Estimates of the incidence of major classes of parental care by birds are drawn from classical studies that preceded both the publication of a massive secondary literature and the revolution driven ...by molecular approaches to avian phylogeny. Here, I review this literature in the light of new phylogenetic hypotheses and estimate the prevalence of six distinct modes of care: use of geothermal heat to incubate eggs, brood parasitism, male only care, female only care, biparental care and cooperative breeding. Female only care and cooperative breeding are more common than has previously been recognized, occurring in 8 and 9% of species, respectively. Biparental care by a pair bonded male and female is the most common pattern of care but at 81% of species, the pattern is less common than once believed. I identify several problems with existing hypotheses for the evolution of parental care and highlight a number of poorly understood contrasts which, once resolved, should help elucidate avian social evolution.
In human societies, cultural norms arise when behaviours are transmitted through social networks via high-fidelity social learning. However, a paucity of experimental studies has meant that there is ...no comparable understanding of the process by which socially transmitted behaviours might spread and persist in animal populations. Here we show experimental evidence of the establishment of foraging traditions in a wild bird population. We introduced alternative novel foraging techniques into replicated wild sub-populations of great tits (Parus major) and used automated tracking to map the diffusion, establishment and long-term persistence of the seeded innovations. Furthermore, we used social network analysis to examine the social factors that influenced diffusion dynamics. From only two trained birds in each sub-population, the information spread rapidly through social network ties, to reach an average of 75% of individuals, with a total of 414 knowledgeable individuals performing 57,909 solutions over all replicates. The sub-populations were heavily biased towards using the technique that was originally introduced, resulting in established local traditions that were stable over two generations, despite a high population turnover. Finally, we demonstrate a strong effect of social conformity, with individuals disproportionately adopting the most frequent local variant when first acquiring an innovation, and continuing to favour social information over personal information. Cultural conformity is thought to be a key factor in the evolution of complex culture in humans. In providing the first experimental demonstration of conformity in a wild non-primate, and of cultural norms in foraging techniques in any wild animal, our results suggest a much broader taxonomic occurrence of such an apparently complex cultural behaviour.
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DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
A safe and effective vaccine will likely be necessary for the control or eradication of malaria which kills 400,000 annually. Our most advanced vaccine candidate to date is RTS,S which is based on ...the Plasmodium falciparum circumsporozoite protein (PfCSP) of the malaria parasite. However, protection by RTS,S is incomplete and short-lived.
Here we summarize results from recent clinical trials of RTS,S and critically evaluate recent studies that aim to understand the correlates of protective immunity and why vaccine-induced protection is short-lived. In particular, recent systems serology studies have highlighted a key role for the necessity of inducing functional antibodies. In-depth analyses of immune responses to CSP in both mouse models and vaccinated humans have also highlighted difficulties in generating the maintaining high-quality antibody responses. Finally, in recent years biophysical and structural studies of antibody binding to PfCSP have led to a better understanding of how highly potent antibodies can block infection, which can inform vaccine design.
We highlight how both structure-guided vaccine design and a better understanding of the immune response to PfCSP can inform a second generation of PfCSP-based vaccines stimulating a broader range of protective targets within PfCSP.
Cooperative breeding in birds is much more prevalent than has been previously realized, occurring in 18.5% of oscine passerines known to have biparental care, and is the predominant social system of ...some ancient oscine clades. Cooperation is distributed unevenly in clades that contain both cooperative and pair breeders, and is usually confined to a few related genera in which it can be ubiquitous. Cooperative clades are species poor compared with pair-breeding clades, because pair breeders evolve migratory habits, speciate on oceanic islands and are more likely to have distributions spread across more than one biogeographic region. These differences reflect the increased capacity for colonization by pair breeders because their young disperse. Thus cooperative breeding has macroevolutionary consequences by restricting rates of speciation and macroecological implications by influencing the assembly of island and migrant faunas.
Food legislation in the European Union and elsewhere includes both hazard- and risk-based approaches for ensuring safety. In hazard-based approaches, simply the presence of a potentially harmful ...agent at a detectable level in food is used as a basis for legislation and/or risk management action. Risk-based approaches allow consideration of exposure in assessing whether there may be unacceptable risks to health.
The advantages and disadvantages of hazard- and risk-based approaches for ensuring the safety of food chemicals, allergens, ingredients and microorganisms were explored at an ILSI Europe workshop.
It was concluded that both types of approach have their place, depending on the context. However, problems can arise when both types of approach are used in regulation by separate agencies that address different aspects of the same agent/substance present in food. This separation of decision-making can result in hazard-based restrictions on marketing and use, whereas risk-based assessments for those exposed show there is reasonable certainty no harm will result. This in turn can lead to contradictory, confusing and ultimately unnecessary actions. Use of hazard-based approaches for foods also means that comparisons with benefits for nutrition and food security cannot be undertaken. This has the potential to lead to bias in the overall conclusions of regulators and risk managers, who may not have been presented with the benefits of particular foods. The value of risk-based approaches is becoming increasingly recognised.
