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1. Reaction norms for size and age at maturity were studied in Epirrita autumnata (Lepidoptera, Geometridae). Growth rates were manipulated by rearing larvae on different levels of food quality and quantity, and instar-specific final weights and development times were recorded. 2. Food level and initial weight of an instar accounted for most of the variance in final weights. Sexual dimorphism in pupal weights could be entirely ascribed to sex differences in initial weights of the last instar. 3. There were problems with considering the reaction norms optimal within the conventional demographic explanatory framework. Because fecundity increases linearly with body size and no costs of large adult size are known, one should expect female larvae to grow larger to increase their individual fitness. It is therefore likely that constraints play a major role in the determination, and evolution, of size in this species. 4. A focus on individual instars may be the best way to reveal the constraints on, and space for, adaptive evolution of insect growth. Some limit to the initial:final weight ratio of an instar, and the fixed number of instars, may represent important constraints. 5. Reaction norms like the ones described in this study lead to strong environmental determination rather than canalization of body size. Food quality throughout larval development may thus be very important for individual fitness and population dynamics in E. autumnata. [ABSTRACT FROM AUTHOR]

An evolutionary explanation should consider the balance between environmentally-based selective pressures, and the resistance of the organism's phenotype to adaptive evolution, with the latter being captured by the concept of constraint. The limited attention to non-adaptive explanations in evolutionary ecology is at least partly caused by methodological difficulties with respect to identifying and quantifying constraints. As an example of an experimental approach evaluating a constraint-based explanation, we present a cross-species comparison of the shape of reaction norms for size and age at maturity. Instar- and sex-specific development times and final sizes were recorded for two distantly-related species of insects ( Lepidoptera), with larval growth rates being manipulated by means of refined starvation treatments. We found that (1) the 'classical' L-shaped reaction norms for final size and development time are characteristic also of individual larval instars; (2) these responses show a high degree of quantitative similarity across the species, different larval instars, and sexes within species; and (3) the similarity among species and sexes is higher for the penultimate than for the final instar. The high degree of similarity suggests that some physiological mechanisms determining such reaction norms are evolutionarily conservative. An alternative explanation (i.e. quantitative similarity of ecologically based selective pressures) appears less likely. The results of a previous study on a third lepidopteran species not only support our general conclusions, but also provide a clear case of adaptive evolution in some aspects of such reaction norms. The present study shows one way how the data required to measure evolutionary conservatism in reaction norms for body size can be obtained empirically. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114, 296-307. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate host plant and habitat preferences of Lycaena dispar, an oligophagous butterfly species endangered in some parts of its European range., In laboratory trials, the females of Estonian populations accepted various species of Rumex as oviposition substrates. Growth performance of the larvae did not differ between the hosts offered (only R. acetosa proved to be unsuitable)., In the field, extensive use of the two most common host species - R. crispus and R. obtusifolius - by the Estonian populations of L. dispar was confirmed. Unlike in the laboratory, larval performance in the field was better on R. obtusifolius than R. crispus. A likely explanation is the more ephemeral character of the aboveground parts of R. crispus plants: these tend to wilt before the larvae of L. dispar have reached the stage adapted to hibernation., A countrywide analysis of landscape occupancy revealed a positive association of the occurrence of L. dispar with ditches and human settlement. We conclude that moderate anthropogenic pressure maintains suitable habitats for L. dispar through creating favourable conditions for R. obtusifolius, the primary host of the butterfly in the region., Due to its generalism in both host and habitat use, L. dispar is not in the need of active conservation measures on the current northern limit of its distribution. The favourable status of the species in Estonia is corroborated by its recent range expansion which parallels similar trends elsewhere in Eastern Europe. [ABSTRACT FROM AUTHOR]

