Colour lightness of dragonfly assemblages across North America and Europe

Dark‐coloured ectotherms absorb energy from the environment at higher rates than light‐coloured ectotherms. The thermal melanism hypothesis (TMH) states that this physical mechanism links the colour lightness of the body surfaces of ectotherms to their thermal environment and hence to their geographical distribution. Studies on different insect taxa in Europe found support for this prediction of the TMH. However, whether these results hold also for other biogeographical regions remains unclear. Here, we quantify and map the colour lightness of dragonfly species in North America and directly compare our results to previously published findings for Europe. We estimated the colour lightness of 152 North American dragonfly species from published illustrations, compiled their distribution data from the literature and combined all these data with six biologically relevant environmental variables. We evaluated the importance of phylogenetic autocorrelation for the spatial variation of mean colour lightness of dragonfly assemblages (grid cells of approximately 50 × 50 km size) by repeating all analyses also for the phylogenetically predicted component of the colour lightness of species and the species‐specific deviation from this prediction. We also accounted for spatial autocorrelation with autoregressive error models. All statistical approaches showed that dragonfly assemblages from both continents consistently tended to be darker coloured in regions with cold climates and lighter coloured in regions with warm climates. Regression slopes, however, were significantly less steep, and the amount of variance explained by environmental variables was lower for North America than for Europe. Our results highlight the importance of colour lightness for the distribution of dragonfly species, but they also indicate that idiosyncrasies of the continents modify the general pattern.     

A test of the relationship between cuticular melanism and immune function in wild‐caught Mormon crickets

Cuticular melanism and innate immune parameters can share common physiological pathways in insects, and this functional connection may contribute to the maintenance of insect colour polymorphisms. However, evidence linking colouration and immune function has been equivocal, particularly when tested in wild populations. The present study investigates phenotypic links between colouration and immune function in migratory Mormon crickets (Anabrus simplex, Haldeman), in which juveniles occur in conspicuous colour variants but mature to become uniformly melanic adults. Wild‐caught insects are used to evaluate the relationship between juvenile colouration and three immune parameters: encapsulation ability, lysozyme‐like activity and phenoloxidase activity. As nymphs, brown crickets are better able to encapsulate an inert implant introduced into the haemocoel than green crickets, although the difference is slight and ceases after they all become darkly‐coloured adults. By contrast, adults that develop from brown nymphs have a higher basal phenoloxidase activity than those that develop from green nymphs, regardless of the fact that all adults are brown. Intrinsic factors other than colouration exert larger effects on immunity: males show stronger encapsulation responses but lower phenoloxidase activity than females, suggesting a sex‐specific trade‐off between these two immune parameters, and adults exhibit higher immune function than nymphs. In summary, modest support is found for a correlation between cuticular melanism and increased immune function in wild Mormon crickets. Additional intrinsic factors such as developmental stage and sex appear to interact with colouration and have a more substantial connection to immune function in the wild.     

Thermal melanism in ectotherms

Whether melanism plays a significant role in thermoregulation has been a persistent question in studies of thermal biology of ectotherms. This review provides a synthesis of the thermal melanism hypothesis which states that dark individuals (i.e. lower skin reflectance) are at an advantage under conditions of low temperature since they heat up faster than light individuals at a given level of solar radiation. Although skin color is an important trait in the thermal biology of ectotherms, it has rarely been explored in non-insect models. We draw on the available literature to assess the validity of four key assumptions that underlie this hypothesis. Ample support was found for the assumption that melanistic diurnal species inhabit cooler areas than lighter species and that melanism results in greater fitness in cold climates. By contrast, little direct support could be found for the assumption that there is a consistent melanism–body size tradeoff. Finally, the assumption that color, thermal physiology and behavior are coadapted has some support but requires further investigation. Overall, the functional, molecular and adaptive mechanisms of thermal melanism await further study.     

