Adaptations to environmental stress in altitudinal populations of two Drosophila species

Abstract.  Opposite clinal variation for desiccation and starvation tolerance are observed in four altitudinal populations (219–2202 m), each of two sympatric and cold adapted species: Drosophila takahashii and Drosophila nepalensis from northern India. The high-altitude populations are more tolerant to desiccation than those from lower altitudes, whereas the reverse trend occurs for starvation tolerance. The magnitude of tolerances are significantly high in D. nepalensis, which is better adapted to cold conditions. During winter months (November to February), there are significant decreases in T _max, T _min and relative humidity along the altitudinal transect. Higher desiccation resistance can develop under cold conditions over short-range, altitudinally varying, geographical areas (250 km) compared with our previously reported long-range (>2000 km), latitudinal variations under tropical climatic conditions. However, significant starvation tolerances are favoured by small body size, higher dispersal rate and higher ambient temperature of the site of origin of populations. Significant correlations of two climatic factors (the mean monthly coefficients of variation of temperature and relative humidity) with these two physiological traits can best explain the observed altitudinal clinal variations under natural conditions.     

Importance of abiotic stress as a range-limit determinant for European plants: insights from species responses to climatic gradients

Aim We examined whether species occurrences are primarily limited by physiological tolerance in the abiotically more stressful end of climatic gradients (the asymmetric abiotic stress limitation (AASL) hypothesis) and the geographical predictions of this hypothesis: abiotic stress mainly determines upper‐latitudinal and upper‐altitudinal species range limits, and the importance of abiotic stress for these range limits increases the further northwards and upwards a species occurs. Location Europe and the Swiss Alps. Methods The AASL hypothesis predicts that species have skewed responses to climatic gradients, with a steep decline towards the more stressful conditions. Based on presence–absence data we examined the shape of plant species responses (measured as probability of occurrence) along three climatic gradients across latitudes in Europe (1577 species) and altitudes in the Swiss Alps (284 species) using Huisman–Olff–Fresco, generalized linear and generalized additive models. Results We found that almost half of the species from Europe and one‐third from the Swiss Alps showed responses consistent with the predictions of the AASL hypothesis. Cold temperatures and a short growing season seemed to determine the upper‐latitudinal and upper‐altitudinal range limits of up to one‐third of the species, while drought provided an important constraint at lower‐latitudinal range limits for up to one‐fifth of the species. We found a biome‐dependent influence of abiotic stress and no clear support for abiotic stress as a stronger upper range‐limit determinant for species with higher latitudinal and altitudinal distributions. However, the overall influence of climate as a range‐limit determinant increased with latitude. Main conclusions Our results support the AASL hypothesis for almost half of the studied species, and suggest that temperature‐related stress controls the upper‐latitudinal and upper‐altitudinal range limits of a large proportion of these species, while other factors including drought stress may be important at the lower range limits.     

Altitudinal patterns of plant species richness on the Baekdudaegan Mountains, South Korea: mid-domain effect, area, climate, and Rapoport’s rule

We studied the altitudinal patterns of plant species richness and examined the effects of geometric constraints, area, and climatic factors on the observed richness patterns along the ridge of the Baekdudaegan Mountains, South Korea. Rapoport’s altitudinal rule was evaluated by examining the relationship between altitudinal range size and midpoint. We also examined the latitudinal effect on species richness. Plant data were collected from 1,100 plots along a 200–1,900 m altitudinal gradient along the ridge of the Baekdudaegan. A total of 802 plant species from 97 families and 342 genera were found. The altitudinal patterns of plant species richness along the ridge of the Baekdudaegan depicted distinctly hump-shaped patterns, although the absolute altitudes of the richness peaks vary somewhat among plant groups. While the mid-domain effect (MDE) was the most powerful explanatory variable in simple regression models, species richness was also associated with climatic factors, especially mean annual precipitation (MAP) and temperature (MAT) in multiple regression models. The relative importance of the MDE and climatic factors were different among plant groups. The MDE was more important for woody plants and for large-ranged species, whereas climatic factors were better predictors for total and herbaceous plants and for small-ranged species. Rapoport’s altitudinal rule and a latitudinal effect on species richness were not supported. Our study suggests that a combined interaction of the MDE and climatic factors influences species richness patterns along the altitudinal gradient of the Baekdudaegan Mountains, South Korea.     

