1,721,060 research outputs found
Cooperation and conflict in pied babblers
No full textCooperative breeding occurs when individuals receive assistance from others in the production of young. Research attention has traditionally focussed on explaining how reproductive altruism can be reconciled with evolutionary theory; however in recent years, more emphasis has been placed on examining the extent of cooperation and conflict within cooperative societies. In this thesis, I present data on conflict and cooperation in cooperatively breeding pied babblers. In Chapter Three, I show that dispersal patterns dictate the circumstances under which helpers encounter unrelated individuals and attempt to breed, and suggest that sex-biases in dispersal might therefore be an important determinant of breeder-helper conflict in cooperative species. Chapter Four describes correlations between dispersal patterns and juvenile aggression: females, the dispersing sex, are more aggressive than males, and more aggressive females disperse earlier than less aggressive females. I then go on to examine offspring care in this species, focussing on food-associated ‘purr’ calls that are given by adults when feeding young. Most studies have shown that the function of food-calling is to ‘switch-on’ nestling begging; however, I found that adult pied babblers continue to use purr calls after young have fledged, and that their primary function is to move mobile offspring around the territory, rather than to elicit begging (Chapter Five). Chapter Six demonstrates that adults actively condition young to associate purr calls with food. Finally, I address trade-offs in cooperatively breeding species in two contexts. First, I show that the decision to fledge young depends critically on group size and the risk of nestling predation: in smaller groups, where predation risk is higher, adults fledge young earlier. This is traded off against allowing young a longer period to develop in the nest (Chapter Seven). I then discuss the trade-off between investing in current and future young and how this might be alleviated by the presence of non-reproductive helpers that care for first-born young, liberating breeders to initiate subsequent broods. Although this is thought to be common among cooperative breeders, the mechanism by which the care of different subsets of offspring is divided between breeders and helpers is not known. In Chapter Eight, I show that breeder-offspring aggression transfers first-born young to helpers; thereby achieving an inter-brood division of labour
Homozygosity and risk of childhood death due to invasive bacterial disease.
Get PDFBACKGROUND: Genetic heterozygosity is increasingly being shown to be a key predictor of fitness in natural populations, both through inbreeding depression, inbred individuals having low heterozygosity, and also through chance linkage between a marker and a gene under balancing selection. One important component of fitness that is often highlighted is resistance to parasites and other pathogens. However, the significance of equivalent loci in human populations remains unclear. Consequently, we performed a case-control study of fatal invasive bacterial disease in Kenyan children using a genome-wide screen with microsatellite markers. METHODS: 148 cases, comprising children aged <13 years who died of invasive bacterial disease, (variously, bacteraemia, bacterial meningitis or neonatal sepsis) and 137 age-matched, healthy children were sampled in a prospective study conducted at Kilifi District Hospital, Kenya. Samples were genotyped for 134 microsatellite markers using the ABI LD20 marker set and analysed for an association between homozygosity and mortality. RESULTS: At five markers homozygosity was strongly associated with mortality (odds ratio range 4.7 - 12.2) with evidence of interactions between some markers. Mortality was associated with different non-overlapping marker groups in Gram positive and Gram negative bacterial disease. Homozygosity at susceptibility markers was common (prevalence 19-49%) and, with the large effect sizes, this suggests that bacterial disease mortality may be strongly genetically determined. CONCLUSION: Balanced polymorphisms appear to be more widespread in humans than previously appreciated and play a critical role in modulating susceptibility to infectious disease. The effect sizes we report, coupled with the stochasticity of exposure to pathogens suggests that infection and mortality are far from random due to a strong genetic basis
Population growth rate as a basis for ecological risk assessment of toxic chemicals
Get PDFAssessing the ecological risks of toxic chemicals is most often based on individual-level responses such as survival, reproduction or growth. Such an approach raises the following questions with regard to translating these measured effects into likely impacts on natural populations. (i) To what extent do individual-level variables underestimate or overestimate population-level responses? (ii) How do toxicant-caused changes in individual-level variables translate into changes in population dynamics for species with different life cycles? (iii) To what extent are these relationships complicated by population-density effects? These issues go to the heart of the ecological relevance of ecotoxicology and we have addressed them using the population growth rate as an integrating concept. Our analysis indicates that although the most sensitive individual-level variables are likely to be equally or more sensitive to increasing concentrations of toxic chemicals than population growth rate, they are dif. cult to identify a priori and, even if they could be identified, integrating impacts on key life-cycle variables via population growth rate analysis is nevertheless a more robust approach for assessing the ecological risks of chemicals. Populations living under density-dependent control may respond differently to toxic chemicals than exponentially growing populations, and greater care needs to be given to incorporating realistic density conditions (either experimentally or by simulation) into ecotoxicological test designs. It is impractical to expect full life-table studies, which record changes in survival, fecundity and development at defined intervals through the life cycle of organisms under specified conditions, for all relevant species, so we argue that population growth rate analysis should be used to provide guidance for a more pragmatic and ecologically sound approach to ecological risk assessment
Data from Froy et al 2018.zip
No full textData from: Declining home range area predicts reduced late-life survival in two wild ungulate populations H Froy, Börger L, Regan CE, Morris A, Morris S, Pilkington JG, Crawley MJ, Clutton-Brock TH, Pemberton JM & Nussey DHEcology Letters 2018This folder contains supporting data for the above publication, plus a data description and general statement. <br
Rank as an Incentive
Get PDFMoney is the prime incentive in economic models. Recent evidence makes it clear that people are also greatly concerned about how their incomes compare with those of others, suggesting that rank may be a strong motivator as well. Three experiments in Vietnam assessed whether students in real-world learning environments were concerned with their performance rankings. The results showed that concern with rank, even when rankings were not publicly revealed, strongly motivated performance on academic tests. Moreover, rank was able to outweigh money as a motivator.
Contrasts in kinship structure in mammalian societies
Get PDFComparative studies of mammals confirm Hamilton’s prediction that differences in cooperative and competitive behavior across species will be related to contrasts in kinship between group members. Although theoretical models have explored the factors affecting kinship within social groups, few have analyzed the causes of contrasts in kinship among related species. Here, we describe interspecific differences in average kinship between group members among social mammals and show that a simple mathematical model that includes the number of breeding females, male reproductive skew, and litter size successfully predicts ~95% of observed variation in average kinship between group members across a sample of mammals. Our model shows that a wide range of conditions can generate groups with low average relatedness but only a small and rather specific set of conditions are likely to generate high average levels of relatedness between their members, providing insight into the relative rarity of advanced forms of cooperation in mammalian societies
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Meerkat helpers do not specialize in particular activities
No full textNatuurwetenskappeSoologiePlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]
Behavioural tactics of breeders in cooperative meerkats
No full textNatuurwetenskappeSoologiePlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]
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