Reproductive parameters vary with social and ecological factors in the polygynous ant Formica exsecta

Due to their haplo‐diploid sex determination system and the resulting conflict over optimal sex allocation between queens and workers, social Hymenoptera have become important model species to study variation in sex allocation. While many studies indeed reported sex allocation to be affected by social factors such as colony kin structure or queen number, others, however, found that sex allocation was impacted by ecological factors such as food availability. In this paper, we present one of the rare studies that simultaneously investigated the effects of social and ecological factors on social insect nest reproductive parameters (sex and reproductive allocation, nest productivity) across several years. We found that the sex ratio was extremely male biased in a polygynous (multiple queens per nest) population of the ant Formica exsecta. Nest‐level sex allocation followed the pattern predicted by the queen‐replenishment hypothesis, which holds that gynes (new queens) should only be produced and recruited in nests with low queen number (i.e. reduced local resource competition) to ensure nest survival. Accordingly, queen number (social factor) was the main determinant on whether a nest produced gynes or males. However, ecological factors had a large impact on nest productivity and therefore on a nest's resource pool, which determines the degree of local resource competition among co‐breeding queens and at what threshold in queen number nests should switch from male to gyne production. Additionally, our genetic data revealed that gynes are recruited back to their parental nests after mating. However, our genetic data are also consistent with some adult queens dispersing on foot from nests where they were produced to nests that never produced queens. As worker production is reduced in gyne‐producing nests, queen migration might be offset by workers moving in the other direction, leading to a nest network characterized by reproductive division of labour. Altogether our study shows that both, social and ecological factors can influence long‐term nest reproductive strategies in insect societies.     

Predicting optimal transmission investment in malaria parasites

In vertebrate hosts, malaria parasites face a tradeoff between replicating and the production of transmission stages that can be passed onto mosquitoes. This tradeoff is analogous to growth‐reproduction tradeoffs in multicellular organisms. We use a mathematical model tailored to the life cycle and dynamics of malaria parasites to identify allocation strategies that maximize cumulative transmission potential to mosquitoes. We show that plastic strategies can substantially outperform fixed allocation because parasites can achieve greater fitness by investing in proliferation early and delaying the production of transmission stages. Parasites should further benefit from restraining transmission investment later in infection, because such a strategy can help maintain parasite numbers in the face of resource depletion. Early allocation decisions are predicted to have the greatest impact on parasite fitness. If the immune response saturates as parasite numbers increase, parasites should benefit from even longer delays prior to transmission investment. The presence of a competing strain selects for consistently lower levels of transmission investment and dramatically increased exploitation of the red blood cell resource. While we provide a detailed analysis of tradeoffs pertaining to malaria life history, our approach for identifying optimal plastic allocation strategies may be broadly applicable.     

Withholding and withdrawing life sustaining treatment from elderly people: towards formal guidelines.

Clinicians often decide either to withhold or to withdraw lifesaving treatment in elderly patients. Considerable disagreement exists about the circumstances in which such actions can be defended. Debates about the scarcity of resources in the NHS add urgency to the need to resolve this disagreement. Competent elderly patients have a legal and moral right to decide whether to receive life sustaining treatment. Such treatment should not be withheld or withdrawn on the basis of a patient''s age alone. Principles for making decisions about life sustaining treatment in incompetent elderly patients can be defended and should exist as written guidelines.     

Paternity confidence and social obligations explain men's allocations to romantic partners in an experimental giving game

Paternal care in humans is facultative, with investment decisions responsive to socioecological context. In particular, paternity confidence is thought to have a significant impact on men's provisioning. However, various aspects of the relationship a man has with his partner can also influence the way he provides for his children. Previous papers have tended to focus either on these kinds of relationship dynamics or on the impact of paternity confidence. However, these categories are often intertwined and parsing their contributions can be conceptually and methodologically difficult. To better understand how paternity confidence and relationship dynamics impact men's investment decisions, we used a series of pictorial vignettes to assess the resource allocation strategies of Himba men. We focus on three traits: mate fidelity, partner type (marital or non-marital), and relationship status (current or former). Results suggest that men prioritize mate fidelity and current reproductive partners in investment decisions, but social obligations to past and current partners and the presence of other male investors also influence decisions. Himba men appear to be balancing social norms related to marriage and fatherhood with individually-driven incentives to invest in current and more faithful partners.     