Geographic patterns in the distribution of social systems in terrestrial arthropods

The role of ecology in the evolution and maintenance of arthropod sociality has received increasing research attention in recent years. In some organisms, such as halictine bees, polistine wasps, and social spiders, researchers are investigating the environmental factors that may contribute to high levels of variation in the degree of sociality exhibited both among and within species. Within lineages that include only eusocial members, such as ants and termites, studies focus more on identifying extrinsic factors that may contribute to the dramatic variation in colony size, number of queens, and division of labour that is evident across these species. In this review, I propose a comparative approach that seeks to identify environmental factors that may have a common influence across such divergent social arthropod groups. I suggest that seeking common biogeographic patterns in the distribution of social systems or key social traits may help us to identify ecological factors that play a common role in shaping the evolution of sociality across different organisms. I first review previous studies of social gradients that form along latitudinal and altitudinal axes. Within families and within species, many organisms show an increasing degree of sociality at lower latitudes and altitudes. In a smaller number of cases, organisms form larger groups or found nests cooperatively at higher latitudes and altitudes. I then describe several environmental factors that vary consistently along such gradients, including climate variables and abundance of predators, and outline their proposed role in the social systems of terrestrial arthropods. Finally, I map distributions of a social trait against several climatic factors in five case studies to demonstrate how future comparative studies could inform empirical research.     

Thermal tolerance trade-offs associated with the right arm of chromosome 3 and marked by the hsr-omega gene in Drosophila melanogaster

Drosophila melanogaster occurs in diverse climatic regions and shows opposing clinal changes in resistance to heat and resistance to cold along a 3000 km latitudinal transect on the eastern coast of Australia. We report here on variation at a polymorphic 8 bp-indel site in the heat shock hsr-omega gene that maps to the right arm of chromosome 3. The frequency of the genetic element marked by the L form of the gene was strongly and positively associated with latitude along this transect, and latitudinal differences in L frequency were robustly associated with latitudinal differences in maximum temperature for the hottest month. On a genetic background mixed for genes from each end of the cline a set of 10 lines was derived, five of which were fixed for the L marker, the absence of In(3R)P and 12 kb of repeats at a second polymorphic site at the 3' end of hsr-omega, and five that were fixed for the S marker, In(3R)P and 15 kb of hsr-omega repeats. For two different measures of heat tolerance S lines outperformed L lines, and for two different measures of cold tolerance L lines outperformed S lines. These data suggest that an element on the right arm of chromosome 3, possibly In(3R)P, confers heat resistance but carries the trade-off of also conferring susceptibility to cold. This element occurs at high frequency near the equator. The alternate element on the other hand, at high frequency at temperate latitudes, confers cold resistance at the cost of heat susceptibility.     

Altitudinal distribution of tropical planktonic Cladocera

The altitudinal distributions of planktonic Cladocera in Africa in three latitudinal bands: 0–10 °, 10–20 ° and 28–31 ° are described. Some species have altitudinal ranges of 2000 m within a latitudinal band of 10 °. It is possible to distinguish tropical species which do not extend up to high altitudes, particularly at higher latitudes. At the lowest latitudes, some species are found only at high altitudes, but occur at progressively lower altitudes with increasing latitude: Daphnia pulex and D. obtusa are good examples. A study in South America, with a smaller database, gives similar results.     

Altitudinal variation in lifespan of Drosophila melanogaster populations from the Firtina Valley,northeastern Turkey

Studies of altitudinal changes in phenotype and genotype can complement studies of latitudinal patterns and provide evidence of natural selection in response to climatic factors. In Drosophila melanogaster, latitudinal variation in phenotype and genotype has been well studied, but altitudinal patterns have rarely been investigated. We studied populations from six different altitudes varying between 35 m and 2173 m in the Firtina Valley in northeastern part of Turkey to evaluate clinal trends in lifespan under experimental conditions. Lifespan in the D. melanogaster populations was examined in relation to altitude, sex, temperature (25 °C and 29 °C), and dietary yeast concentration (5 g/L and 25 g/L). As expected high temperature decrease lifespan in all populations. However, it was shown that lifespan was slightly affected by dietary stress. We found that lifespan decreases significantly under thermal stress conditions with increasing altitude. Moreover, there was a slightly negative relationship between altitude and lifespan, which was closely associated with climatic factors such as temperature and precipitation, may suggest local adaptation to climate.     

