Alpine Insects Research Articles

Interspecific and Intraspecific Transcriptomic Variations Unveil the Potential High-Altitude Adaptation Mechanisms of the Parnassius Butterfly Species.

Parnassius butterflies have significantly advanced our understanding of biogeography, insect-plant interactions, and other fields of ecology and evolutionary biology. However, to date, little is known about the gene expression patterns related to the high-altitude adaptation of Parnassius species. In this study, we obtained high-throughput RNA-seq data of 48 adult Parnassius individuals covering 10 species from 12 localities in China, and deciphered their interspecific and intraspecific expression patterns based on comparative transcriptomic analyses. Though divergent transcriptional patterns among species and populations at different altitudes were found, a series of pathways related to genetic information processing (i.e., recombination, repair, transcription, RNA processing, and ribosome biogenesis), energy metabolism (i.e., oxidative phosphorylation, thermogenesis, and the citrate cycle), and cellular homeostasis were commonly enriched, reflecting similar strategies to cope with the high-altitude environments by activating energy metabolism, enhancing immune defense, and concurrently inhibiting cell growth and development. These findings deepen our understanding about the molecular mechanisms of adaptative evolution to extreme environments, and provide us with some theoretical criteria for the biodiversity conservation of alpine insects.

Thermal biology of aquatic insects in alpine lakes: Insights from diving beetles

Abstract High mountain areas are especially vulnerable to global warming, as they experience faster temperature changes than lowlands in a climate change context. Notably, increased temperatures and frequency of extreme flooding and droughts, and the consequent decrease in ice cover and water availability fluctuations, will induce important physical changes in alpine freshwater systems. Thus, assessing thermal limits and exploring overwintering strategies of aquatic alpine insects is pivotal to understanding how aquatic communities of high‐mountain fresh waters will respond to climate change. However, knowledge on these topics is still scarce for aquatic alpine insects. Here, the thermal biology of adults of five diving beetle species from alpine lakes located in the Sierra Nevada mountain range (southern Iberia) was studied. Cold tolerance was measured estimating the supercooling point (SCP), lower lethal temperature (LLT), tolerance to ice enclosure and to submersion, whereas heat tolerance was assessed from the heat coma temperature and upper lethal temperature. All of the species survived ice enclosure for 3 h. Furthermore, three of the studied species had SCPs higher than their LLTs, suggesting that they could be freeze‐tolerant. All species except Agabus nevadensis also were tolerant to submersion, which could be a key adaptation for overwintering underwater below the ice cover as adults, reducing risk from freezing conditions in the air. The species did not differ significantly in their upper thermal limits, which were similar to those of other dytiscids from lower altitudes. Overall, our results suggest that increasing temperatures is not expected to be the most important threat for the water beetle populations in Sierra Nevada, but rather the colonisation of alpine lakes by lowland dytiscids in a warmer climate scenario.

Is the Abandonment of Organic Grassland a Threat to Alpine Insect Diversity?

Land abandonment is a multifaceted, nonlinear, worldwide phenomenon that is influenced by a variety of factors and opinions. The goal of this study was to understand the significance of land abandonment for true bugs and syrphids in three grassland management regimes that includes abandoned, intensive, and extensive alpine organic grasslands. In 2021 and 2022, we sampled true bugs and syrphids by applying observation plot and sweep netting sampling methods. Extensive grasslands had significantly higher true bug and syrphid abundance compared to abandoned grasslands. However, no difference of species richness was found in studied grassland regimes. Large numbers of unique species (25.5% true bugs and 21.5% syrphids) only occurred in the abandoned grasslands but not in intensive and extensive grasslands. Similarly, true bug assemblages in abandoned grasslands differed significantly from assemblages in intensive and extensive grasslands. We found that extensive grassland can manage to increase true bugs and syrphid abundance. Likewise, undisturbed abandoned grassland is not a threat to insect diversity, and supports the survival of more unique true bug and syrphid species. A mosaic landscape consisting of abandoned grassland along with grassland having different, mainly extensive, management intensity could be an ideal arrangement for alpine biodiversity conservation.

