Neural signalling: Does colocalization imply cotransmission?

Recent results suggest that neurons that contain multiple neurotransmitters may make synaptic connections with different target neurons that are mediated by only a subset of their transmitter complement.     

Does alary dimorphism imply dispersal dimorphism in the waterstrider,Gerris remigis?

ABSTRACT.

• 1 The hypothesis that wing dimorphism reflects dimorphism for dispersal ability is tested in two populations of stream-dwelling waterstriders, Gerris remigis Say, in southern Quebec, Canada.
• 2 Movements were assessed directly by recaptures of marked adults, and indirectly by comparisons of residence times and patterns of disappearance of macropterous and apterous morphs. Sampling was done weekly, over a period of 26 months, and 4828 adult G.remigis were individually marked during this time.
• 3 Movements of >100 m were very rare for both morphs. The movement patterns of the two morphs were very similar, and differed only over the winter, when no macropters moved upstream. This latter observation suggests that macropters may be less successful than apterous individuals at moving overland, or rowing against a current at this time of year.
• 4 Residence times and patterns of disappearance of the two morphs were very similar during all seasons.
• 5 These results suggest that macropterous G.remigis do not, in general, disperse using any means unavailable to the apterous morph, and that macropters in this species should not be simply categorized as long-distance dispersers.

     

Quail and rain in semiarid rangelands: Does management matter?

Rainfall is a strong driver of quail populations on southwestern rangelands and can account for a large portion (~70–95%) of the variability in regional quail production and abundance. Landowners have attempted to moderate these boom-and-bust fluctuations via management; however, presently it is unknown whether management can increase or stabilize quail populations in semiarid environments or whether rainfall remains as influential at small spatial extents. Our objectives were to evaluate the efficacy of management at mitigating the effects of rainfall on northern bobwhite (Colinus virginianus) populations on semiarid rangelands and to quantify the influence of rainfall on bobwhite density at smaller spatial extents. We conducted a study to evaluate these objectives during 2014–2020 in the Rio Grande Plains (n = 11 sites; 1,100‒6,500 ha) and Rolling Plains (n = 4 sites; 1,900‒4,000 ha) of Texas, USA. We estimated bobwhite density during late autumn (Dec‒Jan) on all sites using helicopter surveys within a distance-sampling framework. We also obtained site-level seasonal rainfall (Apr‒Aug) and quantified management intensity via landowner surveys and a scoring rubric to categorize sites into 3 classes (low, medium, and high management intensity). Bobwhite populations during this study experienced a boom-bust cycle in both the Rio Grande Plains and Rolling Plains, with mean bobwhite density fluctuating considerably (0.57‒2.96 bobwhites/ha and 0.02‒2.88 bobwhites/ha, respectively). In the Rio Grande Plains, mean bobwhite density significantly increased from low to high management intensity in 2015 (1.12 ± 0.17 bobwhites/ha vs. 2.87 ± 0.39 bobwhites/ha, respectively), 2016 (1.06 ± 0.20 bobwhites/ha vs. 2.96 ± 0.36 bobwhites/ha, respectively), 2017 (0.73 ± 0.16 bobwhites/ha vs. 1.91 ± 0.32 bobwhites/ha, respectively), and 2019 (0.42 ± 0.14 bobwhites/ha vs. 1.01 ± 0.26 bobwhites/ha, respectively; P < 0.05). In addition, rainfall at the site level accounted for a low amount of the variation in bobwhite density (r² = 0.09; P < 0.01). Similarly, in the Rolling Plains, mean bobwhite density significantly increased from low to high management intensity in 2015 (1.30 ± 0.27 bobwhites/ha vs. 2.20 ± 0.29 bobwhites/ha, respectively) and 2016 (1.26 ± 0.26 bobwhites/ha vs. 2.88 ± 0.34 bobwhites/ha, respectively; P < 0.05). Rainfall at the site level also accounted for a low amount of the variation in bobwhite density (r² < 0.02; P = 0.82). Our findings suggest that management can increase bobwhite density beyond that of less-managed properties but does not completely eliminate inter-annual fluctuations in semiarid environments. In addition, rainfall appears to exert less of an influence on bobwhite density at a site level (e.g., 2,000 ha) than has been documented at a regional level (e.g., ≥8 million ha).     

Does taxonomic homogenization imply functional homogenization in temperate forest herb layer communities?

