A comparative study of body size evolution in moths: evidence of correlated evolution with feeding and phenology-related traits.

Interspecific variation in body size is one of the most popular topics in comparative studies. Despite recent advances, little is known about the patterns and processes behind the evolution of body size in insects. Here, we used a robust data set comprising all geometrid moth species occurring in Northern Europe to examine the evolutionary associations involving body size and several life-history traits under an explicitly phylogenetic framework. We provided new insights into the interactive effects of life-history traits on body size and evidence of correlated evolution. We further established the sequence of trait evolution linking body size with the life-history traits correlated with it. We found that most (but not all) of the studied life-history traits, to some extent, influenced interspecific variation in body size, but interactive effects were uncommon. Both bi- and multivariate phylogenetic analyses indicated that larger species tend to be nocturnal flyers, overwinter in the larval stage, feed on the foliage of trees rather than herbs, and have a generalist feeding behaviour. We found evidence of correlated evolution involving body size with overwintering stage, host-plant growth form, and dietary specialization. The examination of evolutionary transitions within the correlated evolution models signalled that overwintering as larvae commonly preceded the evolution of large sizes, as did feeding on tree foliage and the generalist feeding behaviour. By showing that both body size and all life-history traits correlated with it evolve at very slow rates, we caution against uncritical attempts to propose causal explanations for respective associations based on contemporary ecological settings.

Evolution of wing shape in geometrid moths: phylogenetic effects dominate over ecology.

Locomotory performance is an important determinant of fitness in most animals, including flying insects. Strong selective pressures on wing morphology are therefore expected. Previous studies on wing shape in Lepidoptera have found some support for hypotheses relating wing shape to environment-specific selective pressures on aerodynamic performance. Here, we present a phylogenetic comparative study on wing shape in the lepidopteran family Geometridae, covering 374 species of the northern European fauna. We focused on 11 wing traits including aspect ratio, wing roundness, and the pointedness of the apex, as well as the ratio of forewing and hindwing areas. All measures were taken from images available on the internet, using a combination of tools available in Fiji software and R. We found that wing shape demonstrates a phylogenetically conservative pattern of evolution in Geometridae, showing similar or stronger phylogenetic signal than many of its potential predictors. Several wing traits showed statistically significant associations with predictors such as body size, phenology, and preference for forest habitats. Overall, however, all of these associations remained notably weak, with no wing shape being excluded for any value of the predictors, including body size. We conclude that, in geometrids, wing traits do not readily respond to selective pressures optimizing aerodynamic performance of the moths in different environments. Selection on wing shape may nevertheless operate through other functions of the wings, with the effectiveness of crypsis at rest being a promising candidate for further studies.

Limited sex differences in plastic responses suggest evolutionary conservatism of thermal reaction norms: A meta-analysis in insects.

Temperature has a profound effect on the growth and development of ectothermic animals. However, the extent to which ecologically driven selection pressures can adjust thermal plastic responses in growth schedules is not well understood. Comparing temperature-induced plastic responses between sexes provides a promising but underexploited approach to evaluating the evolvability of thermal reaction norms: males and females share largely the same genes and immature environments but typically experience different ecological selection pressures. We proceed from the idea that substantial sex differences in plastic responses could be interpreted as resulting from sex-specific life-history optimization, whereas similarity among the sexes should rather be seen as evidence of an essential role of physiological constraints. In this study, we performed a meta-analysis of sex-specific thermal responses in insect development times, using data on 161 species with comprehensive phylogenetic and ecological coverage. As a reference for judging the magnitude of sex specificity in thermal plasticity, we compared the magnitude of sex differences in plastic responses to temperature with those in response to diet. We show that sex-specific responses of development times to temperature variation are broadly similar. We also found no strong evidence for sex specificity in thermal responses to depend on the magnitude or direction of sex differences in development time. Sex differences in temperature-induced plastic responses were systematically less pronounced than sex differences in responses induced by variations in larval diet. Our results point to the existence of substantial constraints on the evolvability of thermal reaction norms in insects as the most likely explanation. If confirmed, the low evolvability of thermal response is an essential aspect to consider in predicting evolutionary responses to climate warming.

