Colonization and early succession on artificial hard substrata by meiofauna

An experiment was undertaken at Farol Island, Brazil, to examine colonization of bare aluminium surfaces by microbes and meiofauna. It was hypothesized that a primary source of meiofaunal colonists was sediment resuspended during upwelling events, two of which occurred during the experiment. Microbial biofilms formed on the experimental substrata within 1 day, and continued to develop throughout the experimental period. Among meiofaunal groups copepods also appeared on the first day, and nematodes on the second. Meiofaunal community structure developed in three main phases: an initial phase of 2 days, characterized by low abundances of copepods; a second phase during the first upwelling period characterized by higher abundances of copepods and also by turbellarians; and a third phase from day 13 onwards characterized by relatively stable abundances of a range of taxa including copepods, cirripedes, nematodes and ostracods. Nematode assemblages also developed in three phases, but with different timings coinciding with upwelling events: an initial phase, from the beginning of the experiment to day 9, characterized by few species and low (or no) abundances; a second phase following the first upwelling characterized by moderate abundances of Chromadorina, Chromadorella, Daptonema and Euchromadora sp. 3; a third phase following the second upwelling period (from day 26 onwards) in which Daptonema disappeared and the assemblage was characterized by moderate to high abundances of Euchromadora (species 1 and 2) and Chromadorella. Although shifts in nematode assemblage structure coincided with upwelling events no evidence was found for sediments being the primary source of colonizers on the aluminium substrata, in contrast to our hypothesis.     

Variation in copulation duration in Mnais pruinosa pruinosa Selys (Odonata: Calopterygidae)

Summary The Japanese calopterygid damselfly Mnais pruinosa pruinosa shows three distinct copulation durations (Siva-Jothy and Tsubaki 1989). A variety of factors which might influence copulation duration were investigated. Results indicate that the temperature in the vicinity of copulating pairs, the rate at which males encountered receptive females, territory quality, the rate of agonistic interactions between males, female gravidity and female willingness to oviposit have no effect on copulation duration. The most significant factor was the location of the site at which males captured their mates. We suggest that under natural conditions the location of the capture site provides males with reliable, indirect information about a female's intention to oviposit: it is important for males of this species to acquire such information since sperm precedence, and therefore reproductive success, is in part dependant on the interval experienced by females between copulation and subsequent oviposition. The results are discussed and it is suggested that the three observed mate-securing tactics of M.p. pruinosa are facultative and information-dependant.     

Did the Clean Air Act cause the remarkable decline in sulfur dioxide concentrations?

Over the last three decades, ambient concentrations of sulfur dioxide (SO₂) air pollution have declined by approximately 80%. This paper tests whether the 1970 Clean Air Act and its subsequent amendments caused this decline. The centerpiece of this legislation is the annual assignment of all counties to SO₂ nonattainment or attainment categories. Polluters face stricter regulations in nonattainment counties. There are two primary findings. First, regulators pay little attention to the statutory selection rule in their assignment of the SO₂ nonattainment designations. Second, SO₂ nonattainment status is associated with modest reductions in SO₂ air pollution, but a null hypothesis of zero effect generally cannot be rejected. This finding holds whether the estimated effect is obtained with linear adjustment or propensity score matching. Overall, the evidence suggests that the nonattainment designation played a minor role in the dramatic reduction of SO₂ concentrations over the last 30 years.     

液相色谱/质谱用于饮用水和地下水中的苯脲及三嗪草类除草剂的确认分析

本文介绍了液相色谱／大气压化学电离-质谱联用技术作为确认方法，检测饮用水和地下水中苯脲及三嗪草类除草剂的残留。共分析了16种除草剂，同时对分析方法进行了验证，其中标准偏差、离散度等结果均能满足饮用水的标准方法指南。     

Seasonal variation and social correlates of androgen excretion in male redfronted lemurs (Eulemur fulvus rufus)

The aim of this study was to examine effects of seasonal and social factors on male androgen excretion in a seasonally breeding primate living in multimale-multifemale groups. By combining detailed behavioural observations (>2,500 h) on 3 groups of redfronted lemurs living in Kirindy Forest/Madagascar with non-invasive hormone analysis of >800 faecal samples collected concomitantly from the same animals, we tested predictions on: (1) the effect of social status on immunoreactive testosterone (iT) excretion; (2) seasonal variation of iT across reproductive periods; and (3) the relationship between aggression and iT excretion. The study lasted 14 months, covering two mating and one birth season. The results revealed that males fall into two distinct social classes, with one dominant male and several subordinate males in each group. In contrast to our prediction, the behavioural differences between these two classes were not reflected by differences in androgen levels, making physiological suppression of testicular function an unlikely mechanism of male reproductive competition. As expected for a seasonally breeding animal, iT values were elevated during the mating season. Androgen levels tracked the increase in the rate of reproductive aggression during the mating season as predicted by the challenge hypothesis. An increase in aggression due to spontaneous social instability outside the mating season, however, was not linked to a parallel rise of iT. Furthermore, the highest iT levels were obtained during the birth season, which may be part of a male strategy to remain aggressive during this period of high infanticide risk. These findings suggest that redfronted lemurs do not respond with increases in androgens to short-term challenges and that high androgen levels instead correlate with longer-lasting and predictable situations, such as the mating and birth seasons.     

