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Measurements of melanization in adult (a) Araschnia levana and (b) Inachis io. Extent of melanization: area of indicated spots. Intensity of melanization: grey value of indicated areas. For A. levana total area of all black parts was also measured for extent of melanization.
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Effects of melanization in the juvenile stages of the European map butterfly (Araschnia levana) and the peacock butterfly (Inachis io) on the life history traits, larval and pupal development time and size at maturity, and on adult melanization were investigated. Pupae and 5th instar larvae of A. levana vary in degree of melanization, the latter po...
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... induced by long days has black wings with a white band and some small orange spots. Araschnia levana has two or three generations a year and hibernates as a pupa. Larvae vary in the fifth and last stage almost discretely between black and light brown, whereas pupae vary continuously from light to dark brown. Inachis io has only one adult form ( Fig. 1) and one larval form; 5th instar larvae are jet black with small white dots. The pupae vary more or less discretely from entirely yellowish green to dark brown. Inachis io has one or two generations a year and overwinters as an ...
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... pupae was measured on the wing case as average grey value on a scale of 0 ( = dark) to 255 ( = pale). In adults both intensity of black coloration and size of black pattern elements were quantified. In A. levana the only part where the intensity of black coloration varied beyond measure- ment error was the lower part of the band on the hindwing ( Fig. 1) which was measured as average grey value on the dorsal side. In I. io intensity was measured as the average grey value of the ventral side of the hindwing (Fig. ...
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... pattern elements were quantified. In A. levana the only part where the intensity of black coloration varied beyond measure- ment error was the lower part of the band on the hindwing ( Fig. 1) which was measured as average grey value on the dorsal side. In I. io intensity was measured as the average grey value of the ventral side of the hindwing (Fig. ...
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... evaluate the extent of black parts in the wing, one black spot was measured (Fig. 1). It was selected for ease and accuracy of measurement in a pilot study where the size of all black pattern elements was measured in 40 butterflies. The sizes of all these elements were so strongly correlated that measure- ment of only one element involved little loss of information. For both species one spot on the fore- wing was ...
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... 1). It was selected for ease and accuracy of measurement in a pilot study where the size of all black pattern elements was measured in 40 butterflies. The sizes of all these elements were so strongly correlated that measure- ment of only one element involved little loss of information. For both species one spot on the fore- wing was selected ( Fig. 1). In the summer form of A. levana all black pattern elements on the forewing are merged and the total area of all black pattern elements was measured. The areas were log-transformed before analysis to obtain a normal distribution. In I. io the log-transformed area of the black spot was highly correlated to the log-transformed area of ...
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Variation in wing pattern was measured in the swallowtail butterfly Papilio polyxenes, a Batesian mimic of the butterfly Battus philenor. Males and females differed in the number of yellow spots comprising the proximal spot band on the dorsal surfaces of the wings, with females having fewer spots than do males. This difference results in females be...
Understanding the genetic architecture of adaptive traits has been at the centre of modern evolutionary biology since Fisher; however, evaluating how the genetic architecture of ecologically important traits influences their diversification has been hampered by the scarcity of empirical data. Now, high-throughput genomics facilitates the detailed e...
Citations
... Recent work on monarch butterflies, Danaus plexippus, showed a link between toxin sequestration and warning signals, where male conspicuousness was inversely correlated with oxidative damage (due to an increase in concentrations of sequestered cardenolides) (Blount et al., 2023). Similarly to the red and yellow pigments often seen in warning signals, the production of melanin may incur tradeoffs with other traits, such as developmental time (e.g., melanised juvenile individuals take longer to develop during the early stages; Windig, 1999) or mate choice (for example the less melanised female of Colias philodice butterflies attract higher number of males than the most Journal of Experimental Biology • Accepted manuscript melanised females; Ellers and Boggs, 2004). The maintenance of costly traits, such as melanin pigments and chemical defences, can be affected by the quality of the diet. ...