Biotic homogenization, the decrease in beta diversity among formerly distinct species assemblages, has been recognized as an important form of biotic impoverishment for more than a decade. Although researchers have stressed the importance of the functional dimension to understand its potential ecological consequences, biotic homogenization has mostly been studied at a taxonomic level. Here, we explore the relationship between taxonomic and functional homogenization using data on temperate forest herb layer communities in NW Germany, for which taxonomic homogenization has recently been demonstrated. We quantified beta diversity by partitioning Rao’s quadratic entropy. We found a general positive relationship between changes in taxonomic and functional beta diversity. This relationship was stronger if multiple functional traits were taken into account. Averaged across sites, however, taxonomic homogenization was not consistently accompanied by functional homogenization. Depending on the traits considered, taxonomic homogenization occurred also together with functional differentiation or no change in functional beta diversity. The species shifts responsible for changes in beta diversity differed substantially between taxonomic and functional beta diversity measures and also among functional beta diversity measures based on different traits. We discuss likely environmental drivers for species shifts. Our study demonstrates that functional homogenization must be explicitly studied as an independent phenomenon that cannot be inferred from taxonomic homogenization.     

Does morphological convergence imply functional similarity? A test using the evolution of quadrupedalism in ornithischian dinosaurs

Convergent morphologies are thought to indicate functional similarity, arising because of a limited number of evolutionary or developmental pathways. Extant taxa displaying convergent morphologies are used as analogues to assess function in extinct taxa with similar characteristics. However, functional studies of extant taxa have shown that functional similarity can arise from differing morphologies, calling into question the paradigm that form and function are closely related. We test the hypothesis that convergent skeletal morphology indicates functional similarity in the fossil record using ornithischian dinosaurs. The rare transition from bipedality to quadrupedality occurred at least three times independently in this clade, resulting in a suite of convergent osteological characteristics. We use homology rather than analogy to provide an independent line of evidence about function, reconstructing soft tissues using the extant phylogenetic bracket and applying biomechanical concepts to produce qualitative assessments of muscle leverage. We also optimize character changes to investigate the sequence of character acquisition. Different lineages of quadrupedal ornithischian dinosaur stood and walked differently from each other, falsifying the hypothesis that osteological convergence indicates functional similarity. The acquisition of features correlated with quadrupedalism generally occurs in the same order in each clade, suggesting underlying developmental mechanisms that act as evolutionary constraints.     

Does the cost of incubation set limits to clutch size in common eiders Somateria mollissima?

We examined the effect of natural clutch size on the cost of incubation in a population of common eiders Somateria mollissima nesting in Tromsø, northern Norway. The body condition of females at day 5 in the incubation period was not related to clutch size (3–6 eggs), but females incubating large clutches lost more mass and had a lower body condition at day 20 in the incubation period than females incubating small clutches. Females incubating large clutches had a slightly shorter incubation period and a lower egg predation rate. The results do not support the hypothesis that the female's ability to produce eggs is the only ultimate control of clutch size in eider. Instead the results suggest that there may be an interaction between the allocation of body reserves to eggs and incubation, and that females producing large clutches allocate more of their body reserves to incubation than females producing small clutches, in order to shorten the incubation period and to minimise the risk of predation on eggs.     

Does cutting herbicide rates threaten the sustainability of weed management in cropping systems?

Evolution of herbicide resistance in weeds is a growing problem across the world, and it has been suggested that low herbicide rates may be contributing to this problem. An individual-based simulation model that represents weed population dynamics and the evolution of polygenic herbicide resistance was constructed and used to investigate whether using lower herbicide rates or standard rates at reduced efficacy could reduce the sustainability of cropping systems by causing faster increases in weed population density as herbicide resistance develops. A number of different possible genetic bases for resistance were considered, including monogenic resistance and polygenic resistance conferred by several genes. The results show that cutting herbicide rates does not affect the rate at which weed densities reach critical levels when resistance is conferred exclusively by a single dominant gene. In some polygenic situations, cutting herbicide rates substantially reduces sustainability, due to a combination of faster increase in resistance gene frequency and reduced kill rates in all genotypes, while in other polygenic situations the effect is small. Differences in sustainability depend on combined strength of the resistance genes, variability in phenotypic susceptibility and rate delivered, level of control due to alternative measures, and degree of genetic dominance and epistasis. In the situation where resistance can be conferred by both a single dominant major gene or a number of co-dominant minor genes in combination, the difference made by low rates depends on the relative initial frequency of the major and minor genes. These results show that careful consideration of herbicide rate and understanding the genetic basis of resistance are important aspects of weed management.     