Weather Sensitivity of Sugar Bait Trapping of Nocturnal Moths: A Case Study from Northern Europe.

Assemblages of insects need to be quantitatively sampled in the context of various research questions. Light trapping is the most widely used method for sampling nocturnal Lepidoptera. Attracting moths to sugar baits offers a viable alternative. However, this method is rarely used in professional research despite its popularity among amateur lepidopterists. As the activity of insects is strongly dependent on ambient conditions, the sensitivity of any trapping method to weather parameters needs to be known for the quantitative interpretation of trapping results. In the present paper, we report data on the weather dependence of moth catches obtained by automatic bait traps. The study was performed in Estonia, representing the European hemiboreal forest zone. Portable weather stations set up next to each of the traps were used for collecting weather data. Both abundance and diversity of the moths in the catches depended strongly positively on temperature and negatively on air humidity. Diversity was also negatively correlated with air pressure and positively with the change in pressure during the night. The results show that in situ recording of weather parameters in connection to insect trapping provides useful insights for the study of insect behaviour and the interpretation of the results of monitoring projects.

Entomopathogenic Fungi Infecting Lepidopteran Larvae: A Case from Central Argentina.

Immature stages of insects are vulnerable to various antagonists, including pathogens. While the abiotic factors affecting pathogen prevalence in insect populations are reasonably well documented, much less is known about relevant ecological interactions. We studied the probability of the larvae of three lepidopteran species to die from fungal infection as a function of insect species and food plants in central Argentina. Local free-growing food plants were used to feed the lepidopteran larvae. The prevalence of entomopathogenic fungi remained low (about 5%), which is a value well consistent with observations on similar systems in other regions. Eight fungal species recorded, primarily belonging to Fusarium and Aspergillus, add evidence to the reconsideration of the nutritional modes in these genera in distinguishing the role of some species (complexes) to cause insect infections. Food plant species were found to have a substantial effect on the prevalence of entomopathogenic fungi. This was especially clear for the most abundant fungal species, a representative of the Fusarium fujikuroi complex. Feeding on a particular plant taxon can thus have a specific fitness cost. Compared to the data collected from Northern Europe, the Argentinian assemblages from the families Aspergillaceae and Nectriaceae overlapped at the genus level but did not share species. It remains to be confirmed if this level of divergence in the composition of assemblages of entomopathogenic fungi among distant regions represents a global pattern.

In search of ecological determinants of fungal infections: A semi-field experiment with folivorous moths.

Natural enemies shape the fate of species at both ecological and evolutionary time scales. While the effects of predators, parasitoids, and viruses on insects are well documented, much less is known about the ecological and evolutionary role of entomopathogenic fungi. In particular, it is unclear to which extent may the spatiotemporal distribution patterns of these pathogens create selective pressures on ecological traits of herbivorous insects. In the present study, we reared three lepidopteran species in semi-natural conditions in a European hemiboreal forest habitat. We studied the probability of the insects to die from fungal infection as a function of insect species, food plant, study site, (manipulated) condition of the larvae, and the phenological phase. The prevalence of entomopathogenic fungi remained low to moderate with the value consistently below 10% across the subsets of the data while as many as 23 fungal species, primarily belonging to the families Cordycipitaceae, Aspergillaceae, and Nectriaceae, were recorded. There were no major differences among the insect species in prevalence of the infections or in the structure of associated fungal assemblages. The family Cordycipitaceae, comprising mainly obligatory entomopathogens, dominated among the pathogens of pupae but not among the pathogens of larvae. Overall, there was evidence for a relatively weak impact of the studied ecological factors on the probability to be infected by a fungal pathogen; there were no effects of food plant, study site, or phenology which would be consistent over the study species and developmental stages of the insects. Nevertheless, when the prevalence of particular fungal taxa was studied, Akanthomyces muscarius was found infecting insects fed with leaves of only one of the food plant, Betula spp. Feeding on a particular plant taxon can thus have specific fitness costs. This demonstrates that fungus-mediated effects on insect life history traits are possible and deserve attention.

A supertree of Northern European macromoths.