Condition‐dependence,pleiotropy and the handicap principle of sexual selection in melanin‐based colouration

The signalling function of melanin‐based colouration is debated. Sexual selection theory states that ornaments should be costly to produce, maintain, wear or display to signal quality honestly to potential mates or competitors. An increasing number of studies supports the hypothesis that the degree of melanism covaries with aspects of body condition (e.g. body mass or immunity), which has contributed to change the initial perception that melanin‐based colour ornaments entail no costs. Indeed, the expression of many (but not all) melanin‐based colour traits is weakly sensitive to the environment but strongly heritable suggesting that these colour traits are relatively cheap to produce and maintain, thus raising the question of how such colour traits could signal quality honestly. Here I review the production, maintenance and wearing/displaying costs that can generate a correlation between melanin‐based colouration and body condition, and consider other evolutionary mechanisms that can also lead to covariation between colour and body condition. Because genes controlling melanic traits can affect numerous phenotypic traits, pleiotropy could also explain a linkage between body condition and colouration. Pleiotropy may result in differently coloured individuals signalling different aspects of quality that are maintained by frequency‐dependent selection or local adaptation. Colouration may therefore not signal absolute quality to potential mates or competitors (e.g. dark males may not achieve a higher fitness than pale males); otherwise genetic variation would be rapidly depleted by directional selection. As a consequence, selection on heritable melanin‐based colouration may not always be directional, but mate choice may be conditional to environmental conditions (i.e. context‐dependent sexual selection). Despite the interest of evolutionary biologists in the adaptive value of melanin‐based colouration, its actual role in sexual selection is still poorly understood.     

Carotenoid‐based plumage colouration is predicted by age and parasites in the male European serin

A fundamental assumption of theories on the evolution of sexual signals is that they should be costly to produce in order to honestly signal the quality of the sender. The expression of carotenoid‐based plumage signals is considered to be condition‐dependent, due to the role of carotenoids functioning as pigments and as health modulators. We assessed carotenoid‐based plumage colouration in relation to male condition in a free living population of male European serins Serinus serinus during the breeding season. Male serins were trapped for morphometric and colouration measurements, during a four‐year field study, in order to evaluate the signalling value of colouration in relation to body condition and parasites level. We compared two different forms of colour quantification based on spectral data – the most commonly used tristimulus colour variables and physiological models of avian colour vision – and found that they were highly correlated for this species. We investigated the signalling value of male plumage colouration and it was found to be related to age and ectoparasite load. Plumage double cone and patch size were negatively related to parasites level, whereas SWS ratio was positively related to parasites and age. Colouration was also related with the time since moult. Our results indicate that the colour expression of serin's plumage is age dependent and is related, in complex ways, with the ability to cope with parasitic infection.     

Phylogenetic comparative analysis supports aposematic colouration–body size association in millipede assassins (Hemiptera: Reduviidae: Ectrichodiinae)

The diversity of colour patterns and its importance in interactions with the environment make colouration in animals an intriguing research focus. Aposematic colouration is positively correlated with body size in certain groups of animals, suggesting that warning colours are more effective or that crypsis is harder to achieve in larger animals. Surprisingly, this relationship has not been recovered in studies investigating insects, which may have been confounded by a focus on aposematic taxa that are also gregarious. Millipede assassin bugs (Hemiptera: Reduviidae: Ectrichodiinae) comprise species with cryptic and aposematic colour patterns across a range of body sizes, are typically solitary as adults and are thus an excellent model for investigating a possible association between colouration and body size. Here, we use a comprehensive phylogeny for Ectrichodiinae, ancestral state reconstruction of colouration, and phylogenetic comparative methods to test for a colouration–body size association. The ancestor of Ectrichodiinae is reconstructed as cryptically coloured, with multiple subsequent transitions between aposematic and cryptic colouration. Aposematic colouration is positively associated with male body length and supports the hypothesis that selection on Ectrichodiinae body size may influence evolutionary transitions between aposematic and cryptic colouration or alternatively that selection for aposematic colouration influences body size evolution.     

Energy and interspecific body size patterns of amphibian faunas in Europe and North America: anurans follow Bergmann's rule, urodeles its converse

Aim To describe broad‐scale geographical patterns of body size for European and North American amphibian faunas and to explore possible processes underlying these patterns. Specifically, we propose a heat balance hypothesis, as both heat conservation and heat gain determine the heat balance of ectotherms, and test it along with five other hypotheses that have a possible influence on body size gradients: size dependence, migration ability, primary productivity, seasonality and water availability. Location Western Europe and North America north of Mexico. Methods We processed distribution maps for native amphibian species to estimate the mean body size in 110 × 110 km cells and calculated eight environmental predictors to explore the relationship between environmental gradients and the observed patterns. We used least squares regression modelling and model selection approaches based on information theory to evaluate the relative support for each hypothesis. Results We found consistent body size gradients and similar relationships to environmental variables within each amphibian group in Europe and North America. Annual potential evapotranspiration, a measure of environmental energy, was the strongest predictor of mean body size in both regions. However, the contrasting responses to ambient energy in each group resulted in opposite geographical patterns, i.e. anurans increased in size from high‐ to low‐energy areas in both continents and urodeles showed the opposite pattern. Main conclusions Our results support the heat balance hypothesis, suggesting that the thermoregulatory abilities of anurans would allow them to reach larger sizes in colder climates by optimizing the trade‐off between heating and cooling rates, whereas a lack of such strategies among urodele faunas would explain why these organisms tend to be smaller in cooler areas. These findings may also have implications for the role of climate warming on the global decline of amphibians.     

