Spatial patterns of correlated scale size and scale color in relation to color pattern elements in butterfly wings

Complex butterfly wing color patterns are coordinated throughout a wing by unknown mechanisms that provide undifferentiated immature scale cells with positional information for scale color. Because there is a reasonable level of correspondence between the color pattern element and scale size at least in Junonia orithya and Junonia oenone, a single morphogenic signal may contain positional information for both color and size. However, this color–size relationship has not been demonstrated in other species of the family Nymphalidae. Here, we investigated the distribution patterns of scale size in relation to color pattern elements on the hindwings of the peacock pansy butterfly Junonia almana, together with other nymphalid butterflies, Vanessa indica and Danaus chrysippus. In these species, we observed a general decrease in scale size from the basal to the distal areas, although the size gradient was small in D. chrysippus. Scales of dark color in color pattern elements, including eyespot black rings, parafocal elements, and submarginal bands, were larger than those of their surroundings. Within an eyespot, the largest scales were found at the focal white area, although there were exceptional cases. Similarly, ectopic eyespots that were induced by physical damage on the J. almana background area had larger scales than in the surrounding area. These results are consistent with the previous finding that scale color and size coordinate to form color pattern elements. We propose a ploidy hypothesis to explain the color–size relationship in which the putative morphogenic signal induces the polyploidization (genome amplification) of immature scale cells and that the degrees of ploidy (gene dosage) determine scale color and scale size simultaneously in butterfly wings.     

Physiologically induced color-pattern changes in butterfly wings: mechanistic and evolutionary implications

A mechanistic understanding of the butterfly wing color-pattern determination can be facilitated by experimental pattern changes. Here I review physiologically induced color-pattern changes in nymphalid butterflies and their mechanistic and evolutionary implications. A type of color-pattern change can be elicited by elemental changes in size and position throughout the wing, as suggested by the nymphalid groundplan. These changes of pattern elements are bi-directional and bi-sided dislocation toward or away from eyespot foci and in both proximal and distal sides of the foci. The peripheral elements are dislocated even in the eyespot-less compartments. Anterior spots are more severely modified, suggesting the existence of an anterior-posterior gradient. In one species, eyespots are transformed into white spots with remnant-like orange scales, and such patterns emerge even at the eyespot-less "imaginary" foci. A series of these color-pattern modifications probably reveal "snap-shots" of a dynamic morphogenic signal due to heterochronic uncoupling between the signaling and reception steps. The conventional gradient model can be revised to account for these observed color-pattern changes.     

Heat-shock-induced color-pattern changes of the blue pansy butterfly Junonia orithya: Physiological and evolutionary implications

Temperature shock to early pupae causes wing color-pattern changes in butterflies. These plastic changes are ascribed to the hemolymph level of the cold-shock hormone (CSH) in pupae as well as to other mechanisms. Here, we characterized heat-shock-induced color-pattern changes using the blue pansy butterfly Junonia orithya (Lepidoptera: Nymphalidae). In response to the 38-42 °C heat-shock treatments, parafocal elements (PFEs) were thinned and dislocated away from eyespots; this was the reverse of the direction of the cold-shock-induced changes. Somewhat surprisingly, in response to the lethal 44 °C heat shock, PFEs were modified as in the case of a cold-shock. These modifications were not affected by the removal of the head-prothorax portion of pupae. While the hemolymph-mediated transfer of the possible PFE-modification property induced by the 42 °C treatment was unsuccessful in the parabiosis experiment, the transfer of the factor induced by the 44 °C treatment was successful. In contrast, reduction of the blue background area was obtained not only by the 42 and 44 °C treatments but also by the injection of thapsigargin, a plant-derived stress inducer, in males. The result of this treatment was similar to the natural color patterns of other closely related Junonia species. We also observed an increase in orange coloration by the 42 °C treatment in females, and this change was similar to ecdysteroid-induced modifications. Taken together, the heat-shock-induced PFE modifications in J. orithya can be explained by the levels of CSH, and other modifications are likely to be caused by general stress responses and ecdysteroid effects. We conclude that phenotypic plasticity of the wing color patterns to heat shock results from a combined effect of at least a few different mechanisms. These mechanisms might have been exploited in the color-pattern evolution of some Junonia species.     

