Abnormalities of wing pattern in the Eastern Tiger Swallowtail butterfly, Papilio glaucus

Abstract In much of its range Papilio glaucus L. has two forms of female, black and yellow, and the gene controlling the colour pattern is on the Y chromosome. Thus black mothers produce only black daughters and yellow mothers produce yellow daughters. Reasons are given to explain the occasional exceptions to this rule. The black female form mimics Battus philenor (L.), and an autosomal mutant is described in P.glaucus which is paralleled by a similar aberration in the model - a possible example of a model 'escaping' from a mimic and the mimic 'catching up' at one step.
Sex mosaics are readily seen in the black form of glaucus females and a numberare described from the Strecker collection. The probable cytogenetic constitution of these aberrations is discussed.
Hybrids are described between glaucus and its near relatives, P.rutulus Lucas, P.eurymedon Lucas and P.multicaudatus Kirby. These crosses produce mainly males but, by the use of ecdysterone, females have been obtained in the cross between the black female form of glaucus and the male of rutulus .     

Perturbation of the wing color pattern of a swallowtail butterfly,Papilio xuthus,induced by acid carboxypeptidase

Hypodermal injection of Toughmac-E, a digestive mixture composed of nine digestive components, or Molsin induced perturbation of the wing color pattern in 0- to 2-day-old pupae of Papilio xuthus, but had no effect on prepupae or 3- to 4-day-old pupae. The effective component in Toughmac-E was identified as Molsin, an acid carboxypeptidase of Aspergillus saitoi which specifically liberates tyrosine and phenylalanine from the C-terminal residues of proteins. The pattern perturbation occurred in either side of the fore- and hindwings of both sexes. When this enzyme was administered, stronger melanization than in the normal wings was found in the whole wings of most butterflies, but in other butterflies, the yellow region was enlarged. These findings suggest that the pattern perturbation was caused by changes in the levels of melanin and papiliochromes in scales. Melanin is a black pigment and papiliochromes are yellow pigments; their common precursor is dopamine. The normal pattern is formed by a predetermined balance of melanin and papiliochromes, whereas the deposit of an excess amount of tyrosine and/or phenylalanine disturbs this balance and results in perturbation of the color pattern. Administration of L-dopa or dopamine had no effect on the wing pattern. When the activity of an endogenous acid carboxypeptidase similar to Molsin appears in the early pupa, the summed activities of the endogenous and exogenous acid carboxypeptidases must induce a pattern perturbation. The relations between the endogenous acid carboxypeptidase and its probable substrate, the reserve protein, and the physiological roles of these relations in the regulation, utilization and excretion of amino acids are discussed.     

The pigments of Papilio graphium weiskei: Sarpedobilin and ommin responsible for a unique pattern in a butterfly wing membrane

• 1.1. The pigments of the butterfly Papilio graphium weiskei have been separately extracted from the different coloured zones of the wing membrane and analyzed.
• 2.2. Sarpedobilin 3, a neopterobilin, is present in all parts of the wing, at higher concentrations in the green and blue areas, in traces in the pink zones, the total amount being spectrophotometrically determined at 50 μg per individual.
• 3.3. The pigment from the pink and mauve areas cannot be extracted in the usual conditions, but only after in-situ destruction of the membrane under strong acidic conditions. The substance thus obtained shows redox properties. It is identified with ommin on the basis of the already reported similar red pigment obtained in such conditions “Farbstoffe IV” from other insect species.
• 4.4. In conclusion, the unique wing pattern of P. weiskei where green, blue, mauve and pink zones occur, is due to the superposition of two pigments, sarpedobilin (a derivative of pterobilin) and ommin, present within the membrane.

