Dynamic flash coloration is a type of antipredator coloration where intermittently appearing colour patterns in moving animals misdirect predator attacks by obscuring the precise location and trajectory of the moving prey. Birds and butterflies with differing dorsoventral wing coloration or iridescent surface structures may potentially benefit from such effects. However, we lack an understanding of what makes for an effective dynamic flash colour design and how much it benefits the carrier. Here, we test the effect of colour flashing using small passerine birds preying upon colourful, moving, virtual ‘prey’ stimuli on a touchscreen. We show that at fast speeds, green-to-blue flashing colour patterns can reduce the likelihood of pecks hitting the target, induce greater error in targeting accuracy and increase the number of pecks at a stimulus relative to similarly coloured non-flashing targets. Our results support the idea that dynamic flash coloration can deflect predatory attacks at fast speeds, but the effect may be the opposite when moving slowly.

Viability indicator traits are expected to be integrated extensively across the genome yet sex-limited to ensure that any benefits are sexually concordant. Understanding how such expectations are accommodated requires elucidating the quantitative genetic architecture of candidate traits in and across the sexes. Here we applied an animal modelling approach to partition the autosomal, allosomal, and direct maternal bases of variation in sexual versus non-sexual dorsal wing colouration in the butterfly Eurema hecabe. The sexual colour trait-coherently scattered ultraviolet that is under strong directional selection due to female choice-is brighter and more expansive in males, and overlays non-sexual pigmentary yellow markings that otherwise dominate both wing surfaces in each sex. Our modelling estimated high and sexually equivalent autosomal variances for ultraviolet reflectance (furnishing h2 ~ 0.58 overall and ~0.75 in males), accompanied by smaller but generally significant Z-linked and maternal components. By contrast, variation in non-sexual yellow was largely attributed to Z-linked sources. Intersexual genetic correlations based upon the major source of variation in each trait were high and not different from 1.0, implying regulation by a pool of genes common to each sex. An expansive autosomal basis for ultraviolet is consistent with its hypothesized role as a genome-wide viability indicator and ensures that both sons and daughters will inherit their father's attractiveness.

Indicator models of sexual selection posit that females choose males on the basis of traits that reveal male genetic quality and thereby enjoy increased offspring production. Here, we report that females of the butterfly Eurema hecabe receive indirect benefits from choosing males based on their ultraviolet (UV) wing coloration, a heritable and condition-dependent trait in this species. We first used a large laboratory-bred pedigree to demonstrate a per-family association between inbreeding and male UV trait value. Females exerted choice for UV-bright males within this protocol, and the average male UV trait value increased over six consecutive generations, presumably due to such selection and despite an increasing rate of pedigree-wide inbreeding. We then experimentally imposed a standard strength of inbreeding upon lines of divergent male UV trait values. Inbreeding depressed the siring performance of low UV treatment males more severely and resulted in a marginal reduction of their UV brightness, which rebounded sharply following subsequent outcrossing. These findings are consistent with the ornament-based signaling of genetic quality as a function of underlying individual-level mutational load.

Coloration facilitates evolutionary investigations in nature because the interaction between genotype, phenotype and environment is relatively accessible. In a landmark set of studies, Endler addressed this complexity by demonstrating that the evolution of male Trinidadian guppy coloration is shaped by the local balance between selection for mate attractiveness versus crypsis. This became a textbook paradigm for how antagonistic selective pressures may determine evolutionary trajectories in nature. However, recent studies have challenged the generality of this paradigm. Here, we respond to these challenges by reviewing five important yet underappreciated factors that contribute to colour pattern evolution: (i) among-population variation in female preference and correlated variation in male coloration, (ii) differences in how predators versus conspecifics view males, (iii) biased assessment of pigmentary versus structural coloration, (iv) the importance of accounting for multi-species predator communities, and (v) the importance of considering the multivariate genetic architecture and multivariate context of selection and how sexual selection encourages polymorphic divergence. We elaborate these issues using two challenging papers. Our purpose is not to criticize but to point out the potential pitfalls in colour research and to emphasize the depth of consideration necessary for testing evolutionary hypotheses using complex multi-trait phenotypes such as guppy colour patterns.