Responses of pond-breeding amphibians to wildfire: short-term patterns in occupancy and colonization.

Wildland fires are expected to become more frequent and severe in many ecosystems, potentially posing a threat to many sensitive species. We evaluated the effects of a large, stand-replacement wildfire on three species of pond-breeding amphibians by estimating changes in occupancy of breeding sites during the three years before and after the fire burned 42 of 83 previously surveyed wetlands. Annual occupancy and colonization for each species was estimated using recently developed models that incorporate detection probabilities to provide unbiased parameter estimates. We did not find negative effects of the fire on the occupancy or colonization rates of the long-toed salamander (Ambystoma macrodactylum). Instead, its occupancy was higher across the study area after the fire, possibly in response to a large snowpack that may have facilitated colonization of unoccupied wetlands. Naive data (uncorrected for detection probability) for the Columbia spotted frog (Rana luteiventris) initially led to the conclusion of increased occupancy and colonization in wetlands that burned. After accounting for temporal and spatial variation in detection probabilities, however, it was evident that these parameters were relatively stable in both areas before and after the fire. We found a similar discrepancy between naive and estimated occupancy of A. macrodactylum that resulted from different detection probabilities in burned and control wetlands. The boreal toad (Bufo boreas) was not found breeding in the area prior to the fire but colonized several wetlands the year after they burned. Occupancy by B. boreas then declined during years 2 and 3 following the fire. Our study suggests that the amphibian populations we studied are resistant to wildfire and that B. boreas may experience short-term benefits from wildfire. Our data also illustrate how naive presence-non-detection data can provide misleading results.     

Distribution and ecology of leptocephali of the congrid eel, Ariosoma scheelei, around Sulawesi Island, Indonesia

A survey for leptocephali around Sulawesi Island in the central Indonesian Seas during May 2001 found that the leptocephali of the congrid eel, Ariosoma scheelei, were present in all seven areas that were sampled. A total of 551 leptocephali (22–166 mm TL) were collected, and A. scheelei was by far the most abundant species of leptocephali collected during the survey. The wide range of sizes in most areas indicated that spawning had occurred during a period of several months in many different areas, although the exact spawning locations were not determined. The larger size classes were more abundant in all areas except in Tomini Bay on the northeast side of Sulawesi Island. The highest catch rates were observed at the eastern edge of the Java Sea and to the north in the Celebes Sea near Makassar Strait. Premetamorphic leptocephali were also collected in surface samples at 11 stations (N=62), but metamorphosing leptocephali (N=86) were only caught in IKMT tows that fished from the surface to about 200 m. Metamorphosing leptocephali were collected primarily at two stations in the Java Sea and Makassar Strait where a surface layer of lower-salinity water was detected. Their total lengths (105.3–153.3 mm) and the largest premetamorphic individuals suggested that this species can reach maximum sizes of about 165 mm before beginning to metamorphose. It is hypothesized that this species may be abundant in the Indonesian Seas region and that it has ecological traits such as large size at recruitment and a small size at reproduction that have made it successful in many regions of the Indo-Pacific.     

The importance of handling time for the flight directionality in bees

Summary Individual workers of the honeybee (Apis mellifera), trained to collect food from a patch of artificial flowers, were used to test the following hypotheses about the mechanism leading to a decrease in flight directionality when moving from one flower to the next. Directionality decreases with (1) an increasing amount of energy taken from a flower, (2) an increasing amount of time spent on a flower, or (3) an increasing profitability of the flower, i.e. rate of nectar uptake. The bees were tested singly on an arrangement with equidistant flowers. They could move from a decision point forward, right, left, or backwards to the next flower. The rewards at the decision point were altered. When rewards at this point were compared that offered the same quality of nectar (50% sugar solution), the time hypothesis (2) was consistent with the observed behaviour of the bees. When conditions were compared that involved two different reward qualities (50% and 25% sugar solation), none of the original hypotheses could entirely account for the results.It is suggested that a slight modification of the time hypothesis would be consistent with the observations: The bees might possibly forget their arrival direction on the flower with increasing time, but forgetting the direction of the last flower visited is intensified with more concentrated rewards.     

Call structure may affect male mating success in the quacking frog<Emphasis Type="Italic"> Crinia georgiana</Emphasis> (Anura: Myobatrachidae)

We investigated the relationship between mating success, male size and variation in the advertisement call in the frog Crinia georgiana under field conditions. Mating success in 91 males was determined by following 32 females as they moved through the chorus. Our analyses indicated that successful males had a higher number of pulses in the first note and/or called at a higher rate. However, we did not detect a significant relationship between mating success and dominant frequency, the property that varied most strongly with body size, suggesting that size is not an important influence on mate choice in this species. Even so, smaller males were more successful if they called at a higher rate whereas larger males were more successful if they had more pulses in their first note. Accordingly, males of different size may use different calling tactics to attract females. These results provide a framework for further experimental studies aimed at investigating the independent impacts of both inter- and intra-sexual selection on the advertisement call and body size of C. georgiana.