Confidence in crisis? Understanding trust in government and public attitudes toward mandatory state health powers

In response to the possibility of a bioterror attack using smallpox, many states have updated and revised their current public health laws in line with the Model Act, which would effectively give states the right to invoke mandatory state health powers, such as quarantine or vaccine. Previous studies have supported the importance of allying with the public in creating and implementing effective bioterror response policies. Historical case studies and recent research suggest that when the public is not supportive of government health policies, they may be less willing to comply. In this study we analyze a recent survey to determine the effects of a set of variables, including aspects of trust in government that have been found in previous studies to influence public opposition to compulsory government health policies, on opinions about compulsory vaccination and quarantine.     

Is the historical war against wildlife over in southern Europe?

Most southern European regions have experienced a rapid economical change during the last decades, moving from a historical economy based on agriculture to a society based on industry and technology. We test here whether causes of admission of birds admitted to a large southern European rehabilitation centre, during a 14-year period (1994–2007), reflect these socio-economical changes. Specifically, we estimated the trends in the number of birds admitted to the centre by shooting (S) over the number of birds admitted due to impacts caused by infrastructures (I), for the 10 most commonly admitted species with complete time series available. Species were grouped in three groups following ecological traits: raptors (diurnal and nocturnal) and aquatic birds. Trends were estimated by means of the slope of a linear regression of the log-transformed S/I ratio over time, which provided the finite population growth rate ( λ ) and its 95% confidence intervals. We used the ratio to prevent possible biases caused by changes in wild population densities over the years. We conclude that the overall trend in the S/I ratio, as well as the trends for all three bird groups considered, were negative, and indicated a c . 10% annual reduction in the number of birds admitted by shooting in relation to those admitted by infrastructure-related injuries. Causal relationships were analysed by means of Poisson regressions on absolute numbers. Importantly we show that despite the direct historical war against wildlife seems to be coming to an end in southern Europe, impact to wildlife continues in an indirect way, as collateral damages caused by our post-industrial way of life. So the overall scenario is most likely not one of improved conservation status in southern Europe, but rather one of shifting ways of impacting wildlife in parallel with socio-economic changes.     

Does size really matter? Weight and values in public health

The medical community has long regarded obesity and overweight as serious health risks, and popular culture reflects these concerns. A focus on body weight reduction motivates many contemporary exercise and diet practices, especially among women. Yet, there is significant evidence that those risks have been exaggerated, that weight loss regimens may be more detrimental to health than moderate obesity, and that pressure to be thin leads to disordered eating and unhealthy lifestyle choices. This paper examines the problematic manners in which some national health policies regard the problems of overweight and obesity. It contends that concepts of aesthetics, grounded in 19th-century beliefs about the body, guide clinicians to emphasize measurement of the body in health assessment at potential cost to individual wellness.     

Does the cytotoxic effect of transient amyloid oligomers from common equine lysozyme in vitro imply innate amyloid toxicity?

In amyloid diseases, it is not evident which protein aggregates induce cell death via specific molecular mechanisms and which cause damage because of their mass accumulation and mechanical properties. We showed that equine lysozyme assembles into soluble amyloid oligomers and protofilaments at pH 2.0 and 4.5, 57 degrees C. They bind thioflavin-T and Congo red similar to common amyloid structures, and their morphology was monitored by atomic force microscopy. Molecular volume evaluation from microscopic measurements allowed us to identify distinct types of oligomers, ranging from tetramer to octamer and 20-mer. Monomeric lysozyme and protofilaments are not cytotoxic, whereas the oligomers induce cell death in primary neuronal cells, primary fibroblasts, and the neuroblastoma IMR-32 cell line. Cytotoxicity was accessed by ethidium bromide staining, MTT reduction, and TUNEL assays. Primary cultures were more susceptible to the toxic effect induced by soluble amyloid oligomers than the neuroblastoma cell line. The cytotoxicity correlates with the size of oligomers; the sample incubated at pH 4.5 and containing larger oligomers, including 20-mer, appears to be more cytotoxic than the lysozyme sample kept at pH 2.0, in which only tetramers and octamers were found. Soluble amyloid oligomers may assemble into rings; however, there was no correlation between the quantity of rings in the sample and its toxicity. The cytotoxicity of transient oligomeric species of the ubiquitous protein lysozyme indicates that this is an intrinsic feature of protein amyloid aggregation, and therefore soluble amyloid oligomers can be used as a primary therapeutic target and marker of amyloid disease.     

