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At least 127 records · Page 7Linked to original sources

PubMed2004

Effects of habitat fragmentation on the genetic structure of the monophagous butterfly Polyommatus coridon along its northern range margin.

Population genetic patterns of species at their range margin have important implications for species conservation. We performed allozyme electrophoresis of 19 loci to investigate patterns of the genetic structure of 17 populations (538 individuals) of the butterfly Polyommatus coridon, a monophagous habitat specialist with a patchy distribution. The butterfly and its larval food plant Hippocrepis comosa reach their northern distribution margin in the study region (southern Lower Saxony, Germany). Butterfly population size increased with host plant population size. The genetic differentiation between populations was low but significant (FST = 0.013). No isolation-by-distance was found. Hierarchical F-statistics revealed significant differentiation between a western and an eastern subregion, separated by a river valley. The combination of genetic and ecological data sets revealed that the expected heterozygosity (mean: 18.5%) decreased with increasing distance to the nearest P. coridon population. The population size of P. coridon and the size of larval food plant population had no effect on the genetic diversity. The genetic diversity of edge populations of P. coridon was reduced compared to populations from the centre of its distribution. This might be explained by (i). an increasing habitat fragmentation towards the edge of the distribution range and/or (ii). a general reduction of genetic variability towards the northern edge of its distribution.

Animals↗

PubMedDate not supplied

Concerted evolution and developmental integration in modular butterfly wing patterns.

Developing organisms are thought to be modular in organization so that traits in different modules evolve independently whereas traits within a module change in a concerted manner. The eyespot pattern in Bicyclus anynana butterflies provides an ideal system where morphological modularity can be dissected and different levels of genetic integration analyzed. Several lines of evidence show that all eyespots in an individual butterfly are genetically integrated, suggesting that the whole pattern, rather than the separate eyespots, should be considered as a single character. However, despite the strong genetic correlations between the two eyespots on the dorsal forewing of B. anynana, there is great potential for independent changes. Here we use laboratory lines selected in different directions for the size of those eyespots to study correlated responses in the whole eyespot pattern. We show clear changes in eyespot size across all wing surfaces, which depend on eyespot position along the anterior-posterior axis. There are also changes in the number of extra eyespots and in eyespot color composition but no changes in eyespot position relative to wing margin. Our analysis of eyespot pattern modularity is discussed in the light of what is known about the cellular and genetic mechanisms of eyespot formation and the great potential for evolutionary diversification in butterfly wing patterns.

Analysis of Variance↗

PubMedDate not supplied

Mutants highlight the modular control of butterfly eyespot patterns.

The eyespots on butterfly wings are thought to be serially homologous pattern elements. Yet eyespots differ greatly in number, shape, color, and size, within and among species. To what extent do these serially homologues have separate developmental identities, upon which selection acts to create diversity? We examined x-ray-induced mutations for the eyespots of the nymphalid butterfly Bicyclus anynana that highlight the modular control of these serially homologous wing pattern elements. These mutations reduce or eliminate individual eyespots, or groups of eyespots, with no further effect on the wing color pattern. The collection of mutants highlights a greater potential developmental repertoire than that observed across the genus Bicyclus. We studied in detail one such mutation, of codominant effect, that causes the elimination of two adjacent eyespots on the ventral hindwing. By analyzing the expression of genes known to be involved in eyespot formation, we found an alteration in the differentiation of the "organizing" cells at the eyespot's center. No such cells differentiate in the wing subdivisions lacking the two eyespots in the mutants. We propose several developmental models, based on wing compartmentalization in Drosophila, that provide the first framework for thinking about the molecular evolution of butterfly wing pattern modularity.

Animals↗

PubMed2002

Modularity, individuality, and evo-devo in butterfly wings.

Modularity in animal development is thought to have facilitated morphological diversification, but independent change of those traits integrated within a module might be restricted. Correlations among traits describe potential developmental constraints on evolution. These have often been postulated to explain patterns of morphological variation and have been examined theoretically but seldom analyzed experimentally. Here, we use artificial selection to explore the modular organization of butterfly wing patterns and the extent to which their evolution is constrained by the genetic correlations among repeated pattern elements. We show that, in Bicyclus anynana butterflies, despite the evidence that all eyespots are developmentally coupled, the response to selection for increased size of one individual eyespot can proceed in a manner largely independent from selection imposed on another eyespot. We argue that among-eyespot correlations are unlikely to have constrained the evolutionary diversification of butterfly wing patterns but might be important when only limited time is available for adaptive evolution to occur. The ease with which we have been able to produce independent responses to artificial selection on different eyespots may be linked to a legacy of natural selection favoring individuality. Our results are discussed within the context of the evolution of modularity and individuality of serially repeated morphological traits.

