Evolution of pathogen-specific improved survivorship post-infection in populations of Drosophila melanogaster adapted to larval crowding.

The environment experienced by individuals during their juvenile stages has an impact on their adult stages. In holometabolous insects like Drosophila melanogaster, most of the resource acquisition for adult stages happens during the larval stages. Larval-crowding is a stressful environment, which exposes the larvae to scarcity of food and accumulation of toxic waste. Since adult traits are contingent upon larval stages, in larval-crowding like conditions, adult traits are prone to get affected. While the effect of resource limited, poor-developmental environment on adult immune response has been widely studied, the effect of adaptation to resource-limited developmental environment has not been studied, therefore in this study we assayed the evolution of ability to survive infection in adult stages as a correlated response to adaptation to larval crowding environments. Using four populations of Drosophila melanogaster adapted to larval crowding for 240 generations and their respective control populations, we show that populations adapted to larval crowding show an improved and evolved post-infection survivorship against a gram-negative bacteria Pseudomonas entomophila. Whereas, against a gram-positive bacteria Enterococcus faecalis, no difference in post-infection survivorship was observed across control and selected populations. In this study, we report the co-related evolution of pathogen-specific increased survivorship post-infection in populations of Drosophila melanogaster as a result of adaptation to larval crowding environment.

Evolution of the metabolome in response to selection for increased immunity in populations of Drosophila melanogaster.

We used NMR-based metabolomics to test two hypotheses-(i) there will be evolved differences in the metabolome of selected and control populations even under un-infected conditions and (ii) post infection, the metabolomes of the selected and control populations will respond differently. We selected replicate populations of Drosophila melanogaster for increased survivorship (I) against a gram-negative pathogen. We subjected the selected (I) and their control populations (S) to three different treatments: (1) infected with heat-killed bacteria (i), (2) sham infected (s), and (3) untreated (u). We performed 1D and 2D NMR experiments to identify the metabolic differences. Multivariate analysis of the metabolic profiles of the untreated (Iu and Su) flies yielded higher concentrations of lipids, organic acids, sugars, amino acids, NAD and AMP in the Iu treatment as compared to the Su treatment, showing that even in the absence of infection, the metabolome of the I and S regimes was different. In the S and I regimes, post infection/injury, concentration of metabolites directly or indirectly associated with energy related pathways (lipids, organic acids, sugars) declined while the concentration of metabolites that are probably associated with immune response (amino acids) increased. However, in most cases, the I regime flies had a higher concentration of such metabolites even under un-infected conditions. The change in the metabolite concentration upon infection/injury was not always comparable between I and S regimes (in case of lactate, alanine, leucine, lysine, threonine) indicating that the I and S regimes had evolved to respond differentially to infection and to injury.

Identification and characterization of novel natural pathogen of Drosophila melanogaster isolated from wild captured Drosophila spp.

Drosophila melanogaster is an emerging model system for the study of evolutionary ecology of immunity. However, a large number of studies have used non natural pathogens as very few natural pathogens have been isolated and identified. Our aim was to isolate and characterize natural pathogen/s of D. melanogaster. A bacterial pathogen was isolated from wild caught Drosophila spp., identified as a new strain of Staphylococcus succinus subsp. succinus and named PK-1. This strain induced substantial mortality (36-62%) in adults of several laboratory populations of D. melanogaster. PK-1 grew rapidly within the body of the flies post infection and both males and females had roughly same number of colony forming units. Mortality was affected by mode of infection and dosage of the pathogen. However mating status of the host had no effect on mortality post infection. Given that there are very few known natural bacterial pathogens of D. melanogaster and that PK-1 can establish a sustained infection across various outbred and inbred populations of D. melanogaster this new isolate is a potential resource for future studies on immunity.

Local adaptation to developmental density does not lead to higher mating success in Drosophila melanogaster.

