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Data from: Cold adaptation increases rates of nutrient flow and metabolic plasticity during cold exposure in Drosophila melanogaster

Metabolic flexibility is an important component of adaptation to stressful environments, including thermal stress and latitudinal adaptation. A long history of population genetic studies suggest that selection on core metabolic enzymes may shape life histories by altering metabolic flux. However, the direct relationship between selection on thermal stress hardiness and metabolic flux has not previously been tested. We investigated flexibility of nutrient catabolism during cold stress in Drosophila melanogaster artificially selected for fast or slow recovery from chill coma (i.e. cold-hardy or -susceptible), specifically testing the hypothesis that stress adaptation increases metabolic turnover. Using 13C-labelled glucose, we first showed that cold-hardy flies more rapidly incorporate ingested carbon into amino acids and newly synthesized glucose, permitting rapid synthesis of proline, a compound shown elsewhere to improve survival of cold stress. Second, using glucose and leucine tracers we showed that cold-hardy flies had higher oxidation rates than cold-susceptible flies before cold exposure, similar oxidation rates during cold exposure, and returned to higher oxidation rates during recovery. Additionally, cold-hardy flies transferred compounds among body pools more rapidly during cold exposure and recovery. Increased metabolic turnover may allow cold-adapted flies to better prepare for, resist and repair/tolerate cold damage. This work illustrates for the first time differences in nutrient fluxes associated with cold adaptation, suggesting that metabolic costs associated with cold hardiness could invoke resource-based trade-offs that shape life histories.

Data from: Selection at the Esterase-2 locus of Drosophila buzzatii? Perturbation-reperturbation experiments

Apparent selection affecting starch gel electrophoretic alleles at the Esterase-2 locus of Drosophila buzzatii has been detected in laboratory and natural populations. Perturbation-reperturbation of allele frequencies in replicated laboratory populations attempts to test direct selective effects at the locus versus effects of linked loci. Sequential gel electrophoresis has identified more alleles within starch classes, and three of these alleles (within the a, b and c starch alleles) were used in cage population experiments. Allele a/1.00/1.00/1.00 was set up in 10 replicate populations with allele c/1.00/1.00/1.00, and in an independent 10 replicate populations with allele b/0.99/1.01/1.00. For each set, three reperturbations were done. Replicate populations generally showed similar patterns of allele frequency change and clear directionality: effects of selection, not drift. However, four populations deviated from their replicates, indicating dissipation of linkage disequilibrium. Estimates of pre-adult viability in the F2 of pair-wise crosses among 12 sequential gel electrophoretic alleles showed very variable modes of inheritance and relative viability fitnesses. Together with the diversity of patterns of allele frequency change in the cage populations, these results suggest a gene complex, with selection acting on an interacting set of loci which may include Esterase-2.

opencc-zeroDec 2017View details →

Data from: Developmental and transcriptomal responses to seasonal dietary shifts in the cactophilic Drosophila mojavensis of North America

Drosophila mojavensis normally breeds in necrotic columnar cactus, but they also feed and breed in Opuntia fruit (prickly pear) which serves as a seasonal resource. The prickly pear fruits are much different chemically from cacti, mainly in their free sugars and lipid content, raising the question of the effects of this seasonal shift on fitness and on gene expression. Here we reared three isofemale strains of D. mojavensis collected from different parts of the species' range on semi-natural medium of either cactus or prickly pear fruit and measured the development time, survival, body weights and desiccation resistance. All these parameters were affected by diet and by interaction with strain and or sex. Interestingly, however, there appear to be tradeoffs: flies developed faster in prickly pear and the emerging adults were heavier, but those having grown in cactus were more resistant to desiccation. We also evaluated gene expression of emerging male and female adult flies using RNA-Seq. While more genes were down-regulated in prickly pear fruit than up-regulated in both sexes, the sexes did differ in expression patterns. The majority of the genes that were preferentially expressed comparing prickly pear fruit vs cactus underlie metabolism. Genes involved with carbohydrate and lipid metabolism, as well as with the amino acid serine, and their relationship to growth and development reflect the ways in which these dietary differences affect the flies.

opencc-zeroDec 2012View details →

Data from: Genetic history of a colonising population: Drosophila buzzatii (Diptera: Drosophilidae) in Australia