For animals that synthesise their chemical compounds de novo, resources, particularly proteins, can influence investment in chemical defences and nitrogen-based wing colouration such as melanin. Competing for the same resources often leads to trade-offs in resource allocation. We manipulated protein availability in the larval diet of the wood tiger moth, Arctia plantaginis, to test how early life resource availability influences relevant life history traits, melanin production, and chemical defences. We expected higher dietary protein to result in more effective chemical defences in adult moths and a higher amount of melanin in the wings. According to the resource allocation hypothesis, we also expected individuals with less melanin to have more resources to allocate to chemical defences. We found that protein-deprived moths had a slower larval development, and their chemical defences were less unpalatable for bird predators, but the expression of melanin in their wings did not differ from that of moths raised on a high-protein diet. The amount of melanin in the wings, however, unexpectedly correlated positively with chemical defences. Our findings demonstrate that the resources available in early life have an important role in the efficacy of chemical defences, but melanin-based warning colours are less sensitive to resource variability than other fitness-related traits.
... A somewhat similar pattern is found in the European peacock butterfly Aglais io, which was also collected in Bryansk and St. Petersburg and studied in a similar experimental setting (Ryzhkova & Lopatina, 2015a, b). The 12-h photoperiod affects the temperature-dependent immature development only weakly in this species-even negligibly in the more northern butterflies-but leads to a clear reduction in pupal body mass, which is also true of a Belgian population (Windig, 1999) and possibly indicates that the stressfulness of the late-season photoperiodic conditions might constrain adaptation. ...
An interplay of genetic divergence and phenotypic plasticity in shaping geographic variation is increasingly receiving attention in the entomological literature. Two major environmental variables that govern life histories are temperature and photoperiod. Studies of thermal and photoperiodic reaction norms help understand how insect diversity evolved and how insects respond to environmental change. We studied survival, development and body mass in three geographic populations of the beetle Cassida vibex reared in the laboratory under several combinations of constant temperature (16, 19, 22, 25, and 28°C) and photoperiod (short‐day and long‐day). The three collection sites are situated along a climatic gradient and separated by hundreds of kilometers. Each population subtly but significantly differs in the absolute values of survival rate, developmental rate, and body mass as well as in the thermal and photoperiodic plasticity of these traits, but the geographic differences do not form a latitudinal cline. The southernmost population from a relatively warm climate survives worse at low temperature than the other two, but the overall survival is lowest in the latitudinally intermediate population. Short‐day conditions tend to accelerate postembryonic development and increase the slope of the developmental rate‐temperature relationship, especially so in the intermediate population, followed by the southernmost and then by the northernmost population. The latter, which inhabits a harsh climate, has the fastest and most temperature‐sensitive development, regardless of photoperiod, and attains the largest body mass among the three populations. The intermediately located and photoperiodically plastic population, which lives in a cool but mild climate, in contrast, has the smallest body size. Thus, although the importance of short‐day conditions as a seasonal cue increases poleward, the photoperiodic responses do not always become more pronounced in colder, high‐latitude environments. Our results emphasize that insect life‐history traits can exhibit quite sophisticated patterns of variation along climatic gradients. This article is protected by copyright. All rights reserved
... In many lepidopteran species, melanisation of the pupal cuticle is a plastic response to the environment. Non-melanised pupae are lighter (pale)green (Hazel & West, 1996) or pink (Smith et al., 1988) while melanised pupae are brown (Starnecker, 1996;Windig, 1999). The environmental parameters affecting this pupal colour variation, for example light conditions, relative humidity, diet and pupation substrate characteristics have been extensively studied in butterflies (reviewed in Mayekar and Kodandaramaiah (2017)). ...
We tested the effect of larval density on pupal colour plasticity in the butterfly Mycalesis mineus. Pupal colour of this species is known to be a plastic phenotype, being either brown or green. Colour is correlated with pupation substrate: pupae on leaves are almost exclusively green, whereas off‐leaf substrates (stem, soil, etc.) include both green and brown pupae. We hypothesised that brown pupae are more frequent at high larval densities and tested this hypothesis using two experiments. In the first experiment, we reared larvae at different densities in plastic containers, which provided a restricted choice of pupation substrates. There was no influence of density on pupal colour. In the second experiment, we simulated more natural conditions, wherein larvae were reared in nylon mesh sleeves and had a greater choice of pupation substrates. Here, there was a strong correlation between larval density and the proportion of brown pupae. We discuss why results from the two experiments may have differed and what can be concluded about factors influencing pupal colour. We also discuss the importance of choice of experimental protocols, especially in relation to how realism trades off with practicality and control.
... In other arthropods, not only cuticle melanisation, but also adult size was found to be negatively correlated with developmental rate (Ma et al., 2008;Windig, 1999). Similarly, we found that rapidly Asterisks mark statistically significant effects (P<0.05); ...