Animals↗

PubMed2003

Quantitative description and discrimination of butterfly wing patterns using moment invariant analysis.

Studies examining and using pattern variation in insects for identification and characterization of individuals and populations have been limited by the methods available for quantifying wing patterns objectively. In this paper, differences in wing pattern are demonstrated statistically using moment invariant data sets generated automatically from digitized images of the speckled wood butterfly, Pararge aegeria (Linnaeus). Studies with other biological subjects have already shown moment invariants to work well with outline shapes and silhouettes. A pilot study with replicated monochrome photographs of a single butterfly showed the method could detect pattern differences between wing surfaces, even in the presence of simulated wing fading and damage. In a further study of the wings of 228 specimens, multivariate analyses of variance using the moment data reliably detected differences between groups of butterflies according to sex, geographical origin and culture history. Potential applications and future improvements of the moment methodology are considered.

Analysis of Variance↗

PubMed2004

Germline transformation of the butterfly Bicyclus anynana.

Ecological and evolutionary theory has frequently been inspired by the diversity of colour patterns on the wings of butterflies. More recently, these varied patterns have also become model systems for studying the evolution of developmental mechanisms. A technique that will facilitate our understanding of butterfly colour-pattern development is germline transformation. Germline transformation permits functional tests of candidate gene products and of cis-regulatory regions, and provides a means of generating new colour-pattern mutants by insertional mutagenesis. We report the successful transformation of the African satyrid butterfly Bicyclus anynana with two different transposable element vectors, Hermes and piggyBac, each carrying EGFP coding sequences driven by the 3XP3 synthetic enhancer that drives gene expression in the eyes. Candidate lines identified by screening for EGFP in adult eyes were later confirmed by PCR amplification of a fragment of the EGFP coding sequence from genomic DNA. Flanking DNA surrounding the insertions was amplified by inverse PCR and sequenced. Transformation rates were 5% for piggyBac and 10.2% for Hermes. Ultimately, the new data generated by these techniques may permit an integrated understanding of the developmental genetics of colour-pattern formation and of the ecological and evolutionary processes in which these patterns play a role.

Animals↗

PubMed2004

Correlations between adult mimicry and larval host plants in ithomiine butterflies.

The apparent paradox of multiple coexisting wing pattern mimicry 'rings' in tropical butterflies has been explained as a result of microhabitat partitioning in adults. However, very few studies have tested this hypothesis. In neotropical forests, ithomiine butterflies dominate and display the richest diversity of mimicry rings. We show that co-mimetic species occupy the same larval host-plant species significantly more often than expected in two out of five communities that we surveyed; in one of these, the effect remains significant after phylogenetic correction. This relationship is most probably a result of a third correlated variable, such as microhabitat. Host-plant microhabitat may constrain adult movement, or host-plant choice may depend on butterfly microhabitat preferences and mimicry associations. This link between mimicry and host plant could help explain some host-plant and mimicry shifts, which have been important in the radiation of this speciose tropical group.

Adaptation, Biological↗

PubMed2006

Exaggeration and suppression of iridescence: the evolution of two-dimensional butterfly structural colours.

Many butterfly species possess 'structural' colour, where colour is due to optical microstructures found in the wing scales. A number of such structures have been identified in butterfly scales, including three variations on a simple multi-layer structure. In this study, we optically characterize examples of all three types of multi-layer structure, as found in 10 species. The optical mechanism of the suppression and exaggeration of the angle-dependent optical properties (iridescence) of these structures is described. In addition, we consider the phylogeny of the butterflies, and are thus able to relate the optical properties of the structures to their evolutionary development. By applying two different types of analysis, the mechanism of adaptation is addressed. A simple parsimony analysis, in which all evolutionary changes are given an equal weighting, suggests convergent evolution of one structure. A Dollo parsimony analysis, in which the evolutionary 'cost' of losing a structure is less than that of gaining it, implies that 'latent' structures can be reused.

