Colour association influences honey bee choice between sucrose concentrations

Certain colours associated with floral food resources are more quickly learned by honey bees (Apis mellifera) than are other colours. But the impact of colour, and other floral cues, on bee choice behaviour has not yet been determined. In these experiments, colour association and sugar concentration of reward were varied to assess how they interact to affect bee choice behaviour. Thirty-five bees were individually given binary choices between blue and yellow artificial flowers that contained either the same rewards or rewards of different sucrose concentrations. Honey bee choice between sucrose concentrations was affected by colour association and this effect was greatest when absolute difference between rewards was the lowest. The honey bee's ability to maximize energetic profitability during foraging is constrained by floral cue effectiveness.     

反义RNA技术在植物基因工程领域中的应用

反义RNA技术在植物基因工程领域中的应用包括：a．番茄和其他水果的成熟控制;b．植物的抗病性;c．改变花卉的颜色;d．植物淀粉合成的控制;e．油料植物种子中脂肪酸合成的控制;f．杂交种子生产中雄性不育性的控制;g．其他.     

Tree recruitment at the treeline across the Continental Divide in the Northern Rocky Mountains,USA: the role of spring snow and autumn climate

ABSTRACT

Background: Topoclimate can influence tree establishment within treeline ecotones. Yet much less is known about how regional topography, such as the Continental Divide, Rocky Mountains, mediates the role of climate in governing treeline dynamics.

Aims: To utilise the Continental Divide to test whether contrasts in growing-season moisture regimes to the west (summer-dry) and east (summer-wet) impact the spatio-temporal patterns of tree establishment and rates of treeline advance in the Northern Rocky Mountains.

Methods: We sampled trees at sites on north- and south-facing slopes, west and east of the Continental Divide. We used dendroecological techniques to reconstruct patterns of tree establishment. Age-structure data were quantitatively compared with climate to evaluate possible mechanistic linkages.

Results: Across all sites, 96% of trees established after 1950. There was a treeline advance (range = 39–140 m) accompanied by increases in tree density. Significantly more trees established during wet springs on both sides of the Divide.

Conclusions: Overall, snow duration in spring and autumn temperatures appear to influence patterns of tree recruitment at the treeline. Continued warming will likely amplify the role of autumn climate in regulating tree establishment throughout treeline ecotones in the Northern Rocky Mountains, particularly west of the Divide where summer-dry conditions persist.     

Spatial patterns of white stork (Ciconia ciconia) migratory phenology in the Iberian Peninsula

In contrast to the attention attracted by temporal trends of phenology, the spatial patterns of arrivals, departures or stays of trans-Saharan birds are still nowadays largely unknown in most of their European breeding areas. In the case of the white stork (Ciconia ciconia), some studies have attempted to describe its migratory patterns throughout some European countries but, to our knowledge, no one has related these patterns to some kind of explanatory variable which offers an ecologically-based explanation for the heterogeneous phenology observable among populations. Here, arrivals, departures and stays of this species, recorded in hundreds of Spanish localities, were related to a set of environmental, geographical, biological and spatial predictors, and modeled by multiple regression. The best model for arrival dates accounted for up to 34% of variability of data and pointed towards an earlier arrival in those populations located in south-western Iberia and with higher population densities. This last relationship is probably due to the competition for nest-site fidelity maintenance. However, no variable was able to explain properly the blurred spatial pattern recorded for departure dates. Departure decisions are strongly influenced by social behavior in this species and depend on collective decisions influenced by peculiar local environmental conditions of each year rather than macrogeographical gradients. Environmental, geographical or spatial variables also did not capture much of the observed variability in the length of the stays among populations. However, this variable was strongly related to the arrival and departure dates of populations. White storks stay longer in localities with earlier arrivals and, especially, later departures.     

Do leaf domatia mediate intraguild predation and host plant resistance to Oligonychus aceris (Shimer) on Red Sunset Maple (Acer rubrum)?