In cohort splitting diverging sub-cohorts may show substantial differences in their growth and developmental rates. Although in the past causes and adaptive value of cohort splitting were studied in detail, individual-level consequences of cohort splitting are still rather overlooked. Life history theory predicts that considerably increased growth and developmental rates should be traded off against other costly life history traits. However, it is not clear whether one should expect such associations in adaptive developmental plasticity scenarios, because natural selection might have promoted genotypes that mitigate those potential costs of rapid development. To address these contrasting propositions, we assessed life history traits in the wolf spider Pardosa agrestis, both collected from natural habitat and reared in laboratory. We found that some traits are negatively associated with developmental rates in spiders collected from nature, but these associations were relaxed to a considerable extent in laboratory reared specimens. In general, we observed no consistent trend for the presence of developmental costs, although some results might suggest higher relative fecundity costs in rapidly developing females. Our study provides a detailed approach to the understanding of individual-level consequences of cohort splitting, and to the associations between key life history traits in adaptive developmental plasticity scenarios.
... Recent studies have shown that production of melanin pigmentation can be sensitive to certain dietary conditions, such as availability of protein in the diet, and increase diet-mediated variation in cryptic coloration (Lee, Simpson, & Wilson, 2008). These limitations can be especially critical for herbivorous insects, due to the low levels of usable nitrogen in foliage (Morehouse & Rutowski, 2010;Ojala, Lindström, & Mappes, 2007;Safranek & Riddiford, 1975;Talloen, Van Dyck, & Lens, 2004;Windig, 1999). As a result, these same amino acid precursors are likely to compete with other important functions such as the formation of chitin, cocoons and immunological defence (Andersen, 1979;Lee et al., 2008). 5. We conclude that low plasticity in warning signal characteristics makes signal expression robust under varying dietary conditions. ...
Trade‐offs have been shown to play an important role in the divergence of mating strategies and sexual ornamentation, but their importance in explaining warning signal diversity has received less attention. In aposematic organisms, allocation costs of producing the conspicuous warning signal pigmentation under nutritional stress could potentially trade‐off with life‐history traits and maintain variation in warning coloration.
We studied this with an aposematic herbivore Arctia plantaginis (Arctiidae), whose larvae and adults show extensive variation in aposematic coloration. In larvae, less melanic coloration (i.e. larger orange patterns) produces a more efficient warning signal against predators, whereas high amounts of melanism (smaller orange pattern) enhance thermoregulation, correlate with better immunity and make individuals harder to detect for naïve predators.
We conducted a factorial rearing experiment with larvae originating from lines selected for either small or large orange signal size, which were reared on an artificial diet that had either low or high protein content. Protein content of the diet is critical for melanin production. We measured the effects of diet on individual coloration, life‐history traits, immune defence and reproductive output. We also compared the responses to dietary conditions between the small and large larval signal genotypes.
Protein content of the diet did not affect warning coloration in the larval stage, but larval signal sizes differed significantly among selection lines, confirming that its variation is mainly genetically determined. In adults, signal line or diet did not affect coloration in hindwings, but males' forewings had more melanin on the high than on low protein diet. Contrary to coloration, diet quality had a stronger impact on life‐history traits: individuals developed for longer had smaller hindwing sizes in females and lower immune defence on the low protein content diet compared with the high. These costs were higher for more melanic larval signal genotypes in terms of development time and female hindwing size.
We conclude that low plasticity in warning signal characteristics makes signal expression robust under varying dietary conditions. Therefore, variation in diet quality is not likely to constrain signal expression, but can have a bigger impact on performance.
... The majority of studies on pupal plasticity have ignored developmental time, and our results highlight the need to further investigate the role of this important life history trait in phenotypic plasticity, especially in tropical species. Interestingly, in temperate peacock butterflies, Inachis io, paler pupae appear to develop faster than darker pupae [77]. ...