In this study, we investigate the effect of local adaptation to developmental density on male mating success in laboratory populations of Drosophila melanogaster. Mating success is known to be influenced by body condition which can in turn be influenced by local adaptation. We test the hypothesis that males adapted to a given environment have higher mating success when assayed in that environment. We used males selected for adaptation to high larval density and their controls which are reared at low larval density. We grew assay males in low and high densities whereas the focal females (raised at low larval density) used for the experiment belonged to the common ancestor of selected and control populations. We considered selected males grown at high density and control males grown at low density as 'adapted'. Similarly, we considered selected males grown at low density and control males grown at high density as 'nonadapted'. Selected male belonging to a given treatment (larval density) was made to compete with control male of the same treatment for mating with ancestral female. We quantified components of reproductive fitness: mating latency, copulation duration, mating success and number of progeny sired by the 'adapted' and 'nonadapted' males. The results show that local adaptation does not lead to higher mating success in populations adapted to their own larval rearing environment.

Evolution of increased adult longevity in Drosophila melanogaster populations selected for adaptation to larval crowding.

In holometabolous animals such as Drosophila melanogaster, larval crowding can affect a wide range of larval and adult traits. Adults emerging from high larval density cultures have smaller body size and increased mean life span compared to flies emerging from low larval density cultures. Therefore, adaptation to larval crowding could potentially affect adult longevity as a correlated response. We addressed this issue by studying a set of large, outbred populations of D. melanogaster, experimentally evolved for adaptation to larval crowding for 83 generations. We assayed longevity of adult flies from both selected (MCUs) and control populations (MBs) after growing them at different larval densities. We found that MCUs have evolved increased mean longevity compared to MBs at all larval densities. The interaction between selection regime and larval density was not significant, indicating that the density dependence of mean longevity had not evolved in the MCU populations. The increase in longevity in MCUs can be partially attributed to their lower rates of ageing. It is also noteworthy that reaction norm of dry body weight, a trait probably under direct selection in our populations, has indeed evolved in MCU populations. To the best of our knowledge, this is the first report of the evolution of adult longevity as a correlated response of adaptation to larval crowding.

Rethinking inheritance, yet again: inheritomes, contextomes and dynamic phenotypes.

In recent years, there have been many calls for an extended evolutionary synthesis, based in part upon growing evidence for nongenetic mechanisms of inheritance, i.e., similarities in phenotype between parents and offspring that are not due to shared genes. While there has been an impressive marshalling of evidence for diverse forms of nongenetic inheritance (epigenetic, ecological, behavioural and symbolic), there have been relatively few studies trying to integrate the different forms of inheritance into a common conceptual structure, a development that would be important to formalize elements of the extended evolutionary synthesis. Here, we propose a framework for an extended view of inheritance and introduce some conceptual distinctions that we believe, are important to this issue. In this framework, the phenotype is conceived of as a dynamic entity, its state, at any point in time resulting from intertwined effects of previous phenotypic state, and of hereditary materials (DNA and otherwise) and environment. We contrast our framework with the standard gene-based view of inheritance, and also discuss our framework in the specific context of recent attempts to accommodate nongenetic inheritance within the framework of classical quantitative genetics and the Price equation. In particular, we believe that the extended view of inheritance and effects on the phenotype developed here is particularly well-suited to individual-based simulation studies of evolutionary dynamics. The results of such simulations, in turn, could be useful for assessing, how well extended models based on quantitative genetics or the Price equation perform at capturing complex evolutionary dynamics.

Egg Viability, Mating Frequency and Male Mating Ability Evolve in Populations of Drosophila melanogaster Selected for Resistance to Cold Shock.

BACKGROUND: Ability to resist temperature shock is an important component of fitness of insects and other ectotherms. Increased resistance to temperature shock is known to affect life-history traits. Temperature shock is also known to affect reproductive traits such as mating ability and viability of gametes. Therefore selection for increased temperature shock resistance can affect the evolution of reproductive traits. METHODS: We selected replicate populations of Drosophila melanogaster for resistance to cold shock. We then investigated the evolution of reproductive behavior along with other components of fitness- larval survivorship, adult mortality, fecundity, egg viability in these populations. RESULTS: We found that larval survivorship, adult mortality and fecundity post cold shock were not significantly different between selected and control populations. However, compared to the control populations, the selected populations laid significantly higher percentage of fertile eggs (egg viability) 24 hours post cold shock. The selected populations had higher mating frequency both with and without cold shock. After being subjected to cold shock, males from the selected populations successfully mated with significantly more non-virgin females and sired significantly more progeny compared to control males. CONCLUSIONS: A number of studies have reported the evolution of survivorship in response to selection for temperature shock resistance. Our results clearly indicate that adaptation to cold shock can involve changes in components of reproductive fitness. Our results have important implications for our understanding of how reproductive behavior can evolve in response to thermal stress.