Ecological and life-history data on the Northern European macromoth (Lepidoptera: Macroheterocera) fauna is widely available and ideal for use in answering phylogeny-based research questions: for example, in comparative biology. However, phylogenetic information for such studies lags behind. Here, as a synthesis of all currently available phylogenetic information on the group, we produce a supertree of 114 Northern European macromoth genera (in four superfamilies, with Geometroidea considered separately), providing the most complete phylogenetic picture of this fauna available to date. In doing so, we assess those parts of the phylogeny that are well resolved and those that are uncertain. Furthermore, we identify those genera for which phylogenetic information is currently too poor to include in such a supertree, or entirely absent, as targets for future work. As an aid to studies involving these genera, we provide information on their likely positions within the macromoth tree. With phylogenies playing an ever more important role in the field, this supertree should be useful in informing future ecological and evolutionary studies.

Degenerated, Undifferentiated, Rearranged, Lost: High Variability of Sex Chromosomes in Geometridae (Lepidoptera) Identified by Sex Chromatin.

Sex chromatin is a conspicuous body that occurs in polyploid nuclei of most lepidopteran females and consists of numerous copies of the W sex chromosome. It is also a cytogenetic tool used to rapidly assess the W chromosome presence in Lepidoptera. However, certain chromosomal features could disrupt the formation of sex chromatin and lead to the false conclusion that the W chromosome is absent in the respective species. Here we tested the sex chromatin presence in 50 species of Geometridae. In eight selected species with either missing, atypical, or normal sex chromatin patterns, we performed a detailed karyotype analysis by means of comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH). The results showed a high diversity of W chromosomes and clarified the reasons for atypical sex chromatin, including the absence or poor differentiation of W, rearrangements leading to the neo-W emergence, possible association with the nucleolus, and the existence of multiple W chromosomes. In two species, we detected intraspecific variability in the sex chromatin status and sex chromosome constitution. We show that the sex chromatin is not a sufficient marker of the W chromosome presence, but it may be an excellent tool to pinpoint species with atypical sex chromosomes.

Why do males emerge before females? Sexual size dimorphism drives sexual bimaturism in insects.

Conspecific females and males often follow different development trajectories which leads to sex differences in age at maturity (sexual bimaturism, SBM). Whether SBM is typically selected for per se (direct selection hypothesis) or merely represents a side-effect of other sex-related adaptations (indirect selection hypothesis) is, however, still an open question. Substantial interspecific variation in the direction and degree of SBM, both in invertebrates and vertebrates, calls for multi-species studies to understand the relative importance of its evolutionary drivers. Here we use two complementary approaches to evaluate the evolutionary basis of SBM in insects. For this purpose, we assembled an extensive literature-derived data set of sex-specific development times and body sizes for a taxonomically and ecologically wide range of species. We use these data in a meta-analytic framework to evaluate support for the direct and indirect selection hypotheses. Our results confirm that protandry - males emerging as adults before females - is the prevailing form of SBM in insects. Nevertheless, protandry is not as ubiquitous as often presumed: females emerged before males (= protogyny) in about 36% of the 192 species for which we had data. Moreover, in a considerable proportion of species, the sex difference in the timing of adult emergence was negligible. In search for the evolutionary basis of SBM, we found stronger support for the hypothesis that explains SBM by indirect selection. First, across species, the direction and degree of SBM appeared to be positively associated with the direction and degree of sexual size dimorphism (SSD). This is consistent with the view that SBM is a correlative by-product of evolution towards sexually dimorphic body sizes. Second, within protandrous species, the degree of protandry typically increased with plastic increase in development time, with females prolonging their development more than males in unfavourable conditions. This pattern is in conflict with the direct selection hypothesis, which predicts the degree of protandry to be insensitive to the quality of the juvenile environment. These converging lines of evidence support the idea that, in insects, SBM is generally a by-product of SSD rather than a result of selection on the two sexes to mature at different times. It appears plausible that selective pressures on maturation time per se generally cannot compete with viability- and fecundity-mediated selection on insect body sizes. Nevertheless, exceptions certainly exist: there are undeniable cases of SBM where this trait has evolved in response to direct selection. In such cases, either the advantage of sex difference in maturation time must have been particularly large, or fitness effects of body size have been unusually weak.