In many ways, the study of animal coloration is one of terminology. This is particularly true for defensive color patterns, which—depending upon putative function—may be referred to as aposematic, cryptic, dazzling, deflective, deimatic, disruptive, flash or flicker, illusionary, masquerade, or mimetic (Stevens et al. 2008; Stevens and Merilaita 2009; Kelley and Kelly 2014). In their review, Postema et al. (2022) propose a further classification scheme based upon the potential multifunctionality of defensive color patterns. The rationale for this in part comes from recent literature emphasizing the role of “multiple interacting selection pressures” that shape animal color signals (Cuthill et al. 2017, as cited in the review). The notion that animal coloration is subject to multiple sources of selection is certainly not new, and in this sense, the review will find favor with the exponents of sensory drive theory (Endler 1992, 1993). Postema et al. identify six scenarios likely to generate conflicting selection on defensive animal color patterns. These include scenarios involving variation among multiple viewers and visual environments, alternative (non-sensory) functions, and ontogenetic color variation. All but the latter invoke multiple contemporaneous sources of selection. Ontogenetic variation involves colouration that individuals might display at different life stages, and which might hence be subject to different sources or intensities of selection (as might different nuptial or seasonal forms, which are not mentioned). All scenarios—including ontogenetic variation—are amenable to interrogation according to the principles of sensory drive, provided that proper care is taken to recognize the salient sources of variation in selective context; that is, differences among viewers, viewing conditions, and any potential non-sensory influences on visual appearance. As a general point, this review reiterates the importance of remaining circumspect in relation to the potential diversity of influences upon animal color patterns.

An inspirational advocate for adaptation, animal behaviour and natural history.

Abstract Many aposematic species show variation in their color patterns even though selection by predators is expected to stabilize warning signals toward a common phenotype. Warning signal variability can be explained by trade‐offs with other functions of coloration, such as thermoregulation, that may constrain warning signal expression by favoring darker individuals. Here, we investigated the effect of temperature on warning signal expression in aposematic Amata nigriceps moths that vary in their black and orange wing patterns. We sampled moths from two flight seasons that differed in the environmental temperatures and also reared different families under controlled conditions at three different temperatures. Against our prediction that lower developmental temperatures would reduce the warning signal size of the adult moths, we found no effect of temperature on warning signal expression in either wild or laboratory‐reared moths. Instead, we found sex‐ and population‐level differences in wing patterns. Our rearing experiment indicated that ~70% of the variability in the trait is genetic but understanding what signaling and non‐signaling functions of wing coloration maintain the genetic variation requires further work. Our results emphasize the importance of considering both genetic and plastic components of warning signal expression when studying intraspecific variation in aposematic species.

The concept of animal personality is based on consistent individual differences in behaviour, yet little is known about the factors responsible for such variation. Theory based on sex-specific selection predicts sexual dimorphism in personality-related traits and, in some cases, differences in trait variances between the sexes. In this study, we examined the sources of individual variation for boldness behaviour in guppies (Poecilia reticulata). We first demonstrated heightened boldness expression in males relative to females across feral wild types, artificially selected domestic 'designer' guppies, and putative hybrids of the two. Boldness and body size covaried at the strain level but were not associated among individuals within strains. We also found high and repeatable behavioural differences among individuals (0.40 > intraclass r > 0.60) in all sex/strain groups except hybrid strain females. However, there was no evidence for the heightened inter-individual male variance anticipated for personality traits subject to certain forms of directional sex-specific selection. Domestic fish were boldest overall, and indicated the largest sex difference, which is consistent with genetic linkage between boldness and male ornamental colouration. Consistently high intrinsic variation in boldness behaviour, which extends to inbred domesticated fish, may in part underpin the invasive potential of this species.