Adaptation, Physiological↗

PubMed2000

A model for colour pattern formation in the butterfly wing of Papilio dardanus.

The butterfly Papilio dardanus is well known for the spectacular phenotypic polymorphism in the female of the species. We show that numerical simulations of a reaction diffusion model on a geometrically accurate wing domain produce spatial patterns that are consistent with many of those observed on the butterfly. Our results suggest that the wing coloration is due to a simple underlying stripe-like pattern of some pigment-inducing morphogen. We focus on the effect of key factors such as parameter values for mode selection, threshold values which determine colour, wing shape and boundary conditions. The generality of our approach should allow us to investigate other butterfly species. The relationship between these key factors and gene activities is discussed in the context of recent biological advances.

Animals↗

PubMed2005

Does habitat fragmentation affect temperature-related life-history traits? A laboratory test with a woodland butterfly.

Habitat fragmentation may change local climatic conditions leading to altered selection regimes for life-history traits in small ectotherms, including several insects. We investigated temperature-related performance in terms of fitness among populations of the woodland butterfly Pararge aegeria (L.) originating from populations of a closed, continuous woodland landscape versus populations of an open, highly fragmented agricultural landscape in central Belgium. Female fecundity and longevity were evaluated in a temperature-gradient experiment. As predicted, females of woodland landscape origin reached higher maximum daily fecundity and lifetime number of eggs than did agricultural landscape females at low ambient temperatures, but this reversed at high ambient temperature. Egg weight decreased with temperature, and eggs of woodland butterflies were smaller. Contrary to what is generally assumed, remaining thorax mass was a better predictor of lifetime reproductive output than was abdomen mass. Since we used the F2 generation from wild-caught females reared under common garden conditions, the observed effects are likely to rely on intrinsic, heritable variation. Our results suggest that differential selection regimes associated with different landscapes intervene by intraspecific variation in the response of a butterfly to variation in ambient temperature, and may thus be helpful when making predictions of future impacts on how wild populations respond to environmental conditions under a global change scenario, with increasing temperatures and fragmented landscapes.

Adaptation, Physiological↗

PubMed2005

Female Bicyclus anynana butterflies choose males on the basis of their dorsal UV-reflective eyespot pupils.

Sexual and natural selection pressures are thought to shape the characteristic wing patterns of butterfly species. Here we test whether sexual selection by female choice plays a role in the maintenance of the male wing pattern in the butterfly Bicyclus anynana. We perform one of the most extensive series of wing pattern manipulations in butterflies, dissecting every component of the 'bulls-eye' eyespot patterns in both ventral and dorsal wing surfaces of males to test the trait's appeal to females. We conclude that females select males on the basis of the size and brightness of the dorsal eyespot's ultraviolet reflecting pupils. Pupil absence is strongly selected against, as are artificially enlarged pupils. Small to intermediate (normal sized) pupils seem to function equally well. This work contradicts earlier experiments that suggest that the size of dorsal eyespots plays a role in female choice and explains why male dorsal eyespots are very variable in size and often have indistinct rings of coloration, as the only feature under selection by females seems to be the central white pupil. We propose that sexual selection by female choice, rather than predator avoidance, may have been an important selective factor in the early stages of eyespot evolution in ancestral Lepidopteran lineages.

Animals↗

PubMed2006

Structural or pigmentary? Origin of the distinctive white stripe on the blue wing of a Morpho butterfly.

A few species of Morpho butterflies have a distinctive white stripe pattern on their structurally coloured blue wings. Since the colour pattern of a butterfly wing is formed as a mosaic of differently coloured scales, several questions naturally arise: are the microstructures the same between the blue and white scales? How is the distinctive whiteness produced, structurally or by means of pigmentation? To answer these questions, we have performed structural and optical investigations of the stripe pattern of a butterfly, Morpho cypris. It is found that besides the dorsal and ventral scale layers, the wing substrate also has the corresponding stripe pattern. Quantitative optical measurements and analysis using a simple model for the wing structure reveal the origin of the higher reflectance which makes the white stripe brighter.