Repeated Alpine Flight Loss Within the Widespread New Zealand StoneflyNesoperla fulvescensHare (Plecoptera: Gripopterygidae)

AbstractFlight loss is a common feature of upland insect assemblages, with recent studies detecting parallel wing reduction events across independent alpine lineages. However, the geographic scale over which such repeated evolution can operate remains unclear. In this study, we use genotyping-by-sequencing to assess the genomic relationships among vestigial-winged and full-winged populations of the widespread New Zealand stonefly Nesoperla fulvescens, to test for repeated wing loss events over small spatial scales. Biogeographic analyses indicate that alpine wing loss in this widespread species is restricted to a single, narrow mountain range. Intriguingly, our coalescent analyses indicate that upland vestigial-winged N. fulvescens populations are not sister to one another, suggesting wings have been lost independently in disjunct populations of this species, over a <30 km scale. Our results suggest that selection against flight above the alpine treeline can drive rapid and repeated adaptation even across narrow spatial scales. We propose that such repetitive processes may represent a far more pervasive feature of alpine insect adaptation than is currently recognized.

Persistent, Bioaccumulative, and Toxic Chemicals in Wild Alpine Insects: A Methodological Case Study.

With their high persistence in the environment and their potential for long‐range atmospheric transport, persistent, bioaccumulative, and toxic chemicals (PBTs) may be among the numerous anthropogenic threats to insect populations worldwide. The effects of PBTs on insects have been investigated in the laboratory, but topical field studies are scarce. A reason might be the multiple challenges faced by PBT‐related field studies on wild insects. We studied two species of bumblebees (Bombus spp.) and of ants (Formica spp.) in two high‐elevation locations in the Austrian and German Alps to tackle two of these challenges. First, PBTs occur in minuscule concentrations compared with other substances in the environment. Therefore, the practicability of body burden data from pooled individuals was tested. Second, fitness proxies like fecundity, which typically are endpoints for chemical toxicity, are difficult to quantify in the field. Hence, fluctuating asymmetry of bumblebee wings and ant heads was tested as an alternative endpoint. To exclude the possibility that fluctuating asymmetry was caused by genetic stressors, inbreeding levels were estimated using population‐genetic markers, and their relationships to fluctuating asymmetry in the same individuals were assessed. We successfully quantified polychlorinated biphenyls and Hg as PBTs using the pooled samples and found PBT data from pooled individuals useful, in that significant correlations to fluctuating asymmetry were identified in bumblebees and ants. This finding confirmed the potential of fluctuating asymmetry to indicate PBT effects in wild insects. Inbreeding did not interfere with PBT links to fluctuating asymmetry in any instance. Our findings contribute to the development of a quantitative methodological framework for investigating the effects of persistent environmental chemicals on wild insects. Environ Toxicol Chem 2022;41:1215–1227. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Genomic signatures of parallel alpine adaptation in recently evolved flightless insects

Natural selection along elevational gradients has potential to drive predictable adaptations across distinct lineages, but the extent of such repeated evolution remains poorly studied for many widespread alpine taxa. We present parallel genomic analyses of two recently evolved flightless alpine insect lineages to test for molecular signatures of repeated alpine adaptation. Specifically, we compare low-elevation vs. alpine stonefly ecotypes from parallel stream populations in which flightless upland ecotypes have been independently derived. We map 67,922 polymorphic genetic markers, generated across 176 Zelandoperla fenestrata specimens from two independent alpine stream populations in New Zealand's Rock and Pillar Range, to a newly developed plecopteran reference genome. Genome-wide scans revealed 31 regions with outlier single nucleotide polymorphisms (SNPs) differentiating lowland vs. alpine ecotypes in Lug Creek, and 37 regions with outliers differentiating ecotypes in Six Mile Creek. Of these regions, 13% (8/60) yielded outlier SNPs across both within-stream ecotype comparisons, implying comparable genomic shifts contribute to this repeated alpine adaptation. Candidate genes closely linked to repeated outlier regions include several with documented roles in insect wing-development (e.g., dishevelled), suggesting that they may contribute to repeated alpine wing reduction. Additional candidate genes have been shown to influence insect fecundity (e.g., ovo) and lifespan (e.g., Mrp4), implying that they might contribute to life history differentiation between upland and lowland ecotypes. Additional outlier genes have potential roles in the evolution of reproductive isolation among ecotypes (hedgehog and Desaturase 1). These results demonstrate how replicated outlier tests across independent lineages can potentially contribute to the discovery of genes underpinning repeated adaptation.