     

Colour pattern specification in the Mocker swallowtail Papilio dardanus: the transcription factor invected is a candidate for the mimicry locus H

The swallowtail butterfly, Papilio dardanus, is an iconic example of a polymorphic Batesian mimic. The expression of various female-limited colour forms is thought to be controlled by a single autosomal locus, termed H, whose function in determining the wing pattern remains elusive. As a step towards the physical mapping of H, we established a set of 272 polymorphic amplified fragment length polymorphism (AFLP) markers (EcoRI-MseI). Segregation patterns in a 'female-informative' brood (exploiting the absence of crossing over in female Lepidoptera) mapped these AFLPs to 30 linkage groups (putative chromosomes). The difference between the hippocoon and cenea female forms segregating in this family resides on a single one of these linkage groups, defined by 14 AFLPs. In a 'male-informative' cross (markers segregating within a linkage group), a pair of AFLPs co-segregated closely with the two female forms, except in four recombinants out of 19 female offspring. Linkage with these AFLP markers using four further female-informative families demonstrated that the genetic factor determining other morphs (poultoni, lamborni and trimeni) also maps to this same linkage group. The candidate gene invected, obtained in a screen for co-segregation of developmental genes with the colour forms, resides in a 13.9 cM interval flanked by the two AFLP markers. In the male-informative family invected co-segregated perfectly with the hippocoon/cenea factor, despite the four crossovers with the AFLPs. These findings make invected, and possibly its closely linked paralogue engrailed, strong candidates for H. This is supported by their known role in eyespot specification in nymphalid butterfly wings.     

Accommodating natural and sexual selection in butterfly wing pattern evolution

Visual patterns in animals may serve different functions, such as attracting mates and deceiving predators. If a signal is used for multiple functions, the opportunity arises for conflict among the different functions, preventing optimization for any one visual signal. Here we investigate the hypothesis that spatial separation of different visual signal functions has occurred in Bicyclus butterflies. Using phylogenetic reconstructions of character evolution and comparisons of evolutionary rates, we found dorsal surface characters to evolve at higher rates than ventral characters. Dorsal characters also displayed sex-based differences in evolutionary rates more often than did ventral characters. Thus, dorsal characters corresponded to our predictions of mate signalling while ventral characters appear to play an important role in predator avoidance. Forewing characters also fit a model of mate signalling, and displayed higher rates of evolution than hindwing characters. Our results, as well as the behavioural and developmental data from previous studies of Bicyclus species, support the hypothesis that spatial separation of visual signal functions has occurred in Bicyclus butterflies. This study is the first to demonstrate, in a phylogenetic framework, that spatial separation of signals used for mate signalling and those used for predator avoidance is a viable strategy to accommodate multiple signal functions. This signalling strategy has important ramifications on the developmental evolution of wing pattern elements and diversification of butterfly species.     

Evolution of the mimetic African swallowtail butterfly Papilio dardanus: molecular data confirm relationships with P. phorcas and P. constantinus

Sister group relationships of the African Mocker Swallowtail, Papilio dardanus, were determined using mitochondrial 16S rRNA and Cytochrome B sequences, and nuclear Elongation Factor EF-la and the ITS-1 region of the ribosomal RNA locus. All four data sets placed P. dardanus as the sister species of P. phorcas, with P. constantinus as the next closest relative, and quite distinct from other African Papilios such as P. nobilis. These data support earlier morphological studies indicating that the only two African Papilio species with multiple female colour forms have a common ancestor not shared with any other living species. This information is important for conclusions about the evolution of female-limited mimicry in swallowtail butterflies, and successful use of the ITS-1 gene opens up new possibilities for studying this phenomenon within P. dardanus.     

Cryptic genetic and wing pattern diversity in a mimetic Heliconius butterfly

Despite rampant colour pattern diversity in South America, Heliconius erato exhibits a ‘postman’ wing pattern throughout most of Central America. We examined genetic variation across the range of H. erato, including dense sampling in Central America, and discovered a deep genetic break, centred on the mountain range that runs through Costa Rica. This break is characterized by a novel mitochondrial lineage, which is nearly fixed in northern Central America, that branches basal to all previously described mitochondrial diversity in the species. Strong genetic differentiation also appears in Z‐linked and autosomal markers, and it is further associated with a distinct, but subtle, shift in wing pattern phenotype. Comparison of clines in wing phenotype, mtDNA and nuclear markers indicate they are all centred on the mountains dividing Costa Rica, but that cline width differs among data sets. Phylogeographical analyses, accounting for this new diversity, rewrite our understanding of mimicry evolution in this system. For instance, these results suggest that H. erato originated west of the Andes, perhaps in Central America, and as many as 1 million years before its co‐mimic, H. melpomene. Overall our data indicate that neutral genetic markers and colour pattern loci are congruent and converge on the same hypothesis—H. erato originated in northwest South America or Central America with a ‘postman’ phenotype and then radiated into the wealth of colour patterns present today.     

