To forage effectively amongst flowers, some bee species utilize olfactory cues left by previous visitors in addition to direct
assessment of visual cues to identify rewarding flowers. This ability can be more advantageous if the bees can recognize and
use scent marks left by heterospecifics, not just marks left by members of their own species. We conducted field experiments
to investigate whether the sweat bee Halictus aerarius avoids visiting flowers of trailing water willow Justicia procumbens emptied by other bee species. We found that H. aerarius rejected the flowers visited by both heterospecifics and conspecifics. They also rejected visited flowers artificially replenished
with nectar. Our results demonstrate that social bees outside the Apidae can detect marks left on flowers by heterospecifics
but that (on this plant species) they are unable to discriminate against flowers by directly detecting nectar volume. H. aerarius exhibited different rejection rates according to the identity of the previous bee species. We suggest that the frequency
of rejection responses may depend on the amount of chemical substances left by the previous bee. In general, the use of scent
marks left by previous visitors is almost certainly advantageous, enabling foragers to avoid flowers with depleted nectar
levels and thereby improving their foraging efficiency. 相似文献
The use of recycled material is a key building block for the circular economy. In this study, we explore the impact of recycling laws in Japan on the use of recycled materials in the production process of intermediate plastics. Using a difference-in-differences approach, we investigate whether the input share of recycled plastics in intermediate plastic products increased after the Container and Packaging Recycling Law (CPR Law) was enforced in 1997 in Japan. Results indicate that the input share of recycled plastics increased by 1 percentage point after the law’s implementation. Meanwhile, the input share of virgin plastic materials, such as polyethylene, polypropylene, and vinyl chloride, per plastic product decreased by 3 percentage points on average. These results suggest that the CPR law helped shift inputs from virgin plastics to recycled plastic materials even though the impact size has been small. To further encourage the use of recycled plastic materials, policy interventions should directly incentivize producers to increase the use of recycled plastics.
Suspended particulate matter (SPM) and fine particulate matter (less than or equal to 2.5 μm: PM2.5) have generally been decreasing for the last decade in Tokyo, Japan. To elucidate the major cause of this decrease, the authors investigated the different trends of airborne particulates (both SPM and PM2.5 concentrations) by evaluating comparisons based on the location of the monitoring stations (roadside vs. ambient), days of the week (weekdays vs. Sundays), and daily fluctuation patterns (2002 vs. 2010). Hourly mean SPM and PM2.5 concentrations were obtained at four monitoring stations (two roadside stations, two ambient stations) in Tokyo, Japan. Annual mean concentrations of each day of the week and of each hour of the day from 2002 to 2010 were calculated. The results showed that (1) the daily differences in annual mean concentration decreased only at the two roadside monitoring stations; (2) the high hourly mean concentrations observed on weekdays during the daily rush hour at the two roadside monitoring stations observed in 2002 diminished in 2010; (3) the SPM concentration that decreased the most since 2002 was the PM2.5 concentration; and (4) the fluctuation of hourly concentrations during weekdays at the two roadside monitoring stations decreased. A decreasing trend of airborne particulates during the daily rush hour in Tokyo, Japan, was observed at the roadside monitoring stations on weekdays since 2002. The decreasing PM2.5 concentration resulted in this decreasing trend of airborne particulate concentrations during the daily rush hours on weekdays, which indicates fewer emissions were produced by diesel vehicles.
ImplicationsThe authors compared the trends of SPM and PM2.5 in Tokyo by location (roadside vs. ambient), days of the week (weekdays vs. Sundays), and daily fluctuation patterns (2002 vs. 2010). The high hourly mean concentrations observed at the roadside location during rush hour on weekdays in 2002 diminished in 2010. The SPM concentration that decreased during rush hour the most was the PM2.5 concentration. This significant decrease in the PM2.5 concentration resulted in the general decreasing trend of SPM concentrations during the rush hours on weekdays, which indicates fewer emissions were produced from diesel vehicles. 相似文献
Flow regulation causes various environmental impacts in the downstream reaches of impounded rivers. The S?o Francisco River
(SF) basin is Brazil’s third most important watershed. Several dams have been built in its course in the last four decades,
mostly for flow regulation and hydropower generation. This paper presents an evaluation of historical changes in the flood
regime. Three regions of the SF River basin, which are under the influence of different levels of regulation, were studied:
the lower, middle, and upper SF River. The components of magnitude, frequency, and duration of floods were quantified for
each region from 1940 to 1960 (prior to the construction of the first dam) and from 1986 to 2006 (after the last dam). The
results have shown the inexistence of big floods in the downstream areas, decreasing durations of small floods as well as
significant changes in the annual seasonality of floods. Reductions in the flood frequency were verified in all stretches,
even in non-regulated systems, such as the lower Velhas River. The climate variation, which occurred in both period, was not
able to explain the changes in the flood regime of S?o Francisco River; therefore, dams and other anthropogenic activity are
the main factors promoting the temporal variability of streamflows in the S?o Francisco basin. 相似文献
To understand the evolution of weapons, we must understand both their functions and relative importance compared to body size
in determining fighting success. Many decapod crustaceans develop disproportionately large chelipeds for their body size and
use them as a weapon in agonistic interaction. There are, however, examples where weapons are merely signals of resource holding
potential (RHP) and the RHP is actually determined by body size. We investigated the function and relative efficacy of body
size and major cheliped size in male–male contests for females in the hermit crab Diogenes nitidimanus. Contests over females took two forms: (1) males preemptively guarded females and opponents did not fight with the guarding
male. Cheliped size contributed significantly to the settlement of these contests and probably functioned as a visual signal
for the opponents. (2) Guarding males engaged in physical combat with an opponent. In these cases, both body and cheliped
sizes affected contest outcomes. The effect size for cheliped size was as strong, or stronger, than that for body size. These
results suggest that large chelipeds have evolved as a true weapon and are effective in escalated fights for resources. Therefore
they are also efficient visual signals for settling contests with only display. Our results are a rare example that clearly
demonstrate that weapons are a more important determinant of fights than body size when both body and weapon size affect resource
acquisition. 相似文献
Sweet potato shochu is a traditional Japanese spirit produced mainly in the South Kyushu area in Japan. The amount of stillage reaches approximately 8 × 105tons per year. Wastewater mainly containing stillage from the production of sweet potato-shochu was treated thermophilically in a fullscale treatment plant using fixed-bed reactors(8 reactors × 283 m3). Following the addition of Ni2+ and Co2+, the reactors have been stably operated for six years at a high chemical oxygen demand(COD) loading rate of 14 kg/(m3·day). Analysis of coenzyme content and microbial communities indicated that similar microbial communities were present in the liquid phase and on the fiber carriers installed in reactors. Bacteria in the phyla Firmicutes as well as Bacteroidetes were dominant bacteria, and Methanosarcina thermophila as well as Methanothermobacter crinale were dominant methanogens in the reactors. This study reveals that stillage from sweet potato-shochu production can be treated effectively in a full-scale fixed-bed reactor under thermophilic conditions with the help of Ni2+and Co2+. The high diversity of bacterial community and the coexistence of both aceticlastic and hydrogenotrophic methanogens contributed to the excellent fermentation performance. 相似文献