The evolution of male nuptial colour in a sexually dimorphic group of fishes (Percidae: Etheostomatinae)

To test hypotheses explaining variation in elaborate male colouration across closely related species groups, ancestral‐state reconstructions and tests of phylogenetic signal and correlated evolution were used to examine the evolution of male body and fin colouration in a group of sexually dichromatic stream fishes known as darters (Percidae: Etheostomatinae). The presence or absence of red–orange and blue–green male colour traits were scored across six body regions in 99 darter species using a recently estimated amplified fragment length polymorphism (AFLP) phylogeny for comparative analyses. Ancestral‐state reconstructions infer the most recent common ancestor of darters to lack red–orange colour and possess blue–green colour on different body regions, suggesting variation between species is due to independent gains of red–orange and losses of blue–green. Colour traits exhibit substantial phylogenetic signal and are highly correlated across body regions. Comparative analyses were repeated using an alternative phylogenetic hypothesis based on one mitochondrial and two nuclear genes, yielding similar results to analyses based on the AFLP phylogeny. Red–orange colouration in darters appears to be derived; whereas, blue–green appears to be ancestral, which suggests that different selection mechanisms may be acting on these two colour classes in darters.     

Temperature‐driven color lightness and body size variation scale to local assemblages of European Odonata but are modified by propensity for dispersal

1. Previous macrophysiological studies suggested that temperature‐driven color lightness and body size variations strongly influence biogeographical patterns in ectotherms. However, these trait–environment relationships scale to local assemblages and the extent to which they can be modified by dispersal remains largely unexplored. We test whether the predictions of the thermal melanism hypothesis and the Bergmann's rule hold for local assemblages. We also assess whether these trait–environment relationships are more important for species adapted to less stable (lentic) habitats, due to their greater dispersal propensity compared to those adapted to stable (lotic) habitats.
2. We quantified the color lightness and body volume of 99 European dragon‐ and damselflies (Odonata) and combined these trait information with survey data for 518 local assemblages across Europe. Based on this continent‐wide yet spatially explicit dataset, we tested for effects temperature and precipitation on the color lightness and body volume of local assemblages and assessed differences in their relative importance and strength between lentic and lotic assemblages, while accounting for spatial and phylogenetic autocorrelation.
3. The color lightness of assemblages of odonates increased, and body size decreased with increasing temperature. Trait–environment relationships in the average and phylogenetic predicted component were equally important for assemblages of both habitat types but were stronger in lentic assemblages when accounting for phylogenetic autocorrelation.
4. Our results show that the mechanism underlying color lightness and body size variations scale to local assemblages, indicating their general importance. These mechanisms were of equal evolutionary significance for lentic and lotic species, but higher dispersal ability seems to enable lentic species to cope better with historical climatic changes. The documented differences between lentic and lotic assemblages also highlight the importance of integrating interactions of thermal adaptations with proxies of the dispersal ability of species into trait‐based models, for improving our understanding of climate‐driven biological responses.

     

Colour‐variable birds have broader ranges,wider niches and are less likely to be threatened

Coloration fulfils a variety of adaptive functions in animals. Colour variability, both between and within species, can be caused by different colours being favoured for different functions and in different environments. Thus, species with highly variable coloration may have greater potential to persist in new and changing environments. As a consequence, such colour‐variable species may be more able to adapt, colonize new areas and niches, occupy larger ranges, speciate more readily and in general be less vulnerable to environmental change and extinction. These predictions have been supported by comparative analyses on amphibians and reptiles. However, as coloration in ectotherms plays a key role in thermoregulation, it is unclear whether these results can be generalized to endotherms, such as birds and mammals. Here, we test the hypothesis that more colour‐variable endotherms occupy larger ranges/niches and are less vulnerable to the threat of extinction by focussing on colour variation in Australian parrots and passerine birds. As predicted, colour variability was correlated with range size (parrots and passerines) and niche breadth (dietary heterogeneity, parrots only). These relationships support the predicted link between colour variability and adaptability, whereby range size and niche breadth may be a cause of colour variability or vice versa. Irrespective, and as predicted, colour variability was lower in threatened species, even after statistically controlling for other confounding variables. Hence, our study supports the hypothesis that colour‐variable species in general are more resilient to environmental change.     

