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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

The article focuses on a research conducted in order to evaluate the effect of the number of male co-inhabitants experienced early in adult life on male mating behavior in Drosophila melanogaster and to identify the effects of changes in mating behavior on male competitive fitness. It discusses the existence of non-linear relationship between early life experience and fitness components and a significant effect of co-inhabitant number on copulation duration and sperm defense.

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. [ABSTRACT FROM AUTHOR]

1. Despite considerable theoretical work, the evolution of population stability has rarely been investigated empirically. Moreover, it is not clear whether different stability properties of a population evolve together, or independently. 2. We investigate the evolution of two aspects of population stability using laboratory populations of Drosophila melanogaster selected for faster preadult development and early reproduction, and their matched controls. 3. We show that the constancy stability of the selected populations is significantly higher than their controls, confirming a previous observation that population stability can evolve as a by-product of life-history evolution. This enhanced constancy stability is due to a reduced maximal per capita growth rate, brought about by a reduction in fecundity of the selected populations as a result of the trade-off between developmental rate and fecundity. 4. Persistence stability, as reflected by the probability of extinction, does not differ significantly between selected and control populations. 5. We also show how seemingly trivial experimental details, such as the protocol for restarting extinct populations, can interact with life-history traits to alter the manifestation of the stability properties of a population. [ABSTRACT FROM AUTHOR]

Theory predicts that intralocus sexual conflict can constrain the evolution of sexual dimorphism, preventing each sex from independently maximizing its fitness. To test this idea, we limited genome-wide gene expression to males in four replicate Drosophila melanogaster populations, removing female-specific selection. Over 25 generations, male fitness increased markedly, as sexually dimorphic traits evolved in the male direction. When male-evolved genomes were expressed in females, their fitness displayed a nearly symmetrical decrease. These results suggest that intralocus conflict strongly limits sex-specific adaptation, promoting the maintenance of genetic variation for fitness. Populations may carry a heavy genetic load as a result of selection for separate genders. [ABSTRACT FROM AUTHOR]

Presents a study which analyzed the larval phase of the populations of Drosophila melanogaster. Selection of several populations of the species for faster development and early reproduction; Materials and methodology; Results and discussion.

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In experimental evolutionary studies, altering sex ratio in populations imposes sex‐biased intrasexual and intersexual interactions, which is useful to study the effect of sexual selection and sexual conflict in such populations. We studied cuticular hydrocarbon (CHC) patterns of 170 generations‐old operational sex ratio‐altered Drosophila melanogaster population to investigate the evolutionary outcomes of such selection lines. Our results indicate that the competing sex in each of the selection lines has less variable CHC profile than the less abundant sex, potentially due to sexual selection. The intensity of sexual selection is possibly influenced by intense competition among the abundant sex as well as potential mate choice due to easy availability of mates for the rarer sex in the population. This result is even more striking since the male‐biased replicates were previously shown to have diverged in terms of mate preferences due to sexually antagonistic coevolution (SAC). The precopulatory isolating mechanism underlying such divergent mate preference could be sexual signals such as CHCs since they evolve rapidly and are involved in D. melanogaster mate recognition. Therefore, we also investigate whether CHC profiles diverged in male‐biased replicates in comparison to female‐biased replicates. We found no evidence that cuticular hydrocarbon profiles of male‐biased and female‐biased populations have evolved due to SAC. This study indicates that the differentiation of sexual traits may not be credited to sexual conflict despite populations isolated due to high sexual conflict evolve divergent cuticular hydrocarbon profiles. [ABSTRACT FROM AUTHOR]

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 sex-linked 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. [ABSTRACT FROM AUTHOR]

Intralocus sexual conflict occurs when males and females experience sex-specific selection on a shared genome. With several notable exceptions, intralocus sexual conflict has been investigated in constant environments to which the study organisms have had an opportunity to adapt. However, a change in the environment can result in differential or even opposing selection pressures on males and females, creating sexual conflict. We used experimental evolution to explore the interaction between intralocus sexual conflict, sexual dimorphism and environmental variation in Drosophila melanogaster. Six populations were selected for adult desiccation resistance (D), with six matched control populations maintained in parallel (C). After 46 generations, the D populations had increased in survival time under arid conditions by 68% and in body weight by 20% compared to the C populations. The increase in size was the result of both extended development and faster growth rate of D juveniles. Adaptation to the stress came at a cost in terms of preadult viability and female fecundity. Because males are innately less tolerant of desiccation stress, very few D males survived desiccation-selection; while potentially a windfall for survivors, these conditions mean that most males' fitness was determined posthumously. We conjectured that selection for early maturation and mating in males was in conflict with selection for survival and later reproduction in females. Consistent with this prediction, the sexes showed different patterns of age-specific desiccation resistance and resource acquisition, and there was a trend towards increasingly female-biased sexual size dimorphism. However, levels of desiccation resistance were unaffected, with D males and females increasing in parallel. Either there is a strong positive genetic correlation between the sexes that limits independent evolution of desiccation resistance, or fitness pay-offs from the strategy of riding out the stress bout are great enough to sustain concordant selection on the two sexes. We discuss the forces that mould fitness in males under a regimen where trade-offs between survival and reproduction may be considerable. [ABSTRACT FROM AUTHOR]

The article highlights a study on the correlation between feeding rate and development in Drosophila (D.) melanogaster. It says that eight populations of D. melanogaster were selected for the study in which four were for faster development and early reproduction. It has been found that reduced larval feeding rate is a strong evolutionary correlate of faster development in Drosphila.

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]