Does agonistic dominance imply feeding priority in lemurs? a study in Eulemur fulvus mayottensis

We studied agonistic dominance and priority of access to a limited drinking resource in two captive groups of Eulemur fulvus mayottensis.Gender is not systematically related to agonistic dominance or to drinking priority. The dominance hierarchy obtained in the drinking competition test is correlated with the baseline hierarchy in the absence of induced competition, but not with drinking priority. We analyze results within the framework of recent dicussions on female dominance in Malagasy prosimians.     

Morphological differentiation in the widespread fish Galaxias maculatus: do darker environments imply bigger eyes?

Hydrobiologia - The visual capacity of aquatic organisms is, in general, related to light penetration in the water. Therefore, aquatic environments that differ in color can potentially contribute...     

Is wildlife research useful for wildlife conservation in the tropics? A review for Borneo with global implications

The urgency of the tropical biodiversity crisis continues to be a major justification for wildlife research and its funding. To examine the benefits of this research for on-the-ground conservation, we focused on Borneo, where conservation has a long history and we have direct experience. We compiled, categorized and evaluated 284 publications from a broad variety of sources, 153 from peer-reviewed journals. We found that few studies address threats to species and fewer still provide input for or guidance to effective management. We consider various reasons for these shortcomings. Research is seldom judged on its relevance to pragmatic problem solving. Furthermore, many research programs lack the necessary long-term vision and organizational structure for useful applied research. We consulted conservation leaders about our conclusions and all responses suggest that our concerns are not unique to Borneo but reflect wider problems. We conclude that conservation research across most of the tropics is failing to address conservation needs. We make a number of recommendations based on our findings. Conservation biologists should place a higher priority on addressing practical conservation needs and goals.     

Biofilms in vitro and in vivo: do singular mechanisms imply cross-resistance?

Microbial biofilm has become inexorably linked with man's failure to control them by antibiotic and biocide regimes that are effective against suspended bacteria. This failure relates to a localized concentration of biofilm bacteria, and their extracellular products (exopolymers and extracellular enzymes), that moderates the access of the treatment agent and starves the more deeply placed cells. Biofilms, therefore, typically present gradients of physiology and concentration for the imposed treatment agent, which enables the less susceptible clones to survive. Such clones might include efflux mutants in addition to genotypes with modifications in single gene products. Clonal expansion following subeffective treatment would, in the case of many antibiotics, lead to the emergence of a resistant population. This tends not to occur for biocidal treatments where the active agent exhibits multiple pharmacological activity towards a number of specific cellular targets. Whilst resistance development towards biocidal agents is highly unlikely, subeffective exposure will lead to the selection of less susceptible clones, modified either in efflux or in their most susceptible target. The latter might also confer resistance to antibiotics where the target is shared. Thus, recent reports have demonstrated that sublethal concentrations of the antibacterial and antifungal agent triclosan can select for resistant mutants in Escherichia coli and that this agent specifically targets the enzyme enoyl reductase that is involved in lipid biosynthesis. Triclosan may, therefore, select for mutants in a target that is shared with the anti-E. coli diazaborine compounds and the antituberculosis drug isoniazid. Although triclosan may be a uniquely specific biocide, sublethal concentrations of less specific antimicrobial agents may also select for mutations within their most sensitive targets, some of which might be common to therapeutic agents. Sublethal treatment with chemical antimicrobial agents has also been demonstrated to induce the expression of multidrug efflux pumps and efflux mutants. Whilst efflux does not confer protection against use concentrations of biocidal products it is sufficient to confer protection against therapeutic doses of many antibiotics. It has, therefore, been widely speculated that biocide misuse may have an insidious effect, contributing to the evolution and persistence of drug resistance within microbial communities. Whilst such notions are supported by laboratory studies that utilize pure cultures, recent evidence has strongly refuted such linkage within the general environment where complex, multispecies biofilms predominate and where biocidal products are routinely deployed. In such situations the competition, for nutrients and space, between community members of disparate sensitivities far outweighs any potential benefits bestowed by the changes in an individual's antimicrobial susceptibility.