The effect of paternal investment on female fertility intention in South Korea

Life history theory views reproduction as an outcome of resource allocation. The allocation of resources such as parental investments of time, energy and material resources involves trade-offs between number of offspring and timing of reproduction. Within the framework of mammalian parental investment, the outstanding feature of human reproduction is the high level of paternal care. Although empirical evidence suggests that human paternal investment may have evolved as a reproductive strategy to reduce infant and child mortality rates, the effects of actual paternal investment, including allocating time to child care, on female reproductive decisions have received relatively little attention. We examined the trade-off from two perspectives using a representative sample of married South Korean women aged 20–44 in 2005 (n=977). First, paternal investment in domestic labor, including child care and housework, was expected to be associated with women's preference regarding future reproduction. Second, relative paternal investment was expected to increase women's preference for future reproduction, especially among employed women. We found that increased paternal investment in child care and housework remarkably enhanced women's intention to have a second child, especially among employed women. In addition, although family members provide a low percentage of child care in South Korea, such help is likely to be a useful resource for second childbirth among employed women. Somewhat expectedly, older age and longer time since first birth had negative effects on women's second-child intention. There is growing evidence that, in the lowest fertility societies, paternal investment may be an essential resource for promoting future reproductive behavior of women, especially employed women.     

Measuring the quality of later life.

This paper examines quality of life as a scientific construct with a wide range of applications. The assessment of patients'' quality of life is assuming increasing importance in medicine and health care. Illnesses, diseases and their treatments can have significant impacts on such areas of functioning as mobility, mood, life satisfaction, sexuality, cognition and ability to fulfil occupational, social and family roles. The emerging quality of life construct may be viewed as a paradigm shift in outcome measurement since it shifts the focus of attention from symptoms to functioning. This holistic approach more clearly establishes the patient as the centre of attention and subsumes many of the traditional measures of outcome. Quality of life assessment is particularly relevant to ageing populations both for healthy elderly and for those who develop chronic diseases where maintenance of quality of life rather than cure may be the primary goal of treatment. This paper introduces the concept of quality of life and describes the significant difficulties in definition, measurement and interpretation that must be addressed before such measures can be used as reliable and valid indicators of disease impact and treatment outcomes. It is argued that approaches to quality of life assessment in the elderly should incorporate advances in knowledge about the psychological adaptation to ageing. Consequently, the unique perspective of the individual on his or her own quality of life must be incorporated into outcome assessments aimed at improving the quality of health care. Incorporating measures of subjective outcome such as quality of life into policy decisions on resource allocation in health care will prove one of the major challenges for health services over the next decade.     

Access to adult liver transplantation in Canada: a survey and ethical analysis.

OBJECTIVES: To describe the substantive and procedural criteria used for placing patients on the waiting list for liver transplantation and for allocating available livers to patients on the waiting list; to identify principal decision-makers and the main factors limiting liver transplantation in Canada; and to examine how closely cadaveric liver allocation resembles theoretic models of source allocation. DESIGN: Mailed survey. PARTICIPANTS: Medical directors of all seven Canadian adult liver transplantation centres, or their designates. Six of the questionnaires were completed. OUTCOME MEASURES: Relative importance of substantive and procedural criteria used to place patients in the waiting list for liver transplantation and to allocate available livers. Identification of principal decision-makers and main limiting factors to adult liver transplantation. RESULTS: Alcoholism, drug addiction, HIV positivity, primary liver cancer, noncompliance and hepatitis B were the most important criteria that had a negative influence on decisions to place patients on the waiting list for liver transplantation. Severity of disease and urgency were the most important criteria used for selecting patients on the waiting list for transplantation. Criteria that were inconsistent across the centres included social support (for deciding who is placed on the waiting list) and length of time on the waiting list (for deciding who is selected from the list). Although a variety of people were reported as being involved in these decisions, virtually all were reported to be health to be health care professionals. Thirty-seven patients died while waiting for liver transplantation in 1991; the scarcity of cadaveric livers was the main limiting factor. CONCLUSIONS: Criteria for resource allocation decisions regarding liver transplantation are generally consistent among the centres across Canada, although some important inconsistencies remain. Because patients die while on the waiting list and because the primary limiting factor is organ supply, increased organ acquisition efforts are needed.     

