Relative importance of multiple plumage ornaments as status signals in golden whistlers (<Emphasis Type="Italic">Pachycephala pectoralis</Emphasis>)

Status signals are traits that advertise an individual’s competitive abilities to conspecifics during aggressive disputes. Most studies of status signals in birds have focussed on melanin-based plumage signals, but recent research shows that carotenoid-based signals may also play a role in aggressive signaling. We assessed the relative importance of melanin- and carotenoid-based plumage patches as agonistic signals in a small passerine, the golden whistler (Pachycephala pectoralis). Display signals in male golden whistlers include an unpigmented white throat patch, a carotenoid-based yellow breast and nape band, and a melanin-based black chin-stripe. We found that only the white throat patch was correlated with contest-related attributes. Males possessing large throat patches defended larger territories and commenced breeding earlier. When caged males with either experimentally reduced, or unmanipulated throat patches were presented to conspecifics, those with experimentally reduced patches attracted less aggression from male subjects. Focal males also responded faster to caged males with throat patches similar in size to their own, suggesting that they may assess relative throat patch size before engaging in aggressive encounters. Females did not discriminate between “reduced” or “control” treatments. Our data strongly suggest that only the unpigmented throat patch functions as a status signal. As this signal is unlikely to have significant development costs, honesty may be maintained through social costs.     

The relationship between dewlap size and performance changes with age and sex in a Green Anole (Anolis carolinensis) lizard population

Ornaments are believed to signal an individual's ability to reproduce successfully and/or survive. Since an individual's fitness is often influenced by multiple traits (e.g. number of copulations, ability to acquire nest sites or to escape predators), which are difficult to quantify simultaneously, we examine performance traits (bite force, jumping performance) believed to be relevant to an individual's fitness. Specifically, we ask whether variation in dewlap size is related to variation in body size, bite force and jumping ability in the lizard Anolis carolinensis. Our results show that dewlap size is correlated with jumping capacity across all individuals, whereas the relationships between dewlap size, body size and bite force differ depending on sex/age class. We argue that selection against relatively large dewlaps at the transition between small mature and large mature males might be responsible for the lack of a relationship within large males. The absence or presence of a correlation between dewlap size and bite force, on the other hand, might be explained by differences in behaviour, such as territory establishment, anti-predator tactics, and/or mate choice. Our work thus suggests that selective forces influencing the evolution of ornaments may operate differently on different sexes and life-history stages.     

Safety evaluation of cable barriers installation on rural highways in British Columbia

Objective: The objective of this study was to evaluate the safety effectiveness of cable barrier systems installation on rural highway sections in British Columbia, Canada.

Methods: Data on police-attended serious collisions (injury?+?fatality) on a number of rural highway sections in British Columbia, Canada, were used in the analysis. An empirical Bayes (EB) approach was employed to ensure that the evaluation results were reliable and to account for the regression to the mean artifact. Safety performance functions (SPFs) were developed using data collected at similar sites. For both median cable barrier (MCB) and roadside cable barrier (RCB) sections, the evaluation was undertaken using all serious collisions, truck serious collisions, and off-road serious collisions.

Results: For MCB sections, the evaluation results showed statistically significant reductions of 21.7, 53.8, and 34.8% in all serious collisions, truck serious collisions, and off-road left (ORL) combined with head-on (HO) serious collisions. For RCB sections, statistically significant reductions of 74.7, 100, and 100% were found in all serious collisions, truck serious collisions, and off-road right (ORR) serious collisions, respectively. The impact of the after period on the evaluation results was explored. It was found that the changes in safety become more stable using an after period of 2–5 years.

Conclusions: Cable barriers were successful in reducing the frequency of serious collisions on provincial highways in British Columbia.     

Toxicity of analytically cleaned pentabromodiphenylether after prolonged exposure in estuarine European flounder (Platichthys flesus), and partial life-cycle exposure in fresh water zebrafish (Danio rerio)

Residues of polybrominated diphenylethers (PBDEs), extensively applied as flame retardants, are widely spread in the aquatic environment and biota. The present study investigates effects of the environmentally relevant lower brominated diphenylethers in two fish species in vivo under controlled laboratory conditions. Euryhaline flounder (Platichthys flesus) and freshwater zebrafish (Danio rerio) were exposed to a range of concentrations of a commercial pentabromodiphenylether mixture, DE-71. Chemical analysis of exposed fish showed a pattern of PBDE congeners that was very similar to that in wild fish. The resulting range included environmentally relevant, as well as higher levels. Animals were investigated histopathologically with emphasis on endocrine and reproductive organs. In zebrafish, hatching of embryos and larval development were assessed. Biochemical parameters were investigated in flounder as markers for suggested dioxin-like activity (ethoxyresorufin-O-deethylase=EROD), and activation of endogenous estrogen synthesis (gonad aromatase activity). Thyroid hormones were analyzed in plasma in both species. Benchmark analysis using internal PBDE concentrations showed a mild dose-dependent decrease of hepatic EROD and ovarian aromatase activities, and plasma thyroxin levels in flounder, and an increase of plasma thyroid hormone levels in zebrafish. These trends did not result in statistically significant differences from control fish, and major histopathological changes were not observed. Reproduction in zebrafish appeared to be the most sensitive parameter with statistically significantly reduced larval survival and non-significant indications for decreased egg production at internal levels that were more than 55 times the highest environmental recordings. The present results indicate limited risk for endocrine or reproductive effects of current environmental PBDE contamination in fish.     