Molecular phylogeny, classification, biogeography and diversification patterns of a diverse group of moths (Geometridae: Boarmiini).

Understanding how and why some groups have become more species-rich than others, and how past biogeography may have shaped their current distribution, are questions that evolutionary biologists have long attempted to answer. We investigated diversification patterns and historical biogeography of a hyperdiverse lineage of Lepidoptera, the geometrid moths, by studying its most species-rich tribe Boarmiini, which comprises ca. 200 genera and ca. known 3000 species. We inferred the evolutionary relationships of Boarmiini based on a dataset of 346 taxa, with up to eight genetic markers under a maximum likelihood approach. The monophyly of Boarmiini is strongly supported. However, the phylogenetic position of many taxa does not agree with current taxonomy, although the monophyly of most major genera within the tribe is supported after minor adjustments. Three genera are synonymized, one new combination is proposed, and four species are placed in incertae sedis within Boarmiini. Our results support the idea of a rapid initial diversification of Boarmiini, which also implies that no major taxonomic subdivisions of the group can currently be proposed. A time-calibrated tree and biogeographical analyses suggest that boarmiines appeared in Laurasia ca. 52 Mya, followed by dispersal events throughout the Australasian, African and Neotropical regions. Most of the transcontinental dispersal events occurred in the Eocene, a period of intense geological activity and rapid climate change. Diversification analyses showed a relatively constant diversification rate for all Boarmiini, except in one clade containing the species-rich genus Cleora. The present work represents a substantial contribution towards understanding the evolutionary origin of Boarmiini moths. Our results, inevitably biased by taxon sampling, highlight the difficulties with working on species-rich groups that have not received much attention outside of Europe. Specifically, poor knowledge of the natural history of geometrids (particularly in tropical clades) limits our ability to identify key innovations underlying the diversification of boarmiines.

Fungi Recorded on Folivorous Lepidoptera: High Diversity Despite Moderate Prevalence.

The knowledge about the diversity and ecological role of entomopathogenic fungi is primarily based on agroecosystems whereas information derived from natural insect populations is much more limited. To contribute to filling this gap, we recorded the prevalence of fungal infections in laboratory rearing experiments with five species of Lepidoptera, and in a field rearing experiment including one of these moths. The diversity of detected fungi was found to be high; we isolated 25 species of fungi from insects that had died in the course of these experiments. Six species belonged to the family Cordycipitaceae known to include unambiguous insect pathogens. The trophic niche of the representatives of other taxa is less clear and requires further studies. Regarding the most abundant species, Cordyceps farinosa, in which this question could be addressed, there was no indication of specialization on particular insect hosts, whereas several of the less common species may have been recorded from lepidopteran hosts for the first time. Across the subsets of the data, the prevalence of fungal infections generally remained below 5%. Our results are thus consistent with the idea that entomopathogenic fungi are always present in insect populations but rarely reach epizootic levels. The detected species richness shows that much is to be gained from mapping the diversity of fungal species associated with folivorous insects in natural populations.

Description of Nola estonica sp. nov., with comparison to N. aerugula and N. atomosa stat. rev. (Lepidoptera, Nolidae, Nolinae).

Nola estonica unap sp. nov. (Lepidoptera, Nolidae, Nolinae) is described based on type material from Estonia. The lectotype is designated for Glaphyra atomosa Bremer, 1861, which is reinstated from a subspecies of Nola aerugula (Hbner, [1793]) to a full species: Nola atomosa (Bremer, 1861) stat. rev. The status of these three taxa as separate species is supported by the results of phylogenetic analysis of DNA barcodes, as well as external and genital morphology of adult specimens. Two new synonyms are established as follows: Nola atomosa (Bremer, 1861) = Nola candidalis Staudinger, 1892 syn. nov. and Nola shin Inoue, 1982 syn. nov. N. estonica occurs sympatrically with N. aerugula in Estonia, and with N. atomosa in South Korea and easternmost Russia. While the available data suggest a disjunct distribution of N. estonica (eastern Europe and the temperate Far East), it appears highly possible that the species has a wide transpalaearctic distribution.