The origins of allometry: size and shape polymorphism in the common waterstrider, Gerris remigis Say (Heteroptera, Gerridae)

Changes in size, whether ontogenetic or phylogenetic, tend to be associated with changes in shape. This allometry can arise through two different evolutionary mechanisms: (1) selection acting primarily on overall size may be associated with changes in shape because of physiological and mechanical constraints or differential responses of different body components; or (2) selection acting primarily on shape (on the size of specific body components) may be associated with changes in overall size because of genetic correlations, and thus correlated responses, of other body components. To assess the relative importance of these two mechanisms, shape polymorphism is examined along two axes of size dimorphism (sex and wing morphology) in the common waterstrider, Gerris remigis Say. Eight measurements were made of body and appendage components of 234 adults, from three independent populations. Univariate and multivariate analyses reveal that both sexes and wing morphs differ significantly in size and shape. Shape differentiation along the two axes of size dimorphism is found to be dissimilar, partially independent of size, and strongly correlated with the ecological specialization of the various morphs. These observations suggest that selection is acting directly on shape, and thus that allometry in this species primarily reflects shape-mediated changes in size (mechanism 2), rather than size-mediated changes in shape. The role of developmental processes in facilitating this shape differentiation is discussed.     

The relationship between eyespot shape and wing shape in the butterfly Bicyclus anynana: A genetic and morphometrical approach

The African butterfly, Bicyclus anynana, normally possesses circular eyespots on its wings. Artificial selection lines, which express ellipsoidal eyespots on the dorsal surface of the forewing, were used to investigate correlated changes in wing shape. Morphometric analysis of linear wing measurements and wing scale counts provided evidence that eyespot shape was correlated with localised shape changes in the corresponding wing-cell, with overall shape changes in the wing, and with the density/arrangement of scales around the eyespot area.     

Thermal evolution of pre-adult life history traits, geometric size and shape, and developmental stability in Drosophila subobscura

Replicated lines of Drosophila subobscura originating from a large outbred stock collected at the estimated Chilean epicentre (Puerto Montt) of the original New World invasion were allowed to evolve under controlled conditions of larval crowding for 3.5 years at three temperature levels (13, 18 and 22 degrees C). Several pre-adult life history traits (development time, survival and competitive ability), adult life history related traits (wing size, wing shape and wing-aspect ratio), and wing size and shape asymmetries were measured at the three temperatures. Cold-adapted (13 degrees C) populations evolved longer development times and showed lower survival at the highest developmental temperature. No divergence for wing size was detected following adaptation to temperature extremes (13 and 22 degrees C), in agreement with earlier observations, but wing shape changes were obvious as a result of both thermal adaptation and development at different temperatures. However, the evolutionary trends observed for the wing-aspect ratio were inconsistent with an adaptive hypothesis. There was some indication that wing shape asymmetry has evolutionarily increased in warm-adapted populations, which suggests that there is additive genetic variation for fluctuating asymmetry and that it can evolve under rapid environmental changes caused by thermal stress. Overall, our results cast strong doubts on the hypothesis that body size itself is the target of selection, and suggest that pre-adult life history traits are more closely related to thermal adaptation.     

Morphometrics of the callitrichid forelimb: A case study in size and shape

Mosimann and colleagues formulated a technique that distinguishes between size and shape, based on the concept of geometric similarity and the distinction between log size-and-shape and log shape variables. We extend these formulations in an examination of the forelimb of three callitrichid species (adultSaguinus oedipus, Saguinus fuscicollis, andCallithrix jacchus). We employ principal components analysis to explore the relationship between variance explained by size-and-shape versus shape alone. Independence of shape vectors is examined via correlation analysis. Then we use log shape data to construct intersample (species means) and total sample (between all paris of individuals) matrices of average taxonomic distances. These distance matrices are subjected to cluster analysis and principal coordinate ordinations. Results of principal components analysis suggest that after isometric size is removed, there remains sufficient shape information to discriminate among the three taxa. Careful examination and quantification of the relationships between shape and size suggest that size information (e.g., geometric mean) is fundamental for understanding shape differences within and among callitrichid species; in other words, most aspects of forelimb shape are significantly correlated with size. Contrary to conventional wisdom, we also demonstrate that such correlations are not spurious. Ordinations and clustering of log shape distance matrices (based on means and individuals) support the notion that, despite differences in size, the two tamarins are more similar in shape than either is toC. jacchus (despite size similarity betweenS. fuscicollis andC. jacchus). Although shape variation in the forelimb of calliirichids may have a functional component, the phylogenetic signal remains strong and serves to group individuals accordingly.     

