vFitness: a web-based computing tool for improving estimation of <Emphasis Type="Italic">in vitro</Emphasis> HIV-1 fitness experiments

Background  

The replication rate (or fitness) between viral variants has been investigated in vivo and in vitro for human immunodeficiency virus (HIV). HIV fitness plays an important role in the development and persistence of drug resistance. The accurate estimation of viral fitness relies on complicated computations based on statistical methods. This calls for tools that are easy to access and intuitive to use for various experiments of viral fitness.     

The enigmatic nature of altruism in organ transplantation: a cross-cultural study of transplant physicians' views on altruism

Background

Although altruism is a key principle in our current organ donation and transplantation system, the meanings and implications of the term have been widely debated. Recently, a new type of living organ donation--anonymous and non-directed, also called living altruistic donation (LAD)--has brought the issue into sharper focus. Transplant physicians' views on altruism might influence their attitudes and actions toward living altruistic donors. This study aimed to explore such views among transplant physicians in France and Quebec.

Findings

A total of 27 French and 19 Quebec transplant physicians participated in individual, semi-structured interviews between October 2004 and December 2005. The majority of these participants associated altruism with gratuitousness and saw altruistic acts as multiple and varied, ranging from showing consideration to saving a person's life.

Conclusions

The transplant physicians' discourses on altruism were quite diverse, leading us to question the relevance of the concept in organ transplantation and the appropriateness of the term "living altruistic donation."

     

Exact versus heuristic models of kin selection

This paper examines the conditions under which the classical inclusive fitness formulation of Hamilton (1964) provides an adequate approximation to the dynamics of gene frequency change and to conditions for genetic equilibrium, in the “additive” model of altruism between sibs of Uyenoyama and Feldman (1981). It is concluded that the classical formulation is adequate, provided that either the effect of the gene on the probability of behaving altruistically is low or the costs and benefits of altruism are small, unless the benefit/cost ratio k is very close to 2, the value that must be exceeded for altruism to be favoured. In addition, the gene for altruism must be underdominant, recessive or partially recessive in its effect on the probability of behaving altruistically, for the inclusive fitness predictions to break down significantly.     

Human Beings as Evolved Nepotists

Inclusive fitness theory provides a compelling explanation for the evolution of altruism among kin. However, a completely satisfactory account of non-kin altruism is still lacking. The present study compared the level of altruism found among siblings with that found among friends and mates and sought to reconcile the findings with an evolutionary explanation for human altruism. Participants (163 males and 156 females) completed a questionnaire about help given to a sibling, friend, or mate. Overall, participants gave friends and mates as much or more help than they gave siblings. However, as the cost of help increased, siblings received a progressively larger share of the help, whereas friends and mates received a progressively smaller share, despite the fact that participants were closer emotionally to friends and mates than they were to siblings. These findings help to explain the relative standing of friends and mates as recipients of altruistic aid.

Exposure to light enhances pre-adult fitness in two dark-dwelling sympatric species of ants

Background  

In insects, circadian clocks play a key role in enhancing fitness by regulating life history traits such as developmental time and adult lifespan. These clocks use environmental light/dark (LD) cycles to fine-tune a wide range of behavioral and physiological processes. To study the effect of environmental LD conditions on pre-adult fitness components, we used two dark-dwelling sympatric species of ants (the night active Camponotus compressus and the day active Camponotus paria), which normally develop underground and have fairly long pre-adult developmental time.     

An experimental test for indirect benefits in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

Background  

Despite much empirical attention, tests for indirect benefits of mate choice have rarely considered the major components of sexual and nonsexual offspring fitness relevant to a population. Here we use a novel experimental design to test for the existence of any indirect benefits in a laboratory adapted population of D. melanogaster. Our experiment compared the fitness (mating success, longevity, and productivity) of individuals possessing genomes that derived two generations previously from males that were either entirely successful (studs) or wholly unsuccessful (duds) at achieving mates in three subsequent rounds of mating trials.     

The genetic architecture of fitness in a seed beetle: assessing the potential for indirect genetic benefits of female choice

Background  

Quantifying the amount of standing genetic variation in fitness represents an empirical challenge. Unfortunately, the shortage of detailed studies of the genetic architecture of fitness has hampered progress in several domains of evolutionary biology. One such area is the study of sexual selection. In particular, the evolution of adaptive female choice by indirect genetic benefits relies on the presence of genetic variation for fitness. Female choice by genetic benefits fall broadly into good genes (additive) models and compatibility (non-additive) models where the strength of selection is dictated by the genetic architecture of fitness. To characterize the genetic architecture of fitness, we employed a quantitative genetic design (the diallel cross) in a population of the seed beetle Callosobruchus maculatus, which is known to exhibit post-copulatory female choice. From reciprocal crosses of inbred lines, we assayed egg production, egg-to-adult survival, and lifetime offspring production of the outbred F1 daughters (F1 productivity).     

A system for studying evolution of life-like virtual organisms

Background  

Fitness landscapes, the dependences of fitness on the genotype, are of critical importance for the evolution of living beings. Unfortunately, fitness landscapes that are relevant to the evolution of complex biological functions are very poorly known. As a result, the existing theory of evolution is mostly based on postulated fitness landscapes, which diminishes its usefulness. Attempts to deduce fitness landscapes from models of actual biological processes led, so far, to only limited success.     

The evolution of competition and policing: opposing selection within and among groups

Background  

Although selection favors exploitative competition within groups, a group of hypercompetitive individuals may be less productive than a cooperative group. When competition is costly for group fitness, among-group selection can favor groups with 'policing' individuals who reduce within-group competition at a cost to their own fitness, or groups of individuals who restrain their competitive intensity ('self policing'). We examine these possibilities in a series of explicit population-genetic models.     