Latitudinal and altitudinal diversity patterns and Rapoport effects in north-west European land snails and their causes

The latitudinal and altitudinal range sizes of north-west European land-snail species increase with increasing latitude/altitude. These Rapoport effects are not caused by northern/high-altitude species with wider latitudinal/altitudinal ranges and southern/low-altitude species with narrower latitudinal/altitudinal ranges, as predicted by the climatic variability hypothesis. They are instead caused mainly by different northern/upper borders of species occurring in the south part of the study area or at low and intermediate altitudes, respectively. This pattern indicates that the observed Rapoport effects are the result mainly of differential northward/upward expansion of species that were restricted to southern/low or intermediate altitude refugia during the glacials. Although all species occurring in a refugium experienced the same climatic conditions, there is stochastic variation in their climatic tolerance. Species with broader climatic tolerance were able to expand farer northwards/upwards postglacial. The altitudinal distribution of species richness in the analysed alpine faunas cannot be explained by the Rapoport-rescue hypothesis, because species richness peaks at intermediate altitudes and because there is no negative correlation between the number of range borders and altitude. The Rapoport-rescue hypothesis alone is probably also insufficient to explain the decrease in species richness with increasing latitude.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 309–323.     

Contrasting altitudinal variation of alpine plant communities along the Swedish mountains

Changes in abiotic factors along altitudinal and latitudinal gradients cause powerful environmental gradients. The topography of alpine areas generates environmental gradients over short distances, and alpine areas are expected to experience greater temperature increase compared to the global average. In this study, we investigate alpha, beta, and gamma diversity, as well as community structure, of vascular plant communities along altitudinal gradients at three latitudes in the Swedish mountains. Species richness and evenness decreased with altitude, but the patterns within the altitudinal gradient varied between sites, including a sudden decrease at high altitude, a monotonic decrease, and a unimodal pattern. However, we did not observe a decline in beta diversity with altitude at all sites, and plant communities at all sites were spatially nested according to some other factors than altitude, such as the availability of water or microtopographic position. Moreover, the observed diversity patterns did not follow the latitudinal gradient. We observed a spatial modularity according to altitude, which was consistent across sites. Our results suggest strong influences of site‐specific factors on plant community composition and that such factors partly may override effects from altitudinal and latitudinal environmental variation. Spatial variation of the observed vascular plant communities appears to have been caused by a combination of processes at multiple spatial scales.     

Phenology responses of temperate butterflies to latitude depend on ecological traits

Global change influences species’ seasonal occurrence, or phenology. In cold‐adapted insects, the activity is expected to start earlier with a warming climate, but contradictory evidence exists, and the reactions may be linked to species‐specific traits. Using data from the GBIF database, we selected 105 single‐brooded Holarctic butterflies inhabiting broad latitudinal ranges. We regressed patterns of an adult flight against latitudes of the records, controlling for altitude and year effects. Species with delayed flight periods towards the high latitudes, or stable flight periods across latitudes, prevailed over those that advanced their flight towards the high latitudes. The responses corresponded with the species’ seasonality (flight of early season species was delayed and flight of summer species was advanced at high latitudes) and oceanic vs. continental climatic niches (delays in oceanic, stability in continental species). Future restructuring of butterfly seasonal patterns in high latitudes will reflect climatic niches, and hence the evolutionary history of participating species.     

ALTITUDINAL CLINAL VARIATION IN WING SIZE AND SHAPE 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.     