•Food safety legislation includes both hazard-based and risk-based approaches.•Advantages and disadvantages of hazard- and risk-based approaches are discussed.•Hazard-based approaches can be useful in some contexts.•Risk-based approaches are more widely used and their value is well recognised.•Separation of hazard- and risk-based assessment can lead to contradictory actions.
► A systematic, stepwise approach to the safety assessment of engineered nanomaterials (ENM) intended for use in foods is proposed. ► A decision tree is used to identify ENM needing nano-specific ...safety assessment; further testing follows a tiered approach. ► The approach is applicable to new generations of ENMs and to ENMs of varying size within the nano-range.
A systematic, tiered approach to assess the safety of engineered nanomaterials (ENMs) in foods is presented. The ENM is first compared to its non-nano form counterpart to determine if ENM-specific assessment is required. Of highest concern from a toxicological perspective are ENMs which have potential for systemic translocation, are insoluble or only partially soluble over time or are particulate and bio-persistent. Where ENM-specific assessment is triggered, Tier 1 screening considers the potential for translocation across biological barriers, cytotoxicity, generation of reactive oxygen species, inflammatory response, genotoxicity and general toxicity. In silico and in vitro studies, together with a sub-acute repeat-dose rodent study, could be considered for this phase. Tier 2 hazard characterisation is based on a sentinel 90-day rodent study with an extended range of endpoints, additional parameters being investigated case-by-case. Physicochemical characterisation should be performed in a range of food and biological matrices. A default assumption of 100% bioavailability of the ENM provides a ‘worst case’ exposure scenario, which could be refined as additional data become available. The safety testing strategy is considered applicable to variations in ENM size within the nanoscale and to new generations of ENM.
Changes in life history are expected when new sources of extrinsic mortality impact on natural populations. We report a new disease, devil facial tumor disease, causing an abrupt transition from ...iteroparity toward single breeding in the largest extant carnivorous marsupial, the Tasmanian devil (Sarcophilus harrisii), in which males can weigh as much as 14 kg and females 9 kg. This change in life history is associated with almost complete mortality of individuals from this infectious cancer past their first year of adult life. Devils have shown their capacity to respond to this disease-induced increased adult mortality with a 16-fold increase in the proportion of individuals exhibiting precocious sexual maturity. These patterns are documented in five populations where there are data from before and after disease arrival and subsequent population impacts. To our knowledge, this is the first known case of infectious disease leading to increased early reproduction in a mammal. The persistence of both this disease and the associated life-history changes pose questions about longer-term evolutionary responses and conservation prospects for this iconic species.
Spirochete motility is enigmatic: It differs from the motility of most other bacteria in that the entire bacterium is involved in translocation in the absence of external appendages. Using the Lyme ...disease spirochete Borrelia burgdorferi (Bb) as a model system, we explore the current research on spirochete motility and chemotaxis. Bb has periplasmic flagella (PFs) subterminally attached to each end of the protoplasmic cell cylinder, and surrounding the cell is an outer membrane. These internal helix-shaped PFs allow the spirochete to swim by generating backward-moving waves by rotation. Exciting advances using cryoelectron tomography are presented with respect to in situ analysis of cell, PF, and motor structure. In addition, advances in the dynamics of motility, chemotaxis, gene regulation, and the role of motility and chemotaxis in the life cycle of Bb are summarized. The results indicate that the motility paradigms of flagellated bacteria do not apply to these unique bacteria.
Investment in offspring depends on the costs and benefits to the carer, which can vary with sex and social status. Investment also depends on the effort of others by allowing for compensation ...(load‐lightening), with biparental care studies showing that this depends on the state and type of the other carer. By contrast, studies on cooperative breeders have solely focussed on the effects of group size rather than its composition (i.e. social environment). Here we propose and provide the first test of the ‘Social Environment’ hypothesis, that is, how the characteristics (here the sex) of other helpers present in the group affect parental care and how this in turn affects offspring fitness in cooperatively breeding red‐winged fairy‐wrens (Malurus elegans). Breeders provisioned nestlings at a higher rate than helpers, but there was no sex difference in provisioning rate. Compensation to increasing group size varied little with sex and status, but strongly depended on social environment. All group members reduced their provisioning rates in response to an increasing number of male (load‐lightening), but not female helpers (additive care). As a result, nestlings received more food and grew faster in the presence of female helpers. The increased nestling growth did convey a fitness advantage due to a higher post‐fledging survival to adulthood. Our study provides the first evidence that parental care can depend on social environment. This could be an important overlooked aspect to explain variation in parental care in cooperative breeders in general and in particular the enormous variation between the sexes, which we reveal in a literature overview.
•We discuss the two possible learning processes underlying conformist transmission.•We present an extended analysis of conformity in a previous study of great tits.•This shows that both conformist ...processes generate similar results and outcomes.•We argue that functional equivalence is likely in most natural contexts.
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