Color pattern formation on the wing of a butterfly Pieris rapae. 2. Color determination and scale development

It has been shown that microcautery on the prospective apical black region of the early pupal forewing of a butterfly, Pieris rapae , causes alteration of the scale color on the adult wing and a delay in histogenesis of the pupal wing. From these results, it has been assumed that the developmental delay of scale cells in the pupal wing alters their developmental fate and the hypothesis that different color fates of scales are determined by differences in the developmental timetables between scale cells is proposed. In this study, we attempted to find the developmental timetables of individual scales expressing specific color to test this hypothesis. It was found that the holes on the upper surface of a scale become larger as they develop and the hole sizes of scales in the white region are always larger than in the black region on the same wings either during pupal period or after eclosion. This suggests that the scale hole size is a good index that reflects developmental rate of the scale and a difference in the hole size between adult scales is attributed to a difference in the developmental timetables when their ancestral scale precursor cells were in the pupal period. A comparison of the hole sizes between adult scales in different color regions suggested that normal white scales were in a more advanced state than were the black ones but white scales induced by microcautery were in a less advanced state than black ones on the same wing. This supports our hypothesis.     

Seasonal wing colour plasticity varies dramatically between buckeye butterfly populations in different climatic zones

1. In the present study, how seasonal wing colour plasticity in buckeye butterflies (Junonia coenia Hübner) differs between populations in different climatic regions, and whether these differences are explained by regional environmental differences or reflect genetic divergences in plasticity is addressed. 2. Using museum specimen data, it is shown that buckeye wing colour variation is much greater in populations from the humid and subtropical climates of the eastern U.S.A. than in populations from the desert and mediterranean climates of the western U.S.A. 3. Museum specimen data further show that wing colour in eastern populations is strongly correlated with seasonal variation in day length and temperature, whereas wing colour in western populations is only weakly associated with these cues. 4. Controlled incubator experiments comparing Southern California and North Carolina populations suggest that regional differences in wing pattern variation are attributable to dramatically increased robustness to environmental variation in western populations. 5. Together these experiments show that while phenotypic variation can be influenced by environmental cues, the range of this variation can genetically diverge between populations in different regions.     

Characterising the Phenotypic Diversity of Papilio dardanus Wing Patterns Using an Extensive Museum Collection

The history of 20^th Century evolutionary biology can be followed through the study of mimetic butterflies. From the initial findings of discontinuous polymorphism through the debates regarding the evolution of mimicry and the step-size of evolutionary change, to the studies on supergene evolution and molecular characterisation of butterfly genomes, mimetic butterflies have been at the heart of evolutionary thought for over 100 years. During this time, few species have received as much attention and in-depth study as Papilio dardanus. To assist all aspects of mimicry research, we present a complete data-derived overview of the extent of polymorphism within this species. Using historical samples permanently held by the NHM London, we document the extent of phenotypic variation and characterise the diversity present in each of the subspecies and how it varies across Africa. We also demonstrate an association between “imperfect” mimetic forms and the transitional race formed in the area where Eastern and Western African populations meet around Lake Victoria. We present a novel portal for access to this collection, www.mimeticbutterflies.org, allowing remote access to this unique repository. It is hoped that this online resource can act as a nucleus for the sharing and dissemination of other collections databases and imagery connected with mimetic butterflies.     