Drosophila buzzatii Patterson & Wheeler, a cactophilic species that feeds and breeds in the rotting tissues of various Opuntia cactus species, was inadvertently introduced to Australia from Argentina sometime during the period 1931–1936. After a bottleneck at introduction, its spread through the cactus distribution was probably very rapid as a result of natural dispersal from the site of introduction and from three other foci colonized from the introduction site by human intervention. By 1940, the Opuntia distribution and consequently that of D. buzzatii was reduced to spatially isolated populations, with probable further bottlenecking of at least some of the D. buzzatii populations. Allozyme data (primarily six polymorphic loci) from flies collected during April 1972 to February 1996 at 67 localities were used to examine current population differentiation and relationships, as well as to infer aspects of their demographic history. Although there is significant isolation-by-distance, genetic relationships among the populations are not simply related to geographical distance, implying that genetic drift has contributed to population differentiation. However, the biotic and, to an extent, the physical environment are not the same in Australia as in Argentina. Consequently, exposure to novel environments has led to local adaptation and further population differentiation. Genetic variation and the structure of Australian populations apparently are determined by founder effects (drift) at the level of individual breeding sites (cactus rots), by diversifying selection among rots within a locality, as well as by drift and geographically varying selection among localities.

opencc-zeroDec 2018View details →

Data from: Genetic redundancy fuels polygenic adaptation in Drosophila

The genetic architecture of adaptive traits is of key importance to predict evolutionary responses. Most adaptive traits are polygenic—i.e., result from selection on a large number of genetic loci—but most molecularly characterized traits have a simple genetic basis. This discrepancy is best explained by the difficulty in detecting small allele frequency changes (AFCs) across many contributing loci. To resolve this, we use laboratory natural selection to detect signatures for selective sweeps and polygenic adaptation. We exposed 10 replicates of a Drosophila simulans population to a new temperature regime and uncovered a polygenic architecture of an adaptive trait with high genetic redundancy among beneficial alleles. We observed convergent responses for several phenotypes—e.g., fitness, metabolic rate, and fat content—and a strong polygenic response (99 selected alleles; mean s = 0.059). However, each of these selected alleles increased in frequency only in a subset of the evolving replicates. We discerned different evolutionary paradigms based on the heterogeneous genomic patterns among replicates. Redundancy and quantitative trait (QT) paradigms fitted the experimental data better than simulations assuming independent selective sweeps. Our results show that natural D. simulans populations harbor a vast reservoir of adaptive variation facilitating rapid evolutionary responses using multiple alternative genetic pathways converging at a new phenotypic optimum. This key property of beneficial alleles requires the modification of testing strategies in natural populations beyond the search for convergence on the molecular level.

Data from: Wolbachia in the Drosophila yakuba complex: pervasive frequency variation and weak cytoplasmic incompatibility, but no apparent effect on reproductive isolation

Three hybridizing species-the clade ((Drosophila yakuba, D. santomea), D. teissieri) -comprise the yakuba complex in the D. melanogaster subgroup. Their ranges overlap on Bioko and São Tomé, islands off west Africa. All three species are infected with Wolbachia, maternally inherited, endosymbiotic bacteria, best known for manipulating host reproduction to favor infected females. Previous analyses reported no cytoplasmic incompatibility (CI) in these species. However, we discovered that Wolbachia from each species cause intra- and interspecific CI. In D. teissieri, analyses of F1 and backcross genotypes show that both host genotype and Wolbachia variation modulate CI intensity. Wolbachia-infected females seem largely protected from intra- and interspecific CI, irrespective of Wolbachia and host genotypes. Wolbachia do not affect host mating behavior or female fecundity, within or between species. The latter suggests little apparent effect of Wolbachia on premating or gametic RI between host species. In nature, Wolbachia frequencies varied spatially for D. yakuba in 2009, with 76% (N = 155) infected on São Tomé, and only 3% (N = 36) infected on Bioko; frequencies also varied temporally in D. yakuba and D. santomea on São Tomé between 2009 and 2015. These temporal frequency fluctuations could generate asymmetries in interspecific mating success, and contribute to postzygotic RI. However, the fluctuations in Wolbachia frequencies that we observe also suggest that asymmetries are unlikely to persist. Finally, we address theoretical questions that our empirical findings raise about Wolbachia persistence when conditions fluctuate and about the stable coexistence of Wolbachia and host variants that modulate Wolbachia effects.