Numerous studies have suggested a general relationship between the degree of host specialization and body size in herbivorous animals. In insects, smaller species are usually shown to be more specialized than larger-bodied ones. Various hypotheses have attempted to explain this pattern but rigorous proof of the body size-diet breadth relationship has been lacking, primarily because the scarceness of reliable phylogenetic information has precluded formal comparative analyses. Explicitly using phylogenetic information for a group of herbivores (geometrid moths) and their host plant range, we perform a comparative analysis to study the body size-diet breadth relationship. Considering several alternative measures of body size and diet breadth, our results convincingly demonstrate without previous methodological issues-a first for any taxon-a positive association between these traits, which has implications for evaluating various central aspects of the evolutionary ecology of herbivorous insects. We additionally demonstrate how the methods used in this study can be applied in assessing hypotheses to explain the body size-diet breadth relationship. By analyzing the relationship in tree-feeders alone and finding that the positive relationship remains, the result suggests that the body size-diet breadth relationship is not solely driven by the type of host plant that species feed on. [ABSTRACT FROM AUTHOR]

Most insect populations are exploited by a complex of different parasitoid species, providing ample opportunities for competitive interactions among the latter. Despite this, resource-mediated competition (i.e., exploitative competition) among insect parasitoids remains poorly documented in natural systems. Here we propose a novel way to infer the presence of competitive interactions from covariance patterns in parasitism levels, and illustrate the use of this approach on a relatively well-defined and simple host-parasitoid system. The parasitism levels caused by three parasitoid species on a shared host showed a highly consistent negative covariance among samples. With the levels of parasitism by one species increasing, the levels of parasitism attributable to the two others decreased. Importantly, negative covariance between parasitism levels by different species appeared at high abundance, but not at low abundance of the phenologically earlier parasitoid species. This as well as several other lines of evidence indicates the importance of competitive interactions in this system. Feeding biology and phenology of the parasitoids suggest that competition in this parasitoid assemblage is primarily resource-mediated rather than occurring through direct interference. The species attacking earlier stages of the host are competitively superior to those attacking their host later in the season. Better dispersal ability and use of alternative host species by the inferior species could contribute to the coexistence of these competing parasitoids. [ABSTRACT FROM AUTHOR]

It is generally believed that harsh climate inhibits growth and development of ectotherms at high latitudes. However, this environmental effect may be counterbalanced by countergradient genetic variation and habitat selection. While there is laboratory evidence for genetically based increases in growth and development rates in amphibians living at high latitudes, it remains unclear how environmental and genetic effects combine in the field to produce gradients of phenotypic variation. We performed a field study on the growth and development of tadpoles and habitat selection of breeding adults of the natterjack toad (Bufo calamita) in Denmark and in Estonia where the average onset of breeding differs by 12 days. Although growth and development of Estonian tadpoles trailed Danish conspecifics during the first half of the larval period, Estonian tadpoles caught up in both body length and developmental stage to Danish tadpoles in the last third of the larval period. Breeding ponds in Denmark were significantly larger and deeper than in Estonia, however, the water temperatures in the ponds did not vary substantially between the countries. In Estonia the toads selected shallower breeding ponds with higher temperature and oxygen concentrations, suggesting, that at higher latitudes active selection of specific water bodies ensures faster growth and development of larvae. The results, together with previous laboratory evidence, indicate that amphibian distribution limits are shaped both by adaptive differences in developmental rates and behavioural plasticity. To cope with harsh climates, amphibians in the north apparently require shallow water bodies -- a habitat particularly vulnerable to anthropogenic degradation. [ABSTRACT FROM AUTHOR]

We have studied the phylogeography of the red-listed Palearctic butterfly Lopinga achine (Nymphalidae: Satyrinae) based on 1,450 base pairs of mitochondrial DNA sequences from 86 individuals representing 12 populations. Our results indicate a strong structuring of genetic variation, with among-population differences accounting for ca. 67% of the variation and almost all populations being significantly differentiated from each other. We surmise that the insular nature of populations as well as the low dispersal ability of the species has given rise to such a pattern. The genetic diversity within populations is low compared to that in other butterflies. Our results point to a scenario where the species originated in the Eastern Palearctic and expanded into Europe. Based on the analyses, we suggest that the Czech population merits the highest conservation priority. The two Swedish populations represent a distinct evolutionary lineage, and hence merit high conservation attention. The Estonian and Asian populations had the highest genetic diversity, and although we do not consider them to be under immediate threat, their genetic diversity should be conserved in the long term. [ABSTRACT FROM AUTHOR]

