Bergmann's rule in alien birds

Native bird species show latitudinal gradients in body size across species (Bergmann's rule), but whether or not such gradients are recapitulated in the alien distributions of bird species are unknown. Here, we test for the existence of Bergmann's rule in alien bird species worldwide, and investigate the causes of the observed patterns. Published databases were used to obtain the worldwide distributions of established alien bird populations, the locations of alien bird introductions, and bird body masses. Randomisation tests and linear models were used to assess latitudinal patterns in the body masses of introduced and established alien bird populations. Established alien bird species exhibit Bergmann's rule, but this is largely explained by where alien bird species have been introduced: latitudinal variation in the body masses of established alien bird species simply reflects latitudinal variation in the body masses of introduced species. There is some evidence that body mass is implicated in whether or not established species’ alien ranges spread towards or contract away from the Equator following establishment. However, most alien bird ranges are encompassed by the latitudinal band(s) to which the species was introduced. Bergmann's rule in alien birds is therefore a consequence of where humans have introduced different species, rather than of natural processes operating after population introduction.     

Patterns of size variation in bees at a continental scale: does Bergmann's rule apply?

Body size latitudinal clines have been widley explained by the Bergmann's rule in homeothermic vertebrates. However, there is no general consensus in poikilotherms organisms in particular in insects that represent the large majority of wildlife. Among them, bees are a highly diverse pollinators group with high economic and ecological value. Nevertheless, no comprehensive studies of species assemblages at a phylogenetically larger scale have been carried out even if they could identify the traits and the ecological conditions that generate different patterns of latitudinal size variation. We aimed to test Bergmann's rule for wild bees by assessing relationships between body size and latitude at continental and community levels. We tested our hypotheses for bees showing different life history traits (i.e. sociality and nesting behaviour). We used 142 008 distribution records of 615 bee species at 50 × 50 km (CGRS) grids across the West Palearctic. We then applied generalized least squares fitted linear model (GLS) to assess the relationship between latitude and mean body size of bees, taking into account spatial autocorrelation. For all bee species grouped, mean body size increased with higher latitudes, and so followed Bergmann's rule. However, considering bee genera separately, four genera were consistent with Bergmann's rule, while three showed a converse trend, and three showed no significant cline. All life history traits used here (i.e. solitary, social and parasitic behaviour; ground and stem nesting behaviour) displayed a Bergmann's cline. In general there is a main trend for larger bees in colder habitats, which is likely to be related to their thermoregulatory abilities and partial endothermy, even if a ‘season length effect’ (i.e. shorter foraging season) is a potential driver of the converse Bergmann's cline particularly in bumblebees.     

An interspecific test of Bergmann's rule reveals inconsistent body size patterns across several lineages of water beetles (Coleoptera: Dytiscidae)

1. Bergmann's rule sensu lato, the ecogeographic pattern relating animals' body size with environmental temperature (or latitude), has been shown to be inconsistent among insect taxa. Body size clines remain largely unexplored in aquatic insects, which may show contrasting patterns to those found in terrestrial groups because of the physiological or mechanical constraints of the aquatic environment. 2. Bergmann's rule was tested using data on body size, phylogeny and distribution for 93 species belonging to four lineages of dytiscid water beetles. The relationship between size and latitude was explored at two taxonomic resolutions – within each independent lineage, and for the whole dataset – employing phylogenetic generalised least‐squares to control for phylogenetic inertia. The potential influence of habitat preference (lotic versus lentic) on body size clines was also considered. 3. Within‐lineage analyses showed negative relationships (i.e. converse Bergmann's rule), but only in two lineages (specifically in those that included both lotic and lentic species). By contrast, no relationship was found between body size and latitude for the whole dataset. 4. These results suggest that there may be no universal interspecific trends in latitudinal variation of body size in aquatic insects, even among closely related groups, and show the need to account for phylogenetic inertia. Furthermore, habitat preferences should be considered when exploring latitudinal clines in body size in aquatic taxa at the interspecific level.     