Data from: Flies on the move: an inherited virus mirrors Drosophila melanogaster's elusive ecology and demography

Vertically transmitted parasites rely on their host's reproduction for their transmission, leading to the evolutionary histories of both parties being intimately entwined. Parasites can thus serve as a population genetic magnifying glass for their host's demographic history. Here, we study the fruitfly Drosophila melanogaster's vertically transmitted sigma virus DMelSV. The virus has a high mutation rate and low effective population size, allowing us to reconstruct at a fine scale how the combined forces of the movement of flies and selection on the virus have shaped its migration patterns. We found that the virus is likely to have spread to Europe from Africa, mirroring the colonization route of Drosophila. The North American DMelSV population appears to be the result of a recent single immigration from Europe, invading together with its host in the late 19th century. Across Europe, DMelSV migration rates are low and populations are highly genetically structured, likely reflecting limited fly movement. Despite being intolerant of extreme cold, viral diversity suggests that fly populations can persist in harsh continental climates and that recolonisation from the warmer south plays a minor role. In conclusion, studying DMelSV can provide insights into the poorly understood ecology of D. melanogaster, one of the best-studied organisms in biology.

opencc-zeroDec 2018View details →

Data from: Comparative analysis of adaptive and neutral markers of Drosophila mediopunctata populations dispersed among forest fragments

Comparison of adaptive and neutral genetic markers is a valuable approach to characterize the evolutionary consequences of populations living in environments threatened by anthropogenic disturbances, such as forest fragmentation. Shifts in allele frequencies, low genetic variability, and a small effective population size can be considered clear signs of forest fragmentation effects (due to genetic drift) over natural populations, while adaptive responses correlate with environmental variables. Brazilian Atlantic Forest had its landscape drastically reduced and fragmented. Now, several forest remnants are isolated from each other by urban and crop areas. We sampled Drosophila mediopunctata populations from eight forest remnants dispersed on two adjacent geomorphological regions, which are physiognomic and climatically quite distinct. Microsatellite data of inversion‐free chromosomes (neutral genetic marker) indicate low structuration among populations suggesting that they were panmictic and greatly influenced by gene flow. Moreover, significant differences in chromosomal inversion frequencies (adaptive genetic marker) among populations and their correlations with climatic and geographical variables indicate that genetic divergence among populations could be an adaptive response to their environment. Nonetheless, we observed a significant difference in inversion frequencies of a population in two consecutive years that may be associated with edge and demographic effects. Also, it may be reflecting seasonal changes of inversion frequencies influenced by great temperature variation due to edge effects. Moreover, the forest fragment size does not affect genetic variation of neutral markers. Our data indicate that despite oscillations in chromosomal inversion frequencies, D. mediopunctata populations from Brazilian Atlantic Forest and their divergence may be driven by adaptive factors to local differences, perhaps because it is a small flying insect easily carried by the wind increasing its migration rates.

opencc-zeroOct 2019View details →

Drosophila carboxypeptidase D (SILVER) is a key enzyme in neuropeptide processing required to maintain locomotor activity levels and survival rate

<p>Neuropeptides are processed from larger preproproteins by a dedicated set of enzymes. The molecular and biochemical mechanisms underlying preproprotein processing and the functional importance of processing enzymes are well‐characterised in mammals, but little studied outside this group. In contrast to mammals, Drosophila melanogaster lacks a gene for carboxypeptidase E (CPE), a key enzyme for mammalian peptide processing. By combining peptidomics and neurogenetics, we addressed the role of carboxypeptidase D (dCPD) in global neuropeptide processing and selected peptide‐regulated behaviours in Drosophila. We found that a deficiency in dCPD results in C‐terminally extended peptides across the peptidome, suggesting that dCPD took over CPE function in the fruit fly. dCPD is widely expressed throughout the nervous system, including peptidergic neurons in the mushroom body and neuroendocrine cells expressing adipokinetic hormone. Conditional hypomorphic mutation in the dCPD‐encoding gene silver in the larva causes lethality, and leads to deficits in starvation‐induced hyperactivity and appetitive gustatory preference, as well as to reduced viability and activity levels in adults. A phylogenomic analysis suggests that loss of CPE is not common to insects, but only occurred in Hymenoptera and Diptera. Our results show that dCPD is a key enzyme for neuropeptide processing and peptide‐regulated behaviour in Drosophila. dCPD thus appears as a suitable target to genetically shut down total neuropeptide production in peptidergic neurons. The persistent occurrence of CPD in insect genomes may point to important further CPD functions beyond neuropeptide processing which cannot be fulfilled by CPE.</p>