Experimental evolution of female traits under different levels of intersexual conflict in Drosophila melanogaster.

A number of studies have documented the evolution of female resistance to mate-harm in response to the alteration of intersexual conflict in the populations. However, the life-history consequence of such evolution is still a subject of debate. In this study, we subjected replicate populations of Drosophila melanogaster to different levels of sexual conflict (generated by altering the operational sex ratio) for over 45 generations. Our results suggest that females from populations experiencing higher level of intersexual conflict evolved increased resistance to mate-harm, in terms of both longevity and progeny production. Females from the populations with low conflict were significantly heavier at eclosion and were more susceptible to mate-harm in terms of progeny production under continuous exposure to the males. However, these females produced more progeny upon single mating and had significantly higher longevity in absence of any male exposure-a potential evidence of trade-offs between resistance-related traits and other life-history traits, such as fecundity and longevity. We also report tentative evidence, suggesting an increased male cost of interacting with more resistant females.

The aging of the immune response in Drosophila melanogaster.

Senescence of functional immunity in invertebrates has been a topic of recent interest. Results from previous studies have been inconsistent with older adults exhibiting wide variation in response to infection. In the present study, we assayed the senescence of functional immune response using a large outbred population of Drososphila melanogaster as the model host and Serratia marcescens as the model pathogen. We assessed the effect of an individual's age, parental age, sex, and mating status on overall antibacterial immunity. We found an improvement of immunity with the progression of age with 13-day-old flies exhibiting lower bacterial load compared with 3-day-old flies. Parental age did not show consistent effects on the antibacterial immunity of the offspring. Neither mating status nor the sex of an individual had any significant effect on immune response.

A stuttering education and bullying awareness and prevention resource: a feasibility study.

PURPOSE: This pretest-posttest study examined the feasibility of using a curriculum-level stuttering education and bullying awareness and prevention program to improve peer attitudes toward children who stutter and attitudes toward bullying. Knowledge about potential responses to bullying and students' liking of the program also were examined. METHOD: Data were obtained from 608 children who participated in the stuttering education and bullying prevention initiative that used the Teasing and Bullying: Unacceptable Behaviour (TAB; Langevin, 2000) Program. Participants completed the Peer Attitudes Toward Children Who Stutter (PATCS; Langevin, 2009; Langevin & Hagler, 2004; Langevin, Kleitman, Packman, & Onslow, 2009) scale, the Provictim scale (Rigby & Slee, 1991, 1993), and bullying involvement and knowledge questionnaires. RESULTS: Statistically and practically significant improvements were found for both questionnaires. Children who did not know someone who stutters had higher change scores on the PATCS than children who knew someone who stutters. In general, children who were uninvolved in bullying had the most positive changes in attitudes and liked the TAB program the most. Victims liked the program significantly more often than children who were perpetrators of bullying or were dually involved in bullying. CONCLUSION: Findings suggest that the TAB program may have the potential to effect positive changes in peer attitudes toward children who stutter and toward bullying. Further research using a randomized experimental design is warranted.

Indoor radon concentration and its possible dependence on ventilation rate and flooring type.

The results of radon concentration measurements carried out in dwellings with natural ventilation for 1 y in Bangalore are reported. Measurements, covering three sessions of the day (morning, afternoon, night) were performed two times in a month for 1 y at a fixed place of each dwelling at a height of 1 m above the ground surface in selected dwellings. The low-level radon detection system (LLRDS), an active method, was used for the estimation of radon concentration. The measurements were aimed to understand the diurnal variation and the effect of ventilation rate and flooring type on indoor radon concentration. The geometric mean (± geometric standard deviation) of indoor radon concentration from about 500 measurements carried out in 20 dwellings is found to be 25.4 ± 1.54 Bq m⁻³. The morning, afternoon and night averages were found to be 42.6 ± 2.05, 15.3 ± 2.18 and 28.5 ± 2.2 Bq m⁻³, respectively. The approximate natural ventilation rates of the dwellings were calculated using the PHPAIDA--the on-line natural ventilation, mixed mode and air infiltration rate calculation algorithm and their effects on indoor radon concentrations were studied. The inhalation dose and the lung cancer risk due to indoor radon exposure were found to be 0.66 mSv y⁻¹ and 11.9 per 106 persons, respectively. The gamma exposure rate was also measured in all the dwellings and its correlation with the inhalation dose rate was studied.