Monitoring and conservation of cryophilous biodiversity: concerns when working with insect populations in vanishing glacial habitats

Abstract Understanding how insects may respond and adapt to global warming is a major challenge when predicting future biodiversity trends in glacial regions at high altitudes and latitudes of our planet. Hydrobiologists, ecologists, ecotoxicologists, molecular biologists, physiologists, and taxonomists are working together to understand the current changes in and foresee future scenarios of alpine insect populations and habitats. Thousands of specimens have been collected from remote areas to study the community structure, species phenology and distribution, and the response to environmental changes. Many of these species are at risk of extinction. In this essay, we raise some burning questions and concerns we would like to share with researchers operating in glacial habitats, in particular, and those working on insect conservation in disappearing habitats, in general: Must we collect many samples and kill many specimens to study spatiotemporal changes in community structure? What is the proportion of individuals captured relative to the actual population size of the species? What are the possible consequences of intensive sampling? Starting from our experience as ecologists, we appeal to the entomological audience to share our concerns and open a constructive scientific debate on cryophilous insect conservation.

The positive effects of the alpine cushion plant Arenaria polytrichoides on insect dynamics are determined by both physical and biotic factors

Cushion plants' significant role for alpine biodiversity has been demonstrated in particular through their positive effects on plant diversity. However, their effects on higher trophic levels (e.g. insects) remain largely unclear. In this study, by field sampling in the Hengduan Mountains (HDM) in southwestern China, we evaluated the effects of an alpine gynodioecious cushion species, Arenaria polytrichoides (Carophyllaceae), on insect richness, abundance and population dynamics at two different elevations (4427 m vs. 4732 m) separately at two time periods (day vs. night) and in two growing seasons (early vs. late). The results showed that the total insect diversity decreases from low to high elevation sites. Some insect species were exclusively detected within A. polytrichoides cushions, leading to an increase in local insect richness from 7% to 35%. The positive effects of cushions on insect diversity could be attributed to unique biotic properties provided by cushions. Firstly, the effects were determined by the sexual dimorphism of the cushion with hermaphroditic cushions supporting higher insect diversity than female cushions. This could be because hermaphroditic cushions provide more resources, such as nectar and pollen grains, for insects than female cushions. Secondly, the cushions' associated beneficiary plants can also provide extra resources for attracting more insects, but this effect was mediated by the micro-environmental conditions. Finally, the magnitude of cushions' positive effects on insect dynamics were stronger under higher than under lower environmental stress. This study confirmed that facilitation by A. polytrichoides cushions in HDM plays an important role in constructing the alpine insect community and further regulating its dynamics. Moreover, the positive effects of cushions on insect dynamics increase with increasing environmental stress. Therefore, the distribution range of insects would quite possibly be expanded into higher elevation under future climate changes, which will induce new challenges for the local alpine ecosystems.

Insect wing loss is tightly linked to the treeline: evidence from a diverse stonefly assemblage

The secondary loss of flight in previously winged insect lineages has long fascinated biologists. Habitat stability and isolation are thought to play important roles in driving wing reduction (Roff 1990, 1994), with exposure to high winds suggested to accelerate this process (Darwin 1859), although the role exposure plays in insect wing loss has never been empirically demonstrated. Here we assess fine‐scale distributional records from a diverse regional stonefly assemblage, to demonstrate a widespread association between wing loss and the treeline in New Zealand. The observed pattern suggests that exposure plays a crucial role driving wing loss in alpine insects.

The many roles of fats in overwintering insects.

Temperate, polar and alpine insects generally do not feed over winter and hence must manage their energy stores to fuel their metabolism over winter and to meet the energetic demands of development and reproduction in the spring. In this Review, we give an overview of the accumulation, use and conservation of fat reserves in overwintering insects and discuss the ways insects modify fats to facilitate their selective consumption or conservation. Many insects are in diapause and have depressed metabolic rates over winter; together with low temperatures, this means that lipid stores are likely to be consumed predominantly in the autumn and spring, when temperatures are higher but insects remain dormant. Although there is ample evidence for a shift towards less-saturated lipids in overwintering insects, switches between the use of carbohydrate and lipid stores during winter have not been well-explored. Insects usually accumulate cryoprotectants over winter, and the resulting increase in haemolymph viscosity is likely to reduce lipid transport. For freeze-tolerant insects (which withstand internal ice), we speculate that impaired oxygen delivery limits lipid oxidation when frozen. Acetylated triacylglycerols remain liquid at low temperatures and interact with water molecules, providing intriguing possibilities for a role in cryoprotection. Similarly, antifreeze glycolipids may play an important role in structuring water and ice during overwintering. We also touch on the uncertain role of non-esterified fatty acids in insect overwintering. In conclusion, lipids are an important component of insect overwintering energetics, but there remain many uncertainties ripe for detailed exploration.