Models of the evolution of altruism

There are two ways of calculating the spread of a gene for altruism. One, originally proposed by Hamilton, is to allow for the effects of the gene on the survival and reproduction of collateral relatives of the individual carrying it (i.e., “inclusive fitness”); this leads to the condition k > 1/r for the spread of the gene, where k is a benefit/cost ratio. The other is to count only the direct offspring of a carrier, but to allow for the altruistic acts performed toward the carrier by its relatives (“neighbour modulated fitness” or “personal fitness”). A recent personal fitness model (L. L. Cavalli Sforza and M. W. Feldman, 1978, Theor. Pop. Biol.14, 268–280) analyses parent-offspring and sib-sib altruism and concludes that k > 1/r is applicable only when fitness components are combined additively. The present paper analyses some simple models in which the phenotypic effects are carefully specified. It is concluded that it is sometimes, but not always, appropriate to combine fitness components additively. The relative roles of inclusive and personal fitness models are compared. The former have the virtue of being easier to think about in causal terms; and the latter of incorporating the evolution of altruism into the corpus of population genetics as an example of frequency-dependent selection.     

Haploinsufficiency and the sex chromosomes from yeasts to humans

Background  

Haploinsufficient (HI) genes are those for which a reduction in copy number in a diploid from two to one results in significantly reduced fitness. Haploinsufficiency is increasingly implicated in human disease, and so predicting this phenotype could provide insights into the genetic mechanisms behind many human diseases, including some cancers.     

The effect of three environmental conditions on the fitness of cytochrome P450 monooxygenase-mediated permethrin resistance in Culex pipiens quinquefasciatus

Background  

The evolution of insecticide resistance and persistence of resistance phenotypes are influenced by the fitness of resistance alleles in the absence of insecticide pressure. Experimental determination of fitness is difficult, but fitness can be inferred by measuring changes in allele frequencies in appropriate environments. We conducted allele competition experiments by crossing two highly related strains of Culex pipiens quinquefasciatus mosquitoes. One strain (ISOP450) was permethrin resistant (due to P450-mediated detoxification) and one was a susceptible strain. Allele and genotype frequencies were examined for 12 generations under three environmental conditions: standard laboratory, temephos exposure (an insecticide to which the P450 detoxification mechanism in ISOP450 confers no resistance and which is commonly used in mosquito control programs) and cold temperature stress (mimics the colder temperatures within the habitat of this mosquito).     

TagSmart: analysis and visualization for yeast mutant fitness data measured by tag microarrays

Background  

A nearly complete collection of gene-deletion mutants (96% of annotated open reading frames) of the yeast Saccharomyces cerevisiae has been systematically constructed. Tag microarrays are widely used to measure the fitness of each mutant in a mutant mixture. The tag array experiments can have a complex experimental design, such as time course measurements and drug treatment with multiple dosages.     

Exploiting gene deletion fitness effects in yeast to understand the modular architecture of protein complexes under different growth conditions

Background  

Understanding how individual genes contribute towards the fitness of an organism is a fundamental problem in biology. Although recent genome-wide screens have generated abundant data on quantitative fitness for single gene knockouts, very few studies have systematically integrated other types of biological information to understand how and why deletion of specific genes give rise to a particular fitness effect. In this study, we combine quantitative fitness data for single gene knock-outs in yeast with large-scale interaction discovery experiments to understand the effect of gene deletion on the modular architecture of protein complexes, under different growth conditions.     

Why reciprocal altruism is not a kind of group selection

Reciprocal altruism was originally formulated in terms of individual selection and most theorists continue to view it in this way. However, this interpretation of reciprocal altruism has been challenged by Sober and Wilson (1998). They argue that reciprocal altruism (as well as all other forms of altruism) evolves by the process of group selection. In this paper, we argue that the original interpretation of reciprocal altruism is the correct one. We accomplish this by arguing that if fitness attaches to (at minimum) entire life cycles, then the kind of fitness exchanges needed to form the group-level in such situations is not available. Reciprocal altruism is thus a result of individual selection and when it evolves, it does so because it is individually advantageous.     

Genetic and potential non-genetic benefits increase offspring fitness of polyandrous females in non-resource based mating system

Background  

The adaptive significance of female polyandry is currently under considerable debate. In non-resource based mating systems, indirect, i.e. genetic benefits have been proposed to be responsible for the fitness gain from polyandry. We studied the benefits of polyandry in the Arctic charr (Salvelinus alpinus) using an experimental design in which the material investments by the sires and maternal environmental effects were controlled.     

Restrictive pulmonary function is more prevalent in patients with ankylosing spondylitis than in matched population controls and is associated with impaired spinal mobility: a comparative study

Introduction  

Pulmonary involvement is a known manifestation in patients with ankylosing spondylitis (AS). However, previous studies have been based on small samples and the reported prevalence and associations with typical clinical features vary. The purpose of this study was to compare pulmonary function (PF) in patients with AS and population controls, and to study associations between PF and disease related variables, cardio-respiratory fitness and demographic variables in patients with AS.     

Specialised placement of morphs within the gall of the social aphid <Emphasis Type="Italic">Pemphigus spyrothecae</Emphasis>

Background  

The strategic placement and aggregation of certain castes within the nests of eusocial insects such as bees and ants results in complex colonies that enjoy increased fitness through improved efficiency of social tasks. To examine if this advanced social phenomenon might apply to social aphids, the location of the numerous morphs within the nests (plant galls) of the aphid species Pemphigus spyrothecae was examined.