Sperm competition and mate harm unresponsive to male-limited selection in Drosophila: an evolving genetic architecture under domestication.

Earlier research by W.R. Rice showed that experimentally limiting gene expression to males in Drosophila melanogaster leads to the rapid evolution of higher fitness. Using a similar male-limited (ML) selection protocol, we confirmed that result and showed that eliminating intralocus sexual conflict results in a comprehensive remodeling of the sexually dimorphic phenotype. However, despite starting from laboratory-evolved descendants of the same founder population used in earlier work, we found no evidence for the increased performance in sperm competition or increased postmating harm to females previously demonstrated. We employed females with both ancestral population genotypes and those of the special "clone generator" females used in ML selection. Despite strong differences in sperm storage or usage patterns between these females, there was no detectable adaptation by males to the specific female stock used in the selection protocol. The lack of evolution of postcopulatory traits suggests either that requisite genetic variation was eliminated by long-term domestication of the base population, or that complex male-by-male-by-female interactions made these traits unavailable to selection. The different evolutionary outcomes produced by two very similar experiments done at different time points underscores the potential for cryptic adaptation in the laboratory to qualitatively affect inferences made using quantitative genetic methodologies.

Reproductive behavior and fitness components in male Drosophila melaogaster are non-linearly affected by the number of male co-inhabitants early in adult life.

Although multiple lines of evidence suggest that early adult life is very important in shaping the reproductive behavior of males, few studies have looked at the fitness consequences of the variation in reproductive behavior induced by differences in early life experience of males. Using a long term laboratory adapted population of Drosophila melanogaster Meigen (Diptera: Drosophilidae), early life experience, in terms of co-inhabitant numbers, was found to affect male mating behavior and at least one fitness component. However, in contrast to previous studies, a non-linear relationship was found between early life experience and fitness components and a significant effect of co-inhabitant number on copulation duration and sperm defense. Both these traits showed a sharp increase as the co-inhabitant numbers changed from 1 to 16. However, there was a decline in the trait values as the co-inhabitant number increased further. The probable causes for the observed non-linear pattern of responses are discussed.

Mating with large males decreases the immune defence of females in Drosophila melanogaster.

Mating has been widely reported to be a costly event for females. Studies indicate that female cost of mating in terms of fecundity and survivorship can be affected by their mates, leading to antagonistic coevolution between the sexes. However, as of now, there is no evidence that the female cost of mating in terms of immune defence is affected by their mates. We assess the effect of different sized males on antibacterial immune defence and reproductive fitness of their mates. We used a large outbred population of Drososphila melanogaster as the host and Serratia marcescens as the pathogen. We generated three different male phenotypes: small, medium and large, by manipulating larval densities. Compared to females mating with small males, those mating with large males had higher bacterial loads and lower fecundity. There was no significant effect of male phenotype on the fraction of females mated or copulation duration (an indicator of ejaculate investment). Thus, our study is the first clear demonstration that male phenotype can affect the cost of mating to females in terms of their antibacterial immune defence. Mating with large males imposes an additional cost of mating to females in terms of reduced immune defence. The observed results are very likely due to qualitative/quantitative differences in the ejaculates of the three different types of males. If the phenotypic variation that we observed in males in our study is mirrored by genetic variation, then, it can potentially lead to antagonistic coevolution of the sexes over immune defence.

Male-limited evolution suggests no extant intralocus sexual conflict over the sexually dimorphic cuticular hydrocarbons of Drosophila melanogaster.