Nestling colouration is adjusted to parent visual performance in altricial birds

Hitherto, most of the investigation on the perceptual efficacy of begging signals has dwelled on how patterns of nestling colouration adjust to predominant nest luminosity. However, visual sensitivity of birds varies across species, which raises the question of whether colouration of traits involved in begging displays is adjusted to parent visual capacities. Here, by comparing nestling colouration and visual sensitivity across 22 altricial bird species, we provide a first test of this hypothesis. Firstly, we assessed differences in performance of typical UV‐tuned and violet‐tuned bird eyes when looking at the nestling traits under the light regimes prevailing at their nests. Secondly, while controlling for common ancestry in a comparative approach, we explored variation in colouration of nestlings in relation to parent visual system. The colour discrimination model indicated a general higher performance of the ultraviolet over the violet eye at detecting gape and body skin traits in either open‐ or hole‐nest light conditions. Gape colouration was associated with parental visual system as the nestlings of UVS species displayed more yellow and less pure ultraviolet mouths than the nestlings of VS species. Thus, our results agree with an adaptive parent–offspring communication scenario where the nestlings’ colours tuned the perception capacities of their parents.     

Wood ant colouration as an ecological indicator for the level of disturbance in managed coniferous forests

The search for ecological indicators of population well-being in natural and managed ecosystems is a crucial aspect of effective biomonitoring, conservation and nature protection. In long-term monitoring programs environmental stress has a measurable effect on naturally selected traits, such as body shape or size. However, changes in colouration provide information about early warning responses. The red wood ant Formica aquilonia is ecologically and territorially dominant among wood ant species in European boreal coniferous forest, and possesses variable red-brownish melanin-based cuticular colouration. F. aquilonia gynes, which are unfertilized queens, exhibit colour variability on the head, propodeum and abdomen, yet only head colour features allow setting clearly visible and symmetrical (left/right) classes of morphs. We studied phenotypic colour variability, melanisation and fluctuating asymmetry of colour patterns in faces of F. aquilonia gynes from natural (forest interiors) and disturbed (clear-cut zones and forest edges) habitats in Finland. We defined five variable, clearly visible and symmetrical (left/right) colour morphs of gynes' faces. Individuals of totally dark morph were present only in disturbed habitats. General analyses of melanisation degree showed, that gynes from disturbed habitats were significantly darker compared to those from forest interiors. Individuals from the same nest tend to have a similar degree of melanisation. The mean darkness of face was highest among individuals from forest-edge nests and the lowest from forest interior nests. In all habitat types the darkness of face increased with an increase in head width. Increase of cuticular melanisation in F. aquilonia gynes in disturbed habitats could be explained with the theory of thermal melanism and stress-induced immune defence. Although some amount of fluctuating asymmetry among left/right symmetrical colour variations on faces of F. aquilonia gynes was found, it was affected neither by habitat type nor by head width. Melanisation degree of red wood ants have a potency to be used as ecological indicator for the level of disturbance in managed coniferous forests and fluctuating asymmetry of colour variations in ants might be studied furtherly in cases of more severe environmental concerns.     

Light enough to travel or wise enough to stay? Brain size evolution and migratory behavior in birds

Brain size relative to body size is smaller in migratory than in nonmigratory birds. Two mutually nonexclusive hypotheses had been proposed to explain this association. On the one hand, the “energetic trade‐off hypothesis” claims that migratory species were selected to have smaller brains because of the interplay between neural tissue volume and migratory flight. On the other hand, the “behavioral flexibility hypothesis” argues that resident species are selected to have higher cognitive capacities, and therefore larger brains, to enable survival in harsh winters, or to deal with environmental seasonality. Here, I test the validity and setting of these two hypotheses using 1466 globally distributed bird species. First, I show that the negative association between migration distance and relative brain size is very robust across species and phylogeny. Second, I provide strong support for the energetic trade‐off hypothesis, by showing the validity of the trade‐off among long‐distance migratory species alone. Third, using resident and short‐distance migratory species, I demonstrate that environmental harshness is associated with enlarged relative brain size, therefore arguably better cognition. My study provides the strongest comparative support to date for both the energetic trade‐off and the behavioral flexibility hypotheses, and highlights that both mechanisms contribute to brain size evolution, but on different ends of the migratory spectrum.     