Insect oviposition preference between Epichloë-symbiotic and Epichloë-free grasses does not necessarily reflect larval performance.

Variation in plant communities is likely to modulate the feeding and oviposition behavior of herbivorous insects, and plant-associated microbes are largely ignored in this context. Here, we take into account that insects feeding on grasses commonly encounter systemic and vertically transmitted (via seeds) fungal Epichloë endophytes, which are regarded as defensive grass mutualists. Defensive mutualism is primarily attributable to alkaloids of fungal origin. To study the effects of Epichloë on insect behavior and performance, we selected wild tall fescue (Festuca arundinacea) and red fescue (Festuca rubra) as grass-endophyte models. The plants used either harbored the systemic endophyte (E+) or were endophyte-free (E-). As a model herbivore, we selected the Coenonympha hero butterfly feeding on grasses as larvae. We examined both oviposition and feeding preferences of the herbivore as well as larval performance in relation to the presence of Epichloë endophytes in the plants. Our findings did not clearly support the female's oviposition preference to reflect the performance of her offspring. First, the preference responses depended greatly on the grass-endophyte symbiotum. In F. arundinacea, C. hero females preferred E+ individuals in oviposition-choice tests, whereas in F. rubra, the endophytes may decrease exploitation, as both C. hero adults and larvae preferred E- grasses. Second, the endophytes had no effect on larval performance. Overall, F. arundinacea was an inferior host for C. hero larvae. However, the attraction of C. hero females to E+ may not be maladaptive if these plants constitute a favorable oviposition substrate for reasons other than the plants' nutritional quality. For example, rougher surface of E+ plant may physically facilitate the attachment of eggs, or the plants offer greater protection from natural enemies. Our results highlight the importance of considering the preference of herbivorous insects in studies involving the endophyte-symbiotic grasses as host plants.

Quantifying the effects of species traits on predation risk in nature: A comparative study of butterfly wing damage.

Evading predators is a fundamental aspect of the ecology and evolution of all prey animals. In studying the influence of prey traits on predation risk, previous researchers have shown that crypsis reduces attack rates on resting prey, predation risk increases with increased prey activity, and rapid locomotion reduces attack rates and increases chances of surviving predator attacks. However, evidence for these conclusions is nearly always based on observations of selected species under artificial conditions. In nature, it remains unclear how defensive traits such as crypsis, activity levels and speed influence realized predation risk across species in a community. Whereas direct observations of predator-prey interactions in nature are rare, insight can be gained by quantifying bodily damage caused by failed predator attacks. We quantified how butterfly species traits affect predation risk in nature by determining how defensive traits correlate with wing damage caused by failed predation attempts, thereby providing the first robust multi-species comparative analysis of predator-induced bodily damage in wild animals. For 34 species of fruit-feeding butterflies in an African forest, we recorded wing damage and quantified crypsis, activity levels and flight speed. We then tested for correlations between damage parameters and species traits using comparative methods that account for measurement error. We detected considerable differences in the extent, location and symmetry of wing surface loss among species, with smaller differences between sexes. We found that males (but not females) of species that flew faster had substantially less wing surface loss. However, we found no correlation between cryptic coloration and symmetrical wing surface loss across species. In species in which males appeared to be more active than females, males had a lower proportion of symmetrical wing surface loss than females. Our results provide evidence that activity greatly influences the probability of attacks and that flying rapidly is effective for escaping pursuing predators in the wild, but we did not find evidence that cryptic species are less likely to be attacked while at rest.

A comprehensive molecular phylogeny of Geometridae (Lepidoptera) with a focus on enigmatic small subfamilies.