Animals↗

PubMed2002

The historical biogeography of two Caribbean butterflies (Lepidoptera: Heliconiidae) as inferred from genetic variation at multiple loci.

Mitochondrial DNA and allozyme variation was examined in populations of two Neotropical butterflies, Heliconius charithonia and Dryas iulia. On the mainland, both species showed evidence of considerable gene flow over huge distances. The island populations, however, revealed significant genetic divergence across some, but not all, ocean passages. Despite the phylogenetic relatedness and broadly similar ecologies of these two butterflies, their intraspecific biogeography clearly differed. Phylogenetic analyses of mitochondrial DNA sequences revealed that populations of D. iulia north of St. Vincent are monophyletic and were probably derived from South America. By contrast, the Jamaican subspecies of H. charithonia rendered West Indian H. charithonia polyphyletic with respect to the mainland populations; thus, H. charithonia seems to have colonized the Greater Antilles on at least two separate occasions from Central America. Colonization velocity does not correlate with subsequent levels of gene flow in either species. Even where range expansion seems to have been instantaneous on a geological timescale, significant allele frequency differences at allozyme loci demonstrate that gene flow is severely curtailed across narrow ocean passages. Stochastic extinction, rapid (re)colonization, but low gene flow probably explain why, in the same species, some islands support genetically distinct and nonexpanding populations, while nearby a single lineage is distributed across several islands. Despite the differences, some common biogeographic patterns were evident between these butterflies and other West Indian taxa; such congruence suggests that intraspecific evolution in the West Indies has been somewhat constrained by earth history events, such as changes in sea level.

Animals↗

PubMed2002

The phylogeography of Amazonia revisited: new evidence from riodinid butterflies.

A fully resolved cladogram for 19 species in the Charis cleonus group of riodinid butterflies, which have closely parapatric ranges throughout the Amazon basin, is used to derive an area cladogram for the region. This represents the first comprehensive species-level analysis using insects and results in a hypothesis of Amazonian area relationships that is the most detailed to date. The Charis area cladogram is interpreted as supporting an historical vicariant split between the Guianas and the remainder of the Amazon and then between the upper and lower Amazon. The latter two clades can be further divided into the six most widely recognized areas of endemism and even smaller endemic centers within these, some of which, especially along the Madeira and lower Amazon Rivers, have never been previously hypothesized for butterflies. The overall pattern of historical interrelationships indicated is Guiana + ((Rondĵnia + (Pará + Belém)) + (Imeri + (Napo + Inambari))). The area relationships for riodinid butterflies show substantial congruence with those presented from the literature for amphibians, reptiles, birds, primates, rodents, and marsupials, suggesting a common vicariant history for these organisms. A summary area cladogram generated by combining area cladograms for all the aforementioned groups of organisms indicated the pattern of historical interrelationships to be (Guiana + (Rondĵnia + (Pará + Belém))) + (Imeri + (Napo + Inambari)). Charis cleonus group species distributions are noticeably larger around the upland periphery of Amazonia and smaller in the central and lower regions. A significant positive correlation between the proportion of range area above 100 m and total range size for each species is used to suggest that past sea-level rises may explain smaller range sizes in low-lying regions and that riverine barriers have been important in shaping the current distribution of C. cleonus group species.

Animals↗

PubMed2004

The cost of melanization: butterfly wing coloration under environmental stress.

Evolutionary studies typically focus on adaptations to particular environmental conditions, thereby often ignoring the role of possible constraints. Here we focus on the case of variation in dorsal wing melanization in a satyrine butterfly Pararge aegeria. Because melanin is a complex polymer, its synthesis may be constrained if ambient conditions limit the resource budget. This hypothesis was tested by comparing melanization among butterflies that fed as larvae on host grasses experiencing different drought-stress treatments. Treatment differences were validated both at the level of the host plant (nitrogen, carbonate, and water content) and of the butterfly (life-history traits: survival, development time, and size at maturity). Melanization rate was measured as average gray value of the basal dorsal wing area. This area, close to the thorax, is known to be functionally significant for basking in order to thermoregulate. Individuals reared on drought-stressed host plants developed paler wings, and development of darker individuals was slower and less stable as estimated by their level of fluctuating asymmetry. These results provide evidence that melanin is indeed costly to synthesize, and that differences in environmental quality can induce phenotypic variation in wing melanization. Therefore, studies dealing with spatial and/or temporal patterns of variation in wing melanization should not focus on adaptive explanations alone, but rather on a cost-benefit balance under particular sets of environmental conditions.