Many species - humans included - employ color as an instrument of deception. One intriguing example of this resides in the conspicuous abstract color patterns displayed on the bodies of female orb weaving spiders. These displays increase prey interception rates and thereby function at least as visual lures. Their chromatic properties however vary extensively, both across and within species, with discrete forms often co-existing in the manner of a stable polymorphism. Variation is principally expressed in terms of signal hue (color per se), but it is unclear how attractiveness scales with this property and if extant morphs are maximally attractive relative to a graded range of potential alternatives. We examined these questions by assessing catch rates among color-manipulated females of the dimorphic jeweled spider Gasteracantha fornicata in their natural webs. The manipulation altered dorsal appearance in a manner akin to adding six new variants of their existing white/yellow phenotypes. This magnified the natural variation in stimulus hue independently of chroma (saturation) across a range spanning most of the color spectrum. Catch rate varied across treatments in simple accordance with how greatly stimulus hue deviated from either of the two extant spider phenotypes. Predictions based on fly-perceived chromatic and achromatic background contrast were clearly unsupported despite dipterans constituting similar to 60 % of identifiable prey. This study supports the importance of signal coloration per se in G. fornicata and suggests that extant lure phenotypes reside in a broadly optimal spectral range for stimulating their aggregate prey community.

Despite the fact their coloration functions as an aposematic signal, and is thus expected to be under stabilizing selection, hibiscus harlequin bugs (Tectocoris diophthalmus) show an impressive level of variation in their iridescent coloration both within and between populations. To date the heritability of coloration in this species remains unknown. Here we focus on a single population in New South Wales (the southern part of this species’ Australian range), with the greatest colour variation. We reared full-sib families of known pedigree in the laboratory and analysed the extent of iridescent coloration at adulthood. We then looked for evidence of heritability, condition dependence and antagonistic sexual selection acting on colour in this species. We found significant heritability in the extent of iridescent coloration for both sexes, as well as in development time and body size, but no evidence that condition dependence played a role in the determination of adult coloration. There was, however, a sex by genotype interaction for iridescent cover, in the form of a negative intersexual genetic correlation: in families where sons had high iridescent cover the daughters had low, and vice versa. Our results suggest that different selective pressures may act on coloration in males and females of this species.

Understanding the genetic architecture of life history plasticity may inform resilience under environmental change, but relatively little is known for the inhabitants of unpredictable wet-dry tropical environments. Here, I explore the quantitative genetics of juvenile growth and development relative to hostplant phenology in the butterfly Eurema hecabe. Wet season generations of this species breed explosively on leguminous annuals whereas dry season generations subsist at low density upon an alternative perennial host. The wet-to-dry season transition is temporally unpredictable and marked by widespread host defoliation, forcing a large cohort of stranded larvae to either pupate prematurely or prolong development in the hope of renewed foliage production. A split-brood experiment demonstrated greater performance on high quality annual as opposed to perennial host foliage and a marked decline under the stressed conditions faced by stranded wet season larvae. Genetic variances for rates of growth and development were equivalent among high quality treatments but strikingly elevated under resource stress, and the associated cross-environment genetic correlations were indistinguishable from zero. The results demonstrate genotype-environment interaction involving both rank order and variance scale, thereby revealing genetic variance for norms of reaction that may reflect variable risk aversion given an unpredictable tropical host phenology.