Functional trade‐offs increase species diversity in experimental plant communities

Functional trade‐offs have long been recognised as important mechanisms of species coexistence, but direct experimental evidence for such mechanisms is extremely rare. Here, we test the effect of one classical trade‐off – a negative correlation between seed size and seed number – by establishing microcosm plant communities with positive, negative and no correlation between seed size and seed number and analysing the effect of the seed size/number correlation on species richness. Consistent with theory, a negative correlation between seed size and seed number led to a higher number of species in the communities and a corresponding wider range of seed size (a measure of functional richness) by promoting coexistence of large‐ and small‐seeded species. Our study provides the first direct evidence that a seed size/number trade‐off may contribute to species coexistence, and at a wider context, demonstrates the potential role of functional trade‐offs in maintaining species diversity.     

Large‐scale geographic variation in iridescent structural ornaments of a long‐distance migratory bird

Iridescent colours produced during moult likely play an important role in pair formation in birds. We sought to quantify geographic variation in such colouration in a duck species, Eurasian teal Anas crecca, in winter (when mating occurs) to evaluate whether this variation reflects birds’ breeding origins or differential individual migration strategies in both males and females. We combined information on feather production region and individual attributes (body size, sex and age) of Eurasian teal from 82 wintering sites in France. Feather production region (moult site or natal origin) was inferred using feather deuterium values (δD_f). We performed spectral measurements to evaluate speculum colour and brightness contrasts for 1052 teal collected over four years. Colouration differed strongly among wintering regions, with birds wintering in eastern France exhibiting higher colour contrast than those wintering in the west. Body size and colouration were positively related. There were no differences in cohort‐specific δD_f values between separate wintering regions in France, indicating that within a winter quarter teal originated from areas across the entire breeding range. Overall, patterns of spatial variation in feather colouration were related most closely to body size which was consistent with predictions of a differential migration hypothesis, with larger and more colour‐contrasting birds wintering closer to their breeding grounds. Because moult speed is also known to affect colour production, early breeders or individuals that skipped reproduction may have invested more or earlier in their feather quality to gain potential advantages in monopolizing future mates.     

The effect of skin reflectance on thermal traits in a small heliothermic ectotherm

Variation in colour patterning is prevalent among and within species. A number of theories have been proposed in explaining its evolution. Because solar radiation interacts with the pigmentation of the integument causing light to either be reflected or absorbed into the body, thermoregulation has been considered to be a primary selective agent, particularly among ectotherms. Accordingly, the colour-mediated thermoregulatory hypothesis states that darker individuals will heat faster and reach higher thermal equilibria while paler individuals will have the opposite traits. It was further predicted that dark colouration would promote slower cooling rates and higher thermal performance temperatures. To test these hypotheses we quantified the reflectance, selected body temperatures, performance optima, as well as heating and cooling rates of an ectothermic vertebrate, Lampropholis delicata. Our results indicated that colour had no influence on thermal physiology, as all thermal traits were uncorrelated with reflectance. We suggest that crypsis may instead be the stronger selective agent as it may have a more direct impact on fitness. Our study has improved our knowledge of the functional differences among individuals with different colour patterns, and the evolutionary significance of morphological variation within species.     

Do highly ornamented and less parasitized males have high quality sperm? – an experimental test for parasite-induced reproductive trade-offs in European minnow (Phoxinus phoxinus)

Parasites take their resources from hosts and thus directly reduce available resources for hosts’ own body functions, such as growth and reproduction. Furthermore, parasite infections cause significant indirect costs to their hosts in terms of increased investments on immune defense. In this study, we investigated the impact of parasite infection on the sperm quality and expression of secondary sexual ornamentation (saturation of the red abdominal colouration and number of breeding tubercles) in the Eurasian minnow (Phoxinus phoxinus). We exposed minnows to a high and low dose of common nonspecific fish ectoparasite, the glochidia larvae of duck mussel (Anodonta anatina) and tested whether parasite infection leads to trade‐off in sperm quality and/or ornamental expression. We found that glochidia infection reduces the curvature of the sperm swimming trajectory, number of breeding tubercles, and possibly male competitive ability, but does not affect expression of male color ornamentation. Furthermore, glochidia infection was found to reduce sperm motility, but only when all the noninfected individuals were excluded from the model. Supporting one of the predictions by phenotype‐linked fertility hypothesis both in high‐infection and low‐infection group male breeding colouration was positively associated with sperm quality. Our results suggest that although glochidia infection may have negative impact on male reproductive success, parasite‐induced costs may not create strong trade‐off between breeding colouration and sperm quality or that such trade‐off become detectable only in resource‐limited conditions.     