Our study aims to investigate the relationships of the major lineages within the moth family Geometridae, with a focus on the poorly studied Oenochrominae-Desmobathrinae complex, and to translate some of the results into a coherent subfamilial and tribal level classification for the family. We analyzed a molecular dataset of 1,206 Geometroidea terminal taxa from all biogeographical regions comprising up to 11 molecular markers that includes one mitochondrial (COI) and 10 protein-coding nuclear gene regions (wingless, ArgK, MDH, RpS5, GAPDH, IDH, Ca-ATPase, Nex9, EF-1alpha, CAD). The molecular data set was analyzed using maximum likelihood as implemented in IQ-TREE and RAxML. We found high support for the subfamilies Larentiinae, Geometrinae and Ennominae in their traditional scopes. Sterrhinae becomes monophyletic only if Ergavia Walker, Ametris Hübner and Macrotes Westwood, which are currently placed in Oenochrominae, are formally transferred to Sterrhinae. Desmobathrinae and Oenochrominae are found to be polyphyletic. The concepts of Oenochrominae and Desmobathrinae required major revision and, after appropriate rearrangements, these groups also form monophyletic subfamily-level entities. Oenochrominae s.str. as originally conceived by Guenée is phylogenetically distant from Epidesmia and its close relatives. The latter is hereby described as the subfamily Epidesmiinae Murillo-Ramos, Sihvonen & Brehm, subfam. nov. Epidesmiinae are a lineage of "slender-bodied Oenochrominae" that include the genera Ecphyas Turner, Systatica Turner, Adeixis Warren, Dichromodes Guenée, Phrixocomes Turner, Abraxaphantes Warren, Epidesmia Duncan & Westwood and Phrataria Walker. Archiearinae are monophyletic when Dirce and Acalyphes are formally transferred to Ennominae. We also found that many tribes were para- or polyphyletic and therefore propose tens of taxonomic changes at the tribe and subfamily levels. Archaeobalbini stat. rev. Viidalepp (Geometrinae) is raised from synonymy with Pseudoterpnini Warren to tribal rank. Chlorodontoperini Murillo-Ramos, Sihvonen & Brehm, trib. nov. and Drepanogynini Murillo-Ramos, Sihvonen & Brehm, trib. nov. are described as new tribes in Geometrinae and Ennominae, respectively.

No Indication of High Host-Plant Specificity in Afrotropical Geometrid Moths.

Specificity is one of the fundamental concepts in ecology. Host specificity of phytophagous insects has been of particular interest because of its crucial role in diversification and life-history evolution. However, the majority of tropical insects remain insufficiently explored with respect to their host-plant relations. A lack of respective data is also hindering the debate over whether higher levels of host-plant specificity prevail in tropical insects compared to temperate ones. We investigated host-plant specificity of forest geometrid moths (Lepidoptera: Geometridae) in equatorial Africa using host-plant acceptability trials with neonate larvae, with the addition of field observations. We compare our experimental data to the (well-known) host-specificity patterns of closely related temperate (hemiboreal) species. Similarly to the temperate region, there were broadly polyphagous tropical species in several clades of Geometridae utilizing hosts belonging to different plant families. Phylogenetic comparative analysis returned no significant differences in host specificity between the two regions. Our study contributes to the evidence that host-plant specificity of herbivores is not necessarily substantially higher in tropical than temperate regions.

Ontogeny of sexual size dimorphism revisited: Females grow for a longer time and also faster.

Sex-specific mechanisms of the determination of insect body sizes are insufficiently understood. Here we use the common heath moth, Ematurga atomaria (Lepidoptera: Geometridae) to examine how larval growth trajectories differ between males and females. We monitored the development of 1379 larvae in controlled laboratory conditions. Sexually dimorphic development times during the first four instars were associated with sexual size dimorphism (SSD) in the beginning of the fifth (last) instar, when females were on average 15% heavier than males. Similarly, the duration of the last instar was about 13% longer in females. Further, we specifically focussed on the estimates of differential (instantaneous) growth rates of the larvae based on 24h mass increments of the 2nd, 3rd, 4th and 5th day in the beginning of the last instar. We calculated 'allometric' differential growth rates as the per-day increase in cube-root-transformed mass of the larvae. We found that allometric growth rates were slightly but significantly larger in females than in males. As this measure of growth rate (in contrast to the relative growth rate, based on the ratio of masses recorded at consecutive measurements) did not depend on body size, it allows an unambiguous separation of the effects of sex and size. We conclude that in accordance with an emerging general pattern, larger female body size in E. atomaria is achieved primarily by means of a longer growth period. Furthermore, our study shows that the differential growth rate can also be sexually dimorphic and contribute to SSD. This contribution, however, is lower than that of the development time by an order of magnitude. In addition to development periods and growth rates, other parameters of the non-linear growth curves of insect larvae also need to be considered in the context of SSD determination. In particular, weight loss prior to pupation was shown to be considerably larger in females than in males.

