Stable social aggregations in an Australian lizard,Egernia stokesii

Social groups in many animal species contain family members, and are maintained by parental care, and then tolerance of related individuals in the group. Lizards rarely show prolonged parental care, and rarely form stable social aggregations, although cohesive groups have been reported in the Australian skink genus, Egernia. A population of Egernia stokesii was surveyed for six seasons on Camel Hill, South Australia. At this site individuals occupied rock crevices for refuges on an isolated rocky outcrop of about 1.5 ha. The population was divided into 17 stable social groups, each containing 2-17 individual lizards. Surveyed juveniles took more than 5 years to reach mature size, and most juveniles and subadults remained in the social group of their parents for that period and longer. There were 2-8 permanent adult members of each group. Group members shared common crevice refuges, basked close together (and sometimes on top of each other) and defecated in common scat piles. There was low mortality after the first 2 years of life, and low dispersal either into or out of the population. Some individuals were "floaters" that did not belong to a social group. Over the study a number of these became established in groups. The social structure of these lizards resembles the family groups reported in many species of birds and mammals where group members help to raise the offspring of relatives. The low level of parental care in lizards suggests that the evolution of this form of social organisation in lizards has resulted from different processes than in other vertebrate taxa.     

Resource selection plasticity and community responses to experimental reduction of a critical resource

Resource selection plasticity and behavioral dominance may influence the ability of a species to respond to changes in resource availability, particularly if dominant species have highly specialized resource requirements. We examined the response of several dominant and subordinate cavity-nesting species to a reduction in the availability of an essential resource (nesting cavities) using the novel experimental approach of blocking the entrances to high-quality cavities. We monitored nest abundance on seven treatment and 13 control sites (aspen groves in a grassland matrix) in British Columbia, Canada, for two years pretreatment (2000-2001), two years during treatment (2002-2003), and two years posttreatment (cavities reopened; 2004-2005). At the community level, nest abundance declined by 50% on treatment sites following cavity blocking and returned to pretreatment levels following cavity reopening. Nest abundance of European Starlings (Sturnus vulgaris), a dominant secondary cavity-nester (SCN), declined by 89% and failed to recover posttreatment. Conversely, nest abundance of Mountain Bluebirds (Sialia currucoides; a subordinate SCN) increased following cavity blocking and remained high following reopening. Tree Swallows (Tachycineta bicolor) were unaffected by cavity blocking. We suggest that starlings, while being the dominant SCN, may be limited by availability of suitable nest sites, whereas bluebirds may be limited by starling abundance. We propose that plasticity in nest site preferences of subordinate cavity-nesters may enable them to contend with natural variation in availability of critical resources, such as nest cavities and food, in addition to coping with interspecific competition. This is the first community-level, multiyear study involving manipulation of nest site availability via experimental cavity blocking.     

Global potential net primary production predicted from vegetation class, precipitation, and temperature

Net primary production (NPP), the difference between CO2 fixed by photosynthesis and CO2 lost to autotrophic respiration, is one of the most important components of the carbon cycle. Our goal was to develop a simple regression model to estimate global NPP using climate and land cover data. Approximately 5600 global data points with observed mean annual NPP, land cover class, precipitation, and temperature were compiled. Precipitation was better correlated with NPP than temperature, and it explained much more of the variability in mean annual NPP for grass- or shrub-dominated systems (r2 = 0.68) than for tree-dominated systems (r2 = 0.39). For a given precipitation level, tree-dominated systems had significantly higher NPP (approximately 100-150 g C m(-2) yr(-1)) than non-tree-dominated systems. Consequently, previous empirical models developed to predict NPP based on precipitation and temperature (e.g., the Miami model) tended to overestimate NPP for non-tree-dominated systems. Our new model developed at the National Center for Ecological Analysis and Synthesis (the NCEAS model) predicts NPP for tree-dominated systems based on precipitation and temperature; but for non-tree-dominated systems NPP is solely a function of precipitation because including a temperature function increased model error for these systems. Lower NPP in non-tree-dominated systems is likely related to decreased water and nutrient use efficiency and higher nutrient loss rates from more frequent fire disturbances. Late 20th century aboveground and total NPP for global potential native vegetation using the NCEAS model are estimated to be approximately 28 Pg and approximately 46 Pg C/yr, respectively. The NCEAS model estimated an approximately 13% increase in global total NPP for potential vegetation from 1901 to 2000 based on changing precipitation and temperature patterns.     