Sexually dimorphic traits are likely to have evolved through sexually antagonistic selection. However, recent empirical data suggest that intralocus sexual conflict often persists, even when traits have diverged between males and females. This implies that evolved dimorphism is often incomplete in resolving intralocus conflict, providing a mechanism for the maintenance of genetic variance in fitness-related traits. We used experimental evolution in Drosophila melanogaster to directly test for ongoing conflict over a suite of sexually dimorphic cuticular hydrocarbons (CHCs) that are likely targets of sex-specific selection. Using a set of experimental populations in which the transmission of genetic material had been restricted to males for 82 generations, we show that CHCs did not evolve, providing experimental evidence for the absence of current intralocus sexual conflict over these traits. The absence of ongoing conflict could indicate that CHCs have never been the target of sexually antagonistic selection, although this would require the existing dimorphism to have evolved via completely sexlinked mutations or as a result of former, but now absent, pleiotropic effects of the underlying loci on another trait under sexually antagonistic selection. An alternative interpretation, and which we believe to be more likely, is that the extensive CHC sexual dimorphism is the result of past intralocus sexual conflict that has been fully resolved, implying that these traits have evolved genetic independence between the sexes and that genetic variation in them is therefore maintained by alternative mechanisms. This latter interpretation is consistent with the known roles of CHCs in sexual communication in this species and with previous studies suggesting the genetic independence of CHCs between males and females. Nevertheless, direct estimates of sexually antagonistic selection will be important to fully resolve these alternatives.

Five-year longitudinal treatment outcomes of the ISTAR Comprehensive Stuttering Program.

UNLABELLED: Replicated evidence of satisfactory 1- and 2-year post-treatment outcomes has been reported for the Comprehensive Stuttering Program (CSP). However, little is known about longer term outcomes of the CSP. Yearly follow-up measures were obtained from 18 participants for 5 consecutive years. At 5-year follow-up, participants were maintaining clinically and statistically significant reductions in stuttering and increases in rates of speech relative to pre-treatment measures. Standardized effect sizes were large. There were no significant differences among the immediate post-treatment and five follow-up measures, indicating that speech gains achieved by the end of the treatment program were stable over the 5-year follow-up period. Insufficient return rates for self-report data for the third to fifth follow-up measurement occasions prohibited analyzing these data. However, non-significant differences among the immediate post-treatment and two follow-up measures indicated that improvements achieved by the end of treatment in speech-related confidence, and perceptions of struggle, avoidance, and expectancy to stutter were stable over the 2-year follow-up period. Significant differences among the speech-related communication attitudes scores indicated that improvements in attitudes made at the end of the treatment program were less stable. Taken together, these results provide further and longer term evidence of the effectiveness of the CSP. EDUCATIONAL OBJECTIVES: Readers will be able to: (1) describe the main components of the Comprehensive Stuttering Program (2) describe a methodology for determining clinically meaningful maintenance of stuttering reductions, and (3) describe the durability and stability of improvements in speech and self-report measures across time.

Radon daughters' concentration in air and exposure of joggers at the university campus of Bangalore, India.

The concentration of radon daughters in outdoor air was measured continuously from January 2006 to December 2006 near the Department of Physics, Bangalore University campus, Bangalore. The concentration was measured by collecting air samples at a height of 1 m above the ground level on a glass micro fibre filter paper with a known air flow rate. The results show that the radon progeny concentration exhibits distinct seasonal and diurnal variations that are predominantly caused by changes in the temperature gradient at the soil-atmosphere interface. The concentration was found to be high from 20.00 to 8.00 hrs, when the turbulence mixing was minimum and low during the rest of the time. In terms of the monthly concentration, January was found to be the highest with September/August being the lowest. The diurnal variations in the concentrations of radon progeny were found to exhibit positive correlation with the relative humidity and anti-correlation with the atmospheric temperature. From the measured concentration, an attempt was made to establish the annual effective dose to the general public of the region and was found to be 0.085 mSv/a. In addition, an attempt was also made for the first time to study the variation of inhalation dose with respect to the physical activity levels. Results show that in the light of both the effect of chemical pollutants and radiation dose due to inhalation of radon daughters, evening jogging is advisable.