Altitude and life‐history shape the evolution of Heliconius wings

Phenotypic divergence between closely related species has long interested biologists. Taxa that inhabit a range of environments and have diverse natural histories can help understand how selection drives phenotypic divergence. In butterflies, wing color patterns have been extensively studied but diversity in wing shape and size is less well understood. Here, we assess the relative importance of phylogenetic relatedness, natural history, and habitat on shaping wing morphology in a large dataset of over 3500 individuals, representing 13 Heliconius species from across the Neotropics. We find that both larval and adult behavioral ecology correlate with patterns of wing sexual dimorphism and adult size. Species with solitary larvae have larger adult males, in contrast to gregarious Heliconius species, and indeed most Lepidoptera, where females are larger. Species in the pupal‐mating clade are smaller than those in the adult‐mating clade. Interestingly, we find that high‐altitude species tend to have rounder wings and, in one of the two major Heliconius clades, are also bigger than their lowland relatives. Furthermore, within two widespread species, we find that high‐altitude populations also have rounder wings. Thus, we reveal novel adaptive wing morphological divergence among Heliconius species beyond that imposed by natural selection on aposematic wing coloration.     

The wing morphology of limnephilid caddisflies in relation to their habitat preferences

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Although sexual size dimorphism (SSD) is common among mammals, there is no clear explanation for its maintenance in nature. Bats are one of the few groups of mammals where reverse SSD appears. In this group, the size of individuals may have very important ecological consequences related with flight. In this study, we examine sexual dimorphism in the wing measurements of 195 adult individuals (141 males and 54 females) of the greater mouse‐eared bat Myotis myotis in the south‐east of the Iberian Peninsula. We also investigated size differences between paired and single males in a swarming roost. The results indicate that there are significant differences in the wing measurements between sexes, females being bigger than males in this respect. While no significant differences in the wing measurements of paired and single males were observed, significant differences were found in their relative weight and fitness, single males being significantly heavier and having a better physical condition. We discuss the implications of SSD for the female of M. myotis in terms of reproductive advantages, trophic niche segregation and a greater ability to move, which may favour gene flow between populations.     

Cranial ontogeny and sexual dimorphism in two new world monkeys: Alouatta caraya (Atelidae) and Cebus apella (Cebidae)

Pattern of skull development and sexual dimorphism was studied in Cebus apella and Alouatta caraya using univariate, bivariate, and multivariate statistics. In both species, sexual dimorphism develops because the common growth trajectory in males extends and because of differences in growth rates between sexes. The expectation that the ontogenetic bases of adult dimorphism vary interspecifically is well substantiated by this study. A. caraya exhibits transitional dimorphism in its subadult stage, although the condylobasal length, zygomatic breadth, and rostrum length are strongly dimorphic in the final adult stage, being greater in males. Most cranial measurements in C. apella exhibit significant dimorphism in the adult stage, being strongly influenced by a faster rate of growth in males. Sexual dimorphism is also evidenced through sex differences in growth rates in several cranial measurements. These results also indicate that different ontogenetic mechanisms are acting in C. apella and A. caraya and reveal differences in the way through which neotropical primates attain adult sexual dimorphism. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

Variation in wing dimorphism of oriental mole cricket Gryllotalpa orientalis: Comparative study in Okinawa and Hyogo populations

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3. We advocate that both landscape metrics (i.e., habitat amount and patch area) should be considered in studies evaluating landscapes' impacts on insect mobility. We discuss results in terms of the species' sexual differences in flight behaviour and the relative importance of both landscape metrics.

     

Sexual dimorphism in weight among the primates: The relative impact of allometry and sexual selection

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Morpho morphometrics: Shared ancestry and selection drive the evolution of wing size and shape in Morpho butterflies

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Morphological and histological examination of short‐wing formation in the winter moth Protalcis concinnata (Insecta: Lepidoptera,Geometridae)

Winter geometrid moths exhibit sexual dimorphism in wing length and female‐specific flightlessness. Female‐specific flightlessness in insects is an interesting phenomenon in terms of sexual dimorphism and reproductive biology. In the winter geometrid moth, Protalcis concinnata (Wileman), adult females have short wings and adult males have fully developed wings. Although the developmental process for wing reduction in Lepidoptera is well studied, little is known about the morphology and the developmental pattern of short‐winged flightless morphs in Lepidoptera. To clarify the precise mechanisms and developmental processes that produce short‐winged morphs, we performed morphological and histological investigations of adult and pupal wing development in the winter geometrid moth P. concinnata. Our findings showed that (a) wing development in both sexes is similar until larval‐pupal metamorphosis, (b) the shape of the sexually dimorphic wings is determined by the position of the bordering lacuna (BL), (c) the BL is positioned farther inward in females than in males, and (d) after the short pupal diapause period, the female pupal wing epithelium degenerates to approximately two‐thirds its original size due to cell death. We propose that this developmental pattern is a previously unrecognized process among flightless Lepidoptera.     