The predatory mites Neoseiulus fallacis (Garman) (Acarina: Phytoseiidae) and Zetzellia mali (Ewing) (Acarina: Stigmaeidae) have the potential to suppress populations of Oligonychus aceris (Shimer) (Acarina: Tetranychidae) on maple cultivars under field conditions. Red Sunset red maples (Acer rubrum) are more resistant to O. aceris than ‘Autumn Blaze’ Freeman maple (Acer × fremanii). Examination of leaves indicated that the mite resistant Red Sunset trees had more leaf domatia than those from Autumn Blaze. Laboratory assays found that maple cultivars did not affect rates of O. aceris consumption by N. fallacis or Z. mali in a 24 h period. Each predator exhibited distinct preferences for O. aceris life stages. N. fallacis consumed significantly more protonymphs and adults of O. aceris, whereas Z. mali consumed more eggs. In contrast, maple cultivars significantly influenced rates of intraguild predation between phytoseiids and stigmaeids. Adult N. fallacis consumed more immature stages of Z. mali on Autumn Blaze than on Red Sunset maple, but adult Z. mali consumed the same numbers of N. fallacis nymphs on both cultivars. These findings provide a potential mechanism to explain the resistance of Red Sunset maples to O. aceris. On Red Sunset maples, where domatia provide Z. mali with refugia from predation by N. fallacis, both predators can contribute to the mortality of O. aceris. In contrast on Autumn Blaze maples Z. mali have no place to hide from N. fallacis, so the contribution of this stigmaeid to O. aceris mortality is greatly diminished. Thus, differential susceptibility of these cultivars to spider mites may be mediated by the capacity of leaf domatia to influence rates of intraguild predation among phytoseiid and stigmaeid predators.     

Sexual reproduction advances autumn leaf colours in mountain birch (Betula pubescens ssp. czerepanovii)

Autumnal change in leaf colour of deciduous trees is one of the most fascinating displays in nature. Current theories suggest that autumn leaf colours are adaptations to environmental stress. Here I report that the number of ripening female catkins altered timing of yellow autumn leaf colours in mountain birch. The tree's autumnal colour change was brought forward if the tree matured plenty of female catkins. Since yellow colour pigments in leaves are unmasked as leaf nitrogen is re-translocated, sexual reproduction may alter resource allocation at times of leaf senescence. Thus, our current view on the reasons for leaf senescence has to be re-examined, and a novel evolutionary explanation is needed for the appearance of yellow autumn leaf colours.     

Coevolution and the adaptive value of autumn tree colours: colour preference and growth rates of a southern beech aphid

The evolutionary explanation for the change in leaf colour during autumn is still debated. Autumn colours could be a signal of defensive commitment towards insects (coevolution) or an adaptation against physical damage because of light at low temperatures (photoprotection). These two hypotheses have different predictions: (1) under the coevolution hypothesis, insects should not prefer red leaves in autumn and grow better in spring on trees with green autumn leaves; and (2) under the photoprotection hypothesis, insects should prefer and grow better on trees with red leaves because they provide better nutrition. Studying colour preference in autumn and growth rates in spring of a southern beech aphid species (Neuquenaphis staryi) on Nothofagus alessandrii, we found preference for green leaves in autumn but no differential performance of aphids in spring. We suggest that aphid preference for green might have evolved to exploit better their host during the autumn rather than to improve their performance in spring.     

Something for the weekend? Examining the bias in avian phenological recording

In this paper we examine the bias towards weekend recording (the weekend effect) in volunteer phenology, using over 14,000 bird migration phenological observations from eight locations in the UK as a data source. Data from 45 bird species were used. Overall, 44% of all records were taken at weekends in contrast to the 28.6% (i.e. two out of seven days) that would be expected if records were evenly spread throughout the week. Whilst there is documented evidence of environmental differences at weekends, particularly in large urban areas, we believe the weekend effect is mostly a consequence of greater recorder effort at weekends. Some birds, likely to be obvious by their behaviour or abundance, had fewer weekend records than the remaining species. The weekend effect, to some extent, differed between locations and between seasons. There was some evidence that, particularly in autumn, the weekend bias may be lessening. If so, this will increase the accuracy of phenological records, making the detection of changes and responses to temperature easier.     

Between-species correlations in the number of migrants at Ulmeth?chi (Switzerland)

We analysed the number of autumn migrants at a bird ringing station over 41 years in the Jura mountains of Switzerland. For 12 irruptive or potentially irruptive bird species, the correlations between their numbers per year were calculated and the species were clustered accordingly. We found high correlations in the number of migrants between the Coal Tit Periparus ater, Great Tit Parus major and Blue Tit Cyanistes caeruleus. Most correlations of passage number between species pairs changed dramatically over time. Only Blue Tit and Coal Tit showed continuously high correlation in this respect. The variation and changes over time in between-species correlations in the number of migrants needs more attention.