Geographic variation in body size, sexual size dimorphism and fitness components of a seed beetle: local adaptation versus phenotypic plasticity

Variation in body size, growth and life history traits of ectotherms along latitudinal and altitudinal clines is generally assumed to represent adaptation to local environmental conditions, especially adaptation to temperature. However, the degree to which variation along these clines is due to adaptation vs plasticity remains poorly understood. In addition, geographic patterns often differ between females and males – e.g. sexual dimorphism varies along latitudinal clines, but the extent to which these sex differences are due to genetic differences between sexes vs sex differences in plasticity is poorly understood. We use common garden experiments (beetles reared at 24, 30 and 36°C) to quantify the relative contribution of genetically‐based differentiation among populations vs phenotypic plasticity to variation in body size and other traits among six populations of the seed‐feeding beetle Stator limbatus collected from various altitudes in Arizona, USA. We found that temperature induces substantial plasticity in survivorship, body size and female lifetime fecundity, indicating that developmental temperature significantly affects growth and life history traits of S. limbatus. We also detected genetic differences among populations for body size and fecundity, and genetic differences among populations in thermal reaction norms, but the altitude of origin (and hence mean temperature) does not appear to explain these genetic differences. This and other recent studies suggest that temperature is not the major environmental factor that generates geographic variation in traits of this species. In addition, though there was no overall difference in plasticity of body size between males and females (when averaged across populations), we did find that the degree to which dimorphism changed with temperature varied among populations. Consequently, future studies should be extremely cautious when using only a few study populations to examine environmental effects on sexual dimorphism.     

Altitudinal and seasonal variation in microsatellite allele frequencies of Drosophila buzzatii

Variation in climate, particularly temperature, is known to affect the genetic composition of populations. Although there have been many studies of latitudinal variation, comparisons of populations across altitudes or seasons, particularly for animal species, are less common. Here, we study genetic variation (microsatellite markers) in populations of Drosophila buzzatii collected along altitudinal gradients and in different seasons. We found no differences in genetic variation between 2 years or between seasons within years. However, there were numerous cases of significant associations between allele frequencies or expected heterozygosities and altitude, with more than half showing nonlinear relationships. While these associations indicate possible selection and local altitudinal adaptation, direct tests gave strong evidence for selection affecting two loci and weaker evidence for five other loci. Two loci that are located within an inversion (including the one with strongest evidence for selection) show a linear increase in genetic diversity with altitude, likely due to thermal selection. Parallel associations with altitude here and with latitude in Australian populations indicate that selection is operating on chromosomal regions marked by some of the loci.     

Effect of altitude on the genetic structure of an Alpine grass, Poa hiemata

Background and Aims

The persistence of plants inhabiting restricted alpine areas under climate change will depend upon many factors including levels of genetic variation in adaptive traits, population structure, and breeding system.

Methods

Using microsatellite markers, the genetic structure of populations of a relatively common alpine grass, Poa hiemata, is examined across three altitudinal gradients within the restricted Australian alpine zone where this species has previously been shown to exhibit local adaptation across a narrow altitudinal gradient.

Key Results

Genetic variation across six microsatellite markers revealed genetic structuring along altitudinal transects, and a reduction in genetic variation at high and low altitude extremes relative to sites central within transects. There was less genetic variation among transect sites compared with altitudinal gradients within transects, even though distances among transects were relatively larger. Central sites within transects were less differentiated than those at extremes.

Conclusions

These patterns suggest higher rates of gene flow among sites at similar altitudes than along transects, a process that could assist altitudinal adaptation. Patterns of spatial autocorrelation and isolation by distance changed with altitude and may reflect altered patterns of dispersal via pollen and/or seed. There was evidence for selfing and clonality in neighbouring plants. Levels of gene flow along transects were insufficient to prevent adaptive changes in morphological traits, given previously measured levels of selection.Key words: Poa hiemata, genetic structure, altitudinal gradient, microsatellite, gene flow, climate change     

Drivers of Collembola assemblages along an altitudinal gradient in northeast China