SPEED AND STAMINA TRADE-OFF IN LACERTID LIZARDS

Abstract.— Morphological and physiological considerations suggest that sprinting ability and endurance capacity put conflicting demands on the design of an animal's locomotor apparatus and therefore cannot be maximized simultaneously. To test this hypothesis, we correlated size‐corrected maximal sprint speed and stamina of 12 species of lacertid lizards. Phylogenetically independent contrasts of sprint speed and stamina showed a significant negative relationship, giving support to the idea of an evolutionary trade‐off between the two performance measures. To test the hypothesis that the trade‐off is mediated by a conflict in morphological requirements, we correlated both performance traits with snout‐vent length, size‐corrected estimates of body mass and limb length, and relative hindlimb length (the residuals of the relationship between hind‐ and forelimb length). Fast‐running species had hindlimbs that were long compared to their forelimbs. None of the other size or shape variables showed a significant relationship with speed or endurance. We conclude that the evolution of sprint capacity may be constrained by the need for endurance capacity and vice versa, but the design conflict underlying this trade‐off has yet to be identified.     

Insularity and the evolution of melanism,sexual dichromatism and body size in the worldwide‐distributed barn owl

Island biogeography has provided fundamental hypotheses in population genetics, ecology and evolutionary biology. Insular populations usually face different feeding conditions, predation pressure, intraspecific and interspecific competition than continental populations. This so‐called island syndrome can promote the evolution of specific phenotypes like a small (or large) body size and a light (or dark) colouration as well as influence the evolution of sexual dimorphism. To examine whether insularity leads to phenotypic differentiation in a consistent way in a worldwide‐distributed nonmigratory species, we compared body size, body shape and colouration between insular and continental barn owl (Tyto alba) populations by controlling indirectly for phylogeny. This species is suitable because it varies in pheomelanin‐based colouration from reddish‐brown to white, and it displays eumelanic black spots for which the number and size vary between individuals, populations and species. Females are on average darker pheomelanic and display more and larger eumelanic spots than males. Our results show that on islands barn owls exhibited smaller and fewer eumelanic spots and lighter pheomelanic colouration, and shorter wings than on continents. Sexual dimorphism in pheomelanin‐based colouration was less pronounced on islands than continents (i.e. on islands males tended to be as pheomelanic as females), and on small islands owls were redder pheomelanic and smaller in size than owls living on larger islands. Sexual dimorphism in the size of eumelanic spots was more pronounced (i.e. females displayed much larger spots than males) in barn owls living on islands located further away from a continent. Our study indicates that insular conditions drive the evolution towards a lower degree of eumelanism, smaller body size and affects the evolution of sexual dichromatism in melanin‐based colour traits. The effect of insularity was more pronounced on body size and shape than on melanic traits.     

Evolution of conspicuous colouration, body size and gregariousness: a comparative analysis of lepidopteran larvae

Protective colouration in animals includes camouflage (i.e., crypsis), that decreases the risk of detection, and conspicuous colouration, which is often used in combination with chemical defences to deter predators from attacking. Experiments have shown that the efficacy of conspicuous colouration increases with increasing size of pattern elements and larger body size. Prey species that have acquired avoidance inducing colouration therefore may be exposed to selection for larger body size, and such colouration may more easily evolve in large than in small prey species. Here we test for a difference in body size between species with different colouration modes and perform a comparative analysis based on phylogenetically independent contrasts to examine if evolutionary shifts in colour pattern have been associated with evolutionary changes in body size, using data for 578 species of moths. Larval body size did not differ between species with signalling and non-signalling larvae, and results from the comparative analysis suggest that these two traits have not evolved in parallel. The lack of association between evolutionary changes in colouration and body size may reflect a confounding influence of lifestyle, because evolutionary shifts from solitary to group-living larvae were associated with decreased larval body length and adult wing span. Because evolutionary changes in larval body size were associated with evolutionary changes in adult wing span the predicted association between colouration and size may have been confounded also by conflicting selection on body size in larvae and adults.