Evolutionary directional asymmetry and shape variation in Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae): an example using hind wings

The western corn rootworm Diabrotica virgifera virgifera LeConte is a pest of maize in the USA and Europe and especially a problem in particular regions of Croatia. In the present study, patterns of variation in hind wing shape were examined. The first objective was to examine the influence of soil type on 10 populations of D. v. virgifera sampled from three regions in Croatia that differed according to edaphic factors and climate. The second objective was to investigate the potential evolutionary presence of directional asymmetry on hind wings. Geometric morphometrics was used to examine these objectives by quantifying the morphological variation within and among individuals and populations. Overall, D. v. virgifera hind wing shape changed according to major soil type classifications in Croatia. The three hind wing morphotypes found varied because of basal radial vein differences, related to landmarks 1, 3, 7, and 14. The findings of the present study show that hind wing shape in D. v. virgifera can be used to differentiate populations based on edaphic factors and may have application as a monitoring tool in the integrated management of D. v. virgifera. In an evolutionary context, the presence of directional asymmetry in the hind wings of D. v. virgifera adds to the ever growing data on the evolution of insect wings. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 110–118.     

Global evaluation of growth in a rural population: comparative analysis of shape and size

In this work the analogies and differences in shape and size between a rural school population (6–14 aged) of the Lozoya-Somosierra region (Madrid) and several recent and past Spanish populations from different environments have been studied. The results show the growth trend as well as the influences of ecological and socioeconomical factors. Paper presented at the 4^th congress of the European Anthropology Association (Florence, Sept. 1984).     

Reaction norms and the genetic basis of phenotypic plasticity in the wing pattern of the butterfly Bicyclus anynana

The genetic basis of the dry-wet season polyphenism of wing pattern in response to temperature shown by Bicyclus anynana was studied, using a split-family design over four temperatures. Reaction norms crossed, but were only linear in the three highest temperatures, and only when larval development time was used as the environmental axis. Significant full-sib additive variances (V_A) and heritabilities (h²) for plasticity were found using slopes of reaction norms in a bootstrap procedure. Heritabilities were lower in intermediate temperatures, mainly due to differences in the residual variances (V_R). There was no clear trend in V_A across temperatures, contrary to the expectation that V_A would have been depleted by natural selection at the extreme temperatures and not depleted at the intermediate temperatures which occur less frequently in the field. Unpredictability in the onset of the following season at intermediate temperatures might lead to selection for diverse flresponses resulting in relatively high V_Rs. Theoretical models linking reaction norms to genetic parameters in separate environments were difficult to apply in this study, particularly because they are based on the assumption that V_Rs are constant. However the reaction norm approach combined with quantitative genetics provided a valuable insight into the evolution of the observed polyphenism.     

Determination of molecular size and shape of hyperbranched polysaccharide in solution

The chemical structure of a water-soluble polysaccharide, coded as TM3b, extracted from sclerotia of Pleurotus tuber-rigium was analyzed to be a hyperbranched beta-D-glucan with beta-(1-->6), beta-(1-->4), and beta-(1-->3)-linked residues, with degree of branching (DB) of 57.6%. The results from size-exclusion chromatography combined with laser light scattering (SEC-LLS) revealed that the hyperbranched polysaccharide easily aggregated in 0.15 M aqueous NaCl, whereas it dispersed as individual chains in DMSO. The weight-average molecular weight (M(w)), radius of gyration, intrinsic viscosity, and chain density of TM3b in DMSO and in 0.15 M aqueous NaCl were measured with SEC-LLS, LLS, and viscometry. The results indicated that single chains and aggregates with aggregation number of 12 coexisted in the aqueous solution, whereas individual molecules of TM3b occurred in DMSO. In view of the molecular parameters, the aggregates in aqueous solution exhibited more compact chain structure than the individual molecules in DMSO. Furthermore, transmission electron microscopy and atomic force microscopy showed that all of the aggregates and individual molecules exhibited spherical particles in the solutions. This work provided the valuable information of chain conformation and molecular morphology of the hyperbranched polysaccharide in different solvents.     