Data from: Sexual conflict and interacting phenotypes: a quantitative genetic analysis of fecundity and copula duration in Drosophila melanogaster

Many reproductive traits that have evolved under sexual conflict may be influenced by both sexes. Investigation of the genetic architecture of such traits can yield important insight into their evolution, but this entails that the heritable component of variation is estimated for males and females – as an interacting phenotype. We address the lack of research in this area through an investigation of egg production and copula duration in the fruit fly, Drosophila melanogaster. Despite egg production rate being determined by both sexes, which may cause sexual conflict, an assessment of this trait as an interacting phenotype is lacking. It is currently unclear whether copula duration is determined by males and/or females. We found significant female, but not male, genetic variance for egg production rate which may indicate reduced potential for ongoing sexually antagonistic coevolution. In contrast, copula duration was determined by significant genetic variance in both sexes. We also identified genetic variation in egg retention among virgin females. Although previously identified in wild populations, it is unclear why this should be present in a laboratory stock. This study provides a novel insight into the shared genetic architecture of reproductive traits that are the subject of sexual conflict.

Data from: Transcriptome modulation during host shift is driven by secondary metabolites in desert Drosophila

High-throughput transcriptome studies are breaking new ground to investigate the responses that organisms deploy in alternative environments. Nevertheless, much remains to be understood about the genetic basis of host plant adaptation. Here, we investigate genome-wide expression in the fly Drosophila buzzatii raised in different conditions. This species uses decaying tissues of cactus of the genus Opuntia as primary rearing substrate and secondarily, the necrotic tissues of the columnar cactus Trichocereus terscheckii. The latter constitutes a harmful host, rich in mescaline and other related phenylethylamine alkaloids. We assessed the transcriptomic responses of larvae reared in Opuntia sulphurea and T. terscheckii, with and without the addition of alkaloids extracted from the latter. Whole-genome expression profiles were massively modulated by the rearing environment, mainly by the presence of T. terscheckii alkaloids. Differentially expressed genes were mainly related to detoxification, oxidation–reduction and stress response; however, we also found genes involved in development and neurobiological processes. In conclusion, our study contributes new data onto the role of transcriptional plasticity in response to alternative rearing environments.

Data from: Genetic variation in social environment construction influences the development of aggressive behavior in Drosophila melanogaster

Individuals are not merely subject to their social environments; they choose and create them, through a process called social environment (or social niche) construction. When genotypes differ in social environment-constructing behaviors, different genotypes are expected to experience different social environments. As social experience often affects behavioral development, quantitative genetics and psychology theories predict that genetic variation in social environment construction should have an important role in determining phenotypic variation; however, this hypothesis has not been tested directly. I identify multiple mechanisms of social environment construction that differ among natural genotypes of Drosophila melanogaster and investigate their consequences for the development of aggressive behavior. Male genotypes differed in the group sizes that they preferred and in their aggressive behavior; both of these behaviors influenced social experience, demonstrating that these behaviors function as social environment-constructing traits. Further, the effects of social experience—as determined in part by social environment construction—carried over to affect focal male aggression at a later time and with a new opponent. These results provide manipulative experimental support for longstanding hypotheses in psychology, that genetic variation in social environment construction has a causal role in behavioral development. More broadly, these results imply that studies of the genetic basis of complex traits should be expanded to include mechanisms by which genetic variation shapes the environments that individuals experience.

opencc-zeroDec 2011View details →

Data from: Altitudinal clinal variation in wing form in African Drosophila melanogaster: one cline or many?

Geographical patterns of morphological variation have been useful in addressing hypotheses about environmental adaptation. In particular, latitudinal clines in phenotypes have been studied in a number of Drosophila species. Some environmental conditions along latitudinal clines—for example, temperature—also vary along altitudinal clines, but these have been studied infrequently and it remains unclear whether these environmental factors are similar enough for convergence or parallel evolution. Most clinal studies in Drosophila have dealt exclusively with univariate phenotypes, allowing for the detection of clinal relationships, but not for estimating the directions of covariation between them. We measured variation in wing shape and size in D. melanogaster derived from populations at varying altitudes and latitudes across sub-Saharan Africa. Geometric morphometrics allows us to compare shape changes associated with latitude and altitude, and manipulating rearing temperature allows us to quantify the extent to which thermal plasticity recapitulates clinal effects. Comparing effect vectors demonstrates that altitude, latitude, and temperature are only partly associated, and that the altitudinal shape effect may differ between Eastern and Western Africa. Our results suggest that selection responsible for these phenotypic clines may be more complex than just thermal adaptation.