When Bergmann's rule fails: evidences of environmental selection pressures shaping phenotypic diversification in a widespread seabird

Organisms tend to exhibit phenotypes that can be shaped by climate, commonly demonstrating clinal variations along latitudinal gradients. In vertebrates, air temperature plays a major role in shaping body size in both ectothermic and endothermic animals. However, additional small‐scale environmental factors can also act as selection pressures in the marine ecosystem (e.g. primary productivity), evidencing multi‐scale processes acting on marine organisms. In this study, we tested Bergmann's rule in a widely distributed seabird, the brown booby Sula leucogaster, in addition to evaluating the relationship of sea surface temperature and chlorophyll α with phenotypes. We used traits from a morphometric dataset (culmen, wing chord, and tarsus length) and body mass of 276 brown boobies distributed on six breeding sites along a latitudinal gradient in the South Atlantic Ocean (0–27°S). We found significant differentiation among colonies, but phenotypic similarities were observed between colonies located at the extremes of the latitudinal gradient. As the colony nearest to the Equator, Saint Peter and Saint Paul archipelago, had the largest and heaviest individuals, the model containing only air temperature explained < 5% of the allometric variation, providing no substantial support for Bergmann's rule. However, when we added the interaction of chlorophyll α and sea surface temperature the deviance explained rose to over 80%. Primary productivity and sea surface temperature do not follow a latitudinal gradient in the ocean and, therefore, the role of small‐scale oceanographic processes in shaping body size and the importance of considering additional environmental variables when testing Bergmann's rule in marine organisms are evident.     

A global assessment of Bergmann's rule in mammals and birds

Bergmann's rule states that endotherms have a large body size in high latitudes and cold climates. However, previous empirical studies have reported mixed evidence on the relationships between body size and latitude, raising the question of why some clades of endotherms follow Bergmann's rule, whereas others do not. Here, we synthesized the interspecific relationships between body size and latitude among 16,187 endothermic species (5422 mammals and 10,765 birds) using Bayesian phylogenetic generalized linear mixed models to examine the strength and magnitude of Bergmann's rule. We further assessed the effect of biological and ecological factors (i.e., body mass categories, dietary guild, winter activity, habitat openness, and climate zone) on the variations in the body mass–latitude relationships by adding an interaction term in the models. Our results revealed a generally weak but significant adherence to Bergmann's rule among all endotherms at the global scale. Despite taxonomic variation in the strength of Bergmann's rule, the body mass of species within most animal orders showed an increasing trend toward high latitudes. Generally, large-bodied, temperate species, non-hibernating mammals, and migratory and open-habitat birds tend to conform to Bergmann's rule more than their relatives do. Our results suggest that whether Bergmann's rule applies to a particular taxon is mediated by not only geographic and biological features, but also potential alternate strategies that species might have for thermoregulation. Future studies could explore the potential of integrating comprehensive trait data into phylogenetic comparative analysis to re-assess the classic ecogeographic rules on a global scale.     

Geographical variation of human gut microbial composition

Although we know there is considerable variation in gut microbial composition within host species, little is known about how this variation is shaped and why such variation exists. In humans, obesity is associated with the relative abundance of two dominant bacterial phyla: an increase in the proportion of Firmicutes and a decrease in the proportion of Bacteroidetes. As there is evidence that humans have adapted to colder climates by increasing their body mass (e.g. Bergmann''s rule), we tested whether Firmicutes increase and Bacteroidetes decrease with latitude, using 1020 healthy individuals drawn from 23 populations and six published studies. We found a positive correlation between Firmicutes and latitude and a negative correlation between Bacteroidetes and latitude. The overall pattern appears robust to sex, age and bacterial detection methods. Comparisons between African Americans and native Africans and between European Americans and native Europeans suggest no evidence of host genotype explaining the observed patterns. The variation of gut microbial composition described here is consistent with the pattern expected by Bergmann''s rule. This surprising link between large-scale geography and human gut microbial composition merits further investigation.     

Rule reversal: Ecogeographical patterns of body size variation in the common treeshrew (Mammalia,Scandentia)

There are a number of ecogeographical “rules” that describe patterns of geographical variation among organisms. The island rule predicts that populations of larger mammals on islands evolve smaller mean body size than their mainland counterparts, whereas smaller‐bodied mammals evolve larger size. Bergmann's rule predicts that populations of a species in colder climates (generally at higher latitudes) have larger mean body sizes than conspecifics in warmer climates (at lower latitudes). These two rules are rarely tested together and neither has been rigorously tested in treeshrews, a clade of small‐bodied mammals in their own order (Scandentia) broadly distributed in mainland Southeast Asia and on islands throughout much of the Sunda Shelf. The common treeshrew, Tupaia glis, is an excellent candidate for study and was used to test these two rules simultaneously for the first time in treeshrews. This species is distributed on the Malay Peninsula and several offshore islands east, west, and south of the mainland. Using craniodental dimensions as a proxy for body size, we investigated how island size, distance from the mainland, and maximum sea depth between the mainland and the islands relate to body size of 13 insular T. glis populations while also controlling for latitude and correlation among variables. We found a strong negative effect of latitude on body size in the common treeshrew, indicating the inverse of Bergmann's rule. We did not detect any overall difference in body size between the island and mainland populations. However, there was an effect of island area and maximum sea depth on body size among island populations. Although there is a strong latitudinal effect on body size, neither Bergmann's rule nor the island rule applies to the common treeshrew. The results of our analyses demonstrate the necessity of assessing multiple variables simultaneously in studies of ecogeographical rules.     