Frugivore gape size and the evolution of fruit size and shape in southern hemisphere floras

Abstract The present study uses differences among frugivore faunas of the southern hemisphere landmasses to test whether frugivore characteristics have influenced the evolution of fruit traits. Strong floristic similarities exist among southern landmasses; for example, 75% of New Zealand vascular plant genera also have species in Australia. However, plants in Australia and South America have evolved in the presence of a range of mammalian frugivores, whereas those in New Zealand, New Caledonia and the Pacific Islands have not. In addition, the avian frugivores in New Zealand and New Caledonia are generally smaller than those of Australia. If frugivore characteristics have influenced the evolution of fruit traits, predictable differences should exist between southern hemisphere fruits, particularly fruit size and shape. Fruit dimensions were measured for 77 New Zealand species and 31 Australian species in trans‐Tasman genera. New Zealand fruits became significantly more ellipsoid in shape with increasing size. This is consistent with frugivore gape size imposing a selective pressure on fruit ingestability. This result is not a product of phylogenetic correlates, as fruit length and width scaled isometrically for Australian species in genera shared with New Zealand. Within‐genus contrasts between New Zealand and Australian species in 20 trans‐Tasman genera showed that New Zealand species have significantly smaller fruits than their Australian counterparts. Within‐genus contrasts between New Zealand and South American species in nine genera gave the same result; New Zealand species had significantly smaller fruits than their South American counterparts. No difference was found in fruit size or shape between New Zealand and New Caledonia congeneric species from 12 genera. These results are consistent with the broad characteristics of the frugivore assemblage influencing the evolution of fruit size and shape in related species. The smaller‐sized New Zealand frugivore assemblage has apparently influenced the evolution of fruit size of colonizing taxa sometimes within a relatively short evolutionary timeframe.     

Myxosporida (Protozoa): The determination and maintenance of spore size and shape

Data are presented which suggest that the size of fish myxosporidan spores is primarily determined by the parasite's development in the tissues or organ's cavities and the spore's shape is determined by the presence of physiologically and behaviorally suitable fish.     

Plastic responses of some life history traits and cellular components of body size in Aphidius ervi as related to the age of its host Acyrthosiphon pisum

Phenotypic plasticity of wing size and shape has been evaluated in Aphidius ervi developing in its host, Acyrthosiphon pisum, parasitized at seven different ages. The parasitoid wing size was used as an estimator of both whole body size and its cellular composition. No size difference was observed in A. ervi adults emerged from aphids 1, 2 or 3 days old at parasitization. Body size then increased in A. ervi emerged from hosts older at parasitization. Body size values as related to host age at parasitization were achieved by adjusting developmental time, developmental rate or both. Parasitoids of similar size, but developed in hosts parasitized at different ages, had different wing cellular composition, while the increase of parasitoid body size was related to a general increase in both cell area and cell number. These results seem to suggest a trade‐off between adult size and developmental time, at least for parasitoids developed at the two extremes of host ages at parasitization, and that A. ervi can reach the same adult size via different trajectories, adapting its ontogenetic processes. Wing shape was typical for all the different parasitoid classes considered and differed strongly between males and females, independent of their size. Parasitoid males (haploids) and females (diploids) did not differ in either cell area or cell number, suggesting a possible sex‐determined dosage compensation in somatic tissue endoreplication. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 439–454.     

Swift laboratory thermal evolution of wing shape (but not size) in Drosophila subobscura and its relationship with chromosomal inversion polymorphism

Latitudinal clinal variation in wing size and shape has evolved in North American populations of Drosophila subobscura within about 20 years since colonization. While the size cline is consistent to that found in original European populations (and globally in other Drosophila species), different parts of the wing have evolved on the two continents. This clearly suggests that 'chance and necessity' are simultaneously playing their roles in the process of adaptation. We report here rapid and consistent thermal evolution of wing shape (but not size) that apparently is at odds with that suggestion. Three replicated populations of D. subobscura derived from an outbred stock at Puerto Montt (Chile) were kept at each of three temperatures (13, 18 and 22 degrees C) for 1 year and have diverged for 27 generations at most. We used the methods of geometric morphometrics to study wing shape variation in both females and males from the thermal stocks, and rates of genetic divergence for wing shape were found to be as fast or even faster than those previously estimated for wing size on a continental scale. These shape changes did not follow a neat linear trend with temperature, and are associated with localized shifts of particular landmarks with some differences between sexes. Wing shape variables were found to differ in response to male genetic constitution for polymorphic chromosomal inversions, which strongly suggests that changes in gene arrangement frequencies as a response to temperature underlie the correlated changes in wing shape because of gene-inversion linkage disequilibria. In fact, we also suggest that the shape cline in North America likely predated the size cline and is consistent with the quite different evolutionary rates between inversion and size clines. These findings cast strong doubts on the supposed 'unpredictability' of the geographical cline for wing traits in D. subobscura North American colonizing populations.     