Longer life span is associated with elevated immune activity in a seasonally polyphenic butterfly.

Seasonal polyphenism constitutes a specific type of phenotypic plasticity in which short-lived organisms produce different phenotypes in different times of the year. Seasonal generations of such species frequently differ in their overall lifespan and in the values of traits closely related to fitness. Seasonal polyphenisms provide thus excellent, albeit underused model systems for studying trade-offs between life-history traits. Here, we compare immunological parameters between the two generations of the European map butterfly (Araschnia levana), a well-known example of a seasonally polyphenic species. To reveal possible costs of immune defence, we also examine the concurrent differences in several life-history traits. Both in laboratory experiments and in the field, last instar larvae heading towards the diapause (overwintering) had higher levels of both phenoloxidase (PO) activity and lytic activity than directly developing individuals. These results suggest that individuals from the diapausing generation with much longer juvenile (pupal) period invest more in their immune system than those from the short-living directly developing generation. The revealed negative correlation between pupal mass and PO activity may be one of the reasons why, in this species, the diapausing generation has a smaller body size than the directly developing generation. Immunological parameters may thus well mediate trade-offs between body size-related traits.

A comparative morphometric study of sensory capacity in geometrid moths.

Diet breadth and the degree of capital breeding have been established as major determinants of species-specific ecology of herbivorous insects. Both of these variables are related to resource foraging and therefore can be expected to have effects on sensory capacity. However, such effects have remained poorly studied, let alone in phylogenetically explicit multi-species comparisons. We contribute to filling this gap in a study of 60 species of geometrid moths (Lepidoptera: Geometridae), using adult head measures (eye size, antennal length and shape, forehead width) as indices of sensory capacity. When controlled for body size, eyes of the more capital breeding species (i.e. those with low contribution of adult feeding to reproduction) were found to be smaller, and female antennae shorter, than in income breeders. Feathery (vs simple filiform) male antennae were more frequently present in the capital breeders and in larger species. Regarding diet breadth, generalist species were found to have relatively wider male foreheads than specialists. The results suggest that (a) breeding strategy rather than diet breadth predicts sensory capacity in geometrids, (b) capital breeding (vs income breeding) is related to low sensory capacity in females, and (c) in contrast, males of the capital breeding species have evolved towards elevated olfactory capacity.

Weak and inconsistent associations between melanic darkness and fitness-related traits in an insect.

The idea that the fitness value of body coloration may be affected by biochemically mediated trade-offs has received much research attention. For example, melanization is believed to interact with other fitness-related traits via competition for substrates, costs associated with the synthesis of melanin or pleiotropic effects of the involved genes. However, genetic correlations between coloration and fitness-related traits remain poorly understood. Here, we present a quantitative-genetic study of a coloration trait correlated to melanin-based cuticular darkness ('darkness', hereafter) in a geometrid moth, Ematurga atomaria. This species has considerable variation in larval appearance. We focus on correlations between larval darkness and fitness-related growth performance traits. Both a half-sib analysis and an 'animal model' approach revealed moderately high heritabilities of larval darkness and indices of growth performance. Heritability estimates of darkness derived from the animal model were, however, considerably higher than those based on the half-sib model suggesting that the determination of coloration includes genetic interactions and epigenetic effects. Importantly, on the host plant with the largest sample size, we found no evidence for either genetic or environmental correlations between darkness and growth parameters. On an alternative host plant, there was some indication of positive genetic and negative environmental correlation between these traits. This shows that respective relationships are environment-specific. Nevertheless, the overall pattern of weak and inconsistent correlations between larval coloration and growth parameters does not support universal trade-offs between these traits and suggests that physiological costs of producing colour patterns do not necessarily interfere with adaptive evolution of coloration.