1. Resting metabolic rate (RMR) is a fundamental feature of animal biology that reflects the baseline level of energy expenditure. There are two main strategies that can address energy demands; animals can reallocate energy from maintenance by reducing RMR to meet energy demands (compensation model) or they can increase intake rate by increasing metabolic activities (performance model).2. Orb‐web spiders are sit‐and‐wait foragers that typically reside at the centre of their web waiting to intercept prey. Given their sedentary resource acquisition strategy, it is predicted that lower RMR is favoured to reduce self‐maintenance energetic costs and to allow greater allocation to oogenesis (i.e., egg sac development).3. In this study, we tested temporal variation in RMR of female Argiope radon (Araneae: Araneidae) spiders in response to mating status. Then we tested the degree to which between‐individual variation in the parental RMR relates to reproductive output and spiderling early life‐history traits.4. Despite the notable between‐individual variation, we found a temporal consistency of RMR in the female spiders at early adulthood. Mated females significantly reduced their RMR by around 35% compared to their unmated stage which supports compensation model. However, there was a significant correlation between female RMR and mass of the egg sac in these spiders which is an evidence for performance model.5. Our findings suggest that energy management in this species is a complex phenomenon, both strategies are in effect simultaneously at within‐ and between‐individual level shaping the individuals' phenotype.

Araneid spiders use abstract color patterns to attract prey. The chromatic properties of these displays vary extensively, both within and across species, and they are frequently polymorphic. Variation is often expressed in terms of signal hue (color per se), but it is unclear precisely how attractiveness scales with this property. We assessed captures among color-manipulated females of the dimorphic jeweled spider Gasteracantha fornicata in their natural webs. The manipulation magnified the natural variation in stimulus hue independently of chroma (saturation) across a range spanning most of the color spectrum. Catch rate varied across treatments in simple accordance with how greatly stimulus hue deviated from either of the two extant phenotypes. Predictions based upon fly-perceived background contrast were unsupported despite dipterans constituting ~60 % of prey. This study isolates the importance of stimulus hue and supports the premise that extant phenotypes reside in an optimal spectral range for prey attraction.

Sensory systems can capture only a fraction of available information, which creates opportunities for deceptive signalling. The sensory traps and sensory bias models have proven valuable for explaining how visual systems and environments shape the design of sexual signals, but their application to deceptive signals is largely limited to the context of pollination. Here we use the ‘jewelled’ orb-web spider Gasteracantha fornicata to experimentally test two longstanding hypotheses for the function of deceptive visual lures. Namely, that they: (1) exploit generalised preferences for conspicuous colouration (sensory bias), or (2) co-opt the otherwise-adaptive foraging response of prey toward flowers (sensory traps). In a field-based study we manipulated the conspicuous dorsal signals of female spiders along two axes—colour pattern and symmetry—to generate a gradient of floral resemblance and monitored the per-individual consequences for prey interception. As predicted by the sensory traps model, the most attractive phenotypes were those with flower-like radial symmetry and solid colour patterns, and their attractiveness equaled that of natural spiders. Taken with recent work demonstrating a close resemblance between G. fornicata and sympatric floral ‘models’, and pollinating insects as primary prey items, our results suggest that the deceptive colour-based lures of spiders function as inter-kingdom sensory traps via floral mimicry, and support the broader extension of sensory-based models to deceptive signalling contexts.

Field-based video recording of courtship between a male and female Stiphodon semoni (Family Gobiidae), afforded the opportunity to discern specific behaviours not reported of sicydiine gobies previously, including tail-wagging and kiss-like behaviour by the male. Furthermore, a subset of behaviours that resemble those from published reports of other sicydiines in courtship and a subset of behaviours that are analogous to those exhibited by guppies (Poecilia reticulata, Family Poeciliidae) are reported and discussed briefly and used to contend that sicydiines are ripe for detailed study of sexual signalling behaviour in fishes.

Summary There is a wealth of research on the way interactions with pollinators shape flower traits. However, we have much more to learn about influences of the abiotic environment on flower colour. We combine quantitative flower colour data for 339 species from a broad spatial range covering tropical, temperate, arid, montane and coastal environments from 9.25ºS to 43.75ºS with 11 environmental variables to test hypotheses about how macroecological patterns in flower colouration relate to biotic and abiotic conditions. Both biotic community and abiotic conditions are important in explaining variation of flower colour traits on a broad scale. The diversity of pollinating insects and the plant community have the highest predictive power for flower colouration, followed by mean annual precipitation and solar radiation. On average, flower colours are more chromatic where there are fewer pollinators, solar radiation is high, precipitation and net primary production are low, and growing seasons are short, providing support for the hypothesis that higher chromatic contrast of flower colours may be related to stressful conditions. To fully understand the ecology and evolution of flower colour, we should incorporate the broad selective context that plants experience into research, rather than focusing primarily on effects of plant–pollinator interactions.

