“Liaisons dangereuses”: The invasive red-vented bulbul ( Pycnonotus cafer ), a disperser of exotic plant species in New Caledonia

International audienceThe biodiversity hotspot of New Caledonia hosts high levels of endemism (74% of flora) that is threatened increasingly by climate change, habitat reduction, and inva-sive species. The fruit-eating red-vented bulbul (Pycnonotus cafer) is currently invading the main island of the archipelago, and its recent dispersal out of urbanized habitats raises questions about its potential to disperse noxious plant seeds along urban corridors and beyond. Indeed, the red-vented bulbul is considered a vector of several introduced plant species in its alien range including Miconia calvescens, Lantana camara, and Schinus terebinthifolius. We conducted a quantitative assessment of the bulbul's fruits consumption by analyzing the gut contents of shot birds. We estimated gut passage times for four species of fruit found in gut contents (S. terebin-thifolius, Myrtastrum rufopunctatum, Passiflora suberosa, and Ficus prolixa) and tested the effects of bird digestion on seed germination rates for two species. Finally, we monitored the movements of individual VHF radio-tagged red-vented bulbuls. All of the consumed fruit species we identified here have red fleshy diaspore, including fruit of the shrub M. rufopunctatum that occurred frequently (9.6%) in bulbul gut samples. Median gut passage times were short (15-41 min), corresponding to short-distance seed transportation (77-92 m). The effect of gut passage was positive for the germination of the invasive S. terebinthifolius and negative for the endemic M. ru-fopunctatum, suggesting a potential bias in the contribution to the dispersal toward alien species. This study provides the first integrated assessment of mechanisms involved in the seed dispersal effectiveness of this high-concern invasive bird species that is expected to face similar plant communities in most of its alien range in tropical islands. More generally, our results enhance knowledge of synergies between non-native frugivores and plant species dispersal

Flight Durations in Bumblebees under Manipulation of Feeding Choices

Foraging bees spend less time flying between flowers of the same species than when flying between individuals of different species. This time saving has been suggested as a possible advantage of flower-constant foraging. We hypothesized that the time required to switch flower type increases if (a) such switches are infrequent and (b) the bees need to decide whether to switch or not. Laboratory reared bumblebees were taught to forage on artificial feeders that were identical in morphology and reward schedule, but were marked by either a blue or a yellow landing surface. In the first two experiments bees foraged alternatively between two feeders. The landing surface was manipulated to coerce the bees to perform either a color-constant or a color-shift flight movement. In Experiment 1 we switched the landing surfaces every 2-3 visits, while in Experiment 2 the bees performed 6-7 color-constant flights before having to perform a color-shift flight. In the third experiment, the bees were presented with binary choices and had to decide to make a color-constant or a color-shift flight. When feeder colors were changed frequently (Experiment 1), we detected no difference between color-constant and color-shift inter-visit times. When bees were repeatedly exposed to one color (Experiment 2), color shifts required a significantly longer time than color-constant flights. When allowed to choose (Experiment 3), bees performed more color-constant flights than color-shift flights. Inter-visit times were similar for color-constant and color-shift flights in this experiment. Overall flight times were slightly but non-significantly longer than in experiments 1 and 2. The results suggest that bees indeed save flight time though flower-constant foraging. However, this time saving is small (~ 1 s / flower visit), and appears only when switches between flower types are infrequent. Additional selective advantages likely favor flower-constant foraging.bees; flight time; flower constancy; handling time; search image

Sea‐air flux of CO2 in the North Pacific using shipboard and satellite data

A method has been developed to produce high‐resolution maps of pCO2 in surface water for the North Pacific using satellite sea surface temperature (SST) data and statistical relationships between measured pCO2 and temperature. In the subtropical North Pacific the pCO2 in seawater is controlled primarily by temperature. Accordingly, pCO2 values that are calculated from the satellite SST data have good agreement with the measured values (rms deviation of ±17 μatm). In the northwestern subpolar region the pCO2 is controlled not only by temperature, but also by significant seasonal changes in the total CO2 concentration, which are caused by seasonal changes in primary production, mixing with subsurface waters, and sea‐air exchange. Consequently, the parameterization of oceanic pCO2 based on SST data alone is not totally successful in the northwestern region (rms deviation of ±40 μatm). The use of additional satellite products, such as wind and ocean color data, as planned for a future study, is considered necessary to account for the pCO2 variability caused by seasonal changes in the total CO2 concentration. The net CO2 flux for the area of the North Pacific included in this study (north of 10°N) has been calculated using the monthly pCO2 distributions computed, and monthly wind speeds from the European Centre for Medium‐Range Weather Forecasts. The region is found to be a net source to the atmosphere of 1.9×1012 to 5.8×1012 moles of CO2 per year (or 0.02–0.07 Gt C/yr), most of the outflux occurring in the sub tropics

Seasonal migration, employer-worker interactions, and shifting ethnic identities in contemporary West Bengal

This article tells of changing social and spatial identities in the countryside of con temporary West Bengal. It draws on a study of interactions between those seeking wage work in agriculture and the people trying to recruit them. We find a continuing and nested process of both self-identification and categorisation. Unconscious as well as conscious ethnic affinities are consolidated and changed. At the same time, identities are used instrumentally by workers to make the outcome of negotiations less demeaning, and by employers to bargain more effectivelyfor the workforce they need. The context is one of the emergence of capitalist production relations in agriculture, presided over by a coalition government led by the Communist Party of India (Marxist). The newly pros perous agriculture has been a source of wealth for capitalist employers, reinforcing constructions of difference in relation to the migrant workers they employ. At the same time, many employers are attracted by the prospects of urban,jobs and life-styles and invest in their children's education. Migrant workers show a similar ambivalence, being attracted by the potential earnings and consumption possibilities arising out of being employed in the West Bengal 'rice bowl', and simultaneously repelled by the dangers they associate with the place

Thigh-length compression stockings and DVT after stroke

Controversy exists as to whether neoadjuvant chemotherapy improves survival in patients with invasive bladder cancer, despite randomised controlled trials of more than 3000 patients. We undertook a systematic review and meta-analysis to assess the effect of such treatment on survival in patients with this disease