Animal Nutritional Physiological Phenomena↗

PubMed2006

Evolution of larval host plant associations and adaptive radiation in pierid butterflies.

Butterflies in the family Pieridae (Lepidoptera: Papilionoidea) feed as larvae on plants belonging primarily to three distantly related angiosperm orders: Fabales (legumes and allied plants), Brassicales (crucifers and related plants containing mustard oil glucosides), and Santalales ('mistletoes'). However, some utilize plants from 13 other families in a further eight orders. We investigated the evolutionary history of host plant use of the Pieridae in the context of a recent phylogenetic hypothesis of the family, using simple character optimization. Although there is a close association between host plant and butterfly higher classification, we find no evidence for cospeciation but a pattern of repeated colonization and specialization. The ancestral host of the family appears to be Fabaceae or Fabales, with multiple independent shifts to other orders, including three to Santalales. The shift to Brassicales, which contain secondary compounds (glucosinolates), promoted diversification and adaptive radiation within the subfamily Pierinae. Subsequent shifts from crucifers to mistletoes (aerial-stem hemiparasites) facilitated further diversification, and more recent shifts from mistletoes to mistletoe host trees led to exploitation of novel host plants outside the conventional three orders. Possible mechanisms underlying these host shifts are briefly discussed. In the Pierinae, a striking association between host plant, larval and adult behaviour, adult phenotype, and mimicry calls for further research into possible relationships between host specialization, plant chemistry and butterfly palatability.

Adaptation, Physiological↗

PubMed2004

Species-specific color-pattern modifications of butterfly wings.

We have previously shown that the systemic injection of sodium tungstate, a general protein-tyrosine phosphatase (PTPase) inhibitor, efficiently produces characteristic color-pattern modifications on the wings of the Painted Lady butterfly, Vanessa cardui. By using this method in the present study, we analyzed modification patterns of six species of Japanese butterflies. Whereas in Vanessa indica the black spots on the forewings reduced in size in response to the treatment, in Lycaena phlaeas the morphologically similar black spots enlarged in size. However, the metallic blue spots on the forewings of V. indica did enlarge in size, showing different behavior even within a single wing surface. The response patterns of Ypthima argus differed markedly from those of other species in that ectopic color-pattern elements were created. Colias erate showed minor modifications that coincidentally resembled the natural color-pattern of a closely related species, Colias palaeno. Through a comprehensive literature search, we confirmed the existence of naturally occurring aberrant color patterns with close similarities to the experimentally induced phenocopies in each of the modified species. Our results point out the possibility that a hypothetical transduction pathway with a PTPase for the scale-cell differentiation globally coordinates the wing-wide color-pattern development in butterflies.

Animals↗

PubMedDate not supplied

Evolutionary redeployment of a biosynthetic module: expression of eye pigment genes vermilion, cinnabar, and white in butterfly wing development.

Ommochromes are common among insects as visual pigments; however, in some insect lineages ommochromes have evolved novel functions such as integument coloration and tryptophan secretion. One role of ommochromes, as butterfly wing pigments, can apparently be traced to a single origin in the family Nymphalidae. The synthesis and storage of ommochrome pigments is a complex process that requires the concerted activity of multiple enzyme and transporter molecules. To help understand how this subcellular process appeared in a novel context during evolution, we explored aspects of ommochrome pigment development in the wings of the nymphalid butterfly Vanessa cardui. Using chromatography and radiolabeled precursor incorporation studies we identified the ommochrome xanthommatin as a V. cardui wing pigment. We cloned fragments of two ommochrome enzyme genes, vermilion and cinnabar, and an ommochrome precursor transporter gene, white, and found that these genes were transcribed in wing tissue at relatively high levels during wing scale development. Unexpectedly, however, the spatial patterns of transcription were not associated in a simple way with adult pigment patterns. Although our results suggest that the evolution of ommochrome synthesis in butterfly wings likely arose in part through novel regulation of vermilion, cinnabar, and white transcription, they also point to a complex relationship between transcriptional prepatterns and pigment synthesis in V. cardui.

Amino Acid Sequence↗