Data from: Adaptive patterns of phenotypic plasticity in laboratory and field environments in Drosophila melanogaster

Identifying mechanisms of adaptation to variable environments is essential in developing a comprehensive understanding of evolutionary dynamics in natural populations. Phenotypic plasticity allows for phenotypic change in response to changes in the environment, and as such may play a major role in adaptation to environmental heterogeneity. Here, the plasticity of stress response in D. melanogaster originating from two distinct geographic regions and ecological habitats was examined. Adults were given a short-term, 5-day exposure to combinations of temperature and photoperiod to elicit a plastic response for three fundamental aspects of stress tolerance that vary adaptively with geography. This was replicated in both the laboratory and in outdoor enclosures in the field. In the laboratory, geographic origin was the primary determinant of the stress response. Temperature and the interaction between temperature and photoperiod also significantly affected stress resistance. In the outdoor enclosures, plasticity was distinct among traits and between geographic regions. These results demonstrate that short-term exposure of adults to ecologically relevant environmental cues results in predictable effects on multiple aspects of fitness. These patterns of plasticity vary among traits and are highly distinct between the two examined geographic regions, consistent with patterns of local adaptation to climate and associated environmental parameters.

Data from: The contribution of spontaneous mutations to thermal sensitivity curve variation in Drosophila serrata

Many traits studied in ecology and evolutionary biology change their expression in response to a continuously varying environmental factor. One well-studied example are thermal performance curves (TPCs); continuous reaction norms that describe the relationship between organismal performance and temperature and are useful for understanding the trade-offs involved in thermal adaptation. We assayed TPCs for locomotor activity in a set of 66 spontaneous mutation accumulation lines in the fly Drosophila serrata. Factor-analytic modeling of the mutational variance-covariance matrix, M, revealed support for three axes of mutational variation in males and two in females. These independent axes of mutational variance corresponded well to the major axes of TPC variation required for different types of thermal adaptation; 'faster-slower' representing changes in performance largely independent of temperature, and the 'hotter-colder' and 'generalist-specialist' axes, representing trade-offs. In contrast to its near-absence from standing variance in this species, a 'faster-slower' axis, accounted for most mutational variance (75% in males and 66% in females) suggesting selection may easily fix or remove these types of mutations in outbred populations. Axes resembling the 'hotter-colder' and 'generalist-specialist' modes of variation contributed less mutational variance but nonetheless point to an appreciable input of new mutations that may contribute to thermal adaptation.

Data from: Introduced Drosophila subobscura populations perform better than native populations during an oviposition choice task due to increased fecundity but similar learning ability

The success of invasive species is tightly linked to their fitness in a putatively novel environment. While quantitative components of fitness have been studied extensively in the context of invasive species, fewer studies have looked at qualitative components of fitness, such as behavioral plasticity, and their interaction with quantitative components, despite intuitive benefits over the course of an invasion. In particular, learning is a form of behavioral plasticity that makes it possible to finely tune behavior according to environmental conditions. Learning can be crucial for survival and reproduction of introduced organisms in novel areas, for example, for detecting new predators, or finding mates or oviposition sites. Here we explored how oviposition performance evolved in relation to both fecundity and learning during an invasion, using native and introduced Drosophila subobscura populations performing an ecologically relevant task. Our results indicated that, under comparable conditions, invasive populations performed better during our oviposition task than did native populations. This was because invasive populations had higher fecundity, together with similar cognitive performance when compared to native populations, and that there was no interaction between learning and fecundity. Unexpectedly, our study did not reveal an allocation trade-off (i.e., a negative relationship) between learning and fecundity. On the contrary, the pattern we observed was more consistent with an acquisition trade-off, meaning that fecundity could be limited by availability of resources, unlike cognitive ability. This pattern might be the consequence of escaping natural enemies and/or competitors during the introduction. The apparent lack of evolution of learning may indicate that the introduced population did not face novel cognitive challenges in the new environment (i.e., cognitive "pre-adaptation"). Alternatively, the evolution of learning may have been transient and therefore not detected.

