角额壁蜂出茧率和活动能力逐年下降的主要原因。     

A practical approximation of pollen dispersal–deposition for calculation of pollen productivity and quantification of vegetation

We compared simple mathematical pollen dispersal–deposition models with Gaussian plume models. The simple mathematical models proved equal or better approximations of real world pollen dispersal–deposition. We concluded that for most standard applications, such as estimating pollen productivity or quantitative vegetation reconstructions, simple mathematical models would perform satisfactory. Such easy-to-use models may lower the threshold to employ quantitative tools to palaeoecological questions.     

Rhythmical timing and spatial scattering of foraging in a homer limpet {Patella rustica)

Homing to a more or less permanent scar after each foragingexcursion is a common movement pattern among intertidal gastropodsand chitons; however, details of the timing and spacing of foragingactivity have been investigated only in a few species. The presentstudy analyzes the short-term behavior of the limpet Patellarustica along the Tyrrhenian coast, Italy, using a motographictechnique to assess the fine organization of its foraging duringfavorable periods of sea roughness. P. rustica becomes activeonce the upper midlittoral is well splashed. It alternates foragingexcursions and resting at home with a periodicity slightly longerthan 12 h, suggesting a tidal-diel pattern. However, periodogramanalysis of the sea level oscillations during the study periodsrevealed no such rhythmicity because tidal oscillations werehidden by irregular variations caused by waves. As a resultof this time partitioning, limpets move, on average, less than50% of their potential activity time. Time partitioning maybe highly adaptive in reducing potential risks. Nevertheless,in the absence of clear external driving cues, the significanceof a very regular and apparently tidal pattern, fairly synchronousamong the different specimens, remains to be explained. Theactivity of P. rustica during each excursion is organized intothree parts: the outgoing journey during which grazing activityprogressively increases, a central part characterized by intensegrazing, and the return characterized by fast displacement anda more or less consistent trail following. Limpets head forrandom directions to reach foraging grounds in successive excursions,showing only a slight avoidance of the direction taken duringthe previous outward journey. This pattern produces a spatialscattering of grazing activity, allowing efficient exploitationof grazing areas distributed radially around home during subsequentexcursions.     

Air pollen dispersal in a tropical area

Volumetric data on airborne pollen have been gathered for two consecutive years at a neotropical location (Caracas). Among the 65 taxa which were identified, pollen from aCupressus species (introduced) and from aCecropia species (indigenous) were dominant. Less numerous but also abundant (daily averages ≥5 grains/m³ air) were pollen from Gramineae, Urticaceae,Alcalypha, Pinus, Piperaceae andMimosa. Pollen grains were recorded daily throughout the year. They increased in numbers during April–May and again during November–December. The first peak was contributed mainly by indigenous species, the second peak mainly by introduced species.     

The relationships between the surface arboreal pollen and the plants of the vegetation in China

This paper attempts to test the relationships between the surface arboreal pollen and the plants across the entire vegetation of China. Twelve genera from major arboreal plants are selected from 680 pollen taxa in a total of 803 surface pollen assemblages for this excise. The pollen data are quantitatively compared with the gridded vegetation map on spatial similarity, direction and distance of pollen dispersal, and pollen accuracy for indicating the plant distribution density.The results show that the distributions of the pollen taxa can reflect the major patterns of the plants. Abies, Larix, Picea, Pinus, Quercus and Betula exhibit high spatial similarities between pollen and source plants. The accuracy for Tsuga, Platycarya, Fagus and Cyclobalanopsis is relatively low, probably due to the low pollen productivities and the absence of samples from southern China. In the disagreement part of the pollen-plant accuracy percentage, the pollen taxa Larix, Platycarya, Fagus and Cyclobalanopsis have high proportions in underestimating plants, likely a “convergent-type” in the pollen deposition; while pollen Tsuga, Quercus, Pinus, Betula and Ulmus have high proportions in overestimating plants, likely a “divergent-type” in the pollen dispersal.Pollen dispersal estimates suggest that southward transportation of the 12 pollen taxa is dominant, and the transport distance can be up to ca. 1000 km. This is mainly caused by several months of persistent north winds from the winter monsoon, particularly in spring seasons in eastern China. The second highest pollen dispersal direction is eastward, which occurs mainly in the boreal or sub-boreal plants of Larix, Abies, Picea, Betula and Acer and is likely influenced by the Westerlies in the mid-latitudes of China. Summer-green and evergreen Platycarya, Fagus and Cyclobalanopsis are mainly dispersed to the north, reflecting the influence of the Asian summer monsoon in eastern and southern China. Results of spatial differentiation analysis using accuracy weighting suggest that the low percentage portion (1-10%) in pollen of Abies, Picea, Betula and Quercus and high percentage portion (>40%) in pollen Pinus are acceptable for the plant representatives.These results, based upon the analyses of surface pollen and modern vegetation types of China, can provide important information for testing the various methods for reconstructing and modelling the environmental or climatic parameters during the recent geological past from palaeovegetation data.     

Effects of male fecundity, interindividual distance and anisotropic pollen dispersal on mating success in a Scots pine (Pinus sylvestris) seed orchard

Quantifying the effect of pollen dispersal and flowering traits on mating success is essential for understanding evolutionary responses to changing environments and establishing strategies for forest tree breeding. This study examined, quantitatively, the effects of male fecundity, interindividual distance and anisotropic pollen dispersal on the mating success of Scots pine (Pinus sylvestris), utilizing a well-mapped Scots pine seed orchard. Paternity analysis of 1021 seeds sampled from 87 trees representing 28 clones showed that 53% of the seeds had at least one potential pollen parent within the orchard. Pronounced variation in paternal contribution was observed among clones. Variations in pollen production explained up to 78% of the variation in mating success, which was 11.2 times greater for clones producing the largest amount of pollen than for clones producing the least pollen. Mating success also varied with intertree distance and direction, which explained up to 28% of the variance. Fertilization between neighboring trees 2.3 m apart was 2.4 times more frequent than between trees 4.6 m apart, and up to 12.4 times higher for trees downwind of the presumed prevailing wind direction than for upwind trees. The effective number of pollen donors recorded in the seed orchard (12.2) was smaller than the theoretical expectation (19.7). Based on the empirical observations, a mating model that best describes the gene dispersal pattern in clonal seed orchards was constructed.