Genome-wide SNPs reveal fine-scale differentiation among wingless alpine stonefly populations and introgression between winged and wingless forms

Insect flight loss is a repeated phenomenon in alpine habitats, where wing reduction is thought to enhance local recruitment and increase fecundity. One predicted consequence of flight loss is reduced dispersal ability, which should lead to population genetic differentiation and perhaps ultimately to speciation. Using a dataset of 15,123 SNP loci, we present comparative analyses of fine-scale population structure in codistributed Zelandoperla stonefly species, across three parallel altitudinal transects in New Zealand's Rock and Pillar mountain range. We find that winged populations (altitude 200-500 m; Zelandoperla decorata) show no genetic structuring within or among streams, suggesting substantial dispersal mediated by flight. By contrast, wingless populations (Zelandoperla fenestrata; altitude 200-1100 m) exhibit distinct genetic clusters associated with each stream, and additional evidence of isolation by distance within streams. Our data support the hypothesis that wing-loss can initiate diversification in alpine insect populations over small spatial scales. The often deep phylogenetic placement of lowland Z. fenestrata within their stream-specific clades suggests the possibility of independent alpine colonization events for each stream. Additionally, the detection of winged, interspecific hybrid individuals raises the intriguing possibility that a previously flightless lineage could reacquire flight via introgression.

Conserved and narrow temperature limits in alpine insects: Thermal tolerance and supercooling points of the ice-crawlers, Grylloblatta (Insecta: Grylloblattodea: Grylloblattidae)

For many terrestrial species, habitat associations and range size are dependent on physiological limits, which in turn may influence large-scale patterns of species diversity. The temperature range experienced by individuals is considered to shape the breadth of the thermal niche, with species occupying temporally and/or geographically stable climates tolerating a narrow temperature range. High-elevation environments experience large temperature fluctuations, with frequent periods below 0°C, but Grylloblatta (Grylloblattodea: Grylloblattidae) occupy climatically stable microhabitats within this region. Here we test critical thermal limits and supercooling points for five Grylloblatta populations from across a large geographic area, to examine whether the stable microhabitats of this group are associated with a narrow thermal niche and assess their capacity to tolerate cold conditions. Thermal limits are highly conserved in Grylloblatta, despite substantial genetic divergence among populations spanning 1500m elevation and being separated by over 500km. Further, Grylloblatta show exceptionally narrow thermal limits compared to other insect taxa with little capacity to improve cold tolerance via plasticity. In contrast, upper thermal limits were significantly depressed by cold acclimation. Grylloblatta maintain coordinated movement until they freeze, and they die upon freezing. Convergence of the critical thermal minima, supercooling point and lower lethal limits point to adaptation to a cold but, importantly, constant thermal environment. These physiological data provide an explanation for the high endemism and patchy distribution of Grylloblatta, which relies on subterranean retreats to accommodate narrow thermal limits. These retreats are currently buffered from temperature fluctuations by snow cover, and a declining snowpack thus places Grylloblatta at risk of exposure to temperatures beyond its tolerance capacity.

Evolution ofNewZealand insects: summary and prospectus for future research

AbstractKnowledge on the evolution of theNewZealand insect fauna is reviewed and outstanding questions are highlighted. TheNewZealand insect fauna is a composite of old and recent lineages and many spectacular examples of evolutionary processes are evident, including species radiations, hybridisation and unusual adaptations. We discuss the origins and evolution of four prominent communities within the insect fauna: terrestrial lowland insects, alpine insects, aquatic insects and insect communities from offshore islands. Within each of these communities, significant lineages are discussed, and in particular the crucial adaptations that enable these lineages to thrive and diversify. Glacial history has had a dramatic impact on theNewZealand insects, and the effects on different lineages are discussed. TheNewZealand insects are unique, yet many are threatened with extinction, and efforts to preserve the fauna are reviewed. Despite the accumulating knowledge, major gaps still exist and these are outlined, as are opportunities to address key questions. The review concludes with a synthesis and a discussion of how systematics, new technologies and integrative approaches have the promise to improve dramatically our understanding ofNewZealand insect evolution.