Latitudinal variation of morphological characteristics in the swallowtail Sericinus montelus Gray, 1798 (Lepidoptera: Papilionidae)

Patterns of latitudinal variation in the phenotype or genotype of an organism may provide evidence for natural selection. In this study, we investigated seven populations of swallowtail Sericinus montelus Gray, 1798 (Lepidoptera: Papilionidae), a non‐migratory species, to explore the latitudinal variation of morphological characteristics in adults. The results showed that body size and the development of dark pigmentation on wings in this species responded strongly to latitude. The body size of both male and female adult of S. montelus was negatively correlated with latitude. These findings provided solid evidence to support the converse Bergmann's rule. We considered that the observed variation in morphological characteristics was most likely mediated by the seasonal length and thermoperiod to adapt to different latitudinal environment (e.g. shortened developmental time of immature stages for smaller body size at higher latitude). Moreover, the tendency towards progressively darker colour patterns (only in adult males) at increasingly low latitudes was consistent with Gloger's rule. We suggested that the observed colour variation was most likely associated with thermoregulation. Slight variation in the morphology of the W‐shaped stripe on the forewing of adult females was also found, and we presumed that the functions of sexual preferences, mimicry and thermoregulation might be involved.     

Knitting patterns of biodiversity,range size and body size in aquatic beetle faunas: significant relationships but slightly divergent drivers

1. Ecogeographical rules refer to recurring patterns in nature, including the latitudinal diversity gradient (LDG), Rapoport's rule and Bergmann's rule, amongst others. In the present study, the existence of these rules was examined for diving beetles (Coleoptera: Dytiscidae), a family of aquatic predatory beetles. 2. Assemblage‐level data were analysed for diving beetles, focusing on species richness, local contribution to beta diversity (LCBD), mean range size and mean body size across the biogeographical provinces of Northern Europe. First, each of these variables was correlated with latitude, and then variation in each variable was modelled using actual environmental variables in boosted regression tree analysis. 3. Species richness was found to decrease with latitude, LCBD increased with latitude, mean range size did not show a significant relationship with latitude, and mean body size decreased with latitude. The latter finding was in contrast to Bergmann's rule. The actual environmental variables best predicting variation in these four response variables varied among the models, although they generally included temperature‐related and land use variables as the most influential ones. 4. The results obtained in the present study suggest that diving beetles conformed to the LDG, did not follow Rapoport's rule, and showed a reversed latitudinal gradient in the context of Bergmann's rule. In addition, species‐poor provinces harboured ecologically most unique faunas, suggesting that species richness and LCBD are complementary measures of biodiversity. 5. Even though general support was not found for most of the ecogeographical rules examined, the findings of the present study are interesting because they suggest that aquatic ectothermic invertebrates may show patterns different from those originally described for terrestrial endothermic vertebrates.     

A Reassessment of Bergmann's Rule in Modern Humans

It is widely accepted that modern humans conform to Bergmann''s rule, which holds that body size in endothermic species will increase as temperature decreases. However, there are reasons to question the reliability of the findings on which this consensus is based. One of these is that the main studies that have reported that modern humans conform to Bergmann''s rule have employed samples that contain a disproportionately large number of warm-climate and northern hemisphere groups. With this in mind, we used latitudinally-stratified and hemisphere-specific samples to re-assess the relationship between modern human body size and temperature. We found that when groups from north and south of the equator were analyzed together, Bergmann''s rule was supported. However, when groups were separated by hemisphere, Bergmann''s rule was only supported in the northern hemisphere. In the course of exploring these results further, we found that the difference between our northern and southern hemisphere subsamples is due to the limited latitudinal and temperature range in the latter subsample. Thus, our study suggests that modern humans do conform to Bergmann''s rule but only when there are major differences in latitude and temperature among groups. Specifically, groups must span more than 50 degrees of latitude and/or more than 30°C for it to hold. This finding has important implications for work on regional variation in human body size and its relationship to temperature.     