Iron-mediated effects on nitrate reductase in marine phytoplankton

The potential activity of nitrate reductase was determined in uni-algal cultures in the laboratory and in natural marine phytoplankton assemblages. In the laboratory bioassays, distinct differences in nitrate reductase activity were observed in iron replete versus depleted cultures for Emiliania huxleyi, Isochrysis galbana and Tetraselmis sp. Cells from iron-depleted cultures had 15 to 50 percent lower enzyme activity than those from iron-replete cultures. Upon addition of iron, nitrate reductase activity was enhanced in depleted cells up to levels comparable to those of the replete cells. Bioassays in the northern North Sea conducted in 1993, under low iron conditions, demonstrated similar results. Upon addition of 2.5 nM iron, a distinct enhancement, to a maximum of three times, of nitrate reductase activity was observed within 32 h after addition. Therefore, iron can stimulate nitrate reductase activity. In spite of the clean techniques used, some nitrate reductase activity was always observed. Iron deficiency was shown to impair nitrate reductase activity, but it is unlikely that nitrate reduction would cease completely.     

A field study of the influence of land management and soil properties on runoff and soil loss in central Spain

Since the 1950s afforestation of degraded land has been the principal means of combatting erosion in a seasonally arid area of central Spain. In the 1970s tree planting of steep hillsides and gully sides was preceded by bench terracing. Experimental sites have been established to monitor runoff and soil losses under mature Pinus forest, 12-year-old Pinus forest, and Cistus matorral. The experiment is being conducted at three scales: large gully or small watershed (c. 3.5 ha), runoff erosion plot (10–21.5 m²), and rainfall simulation plot (1 m²). Monitoring began in October 1992. Discharge was recorded continuously, while sediment loss and soil moisture content were measured on a storm basis. The paper presents summary data on runoff and soil erosion for the three scales and comments on relationships between land management, site characteristics, and these losses. We stress the crucial role of vegetation and its interrelationship with soil properties such as structure and aggregate stability. Matorral was effective in combatting water and soil loss, but we question the practice of afforesting seasonally arid, steeply sided areas that have highly erodible soils.     

Marginalization by collaboration: Environmental justice as a third party in and beyond CALFED

Governance and planning of ecosystem and water management within the California Bay-Delta, a critical component of California's water economy, have been characterized by a range of innovations in collaboration and conflict resolution. Despite legal mandates to incorporate environmental justice, the California Bay-Delta Authority's (CBDA) policy-development process and the subsequent Delta Vision process have systematically marginalized the role of environmental justice in California's water policy. We suggest that environmental justice in Bay-Delta planning can be understood as a “third party” with a tenuous seat at the CALFED water management table. As such environmental justice is a useful lens through which to assess the state's broader commitments and capacities relative to equity as a planning principal and outcome. We interpret the fate of environmental justice within Bay-Delta planning as indicative of the inherent tensions between systems based on increasing market dominance and state legitimation and the values of environmental justice based on distributive, procedural, and cognitive justice. We construct a model of marginalization and environmental injustice in collaborative planning to illustrate these tensions. We draw upon experiences of members of the Environmental Justice Sub-Committee of CBDA's Bay Delta Public Advisory Committee, as well as interviews with other key environmental justice interests, and a comprehensive review of internal and public CBDA documents relating to the environmental justice program including budgets and program plans, and ethnographic field work. We conclude that by learning from the mistakes of Bay-Delta planning, a positive model of collaborative, environmental justice-based planning for water and ecosystem management is possible.     

Evaluation of the Effect of Chemical or Enzymatic Synthesis Methods on Biodegradability of Polyesters

This work compares the biodegradability of polyesters produced by an esterification reaction between glycerol and oleic di-acid (D 18:1) issued from green chemical pathways, via either classical thermo-chemical methods, or an enzymatic method using the immobilized lipase of Candida antartica B (Novozym 435). An elastomeric polymer synthesized by enzymatic catalysis is more biodegradable than an elastomeric thermo-chemical polyester synthesized by a standard chemical procedure. This difference lies in percentage of the dendritic motifs, in values of the degree of substitution, and certainly in cross-links inducing an hyper-branched structure less accessible to the lipolytic enzymes in a waste treatment plant. However, when the elastomeric polymer synthesized by enzymatic catalysis is processed at high temperature as required for certain industrial applications, it presents an identical rate of biodegradation than the chemical polyester. The advantages of the thermo-chemical methods are greater speed and lower cost. Enzymatic synthesis appears be suited to producing polyesters, devoid of metallic catalysts, which must be used without processing at high temperature to keep a high biodegradability.