Altitudinal changes in the diversity of plants and animals have been well documented; however, soil animals received little attention in this context and it is unclear whether their diversity follows general altitudinal distribution patterns. Changbai Mountain is one of few well‐conserved mountain regions comprising natural ecosystems on the Eurasian continent. Here, we present a comprehensive analysis of the diversity and community composition of Collembola along ten altitudinal sites representing five vegetation types from forest to alpine tundra. Among 7834 Collembola individuals, 84 morphospecies were identified. Species richness varied marginally significant with altitude and generally followed a unimodal relationship with altitude. By contrast, the density of Collembola did not change in a consistent way with altitude. Collembola communities changed gradually with altitude, with local habitat‐related factors (soil and litter carbon‐to‐nitrogen ratio, litter carbon content, and soil pH) and climatic variables (precipitation seasonality) identified as major drivers of changes in Collembola community composition. Notably, local habitat‐related factors explained more variation in Collembola assemblages than climatic variables. The results suggest that local habitat‐related factors including precipitation and temperature are the main drivers of changes in Collembola communities with altitude. Specifically, soil and litter carbon‐to‐nitrogen ratio correlated positively with Collembola communities at high altitudes, whereas soil pH correlated positively at low altitudes. This documents that altitudinal gradients provide unique opportunities for identifying factors driving the community composition of not only above‐ but also belowground invertebrates.     

Latitudinal variation for two enzyme loci and an inversion polymorphism in Drosophila melanogaster from Central and South America

Abstract.— Many organisms show latitudinal variation for various genetically determined traits. Such clines may involve neutral variation and originate from historical events or their maintenance may be explained by selection. For Drosophila melanogaster , latitudinal variation for allozymes, inversions, and quantitative traits has been found on several continents. We sampled D. melanogaster populations in Panama and along a transect of 40 latitudinal degrees on the west coast of South America. Negative correlations with latitude were found for Adh^s and _αGpdh^F allele frequencies and for the frequency of the cosmopolitan inversion In(2L)t in Adh^sαpdh^F chromosomes. A positive correlation existed between wing length and latitude. Significant correlations were found between these traits and climatic variables like temperature and rainfall. The observed clines show considerable resemblance to those found on other continents. Gametic disequilibrium between Adh^s and αGpdh^F occurred predominantly at higher latitudes and was caused by the presence of In(2L)t . The reasons for the clinal distributions are discussed and it is argued that selection is the most likely explanation. However, the exact nature of the selective force and the interactions of allozymes with each other and with In(2L)t are complex and not fully understood. In tropical regions In(2L)t -containing genotypes have higher fitness than ST/ST and Adh and αGpdh hitchhike with the inversion, but there is also evidence for balancing selection at the Adh locus.     

Evolution,plasticity and evolving plasticity of phenology in the tree species Alnus glutinosa

Both traits and the plasticity of these traits are subject to evolutionary change and therefore affect the long‐term persistence of populations and their role in local communities. We subjected clones from 12 different populations of Alnus glutinosa, located along a latitudinal gradient, to two different temperature treatments, to disentangle the distribution of genetic variation in timing of bud burst and bud burst plasticity within and among genotypes, populations, and regions. We calculated heritability and evolvability estimates for bud burst and bud burst plasticity and assessed the influence of divergent selection relative to neutral drift. We observed higher levels of heritability and evolvability for bud burst than for its plasticity, whereas the total phenological heritability and evolvability (i.e. combining timing of bud burst and bud burst plasticity) suggest substantial evolutionary potential with respect to phenology. Earlier bud burst was observed for the low‐latitudinal populations than for the populations from higher latitudes, whereas the high‐latitudinal populations did not show the expected delayed bud burst. This countergradient variation can be due to evolution towards increased phenological plasticity at higher latitudes. However, because we found little evidence for adaptive differences in phenological plasticity across the latitudinal gradient, we suggest differential frost tolerance as the most likely explanation for the observed phenological patterns in A. glutinosa.     