Weapon allometry varies with latitude in the New Zealand giraffe weevil

Animal body size commonly shows a relationship with latitude to the degree that this phenomenon is one of the few ‘rules’ discussed in evolutionary ecology: Bergmann's rule. Although exaggerated secondary sexual traits frequently exhibit interesting relationships with body size (allometries) and are expected to evolve rapidly in response to environmental variation, the way in which allometry might interact with latitude has not been addressed. We present data showing latitudinal variation in body size and weapon allometry for the New Zealand giraffe weevil (Lasiorhynchus barbicornis). Males display an extremely elongated rostrum used as a weapon during fights for access to females. Consistent with Bergmann's rule, mean body size increased with latitude. More interestingly, weapon allometry also varied with latitude, such that lower latitude populations exhibited steeper allometric slopes between weapon and body size. To our knowledge, this is the first study to document a latitudinal cline in weapon allometry and is therefore a novel contribution to the collective work on Bergmann's rule and secondary sexual trait variation.     

The converse to Bergmann's rule in bumblebees,a phylogenetic approach

Two patterns commonly emerge when animal body size is analyzed as a function of latitudinal distribution. First, body size increases with latitude, a temperature effect known as Bergmann's rule, and second, the converse to Bergmann's rule, a pattern in which body size decreases with latitude. However, other geographic patterns can emerge when the mechanisms that generate Bergmann's and the converse to Bergmann's clines operate together. Here, we use phylogenetic comparative analysis in order to control for phylogenetic inertia, and we show that bumblebees exhibit the converse to Bergmann's rule. Bumblebee taxa are distributed worldwide in temperate and tropical regions. The largest species are found in places with high water availability during the driest time of the year. Nonetheless, large body size is constrained by extreme temperatures. Bumblebees’ body size could be related to a higher extent to the size of food rewards to be harvested than to the energetic advantages of thermoregulation. Moreover, we found that the body size of eusocial and cuckoo species responded in the same way to environmental variables, suggesting that they have not diverged due to different selective pressures.     

On the validity of Bergmann's rule

Aim We reviewed the occurrence of Bergmann's rule in birds (ninety‐four species) and mammals (149 species), using only studies where statistical significance of the results was tested. We also tested whether studies using different characters as surrogates of body size have a different tendency to conform to Bergmann's rule, whether body size and nest type (in birds) have an influence on the tendency to conform to the rule, and whether sedentary birds conform to the rule more than migratory birds. Location Worldwide. Methods We reviewed published data on geographic and temporal variation in body size, using only studies where the statistical significance of the results was tested. We asked how many species conform to the rule out of all species studied in each order and family. Results Over 72% of the birds and 65% of the mammal species follow Bergmann's rule. An overall tendency to follow the rule occurs also within orders and families. Studies using body mass in mammals show the greatest tendency to adhere to Bergmann's rule (linear measurements and dental measurements show a weaker tendency); while in birds, studies using body mass and other surrogates (linear measurements and egg size) show a similar tendency. Birds of different body mass categories exhibit a similar tendency to follow Bergmann's rule, while in mammals the lower body size categories (4–50 and 50–500 g) show a significantly lower tendency to conform to the rule. Sedentary birds tend to conform to Bergmann's rule more than migratory species. Nest type does not affect the tendency to conform to Bergmann's rule. Main conclusions Bergmann's rule is a valid ecological generalization for birds and mammals.     

Gastrointestinal microbiota of wild and inbred individuals of two house mouse subspecies assessed using high‐throughput parallel pyrosequencing