Disentangling sex allocation in a viviparous reptile with temperature‐dependent sex determination: a multifactorial approach

Females are predicted to alter sex allocation when ecological, physiological and behavioural variables have different consequences on the fitness of male and female offspring. Traditionally, tests of sex allocation have examined single causative factors, often ignoring possible interactions between multiple factors. Here, we used a multifactorial approach to examine sex allocation in the viviparous skink, Niveoscincus ocellatus. We integrated a 16‐year observational field study with a manipulative laboratory experiment to explore whether the effects of the maternal thermal environment interact with the resources available to females for reproduction to affect sex allocation decisions. We found strong effects of temperature on sex allocation in the field, with females born in warm conditions and males in cold conditions; however, this was not replicated in the laboratory. In contrast, we found no effect of female resource availability on sex allocation, either independently, or in interaction with temperature. These results corresponded with an overall lack of an effect of resource availability on any of the life history traits that we predicted would mediate the benefits of differential sex allocation in this system, suggesting that selection for sex allocation in response to resource availability may be relatively weak. Combined, these results suggest that temperature may be the predominant factor driving sex allocation in this system.     

Sex differences in the effects of juvenile and adult diet on age‐dependent reproductive effort

Sexual selection should cause sex differences in patterns of resource allocation. When current and future reproductive effort trade off, variation in resource acquisition might further cause sex differences in age‐dependent investment, or in sensitivity to changes in resource availability over time. However, the nature and prevalence of sex differences in age‐dependent investment remain unclear. We manipulated resource acquisition at juvenile and adult stages in decorated crickets, Gryllodes sigillatus, and assessed effects on sex‐specific allocation to age‐dependent reproductive effort (calling in males, fecundity in females) and longevity. We predicted that the resource and time demands of egg production would result in relatively consistent female strategies across treatments, whereas male investment should depend sharply on diet. Contrary to expectations, female age‐dependent reproductive effort diverged substantially across treatments, with resource‐limited females showing much lower and later investment in reproduction; the highest fecundity was associated with intermediate lifespans. In contrast, long‐lived males always signalled more than short‐lived males, and male age‐dependent reproductive effort did not depend on diet. We found consistently positive covariance between male reproductive effort and lifespan, whereas diet altered this covariance in females, revealing sex differences in the benefits of allocation to longevity. Our results support sex‐specific selection on allocation patterns, but also suggest a simpler alternative: males may use social feedback to make allocation decisions and preferentially store resources as energetic reserves in its absence. Increased calling effort with age therefore could be caused by gradual resource accumulation, heightened mortality risk over time, and a lack of feedback from available mates.     

Commentary: educational initiatives deserve randomised controlled trials.

The media have been full of reports of crisis in the NHS. Although national analyses suggest that the NHS should be able to cope within the increases in spending it has been given, local pressures can leave parts of the service struggling. Firstly, the change to allocation of funds on the basis of population needs has meant that some authorities and trusts have had effective cuts in their budgets, requiring them to trim services. Secondly, the government''s insistence on an annual 3% increase in efficiency may have resulted in authorities taking short term measures that actually decrease efficiency in the long term. Thirdly, health authorities have had to bear the costs of national targets such as reducing waiting lists and junior doctors'' hours as well as local problems such as higher numbers of mentally disordered offenders. However, all these factors can be controlled by national or local management and so their impact is not inevitable.     

Cost-utility analysis.

Decisions have to be made about allocating health resources. Currently the best economic evaluation method for doing this is cost-utility analysis. This compares the costs of different procedures with their outcomes measured in "utility based" units--that is, units that relate to a person''s level of wellbeing. The most commonly used unit is the quality adjusted life year (QALY). QALYs are calculated by estimating the total life years gained from a procedure and weighting each year to reflect the quality of life in that year. To compare outcomes of different programmes the Rosser index is one measure that is widely used to assign quality of life scores to patients. Combined with a measure of life years gained from a procedure, this enables QALYs to be calculated and procedures ranked according to cost per QALY gained. In this article Ray Robinson explains the measures used and discusses how QALY league tables can be used to guide decisions on resource allocation.     

Interactive effects of competition and social environment on the expression of sexual dimorphism

The expression of sexual dimorphism is expected to be influenced by the acquisition of resources available to allocate to trait growth, combined with sex‐specific patterns of resource allocation. Resource acquisition in the wild may be mediated by a variety of ecological factors, such as the density of interspecific competitors. Allocation may in turn depend on social contexts, such as sex ratio, that alter the pay‐off for investment in sexual traits. How these factors interact to promote or constrain the expression and evolution of sexual dimorphism is poorly understood. We manipulated sex ratio and interspecific resource competition over the growing season of red‐spotted newts (Notophthalmus viridescens) in artificial ponds. Fish competitors had a stronger effect on female than male growth, which effectively eliminated the expression of sexual size dimorphism. In addition, newt sex ratio influenced fish growth, leading to reduction in fish mass with an increase in female newt frequency. Fish also reduced the expression of male tail height, a sexually selected trait, but only in tanks with a female‐biased sex ratio. This suggests males alter their resource allocation pattern in response to the strength of sexual selection. Our results demonstrate that ecologically and socially mediated interactions between sex‐specific resource acquisition and allocation can contribute to variation in the expression of sexual dimorphism.     