opencc-zeroMay 2019View details →

Data from: The evolution of male and female mating preferences in Drosophila speciation

The relative importance of male and female mating preferences in causing sexual isolation between species remains a major unresolved question in speciation. Despite previous work showing that male courtship bias and/or female copulation bias for conspecifics occur in many taxa, the present study is one of the first large-scale works to study their relative divergence. To achieve this, we used data from the literature and present experiments across 66 Drosophila species pairs. Our results revealed that male and female mate preferences are both ubiquitous in Drosophila but evolved largely independently, suggesting different underlying evolutionary and genetic mechanisms. Moreover, their relative divergence strongly depended on the geographical relationship of species. Between allopatric species, male courtship and female copulation preferences diverged at very similar rates, evolving approximately linearly with time of divergence. In sharp contrast, between sympatric species pairs, female preferences diverged much more rapidly than male preferences and were the only drivers of enhanced sexual isolation in sympatry and Reproductive Character Displacement (RCD). Not only does this result suggest that females are primarily responsible for such processes as reinforcement, but it also implies that evolved female preferences may reduce selection for further divergence of male courtship preferences in sympatry.

opencc-zeroDec 2012View details →

Data from: Low temperature reveals genetic variability against male-killing Spiroplasma in Drosophila melanogaster natural populations

Spiroplasma endosymbionts are maternally inherited microorganisms which infect many arthropod species. In some Drosophila species, it acts as a reproductive manipulator, spreading in populations by killing the sons of infected mothers. Distinct Drosophila melanogaster populations from Brazil exhibit variable male-killing Spiroplasma prevalences. In this study, we investigated the presence of variability for the male-killing phenotype among Drosophila and/or Spiroplasma strains and verified if it correlates with the endosymbiont prevalence in natural populations. For that, we analyzed the male-killing expression when Spiroplasma strains from different populations were transferred to a standard D. melanogaster line (Canton-S) and when a common Spiroplasma strain was transferred to different wild-caught D. melanogaster lines, both at optimal and challenging temperatures for the bacteria. No variation was observed in the male-killing phenotype induced by different Spiroplasma strains. No phenotypic variability among fly lines was detected at optimal temperature (23 °C), as well. Conversely, significant variation in the male-killing expression was revealed among D. melanogaster lines at 18.5 °C, probably caused by imperfect transmission of the endosymbiont. Distinct lines differed in their average sex ratios as well as in the pattern of male-killing expression as the infected females aged. Greater variation occurred among lines from one locality, although there was no clear correlation between the male-killing intensity and the endosymbiont prevalence in each population. Imperfect transmission or male killing may also occur in the field, thus helping to explain the low or intermediate prevalences reported in nature. We discuss the implications of our results for the dynamics of male-killing Spiroplasma in natural populations.

opencc-zeroJul 2019View details →

Data from: Experimental evolution of response to anoxia in Drosophila: recovery of locomotion following CO2 or N2 exposure

Many insects enter coma upon exposure to anoxia, a feature routinely exploited by experimentalists to handle them. But the genetic and physiological bases of anoxic coma induction and recovery are only partially understood, as are the long-term consequences for the animal's performance. We examined three populations of Drosophila melanogaster (designated B) that have been inadvertently under selection for rapid recovery from CO2 exposure for nearly 40 years (around 1,000 generations) resulting from routine maintenance practices. We contrasted CO2 and N2 (presumed a less reactive gas) knockdown and recovery times of these B flies with six populations of common ancestry (A and C populations) that were not exposed to CO2 over the same period. We found that B populations showed faster and more consistent locomotor recovery than A or C populations after CO2 knockdown, a result also observed with N2 knockdown. A and C populations showed much higher variance in recovery time after CO2 exposure than after N2 exposure, suggesting gas-specific effects on pathways associated with locomotor recovery. While these selection treatments result in considerable variation in life history attributes and body size, with the characteristic intermediacy of B populations, their superiority in resistance to gas exposure and locomotor recovery suggests that it is a direct consequence of prior repeated exposure to anoxia, broadly, and CO2, specifically. Hence we describe a powerful new evolutionary model for the genetic and physiological investigation of anoxic coma in insects.