The genomic and physiological basis of life history variation in a butterfly metapopulation

Unravelling the mechanisms underlying variation in life history traits is of fundamental importance for our understanding of adaptation by natural selection. While progress has been made in mapping fitness-related phenotypes to genotypes, mainly in a handful of model organisms, functional genomic studies of life history adaptations are still in their infancy. In particular, despite a few notable exceptions, the genomic basis of life history variation in natural populations remains poorly understood. This is especially true for the genetic underpinnings of life history phenotypes subject to diversifying selection driven by ecological dynamics in patchy environments--as opposed to adaptations involving strong directional selection owing to major environmental changes, such as latitudinal gradients, extreme climatic events or transitions from salt to freshwater. In this issue of Molecular Ecology,Wheat et al. (2011) now make a significant leap forward by applying the tools of functional genomics to dispersal-related life history variation in a butterfly metapopulation. Using a combination of microarrays, quantitative PCR and physiological measurements, the authors uncover several metabolic and endocrine factors that likely contribute to the observed life history phenotypes. By identifying molecular candidate mechanisms of fitness variation maintained by dispersal dynamics in a heterogeneous environment,they also begin to address fascinating interactions between the levels of physiology, ecology and evolution

Similarities and differences in altitudinal versus latitudinal variation for morphological traits in Drosophila melanogaster

Understanding how natural environments shape phenotypic variation is a major aim in evolutionary biology. Here, we have examined clinal, likely genetically based variation in morphology among 19 populations of the fruit fly (Drosophila melanogaster) from Africa and Europe, spanning a range from sea level to 3000 m altitude and including locations approximating the southern and northern range limit. We were interested in testing whether latitude and altitude have similar phenotypic effects, as has often been postulated. Both latitude and altitude were positively correlated with wing area, ovariole number, and cell number. In contrast, latitude and altitude had opposite effects on the ratio between ovariole number and body size, which was negatively correlated with egg production rate per ovariole. We also used transgenic manipulation to examine how increased cell number affects morphology and found that larger transgenic flies, due to a higher number of cells, had more ovarioles, larger wings, and, unlike flies from natural populations, increased wing loading. Clinal patterns in morphology are thus not a simple function of changes in body size; instead, each trait might be subject to different selection pressures. Together, our results provide compelling evidence for profound similarities as well as differences between phenotypic effects of latitude and altitude

Steroid hormone regulation of C. elegans and Drosophila aging and life history

In the last two decades it has become clear that hormones and gene mutations in endocrine signaling pathways can exert major effects on lifespan and related life history traits in worms, flies, mice, and other organisms. While most of this research has focused on insulin/insulin-like growth factor-1 signaling, a peptide hormone pathway, recent work has shown that also lipophilic hormones play an important role in modulating lifespan and other life history traits. Here we review how steroid hormones, a particular group of lipophilic hormones, affect life history traits in the nematode worm (Caenorhabditis elegans) and the fruit fly (Drosophila melanogaster), with a particular focus on longevity. Interestingly, a comparison suggests that parallel endocrine principles might be at work in worms and flies in these species and that steroid hormones interact with the gonad to affect lifespan

Variation in thermal performance and reaction norms among populations of Drosophila melanogaster

The major goal of evolutionary thermal biology is to understand how variation in temperature shapes phenotypic evolution. Comparing thermal reaction norms among populations from different thermal environments allows us to gain insights into the evolutionary mechanisms underlying thermal adaptation. Here, we have examined thermal adaptation in six wild populations of the fruit fly (Drosophila melanogaster) from markedly different natural environments by analyzing thermal reaction norms for fecundity, thorax length, wing area, and ovariole number under ecologically realistic fluctuating temperature regimes in the laboratory. Contrary to expectation, we found only minor differences in the thermal optima for fecundity among populations. Differentiation among populations was mainly due to differences in absolute (and partly also relative) thermal fecundity performance. Despite significant variation among populations in the absolute values of morphological traits, we observed only minor differentiation in their reaction norms. Overall, the thermal reaction norms for all traits examined were remarkably similar among different populations. Our results therefore suggest that thermal adaptation in D. melanogaster predominantly involves evolutionary changes in absolute trait values rather than in aspects of thermal reaction norms

Obesity and Aging in the Drosophila Model

Being overweight increases the risk of many metabolic disorders, but how it affects lifespan is not completely clear. Not all obese people become ill, and the exact mechanism that turns excessive fat storage into a health-threatening state remains unknown. Drosophila melanogaster has served as an excellent model for many diseases, including obesity, diabetes, and hyperglycemia-associated disorders, such as cardiomyopathy or nephropathy. Here, we review the connections between fat storage and aging in different types of fly obesity. Whereas obesity induced by high-fat or high-sugar diet is associated with hyperglycemia, cardiomyopathy, and in some cases, shortening of lifespan, there are also examples in which obesity correlates with longevity. Transgenic lines with downregulations of the insulin/insulin-like growth factor (IIS) and target of rapamycin (TOR) signaling pathways, flies reared under dietary restriction, and even certain longevity selection lines are obese, yet long-lived. The mechanisms that underlie the differential lifespans in distinct types of obesity remain to be elucidated, but fat turnover, inflammatory pathways, and dysregulations of glucose metabolism may play key roles. Altogether, Drosophila is an excellent model to study the physiology of adiposity in both health and disease