Maternal characteristics and the production and recruitment of sons in the eastern kingbird (<Emphasis Type="BoldItalic">Tyrannus tyrannus</Emphasis>)

Sex allocation theory predicts that if variance in reproductive success differs between the sexes, females who are able to produce high-quality young should bias offspring sex ratio towards the sex with the higher potential reproductive success. We tested the hypothesis that high-quality (i.e., heavy) female eastern kingbirds (Tyrannus tyrannus) that bred early in the breeding season would produce male-biased clutches. A significant opportunity for sexual selection also exists in this socially monogamous but cryptically polygamous species, and we predicted that successful extra-pair (EP) sires would be associated with an excess of male offspring. Although population brood sex ratio did not differ from parity, it increased significantly with female body mass and declined with female breeding date, but was independent of the morphology and display (song) behavior (correlates of reproductive success) of social males and EP sires. Male offspring were significantly heavier than female offspring at fledging. Moreover, the probability that male offspring were resighted in subsequent years declined with breeding date, and was greater in replacement clutches, but lower when clutch size was large. Probability of resighting female offspring varied annually, but was independent of all other variables. Given that variance in reproductive success of male kingbirds is much greater than that of females, and that male offspring are more expensive to produce and have a higher probability of recruitment if fledged early in the season, our results support predictions of sex allocation theory: high-quality (heavy) females breeding when conditions were optimal for male recruitment produced an excess of sons.     

玉米赤霉烯酮暴露导致的秀丽隐杆线虫生殖及发育毒性的世代间比较

利用模式生物秀丽隐杆线虫(Caenorhabditis elegans,C.elegans)对玉米赤霉烯酮(zearalenone,ZEN)暴露导致的生殖、发育缺陷在世代间的可传递性进行了研究。对亲代染毒,后代断毒恢复,实验结果显示,ZEN暴露导致的体长发育缺陷可在线虫后代中得到恢复,而生殖毒性可产生严重缺陷,且这种缺陷在后代中没有明显的恢复。通过多代持续染毒实验,发现ZEN对亲代P0、子一代F1和子二代F2线虫产生的生殖和发育毒性存在差异,其毒性作用强度为P0F2F1。线虫世代之间的发育缺陷和生殖缺陷表现出逐代修复的规律,但修复程度不同,推测与线虫自身修复的复杂应激活动有关。     

Fate of Lu(III) sorbed on 2-line ferrihydrite at pH 5.7 and aged for 12 years at room temperature. I: insights from ICP-OES,XRD, ESEM,AsFlFFF/ICP-MS,and EXAFS spectroscopy

Two-line ferrihydrite (2LFh) was aged for 12 years under ambient conditions and sheltered from light in the presence of Lu(III) used as surrogate for trivalent actinides. 2LFh aging produced hematite rhombohedra with overgrown acicular goethite particles. Analysis of the homogeneous suspension by asymmetrical flow field-flow fractionation (AsFlFFF) coupled to ICP-MS indicated that particles have a mean hydrodynamic diameter of about 140 nm and the strong correlation of the Fe and Lu fractograms hinted at a structural association of the lanthanide with the solid phase(s). Unfortunately, recoveries were low and thus results cannot be considered representative of the whole sample. The suspension was centrifuged and X-ray absorption spectroscopy (XAS) at the Lu L₃-edge on the settled particles indicated that Lu(III) is sixfold coordinated by oxygen atoms, pointing to a retention by structural incorporation within particles. This result is consistent with AsFlFFF results on the same suspension without centrifugation. The detection of next nearest Fe and O atoms were consistent with the structure of goethite, ruling out incorporation within hematite. After centrifugation of the suspension, only nanoparticulate needle-like particles, very likely goethite, could be detected in the supernatant by ESEM. AsFlFFF data of the supernatant were comparable to that obtained for the homogeneous suspension, whereas XAS indicated that Lu(III) is predominantly present as dissolved species in the supernatant. Results from both techniques can be interpreted as a major fraction of Lu present as aqueous ions and a minor fraction as structurally incorporated. Findings from this study are corroborated by STEM-HAADF data and results from DFT calculations in a companion paper.