The effects of gastrointestinal tract microbiota (GTM) on host physiology and health have been the subject of considerable interest in recent years. While a variety of captive bred species have been used in experiments, the extent to which GTM of captive and/or inbred individuals resembles natural composition and variation in wild populations is poorly understood. Using 454 pyrosequencing, we performed 16S rDNA GTM barcoding for 30 wild house mice (Mus musculus) and wild‐derived inbred strain mice belonging to two subspecies (M. m. musculus and M. m. domesticus). Sequenced individuals were selected according to a 2 × 2 experimental design: wild (14) vs. inbred origin (16) and M. m. musculus (15) vs. M. m. domesticus (15). We compared alpha diversity (i.e. number of operational taxonomic units – OTUs), beta diversity (i.e. interindividual variability) and microbiota composition across the four groups. We found no difference between M. m. musculus and M. m. domesticus subspecies, suggesting low effect of genetic differentiation between these two subspecies on GTM structure. Both inbred and wild populations showed the same level of microbial alpha and beta diversity; however, we found strong differentiation in microbiota composition between wild and inbred populations. Relative abundance of ~ 16% of OTUs differed significantly between wild and inbred individuals. As laboratory mice represent the most abundant model for studying the effects of gut microbiota on host metabolism, immunity and neurology, we suggest that the distinctness of laboratory‐kept mouse microbiota, which differs from wild mouse microbiota, needs to be considered in future biomedical research.     

Higher temperatures during development reduce body size in the zebra finch in the laboratory and in the wild

The most commonly documented morphological response across many taxa to climatic variation across their range follows Bergmann's rule, which predicts larger body size in colder climates. In observational data from wild zebra finches breeding across a range of temperatures in the spring and summer, we show that this relationship appears to be driven by the negative effect of high temperatures during development. This idea was then experimentally tested on zebra finches breeding in temperature‐controlled climates in the laboratory. These experiments confirmed that those individualso produced in a hot environment (30 °C) were smaller than those produced in cool conditions (18 °C). Our results suggest a proximate causal link between temperature and body size and suggest that a hotter climate during breeding periods could drive significant changes in morphology within and between populations. This effect could account for much of the variation in body size that drives the well‐observed patterns first described by Bergmann and that is still largely attributed to selection on adult body size during cold winters. The climate‐dependent developmental plasticity that we have demonstrated is an important component in understanding how endotherms may be affected by climate change.     

Major Histocompatibility Complex class IIb polymorphism influences gut microbiota composition and diversity

Animals harbour diverse communities of symbiotic bacteria, which differ dramatically among host individuals. This heterogeneity poses an immunological challenge: distinguishing between mutualistic and pathogenic members of diverse and host‐specific microbial communities. We propose that Major Histocompatibility class II (MHC) genotypes contribute to recognition and regulation of gut microbes, and thus, MHC polymorphism contributes to microbial variation among hosts. Here, we show that MHC IIb polymorphism is associated with among‐individual variation in gut microbiota within a single wild vertebrate population of a small fish, the threespine stickleback. We sampled stickleback from Cedar Lake, on Vancouver Island, and used next‐generation sequencing to genotype the sticklebacks’ gut microbiota (16S sequencing) and their MHC class IIb exon 2 sequences. The presence of certain MHC motifs was associated with altered relative abundance (increase or decrease) of some microbial Families. The effect sizes are modest and entail a minority of microbial taxa, but these results represent the first indication that MHC genotype may affect gut microbiota composition in natural populations (MHC‐microbe associations have also been found in a few studies of lab mice). Surprisingly, these MHC effects were frequently sex‐dependent. Finally, hosts with more diverse MHC motifs had less diverse gut microbiota. One implication is that MHC might influence the efficacy of therapeutic strategies to treat dysbiosis‐associated disease, including the outcome of microbial transplants between healthy and diseased patients. We also speculate that macroparasite‐driven selection on MHC has the potential to indirectly alter the host gut microbiota, and vice versa.     

Urbanization disrupts latitude‐size rule in 17‐year cicadas

Many ectotherms show a decrease in body size with increasing latitude due to changes in climate, a pattern termed converse Bergmann's rule. Urban conditions—particularly warmer temperatures and fragmented landscapes—may impose stresses on development that could disrupt these body size patterns. To test the impact of urbanization on development and latitudinal trends in body size, we launched a citizen science project to collect periodical cicadas (Magicicada septendecim) from across their latitudinal range during the 2013 emergence of Brood II. Periodical cicadas are long‐lived insects whose distribution spans a broad latitudinal range covering both urban and rural habitats. We used a geometric morphometric approach to assess body size and developmental stress based on fluctuating asymmetry in wing shape. Body size of rural cicadas followed converse Bergmann's rule, but this pattern was disrupted in urban habitats. In the north, urban cicadas were larger than their rural counterparts, while southern populations showed little variation in body size between habitats. We detected no evidence of differences in developmental stress due to urbanization. To our knowledge, this is the first evidence that urbanization disrupts biogeographical trends in body size, and this pattern highlights how the effects of urbanization may differ over a species’ range.     