Lepidopteran insects have provided excellent study systems for understanding adaptive phenotypic plasticity. Although there are a few well-studied examples of adult plasticity among tropical butterflies, our understanding of plasticity of larval and pupal stages is largely restricted to temperate butterflies. The environmental parameters inducing phenotypic plasticity and the selective pressures acting on phenotypes are likely to differ across tropical and temperate climate regimes. We tested the influence of relative humidity (RH), a prominent yet under-appreciated tropical climatic component, along with pupation substrate, larval development time, pupal sex and weight in determining pupal colour in the tropical satyrine butterfly Mycalesis mineus. Pupae of this butterfly are either brown or green or very rarely intermediate. Larvae were reared at high (85%) and low (60%) RH at a constant temperature. Proportions of green and brown pupae were expected to vary across low and high RH and pupation substrates in order to enhance crypsis. Brown pupae were more common at low RH than at high RH, as predicted, and developed faster than green pupae. Pupal colour was correlated with pupation substrate. Choice of pupation substrate differed across RH treatments. It is unclear whether pupal colour influences substrate selection or whether substrate influences pupal colour. Our study underscores the need for further work to understand the basis of pupal plasticity in tropical butterflies.
... In contrast to many studies on the costs of bright color signals in vertebrates (e.g., Endler 1980;Hill and Montgomerie 1994;Grether et al. 2001;Hill et al. 2002;Boratynski et al. 2014), our study, along with the others (Saffranek and Riddiford 1975;Windig 1999;Talloen et al. 2004;Stoehr 2006;Ojala et al. 2007;Ma et al. 2008), further emphasizes that melanin-based black patterns can be more costly to produce for herbivorous insect species than bright pigment-based colors. In our data, A. plantaginis individuals that were less melanic as a larva, had a higher reproductive output as an adult due to positive genetic correlation. ...
To predict evolutionary responses of warning signals under selection, we need to determine the inheritance pattern of the signals, and how they are genetically correlated with other traits contributing to fitness. Furthermore, protective coloration often undergoes remarkable changes within an individual's lifecycle, requiring us to quantify the genetic constraints of adaptive coloration across all the relevant life stages. Based on a 12 generation pedigree with > 11 000 individuals of the wood tiger moth (Arctia plantaginis), we show that high primary defense as a larva (large warning signal) results in weaker defenses as adult (less efficient warning color), due to the negative genetic correlation between the efficacy of larval and adult warning coloration. However, production of effective warning coloration as a larva, did not incur any life-history costs and was positively genetically correlated with reproductive output. These results provide novel insights into the evolutionary constraints on protective coloration in animals, and explain the maintenance of variation in the signal expression despite the strong directional selection by predators. By analyzing the genetic and environmental effects on warning signal and life-history traits in all relevant life stages, we can accurately determine the mechanisms shaping the evolutionary responses of phenotypic traits under different selection environments. This article is protected by copyright. All rights reserved.
... Thus, an organism that grows large may do so at the expense of an extended DT and vice versa (Harvey and Strand 2002). The relative costs and benefits of optimizing different life-history traits are likely dependent on a suite of environmental factors, including the density and genotype of social partners (Lewontin 1955;Lewontin and Matsuo 1963;Wade 1985Wade , 2000Windig 1999). Wolf (2003) argued that the environment provided by group mates is often the most important component of the environment experienced by an individual. ...
Indirect genetic effects (IGEs) are the basis of social interactions among conspecifics, and can affect genetic variation of non-social as well as social traits. We used flour beetles (Tribolium castaneum) of two phenotypically distinguishable populations to estimate genetic (co)variances and the effect of IGEs on three life-history traits: development time (DT), growth rate (GR), and pupal body mass (BM). We found that GR was strongly affected by social environment with IGEs accounting for 18% of the heritable variation. We also discovered a sex-specific social effect: male ratio in a group significantly affected both GR and BM. That is, beetles grew larger and faster in male-biased social environments. Such sex-specific IGEs have not previously been demonstrated in a non-social insect. Our results show that beetles that achieve a higher BM do so via a slower GR in response to social environment. Existing models of evolution in age-structured or stage-structured populations do not account for IGEs of social cohorts. It is likely that such IGEs have played a key role in the evolution of developmental plasticity shown by Tenebrionid larvae in response to density. Our results document an important source of genetic variation for GR, often overlooked in life-history theory. This article is protected by copyright. All rights reserved.
... In these documented insect species, the spatiotemporal expression profiles of melanization and the resultant advantages and fitness costs are usually different. For example, melanization is expressed locally in the two dipterans Drosophila polymorpha 4 and Drosophila immigrans 6 , but globally in almost all the documented lepidopterans 2,3,[9][10][11][12][13][14][15][16][17][18] . In terms of temporal expression pattern, melanic phenotype may express in larva [9][10][11] , pupa 14 , adult 2,3,16,19 , larva and adult (Bombyx mori mln mutant strain 20 ), larva and pupa (B. ...