     

Dechlorination comparison of mono-substituted PCBs with Mg/Pd in different solvent systems

It is widely recognized that polychlorinated biphenyls (PCBs) are a dangerous environmental pollutant. Even though the use and production of PCBs have been restricted, heavy industrial use has made them a wide-spread environmental issue today. Dehalogenation using zero-valent metals has been a promising avenue of research for the remediation of chlorinated compounds and other contaminants that are present in the environment. However, zero-valent metals by themselves have shown little capability of dechlorinating polychlorinated biphenyls (PCBs). Mechanically alloying the metal with a catalyst, such as palladium, creates a bimetallic system capable of dechlorinating PCBs very rapidly to biphenyl. This study primarily aims to evaluate the effects of solvent specificity on the kinetics of mono-substituted PCBs, in an attempt to determine the mechanism of degradation. Rate constants and final byproducts were determined for the contaminant systems in both water and methanol, and significant differences in the relative rates of reaction were observed between the two solvents.     

RELATION BETWEEN FISH COMMUNITIES AND RIPARIAN ZONE CONDITIONS AT TWO SPATIAL SCALES1

ABSTRACT: The relation offish community composition to riparian cover at two spatial scales was compared at 18 streams in the agricultural Minnesota River Basin. The two spatial scales were: (1) local riparian zone (a 200 meter wide buffer extending 2 to 3 kilometers upstream of the sampling reach); and (2) the upstream riparian zone (a 200 m wide buffer on the mainstem and all perennial tributaries upstream of the sampling reach). Analysis of variance indicated that streams with wooded‐local riparian zones had greater fish species richness (means = 20 and 15, respectively) and Index of Biotic Integrity (IBI) scores (means = 40 and 26, respectively) than streams with open‐local riparian zones. Streams with wooded‐upstream riparian zones tended (were not statistically significant) to have greater numbers of species (means = 19 and 15, respectively) and IBI scores (means = 33 and 28, respectively) than streams with open‐upstream riparian zones. There was no significant interaction between the riparian zone conditions at the two scales. This study suggests that maintenance of wooded riparian cover along streams could be effective in maintaining or improving fish community composition in streams draining heavily agricultural areas.     

Epa’s Catalyst Research Program: Environmental Impact of Sulfuric Acid Emissions

A sulfuric acid review conference sponsored by EPA's automotive Catalyst Research Program was held recently at Hendersonville, NC, for researchers whose work is funded by EPA. Emissions characterization research indicated that in-use catalyst-equipped vehicles emit low levels of H2SO4, averaging 2.7 mg/mile for 49-state cars and 15 mg/mile for California cars. Research on measurement methodology for H2SO4 and other sulfate compounds has led to the development of several promising techniques based on selective volatilization. In-roadway and off-roadway monitoring programs are providing sulfate data which can lead to improved mathematical predictive models. Acute toxicity studies to date indicate that morphological, biochemical, physiological, and pharmacological alterations due to inhaled H2SO4 alone do not appear to occur at levels less than 1 mg/m³. However, striking effects are noted with combinations of H2SO4 and other pollutants. Participants identified the need for long term chronic H2SO4 exposure studies.