Chemical regulation of body feather microbiota in a wild bird

The microbiota has a broad range of impacts on host physiology and behaviour, pointing out the need to improve our comprehension of the drivers of host–microbiota composition. Of particular interest is whether the microbiota is acquired passively, or whether and to what extent hosts themselves shape the acquisition and maintenance of their microbiota. In birds, the uropygial gland produces oily secretions used to coat feathers that have been suggested to act as an antimicrobial defence mechanism regulating body feather microbiota. However, our comprehension of this process is still limited. In this study, we for the first time coupled high‐throughput sequencing of the microbiota of both body feathers and the direct environment (i.e., the nest) in great tits with chemical analyses of the composition of uropygial gland secretions to examine whether host chemicals have either specific effects on some bacteria or nonspecific broad‐spectrum effects on the body feather microbiota. Using a network approach investigating the patterns of co‐occurrence or co‐exclusions between chemicals and bacteria within the body feather microbiota, we found no evidence for specific promicrobial or antimicrobial effects of uropygial gland chemicals. However, we found that one group of chemicals was negatively correlated to bacterial richness on body feathers, and a higher production of these chemicals was associated with a poorer body feather bacterial richness compared to the nest microbiota. Our study provides evidence that chemicals produced by the host might function as a nonspecific broad‐spectrum antimicrobial defence mechanism limiting colonization and/or maintenance of bacteria on body feathers, providing new insight about the drivers of the host's microbiota composition in wild organisms.     

Body size explains interspecific variation in size–latitude relationships in geographically widespread beetle species

1. In most birds and mammals, larger individuals of the same species tend to be found at higher latitudes, but in insects, body size–latitude relationships are highly variable. 2. Recent studies have shown that larger‐bodied insect species are more likely to decrease in size when reared at increased temperature, compared with smaller‐sized species. These findings have led to the prediction that a positive relationship between body size and latitude should be more prevalent in larger‐bodied insect species. 3. This study measured the body size of > 4000 beetle specimens (12 species) collected throughout North America. Some beetle species increased in size with latitude, while others decreased. Importantly, mean species body size explained c. 30% of the interspecific variation in the size–latitude response. 4. As predicted, larger‐bodied beetle species were more likely to show a positive relationship between body size and latitude (Bergmann's rule), and smaller‐bodied species were more likely to show a negative body size–latitude relationship (inverse Bergmann's rule). 5. These body size–latitude patterns suggest that size‐specific responses to temperature may underlie global latitudinal distributions of body size in Coleoptera, as well as other insects.     

Flight morphology along a latitudinal gradient in a butterfly: do geographic clines differ between agricultural and woodland landscapes?

Bergman and converse Bergman rules, amongst others, describe latitudinal variation in size of organisms, including flying ectotherms like butterflies. However, geographic clines in morphological traits of functional significance for flight performance and thermoregulation may also exist, although they have received less attention within a biogeographical context. Variation in flight‐related morphology has often been studied relative to landscape structure. However, the extent to which landscape effects interact with latitudinal clines of phenotypic variation has rarely been tested. Here we address the effect of latitude, landscape type and the interaction effect on body size and flight‐related morphology in the speckled wood butterfly Pararge aegeria. Male adult butterflies were collected from two replicate populations in each agricultural and woodland landscape types along a 700 km cline in six latitudinal zones. Overall size, adult body mass and wing area increased with latitude in line with Bergmann's rule. Forewing length, however, decreased with latitude. As predicted from thermoregulatory needs in ectotherms, the basal wing part was darker to the north. Latitudinal trends for flight‐related morphological traits were opposite to predictions about flight endurance under cooler conditions that were observed in some non‐lepidopteran insects, i.e. wing loading increased and wing aspect ratio decreased with latitude. Opposite trends can, however, be explained by other aspects of butterfly flight performance (i.e. mate‐location behaviour). As predicted from differences in environmental buffering in woodland landscapes along the latitudinal gradient, significant landscape×latitude interaction effects indicated stronger latitudinal clines and stronger phenotypic variation for size and flight morphology in the agricultural landscape compared to the woodland landscape. In agreement with significant interaction effects, morphological differentiation increased with latitude and was higher between population pairs of agricultural landscape than between population pairs of woodland landscape. These results demonstrate that landscape, latitude and their interaction contribute to the understanding of the complex geographic variation in P. aegeria adult phenotypes across Europe.