Climatic warming disrupts recurrent Alpine insect outbreaks

Climate change has been identified as a causal factor for diverse ecological changes worldwide. Warming trends over the last couple of decades have coincided with the collapse of long-term population cycles in a broad range of taxa, although causal mechanisms are not well-understood. Larch budmoth (LBM) population dynamics across the European Alps, a classic example of regular outbreaks, inexplicably changed sometime during the 1980s after 1,200 y of nearly uninterrupted periodic outbreak cycles. Herein, analysis of perhaps the most extensive spatiotemporal dataset of population dynamics and reconstructed Alpine-wide LBM defoliation records reveals elevational shifts in LBM outbreak epicenters that coincide with temperature fluctuations over two centuries. A population model supports the hypothesis that temperature-mediated shifting of the optimal elevation for LBM population growth is the mechanism for elevational epicenter changes. Increases in the optimal elevation for population growth over the warming period of the last century to near the distributional limit of host larch likely dampened population cycles, thereby causing the collapse of a millennium-long outbreak cycle. The threshold-like change in LBM outbreak pattern highlights how interacting species with differential response rates to climate change can result in dramatic ecological changes.

Evolutionary radiation of the cicada genus Maoricicada Dugdale (Hemiptera: Cicadoidea) and the origins of the New Zealand alpine biota

We have used ancestral character state reconstruction and molecular dating to test hypotheses on the evolution of New Zealand alpine cicadas of the genus Maoricicada Dugdale. Gene trees were estimated from mitochondrial DNA and the nuclear loci elongation factor 1- α , period, and calmodulin and species-level relationships were reconstructed using gene tree parsimony. These analyses suggest that the alpine habitat character state had a single origin and that the ancestral Maoricicada lived in low to mid-elevation habitats. Our reconstructions also strongly support the hypothesis that this ancestor was darkly coloured and had increased pubescence, classic adaptations of alpine insects. Using relaxed-clock Bayesian dating methods, we estimated that the radiation of the alpine Maoricicada species was coincident with the late Miocene acceleration in the rate of uplift of the Southern Alps rather than uplift in the early Miocene. These dates are very similar to those of other alpine taxa, indicating that the New Zealand alpine biota is very young. Our reconstructions suggest that the ancestral Maoricicada may have been preadapted to the alpine environment because it existed before the origin of high mountainous habitats, dwelt at mid-to-low altitudes, and yet possessed the classic alpine insect adaptations of heavy pubescence and dark coloration. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 419‐435.

Conserved oviposition preferences in alpine leaf beetle populations despite host shifts and isolation

Abstract 1. Choosing the plant on which to lay their eggs is the last act of care that most female herbivorous insects bestow upon their offspring. These decisions play a pivotal role in insect–plant interactions, placing host preference under strong selection and contributing to the diversity of phytophagous insects as one of the first traits to adapt to new hosts.2. This study presents a test of whether extreme isolation and exposure to different host plants can produce intra‐specific divergence in oviposition preference in alpine insects. Geographic variation should impose selection to fine‐tune host plant ranking and specificity to the plants normally encountered, to avoid wasting time during the very limited reproductive season experienced at high altitudes.3. Beetles from five populations of Oreina elongata differing in host availability were offered three natural hosts: Cirsium spinosissimum, Adenostyles alliariae, and Adenostyles glabra. A novel application of a continuation ratio model (logistic regression) was made to sequential no‐choice experiments, combined with quasi‐likelihood analysis of multiple‐choice experiments.4. The results show little geographic variation in host plant choice: all populations strongly preferred Cirsium in multiple‐choice trials, and in no‐choice experiments laid around 47% of their remaining eggs during each stage, almost regardless of the host present.5. Enemy‐free space seems to explain the preference for Cirsium, but isolation and exposure to different plants has clearly not caused local adaptation in host plant ranking or specificity. Reasons for this conservatism despite divergence in other characteristics are discussed.