Animals are able to assess the risk of predation and respond accordingly via behavioural and physiological changes. Web-building spiders are in the unique situation where they reside in the middle of their web and are therefore relatively exposed to predators. Thus, these spiders might moderate either their web-building behaviour or their behaviour on the web when exposed to the threat of predation. In this study, we experimentally explored how chemical cues from a predator influence foraging behaviour and metabolic rate in females of the orb-web spider Argiope keyserlingi. We found that female spiders restricted their foraging time budget when exposed to the predator cues from a praying mantid: they responded 11% and 17% quicker to a vibratory stimulus compared with control and non-predator cues, respectively, and spent less time handling the prey. Moreover, spiders were less likely to rebuild the web under predator cues. Female A. keyserlingi exposed to the praying mantid cue significantly elevated their metabolic rate compared with the control group. Our findings revealed short-term modifications over the 2 week trials in foraging behaviour and the physiology of female spiders in response to predator cues. This study suggests that under predator cues the spiders move quicker and this could be facilitated by elevation in metabolic rate. Reduced foraging activity and less frequent web repair/rebuilding would also reduce the spiders' exposure to praying mantid predators.

Advances in understanding non-genetic inheritance have prompted broader interest in environmental effects. One way in which such effects may influence adaptation is via the transmission of acquired habitat biases. Here I explore how natal experience influences adult host orientation in the oligophagous passion vine butterfly Heliconius charithonia. As an exemplar of the 'pupal mating' system, this species poses novelty among diurnal Lepidoptera for the extent to which male as well as female reproductive behaviours are guided by olfactory host cues. I sampled wild adult females breeding exclusively upon Passiflora incarnata, assigned their offspring to develop either upon this species or its local alternative Passiflora suberosa, and then assessed the behaviour of F1 adults in a large rainforest enclosure. Despite the fact that juvenile performance was superior upon P. incarnata, females oviposited preferentially upon their assigned natal species. Mate-seeking males also indicated a bias for the proximity of their natal host, and there was evidence for assortative mating based upon host treatment, although these data are less robust. This study is, to my knowledge, the first to support Hopkins' hostplant principle in butterflies, and points to inducible host preferences capable of reinforcing ecological segregation and ultimately accelerating evolutionary divergence in sympatry.

Temporal variation in reproductive investment, e.g. maternal egg provisioning, has a substantial effect on offspring fitness therefore has received great attention by evolutionary biologists. Maternal allocation into egg size and egg content directly influences performance of offspring in many taxa, but spiders have rarely been investigated in this regard. In this study, we investigate the temporal changes in maternal reproductive investment and offspring performance in an orb-web, Argiope radon. A group of male and female spiders were mated randomly in the laboratory. Female spiders were kept under standard condition until they laid egg sacs. For each egg sac, egg sac mass, egg size and egg protein content were measured across all egg sacs. Once the spiderlings emerged, emerging time and toleration to starvation of the spiderlings were recorded. Egg sacs laid early in life were heavier, have larger eggs and offspring emerge sooner than the egg sacs laid by the old females. The spiderlings from the early egg sacs were more likely to emerge, however, these offspring had less toleration to starvation than the egg sacs laid by old females. There was no significant correlation between egg size and egg protein content with offspring performance. The results showed how the female spiders strategically allocate resources to egg sacs and its consequences on the offspring emerging time and toleration to starvation. This study suggests an adaptive maternal reproductive investment strategy which allows the female spiders to gain maximum fitness in each reproductive bout.