Indices of Anseriform body shape based on the relative size of major skeletal elements and their relationship to reproductive effort

To assess whether relative clutch mass (RCM) in Anseriformes (wildfowl or waterfowl) is constrained by body shape, principal components (PCs) of size‐adjusted measurements of five major skeletal elements of adult males and females of 60 species of Anseriformes provided indices of body shape. PC1 accounted for 69.8% of the variance and contrasted anterior elements (cranium and sternum) to posterior elements (synsacrum, femur and tibiotarsus). PC1 scores were high in species with a ‘duck‐like’ body shape and low in those with a ‘goose‐like’ body shape. Over the phylogeny of Anseriformes, decreased PC1 scores were associated with feeding on land. PC2 accounted for 18.6% of the variance and contrasted core elements (sternum and synsacrum) with peripheral elements (cranium, femur and tibiotarsus). High PC2 scores were associated with dependence on animal food, particularly in diving species. PC3 accounted for 7.7% of the variance and reflected mainly the relative size of the femur, which was low in diving species. Controlling statistically for phylogenetically independent contrasts in female body shape, there was a significant positive partial correlation between RCM and PC1, suggesting that independent of body size, body shape imposes constraints on reproductive effort in Anseriformes. The results suggest that models of the evolution of reproductive effort in this order, and perhaps in other orders, of birds should control for the effects of body shape.     

Pelvic growth: ontogeny of size and shape sexual dimorphism in rat pelves

The mammalian pelvis is sexually dimorphic with respect to both size and shape. Yet little is known about the differences in postnatal growth and bone remodeling that generate adult sexual dimorphism in pelvic bones. We used Sprague-Dawley laboratory rats (Rattus norvegicus), a species that exhibits gross pelvic size and shape dimorphism, as a model to quantify pelvic morphology throughout ontogeny. We employed landmark-based geometric morphometrics methodology on digitized landmarks from radiographs to test for sexual dimorphism in size and shape, and to examine differences in the rates, magnitudes, and directional patterns of shape change during growth. On the basis of statistical significance testing, the sexes became different with respect to pelvic shape by 36 days of age, earlier than the onset of size dimorphism (45 days), although visible shape differences were observed as early as at 22 days. Males achieved larger pelvic sizes by growing faster throughout ontogeny. However, the rates of shape change in the pelvis were greater in females for nearly all time intervals scrutinized. We found that trajectories of shape change were parallel in the two sexes until age of 45 days, suggesting that both sexes underwent similar bone remodeling until puberty. After 45 days, but before reproductive maturity, shape change trajectories diverged because of specific changes in the female pelvic shape, possibly due to the influence of estrogens. Pattern of male pelvic bone remodeling remained the same throughout ontogeny, suggesting that androgen effects on male pelvic morphology were constant and did not contribute to specific shape changes at puberty. These results could be used to direct additional research on the mechanisms that generate skeletal dimorphisms at different levels of biological organization.     

Heightened condition dependent expression of structural coloration in the faces,but not wings,of male and female flies

Structurally colored sexual signals are a conspicuous and widespread class of ornament used in mate choice, though the extent to which they encode information on the quality of their bearers is not fully resolved. Theory predicts that signaling traits under strong sexual selection as honest indicators should evolve to be more developmentally integrated and exaggerated than nonsexual traits, thereby leading to heightened condition dependence. Here, we test this prediction through examination of the sexually dimorphic faces and wings of the cursorial fly Lispe cana. Males and females possess structural UV-white and golden faces, respectively, and males present their faces and wings to females during close-range, ground-based courtship displays, thereby creating the opportunity for mutual inspection. Across a field-collected sample of individuals, we found that the appearance of the faces of both sexes scaled positively with individual condition, though along separate axes. Males in better condition expressed brighter faces as modeled according to conspecific flies, whereas condition scaled with facial saturation in females. We found no such relationships for their wing interference pattern nor abdomens, with the latter included as a nonsexual control. Our results suggest that the structurally colored faces, but not the iridescent wings, of male and female L. cana are reliable guides to individual quality and support the broader potential for structural colors as honest signals. They also highlight the potential for mutual mate choice in this system, while arguing for 1 of several alternate signaling roles for wing interferences patterns among the myriad taxa which bear them.