Polymorphic mimicry in Papilio dardanus: mosaic dominance, big effects, and origins

The mocker swallowtail, Papilio dardanus, has a female-limited polymorphic mimicry. This polymorphism is controlled by allelic variation at a single locus with at least 11 alleles. Many of the alternative morphs are accurate mimics of different species of distasteful butterflies. Geneticists have long been interested in the mechanism by which a single gene can have such diverse and profound effects on the phenotype and in the process by which these complex phenotypic effects could have evolved. Here we present the results of a morphometric analysis of the pleiotropic effects of the mimicry gene on the array of elements that makes up the overall pattern. We show that the patterns controlled by mimicking alleles are more variable and less internally correlated than those controlled by nonmimicking alleles, suggesting the two are subject to different degrees of selection and mutational variance. Analysis of the pleiotropic dominance of the alleles reveals a consistent pattern of dominance within a coevolved genetic background and a mosaic pattern of dominant and recessive effects (including overdominance) in a heterologous genetic background. The alleles of the mimicry gene have big effects on some pattern elements and small effects on others. When the array of big phenotypic effects of the mimicry gene is applied to the presumptive ancestral color pattern, it produces a reasonable resemblance to distasteful models and suggests the initial steps that may have produced the mimicry as well as the polymorphism.     

Neurons innervating the lamina in the butterfly, Papilio xuthus

The butterfly Papilio xuthus has compound eyes with three types of ommatidia. Each type houses nine spectrally heterogeneous photoreceptors (R1–R9) that are divided into six spectral classes: ultraviolet, violet, blue, green, red, and broad-band. Analysis of color discrimination has shown that P. xuthus uses the ultraviolet, blue, green, and red receptors for foraging. The ultraviolet and blue receptors are long visual fibers terminating in the medulla, whereas the green and red receptors are short visual fibers terminating in the lamina. This suggests that processing of wavelength information begins in the lamina in P. xuthus, unlike in flies. To establish the anatomical basis of color discrimination mechanisms, we examined neurons innervating the lamina by injecting Neurobiotin into this neuropil. We found that in addition to photoreceptors and lamina monopolar cells, three distinct groups of cells project fibers into the lamina. Their cell bodies are located (1) at the anterior rim of the medulla, (2) between the proximal surface of the medulla and lobula plate, and (3) in the medulla cell body rind. Neurobiotin injection also labeled distinct terminals in medulla layers 1, 2, 3, 4 and 5. Terminals in layer 4 belong to the long visual fibers (R1, 2 and 9), while arbors in layers 1, 2 and 3 probably correspond to terminals of three subtypes of lamina monopolar cells, respectively. Immunocytochemistry coupled with Neurobiotin injection revealed their transmitter candidates; neurons in (1) and a subset of neurons in (2) are immunoreactive to anti-serotonin and anti-γ-aminobutyric acid, respectively.     

A new model for biological pattern formation

Various non-equilibrium growth models have been used to explore the development of morphology in biological systems. Here we review a class of biological growth models which exhibit fractal structures and discuss the relationship of these models to a variety of other phenomena.     

Color pattern formation on the wing of the butterfly Pieris rapae. 1. Cautery induced alteration of scale color and delay of arrangement formation

Experimental approaches to color pattern formation of lepidopteran insects have been made exclusively by analyzing pattern alterations in adult wings induced by operations. We microcauterized the presumptive black region of the dorsal forewing of the butterfly Pieris rapae and analyzed not only the resultant color pattern in the adult wing but also the cell behavior in the pupal wing epidermis around the injury. Cautery induced color alterations were as follows: (i) cautery up to 49.5 h after pupation resulted in white regions appearing within the black region while later cauteries induced larger white regions; (ii) cautery between 50 and 59.5 h resulted in the white regions induced by the cauteries being dramatically decreased; (iii) cautery after 60 h resulted in white regions that had almost disappeared. The examination of the cell behavior in the pupal wing epidermis after cauteries showed that the row formation of scale precursor cells was delayed. This delayed area varied with the time of cautery, in the same manner as that in the induced white area in the adult wing ((i) – (iii) above). The relationship between scale color alteration and the developmental delay of the scale row formation is discussed.