The influence of intraspecific competition on resource allocation during dependent colony foundation in a social insect

Organisms face a trade-off between investment in fewer, larger offspring, or more, smaller offspring. Most organisms can adjust investment through variation in the size and number of offspring in response to factors such as resource availability and competition. In some social animals, established colonies divide into groups of individuals that become autonomous, a process known as colony fission (also dependent colony foundation in social insects). Resource allocation under fission can be fine-tuned by adjusting the number of new groups (offspring number) and the number of individuals in each new group (offspring size). We assessed the influence of competition on resource allocation during fission in the ant Cataglyphis cursor, by allowing colonies to fission in experimental enclosures of high or low conspecific colony density. The pattern of colony fission was similar to that observed in the field: each fissioning colony produced a few new nests comprising a highly variable number of workers and a single queen, the old queen was often replaced, and new queens were produced in excess. The number of new nests produced depended on the available workforce in the parent colony but was not affected by differences in colony density. Comparison with data from fission under natural field conditions, however, indicates that colonies in enclosures produced fewer, larger new nests, suggesting that resource investment patterns during fission are indeed subject to extrinsic factors. The density of conspecific colonies in the immediate surroundings may be an unreliable estimate of competition intensity and other factors should be considered.     

Competition over Personal Resources Favors Contribution to Shared Resources in Human Groups

Members of social groups face a trade-off between investing selfish effort for themselves and investing cooperative effort to produce a shared group resource. Many group resources are shared equitably: they may be intrinsically non-excludable public goods, such as vigilance against predators, or so large that there is little cost to sharing, such as cooperatively hunted big game. However, group members'' personal resources, such as food hunted individually, may be monopolizable. In such cases, an individual may benefit by investing effort in taking others'' personal resources, and in defending one''s own resources against others. We use a game theoretic “tug-of-war” model to predict that when such competition over personal resources is possible, players will contribute more towards a group resource, and also obtain higher payoffs from doing so. We test and find support for these predictions in two laboratory economic games with humans, comparing people''s investment decisions in games with and without the options to compete over personal resources or invest in a group resource. Our results help explain why people cooperatively contribute to group resources, suggest how a tragedy of the commons may be avoided, and highlight unifying features in the evolution of cooperation and competition in human and non-human societies.     

The economic determinants of land degradation in developing countries

The following paper investigates the economic determinants of land degradation in developing countries. The main trends examined are rural households'' decisions to degrade as opposed to conserve land resources, and the expansion of frontier agricultural activity that contributes to forest and marginal land conversion. These two phenomena appear often to be linked. In many developing areas, a poor rural household''s decision whether to undertake long-term investment in improving existing agricultural land must be weighed against the decision to abandon this land and migrate to environmentally fragile areas. Economic factors play a critical role in determining these relationships. Poverty, imperfect capital markets and insecure land tenure may reinforce the tendency towards short-term time horizons in production decisions, and may bias land use decisions against long-term land management strategies. In periods of commodity booms and land speculation, wealthier households generally take advantage of their superior political and market power to ensure initial access to better quality resources, in order to capture a larger share of the resource rents. Poorer households are confined either to marginal environmental areas where resource rents are limited, or only have access to resources once they are degraded and rents dissipated.<br>Overall trends in land degradation and deforestation are examined, followed by an overview of rural households'' resource management decisions with respect to land management, frontier agricultural expansion, and migration from existing agricultural land to frontiers. Finally, the discussion focuses on the scope for policy improvements to reduce economic constraints to effective land management. <br>     

Fair Resource Allocation to Health Research: Priority Topics for Bioethics Scholarship