1200 years of regular outbreaks in alpine insects

The long-term history of Zeiraphera diniana Gn. (the larch budmoth, LBM) outbreaks was reconstructed from tree rings of host subalpine larch in the European Alps. This record was derived from 47513 maximum latewood density measurements, and highlights the impact of contemporary climate change on ecological disturbance regimes. With over 1000 generations represented, this is the longest annually resolved record of herbivore population dynamics, and our analysis demonstrates that remarkably regular LBM fluctuations persisted over the past 1173 years with population peaks averaging every 9.3 years. These regular abundance oscillations recurred until 1981, with the absence of peak events during recent decades. Comparison with an annually resolved, millennium-long temperature reconstruction representative for the European Alps (r=0.72, correlation with instrumental data) demonstrates that regular insect population cycles continued despite major climatic changes related to warming during medieval times and cooling during the Little Ice Age. The late twentieth century absence of LBM outbreaks, however, corresponds to a period of regional warmth that is exceptional with respect to the last 1000+ years, suggesting vulnerability of an otherwise stable ecological system in a warming environment.

Into thin air: Physiology and evolution of alpine insects

Numerous physical parameters that influence insect physiology vary substantially with altitude, including temperature, air density, and oxygen partial pressure. Here, we review existing literature and present new empirical data to better characterize the high-altitude environment, and then consider how this environment affects the physiology and evolution of insects. Using weather balloon data from fifty-three sites across the globe, we estimate a mean altitudinal temperature lapse rate of 6.0 °C/km. We also present empirically determined lapse rates for P(o(2)) and air density. The temperature decline with elevation may substantially compromise insect thermoregulation at high altitude. However, heat-transfer models predict that lower air density at elevation reduces convective heat loss of insects by to a surprisingly large degree. This effect combined with behavioral thermoregulation and the availability of buffered microhabitats make the net thermal consequences of high-altitude residence strongly context-specific. The decline in P(o(2)) with elevation may compromise insect development and physiology, but its effects are difficult to predict without simultaneously considering temperature and air density. Flying insects compensate for low air densities with both short-term responses, such as increased stroke amplitude (but not wingbeat frequency), and with long-term developmental and/or evolutionary increases in wing size relative to body size. Finally, in contrast to predictions based on Bergmann's Rule, a literature survey of thirty-six insect species suggests that those living in colder, higher altitudes do not tend to have larger body sizes.

Infrared video thermography: a technique for assessing cold adaptation in insects

Insects can survive subzero temperatures by two main strategies: freeze tolerance and freeze avoidance. An array of techniques have been used to investigate the physiological limits of insects to low temperatures, such as differential scanning calorimetry, temperature-controlled cooling apparatus, thermocouples, and computer-controlled chart recording equipment. However, these techniques require animals to be stationary, precluding behavioral data. We used infrared video thermography to investigate cold adaptation in an alpine insect, expanding such investigations to include behavioral response as an indicator of physiological stress. This technique is noninvasive and provides a large amount of physiological information, such as supercooling points, lower lethal temperatures, and hemolymph melting points. Insect supercooling points in response to a constant cooling rate were variable; however, temperatures at the initiation of behavioral stress response were less variable. Assessments of supercooling points and lower lethal temperatures obtained in this way are more biologically meaningful because allowing unhindered movement of insects more closely resembles natural environments.

The relationship between male head size and harem size in the sexually dimorphic mountain stone weta Hemideina maori

Abstract 1. Tree weta are a group of large, flightless orthopterans with pronounced sexual dimorphism. Males have enlarged heads that are used in fighting for possession of cavities in trees or under rocks where females shelter during the day.2. The fieldwork reported here examined the relationship between male head size and mating success in Hemideina maori, an alpine tree weta that shelters under rock slabs that have broken off isolated outcrops or tors.3. The relationship between male head size and harem size in H. maori is not as clear‐cut as thought previously. First, overall body size is a better predictor of male mating success than head size per se. Second, both body size and head size explained a relatively low percentage (19.8%) of the overall variation in mating success. Third, despite the intensity of directional selection being estimated to move the frequency distribution of head size and femur size 0.49 and 0.54 standard deviations from the mean, male heads and femurs were ≈ 2 mm smaller at the main study site than at a second site 100 m higher in elevation. A similar pattern was found for adult females. Additional surveys have indicated that body size in H. maori decreases with decreasing altitude, which is correlated with increasing night‐time temperature.4. Although there are reasons why natural selection might favour weta maturing earlier and at smaller body sizes in warmer environments, relatively large males would still have a mating advantage over smaller males under such conditions. This sexually dimorphic alpine insect might be a good example of the trade‐offs and conflicting demands that sexual selection versus natural selection can place on organisms.