... For example, melanization is expressed locally in the two dipterans Drosophila polymorpha 4 and Drosophila immigrans 6 , but globally in almost all the documented lepidopterans 2,3,[9][10][11][12][13][14][15][16][17][18] . In terms of temporal expression pattern, melanic phenotype may express in larva [9][10][11] , pupa 14 , adult 2,3,16,19 , larva and adult (Bombyx mori mln mutant strain 20 ), larva and pupa (B. mori sooty mutant strain 21 ), or pupa and adult (Helicoverpa armigera 15 ) stages. ...
Melanism has been found in a wide range of species, but the molecular mechanisms involved remain largely elusive. In this study, we studied the molecular mechanisms of the pupal melanism in Spodoptera exigua. The full length cDNA sequences of tyrosine hydroxylase (TH) and dopa decarboxylase (DDC), two key enzymes in the biosynthesis pathway of melanin, were cloned, and their temporal expression patterns in the integument were compared during the larval-pupal metamorphosis process of the S. exigua wild type (SEW) and melanic mutant (SEM) strains. No amino acid change in the protein sequence of TH and DDC was found between the two strains. Both DDC and TH were significantly over-expressed in the integument of the SEM strain at late-prepupa and 0 h pupa, respectively, compared with those of the SEW strain. Feeding 5(th) instar larvae of SEM with diets incorporated with 1 mg/g of the DDC inhibitor L-α-Methyl-DOPA and 0.75 mg/g of the TH inhibitor 3-iodo-tyrosine (3-IT) resulted in 20% pupae with partially-rescued phenotype and 68.2% of pupae with partially- or fully-rescued phenotype, respectively. These results indicate that overexpressions of TH and DDC are involved in the pupal melanization of S. exigua.
... It often occurs spontaneously at low frequencies, and can gradually reach high frequencies or fixation in response to natural selection for field populations [10][11][12] or artificial selection for laboratory populations 13,14 . While holometabolous insects have four developmental stages, melanization is expressed only at one or two particular stages, including larval 4,7,15,16 , pupal 17 , adult [18][19][20][21][22] , larval and adult 8,17 , larval and pupal 23 , or pupal and adult stages 13 . In terms of spatial pattern, melanization is expressed either locally in a particular region of the body, commonly seen in Diptera 24,25 and Coleoptera 26,27 , or globally in the whole body, more often in Lepidoptera. ...
... It often occurs spontaneously at low frequencies, and can gradually reach high frequencies or fixation in response to natural selection for field populations [10][11][12] or artificial selection for laboratory populations 13,14 . While holometabolous insects have four developmental stages, melanization is expressed only at one or two particular stages, including larval 4,7,15,16 , pupal 17 , adult [18][19][20][21][22] , larval and adult 8,17 , larval and pupal 23 , or pupal and adult stages 13 . In terms of spatial pattern, melanization is expressed either locally in a particular region of the body, commonly seen in Diptera 24,25 and Coleoptera 26,27 , or globally in the whole body, more often in Lepidoptera. ...
... SEM's gain in the overall fitness contradicts the naturally-occurring pupal melanism of I. io, which had a fitness cost 17 (Table 5). This is also in contrast with the laboratory-occurring pupal/adult melanism of Helicoverpa armigera, which had the similar pupal melanization phenotype and time course as SEM, but was associated with fitness cost 13 (Table 5). ...
Melanism has long been thought to be a habitat adaptation with a fitness cost. Here we reported a homozygous melanic strain (SEM) of Spodoptera exigua (Hübner) (Insecta: Lepidoptera: Noctuidae) established with black pupae spontaneously occurring within a typical laboratory population (SEW). The melanization is expressed globally, and only in the pupal stage. After pupation, the melanic SEM pupae gradually accumulate melanin to become completely black within 6 hours, whereas the wild-type SEW pupae gradually turn yellow-brown. The melanic SEM strain exhibits faster development in all life stages, heavier pupa weight, more mating time, higher fecundity, and accordingly, higher net reproductive rate and population trend index. While no reproductive isolation was observed between the SEM and SEW strains, the mating times per female of the reciprocal crosses and the SEM intracrosses were significantly higher than those of the SEW intracrosses. This represents a rare case of melanization that has fitness gains, rather than costs. Analysis of the life-history traits of this case and 14 previously reported cases of insect melanism indicate that none of melanization origin, stage, space and variation type determining whether melanism will cause fitness gain or cost.