This article draws attention to the limited amount of scholarship on what constitutes fairness and equity in resource allocation to health research by individual funders. It identifies three key decisions of ethical significance about resource allocation that research funders make regularly and calls for prioritizing scholarship on those topics – namely, how health resources should be fairly apportioned amongst public health and health care delivery versus health research, how health research resources should be fairly allocated between health problems experienced domestically versus other health problems typically experienced by disadvantaged populations outside the funder's country, and how domestic and non‐domestic health research funding should be further apportioned to different areas, e.g. types of research and recipients. These three topics should be priorities for bioethics research because their outcomes have a substantial bearing on the achievement of health justice. The proposed agenda aims to move discussion on the ethics of health research funding beyond its current focus on the mismatch between worldwide basic and clinical research investment and the global burden of disease. Individual funders’ decision‐making on whether and to what extent to allocate resources to non‐domestic health research, health systems research, research on the social determinants of health, capacity development, and recipients in certain countries should also be the focus of ethical scrutiny.     

Resource allocation to testes in walnut flies and implications for reproductive strategy

Testes size often predicts the winner during episodes of sperm competition. However, little is known about the source of nutrients allocated to testes development, or testes plasticity under varying nutrient availability. Among many holometabolous insects, metabolic resources can derive from the larval or adult diet. Distinguishing the source of nutrients allocated to testes can shed light on life history factors (such as maternal influences) that shape the evolution of male reproductive strategies. Here we used an experimental approach to assess resource allocation to testes development in walnut flies (Rhagoletis juglandis) from differing nutritional backgrounds. We fed adult male walnut flies on sugar and yeast diets that contrasted with the larval diet in carbon and nitrogen stable isotope ratios. This design allowed us to assess the dietary source of testes carbon and nitrogen and its change over time. We found significant incorporation of adult dietary carbon into testes, implying that walnut flies are income breeders for carbon (relying more on adult resources). In contrast, we found little evidence that walnut flies incorporate adult dietary nitrogen into testes development. We discuss the implications of these allocation decisions for life history evolution in this species.     

Sex‐allocation conflict and sexual selection throughout the lifespan of eusocial colonies

Models of sex‐allocation conflict are central to evolutionary biology but have mostly assumed static decisions, where resource allocation strategies are constant over colony lifespan. Here, we develop a model to study how the evolution of dynamic resource allocation strategies is affected by the queen‐worker conflict in annual eusocial insects. We demonstrate that the time of dispersal of sexuals affects the sex‐allocation ratio through sexual selection on males. Furthermore, our model provides three predictions that depart from established results of classic static allocation models. First, we find that the queen wins the sex‐allocation conflict, while the workers determine the maximum colony size and colony productivity. Second, male‐biased sex allocation and protandry evolve if sexuals disperse directly after eclosion. Third, when workers are more related to new queens, then the proportional investment into queens is expected to be lower, which results from the interacting effect of sexual selection (selecting for protandry) and sex‐allocation conflict (selecting for earlier switch to producing sexuals). Overall, we find that colony ontogeny crucially affects the outcome of sex‐allocation conflict because of the evolution of distinct colony growth phases, which decouples how queens and workers affect allocation decisions and can result in asymmetric control.     

Bioequivalence of generic aerosol bronchodilators: what are the issues?

I have attempted to address some critical issues relating to the introduction of generic aerosol bronchodilators in Canada. I approached Genpharm to obtain information on the data submitted to the HPB, including the number of subjects involved, but the company refused to divulge this information because it was concerned about the use of such information by its competitors. In addition to the in-vitro testing conducted by the HPB, should a single pharmacodynamic study be sufficient to demonstrate the safety and efficacy of a drug that serves such a critical role in the prevention of serious illness and possibly death? If so, what will constitute the minimum requirements for the design of such a study? In general, what should be the minimum standards required for safety, efficacy and bioequivalence of aerosol bronchodilators? The next phase rests with the provincial governments. What criteria will they use to determine whether a generic aerosol bronchodilator will be considered bioequivalent? It is essential that the criteria for bioequivalence be developed by experts, and ideally those criteria should be agreed upon and accepted by federal and provincial regulatory bodies before a product is given the status of bioequivalence. Unless such a step is taken it will be difficult to have confidence that products can be considered interchangeable. The issue of interchangeability of aerosol bronchodilators demands immediate attention. Regulatory agencies are caught between those groups with vested interests on both sides. Since patients will either benefit or suffer as a consequence of regulatory decisions, action must be taken to ensure that the best decisions are made. Scientists, clinicians and government officials should convene as soon as possible to formulate a satisfactory approach to this problem of interchangeability. The medical and pharmaceutical professions need reliable information, and patients should not be denied less expensive generic drugs if it can be determined that they are comparable to the innovator''s product.