Data from: Similarities and differences in altitudinal versus latitudinal variation for morphological traits in Drosophila melanogaster

Understanding how natural environments shape phenotypic variation is a major aim in evolutionary biology. Here, we have examined clinal, likely genetically-based variation in morphology among 19 populations of the fruit fly (Drosophila melanogaster) from Africa and Europe, spanning a range from sea level to 3000 m altitude and including locations approximating the southern and northern range limit. We were interested in testing whether latitude and altitude have similar phenotypic effects, as has often been postulated. Both latitude and altitude were positively correlated with wing area, ovariole number and cell number. In contrast, latitude and altitude had opposite effects on the ratio between ovariole number and body size, which was negatively correlated with egg production rate per ovariole. We also used transgenic manipulation to examine how increased cell number affects morphology and found that larger transgenic flies, due to a higher number of cells, had more ovarioles, larger wings and, unlike flies from natural populations, increased wing loading. Clinal patterns in morphology are thus not a simple function of changes in body size; instead, each trait might be subject to different selection pressures. Together, our results provide compelling evidence for profound similarities as well as differences between phenotypic effects of latitude and altitude

Data from: Similarities and differences in altitudinal versus latitudinal variation for morphological traits in Drosophila melanogaster

Understanding how natural environments shape phenotypic variation is a major aim in evolutionary biology. Here, we have examined clinal, likely genetically-based variation in morphology among 19 populations of the fruit fly (Drosophila melanogaster) from Africa and Europe, spanning a range from sea level to 3000 m altitude and including locations approximating the southern and northern range limit. We were interested in testing whether latitude and altitude have similar phenotypic effects, as has often been postulated. Both latitude and altitude were positively correlated with wing area, ovariole number and cell number. In contrast, latitude and altitude had opposite effects on the ratio between ovariole number and body size, which was negatively correlated with egg production rate per ovariole. We also used transgenic manipulation to examine how increased cell number affects morphology and found that larger transgenic flies, due to a higher number of cells, had more ovarioles, larger wings and, unlike flies from natural populations, increased wing loading. Clinal patterns in morphology are thus not a simple function of changes in body size; instead, each trait might be subject to different selection pressures. Together, our results provide compelling evidence for profound similarities as well as differences between phenotypic effects of latitude and altitude

The influence of developmental diet on reproduction and metabolism in Drosophila

Abstract Background The adaptive significance of phenotypic changes elicited by environmental conditions experienced early in life has long attracted attention in evolutionary biology. In this study, we used Drosophila melanogaster to test whether the developmental diet produces phenotypes better adapted to cope with similar nutritional conditions later in life. To discriminate among competing hypotheses on the underlying nature of developmental plasticity, we employed a full factorial design with several developmental and adult diets. Specifically, we examined the effects of early- and late-life diets (by varying their yeast and sugar contents) on reproductive fitness and on the amount of energy reserves (fat and glycogen) in two wild-caught populations. Results We found that individuals that had developed on either low-yeast or high-sugar diet showed decreased reproductive performance regardless of their adult nutritional environment. The lower reproductive fitness might be caused by smaller body size and reduced ovariole number. Overall, these results are consistent with the silver spoon concept, which posits that development in a suboptimal environment negatively affects fitness-associated traits. On the other hand, the higher amount of energy reserves (fat) in individuals that had developed in a suboptimal environment might represent either an adaptive response or a side-effect of compensatory feeding. Conclusion Our findings suggest that the observed differences in the adult physiology induced by early-life diet likely result from inevitable and general effects of nutrition on the development of reproductive and metabolic organs, rather than from adaptive mechanisms

Raw Data Klepsatel et al

We followed the life histories of a large number of individual females, derived from three recently caught, geographically distinct wild populations from Austria, Zambia and South Africa over their lifetime. We measured ovariole number, fecundity (daily number of eggs), hatchability (of the offspring of the experimental females) as a function of maternal age, and lifespan (age at death) of experimental females under optimal laboratory conditions. Here we present the demographic raw data for these traits/measurements; each line represents an individual female fly. Fom these raw data, we then estimated individual lifetime fecundity, total lifetime production of viable eggs, and the length of the reproductive and post-reproductive period (these estimates are not shown here but can be found in our publication). For details see our paper, Klepsatel et al. (2013) in Journal of Evolutionary Biology. For additional, more specific (sub-)datasets based on the raw data presented here (e.g., data for survival analysis based on the distribution of age at death), which we have used for particular statistical analyses, or for statistical analyses outputs please contact the corresponding author, Thomas Flatt at [email protected]