Environmental steepness,tolerance gradient,and ecogeographical rules in glassfrogs (Anura: Centrolenidae)

Spatial variation in biological traits reflects evolutionary and biogeographical processes of the history of clades, and patterns of body size and range size can be suitable to recover such processes. In the present study, we test for latitudinal and altitudinal gradients in both body and range sizes in an entire family of tropical anurans, Centrolenidae. We partition the species latitudinal, and altitudinal distributions into an indirect measure of tolerance, and then test its effect on the body size gradient. We use an assemblage‐based approach to correlate the traits with altitudinal and latitudinal axes, taking into account both phylogenetic and spatial autocorrelation in data. Centrolenids lack any gradient in range size but show a positive cline of both body size and adaptive body enlargement with altitude. This pattern is also positively correlated with an altitudinal gradient of cold tolerance, thus lending support to the heat balance hypothesis as an explanation of the body size cline. By using an entire Neotropical clade of anurans, we add further support for Bergmann's rule in ectotherms, warn for a likely effect of environmental steepness in fashioning the gradient, and offer evidence for an historical scenario (the Oligocene–Eocene Andean uplift) as its likely trigger. © 2013 The Linnean Society of London     

Latitudinal variation in herbivory: influences of climatic drivers,herbivore identity and natural enemies

Although a number of investigations have concluded that lower latitudes are associated with increases in herbivore abundance and plant damage, the generality of this pattern is still under debate. Multiple factors may explain the lack of consistency in latitude–herbivory relationships. For instance, latitudinal variation in herbivore pressure may be shaped entirely or not by climatic variables, or vary among herbivore guilds with differing life‐history traits. Additionally, the strength of top–down effects from natural enemies on herbivores might also vary geographically and influence latitude–herbivory patterns. We carried out a field study where we investigated the effects of latitude and climate on herbivory by a seed‐eating caterpillar and leaf chewers, as well as parasitism associated to the former across 30 populations of the perennial herb Ruellia nudiflora (Acanthaceae). These populations were distributed along a 5° latitudinal gradient from northern Yucatan (Mexico) to southern Belize, representing one‐third of the species' latitudinal distribution and the entirety and one‐third of the precipitation and temperature gradient of this species' distribution (respectively). We found opposing latitudinal gradients of seed herbivory and leaf herbivory, and this difference appeared to be mediated by contrasting effects of climate on each guild. Specifically, univariate regressions showed that seed herbivory increased at higher latitudes and with colder temperatures, while leaf herbivory increased toward the equator and with wetter conditions. Multiple regressions including temperature, precipitation and latitude only found significant effects of temperature for seed herbivory and latitude for leaf herbivory. Accordingly, that latitudinal variation in seed herbivory appears to be driven predominantly by variation in temperature whereas latitudinal variation in leaf herbivory was apparently driven by other unexplored correlates of latitude. Parasitism did not exhibit variation with latitude or climatic factors. Overall, these findings underscore that the factors driving latitudinal clines in herbivory might vary even among herbivore species coexisting on the same host plant.     

Climatic selection on genes and traits after a 100 year-old invasion: a critical look at the temperate-tropical clines in Drosophila melanogaster from eastern Australia

Drosophila melanogaster invaded Australia around 100 years ago, most likely through a northern invasion. The wide range of climatic conditions in eastern Australia across which D. melanogaster is now found provides an opportunity for researchers to identify traits and genes that are associated with climatic adaptation. Allozyme studies indicate clinal patterns for at least four loci including a strong linear cline in Adh and a non-linear cline in alpha-Gpdh. Inversion clines were initially established from cytological studies but have now been validated with larger sample sizes using molecular markers for breakpoints. Recent collections indicate that some genetic markers (Adh and In(3R)Payne) have changed over the last 20 years reflecting continuing evolution. Heritable clines have been established for quantitative traits including wing length/area, thorax length and cold and heat resistance. A cline in egg size independent of body size and a weak cline in competitive ability have also been established. Postulated clinal patterns for resistance to desiccation and starvation have not been supported by extensive sampling. Experiments under laboratory and semi-natural conditions have suggested selective factors generating clinal patterns, particularly for reproductive patterns over winter. Attempts are being made to link clinal variation in traits to specific genes using QTL analysis and the candidate locus approach, and to identify the genetic architecture of trait variation along the cline. This is proving difficult because of inversion polymorphisms that generate disequilibrium among genes. Substantial gaps still remain in linking clines to field selection and understanding the genetic and physiological basis of the adaptive shifts. However D. melanogaster populations in eastern Australia remain an excellent resource for understanding past and future evolutionary responses to climate change.