Relative contribution of genetic and environmental factors to determination of wing morphs of the brown planthopper Nilaparvata lugens

Wing dimorphism is a fascinating feature of the ability of insects to adapt to environments. The brown planthopper (BPH) Nilaparvata lugens, a serious pest of rice, can switch between the long- and short-winged morphs. It has been known that environmental factors can affect the wing morph of BPH. However, it is still unclear whether the effect of environment is dependent on BPH genetic backgrounds or not. In the present study, we established the pure-bred lineages of short- and long-winged BPHs via multigenerational selection, and we found that survival and fecundity were similar between these 2 lineages. Wing morphs of the pure-bred lineages were almost fully dependent on genetics, but independent of the environmental factors, nymphal density and rice plant stage, 2 key factors affecting BPH wing morphs. In the unselected BPH population, short- and long-winged morphs were produced depending on those 2 environmental factors, indicating the contribution of environment to wing morph. In the wing-selected lineages, 4 developmental regulated genes of wing, NlInR1, NlInR2, NlAkt, and NlFoxo were expressed stably in the short-winged adults, but almost silenced in the long-winged adults. However, all these genes were expressed normally with a similar level in both the short- and long-winged adults in an unselected population except NlFoxo. The pure-bred lineages of long- and short-winged morphs exhibited different expression patterns of wing development-regulated genes, suggesting the genetic determination of wing morphs. Effects of environmental factors on wing morphs occurred only in the genetic mix population.     

SEX CHROMOSOME LINKED GENETIC VARIANCE AND THE EVOLUTION OF SEXUAL DIMORPHISM OF QUANTITATIVE TRAITS

Theory predicts that sex chromsome linkage should reduce intersexual genetic correlations thereby allowing the evolution of sexual dimorphism. Empirical evidence for sex linkage has come largely from crosses and few studies have examined how sexual dimorphism and sex linkage are related within outbred populations. Here, we use data on an array of different traits measured on over 10,000 individuals from two pedigreed populations of birds (collared flycatcher and zebra finch) to estimate the amount of sex‐linked genetic variance (h²_z). Of 17 traits examined, eight showed a nonzero h²_Z estimate but only four were significantly different from zero (wing patch size and tarsus length in collared flycatchers, wing length and beak color in zebra finches). We further tested how sexual dimorphism and the mode of selection operating on the trait relate to the proportion of sex‐linked genetic variance. Sexually selected traits did not show higher h²_Z than morphological traits and there was only a weak positive relationship between h²_Z and sexual dimorphism. However, given the relative scarcity of empirical studies, it is premature to make conclusions about the role of sex chromosome linkage in the evolution of sexual dimorphism.     

Sexual dichromatism,size dimorphism,and microscale anatomy of white wing stripe in blue tits

Achromatic patches are a common element of plumage patterns in many bird species and there is growing body of evidence that in many avian taxa they can play a signaling role in mate choice. Although the blue tit Cyanistes caeruleus is a well-established model species in the studies on coloration, its white wing patch has never been examined in the context of sex-specific trait expression. In this exploratory study, we examined sexual size dimorphism and dichromatism of greater covert’s dots creating white wing patch and analyzed its correlations with current body condition and crown coloration—a trait with established role in sexual selection. Further, we qualitatively analyzed microstructural barb morphology underlying covert’s coloration. We found significant sexual dimorphism in the dot size independent of covert size and sexual dichromatism in both white dot and blue outer covert’s vane spectral characteristics. Internal structure of covert barbs within the white dot was similar to the one found in barbs from the blue part that is, with a medullary area consisting of dead keratinocytes containing channel-type ß-keratin spongy nanostructure and centrally located air cavities. However, it lacked melanosomes which was the main observed difference. Importantly, UV chroma of covert’s blue vane was positively correlated with crown UV chroma and current condition (the latter only in males), which should be a premise for further research on the signal function of the wing stripe.     

The evolutionary significance of wing dimorphism in carabid beetles (Coleoptera: Carabidae)

A review of data on the background of wing dimorphism in carabid beetles (Coleoptera: Carabidae) and especially of the closely relatedCalathus cinctus andC. melanocephalus is given. In bothCalathus species wing dimorphism is inherited in a simple Mendelian fashion with the brachypterous condition dominant, but inC. melanocephalus the expression of the long winged genotype is under environmental control as well. The development of long winged phenotypes in the latter species is favoured by relatively favourable environmental conditions, such as high temperatures and a high food-supply. The higher fecundity of the larger and heavier long winged females of both species may compensate for losses of long winged phenotypes by flight activities. The evolutionary significance of both types of inheritance is discussed in relation to dispersal. The ‘fixed type’ as found inC. cinctus is considered an opportunistic short term ‘between sites strategy’, whereas the ‘dynamic type’ ofC. melanocephalus represents a flexible long term ‘within sites strategy’.