Within a season, successive generations of short-lived organisms experience different combinations of environmental parameters, such as temperature, food quality and mortality risk. Adult body size of e.g. insects is therefore expected to vary both as a consequence of proximate environmental effects as well as adaptive responses to seasonal cues. In this study, we examined intraspecific differences in body size between successive generations in 12 temperate bivoltine moths (Lepidoptera), with the ultimate goal to critically compare the role of proximate and adaptive mechanisms in determining seasonal size differences. In nearly all species, individuals developing late in the season (diapausing generation) attained a larger adult size than their conspecifics with the larval period early in the season (directly developing generation) despite the typically lower food quality in late summer. Rearing experiments conducted on one of the studied species, Selenia tetralunaria also largely exclude the possibility that the proximate effects of food quality and temperature are decisive in determining size differences between successive generations. Adaptive explanations appear likely instead: the larger body size in the diapausing generation may be adaptively associated with the lower bird predation pressure late in the season, and/or the likely advantage of large pupal size during overwintering. [ABSTRACT FROM AUTHOR]

Different levels of sexual size dimorphism (SSD) have usually been explained by selective forces operating in the adult stage. Developmental mechanisms leading to SSD during the juvenile development have received less attention. In particular, it is often not clear if the individuals of the ultimately larger sex are larger already at hatching/birth, do they grow faster, or do they grow for a longer time. In the case of insects, the question about sexually dimorphic growth rates is still open because most previous studies fail to adequately consider the complexity of larval growth curve, the existence of distinct larval instars in particular. Applying an instar-specific approach, we analysed ontogenetic determination of female-biased SSD in a number of distantly related species of Lepidoptera. The species studied showed a remarkable degree of similarity: SSD appeared invariably earlier than in the final instar, and tended to accumulate during development. The higher weight of the females was shown to be primarily a consequence of longer development within several larval instars. There was some evidence of higher instantaneous growth rates of females in the penultimate instar but not in the final instar. Egg size, studied in one species, was found not to be sexually dimorphic. The high across-species similarity may be seen as an indication of constraints on the set of possible mechanisms of size divergence between the two sexes. The results are discussed from the perspective of the evolution of insect body size in general. In particular, this study confirms the idea about limited evolvability of within-instar growth increments. An evolutionary change towards larger adult size appears always to be realised via moderate changes in relative increments of several larval instars, whereas a considerable change in just one instar may not be feasible. [ABSTRACT FROM AUTHOR]

1. Body size is positively correlated with fecundity in various animals, but the factors that counterbalance the resulting selection pressure towards large size are difficult to establish. Positively size-dependent predation risk has been proposed as a selective factor potentially capable of balancing the fecundity advantage of large size. 2. To construct optimality models of insect body size, realistic estimates of size-dependent predation rates are necessary. Moreover, prey traits such as colouration should be considered, as they may substantially alter the relationship between body size and mortality risk. 3. To quantify mortality patterns, we conducted field experiments in which we exposed cryptic and conspicuous artificial larvae of different sizes to bird predators, and recorded the incidence of bird attacks. 4. The average daily mortality rate was estimated to vary between 4% and 10%. In both cryptic and conspicuous larvae, predation risk increased with prey size, but the increase tended to be steeper in the conspicuous group. No main effect of colour type was found. All the quantitative relationships were reasonably consistent across replicates. 5. Our results suggest that the size dependence of mortality risk in insect prey is primarily determined by the probability of being detected by a predator rather than by a size-dependent warning effect associated with conspicuous colouration. Our results therefore imply that warningly coloured insects do not necessarily benefit more than the cryptic species from large body size, as has been previously suggested. [ABSTRACT FROM AUTHOR]

Populations at range margins may be genetically different from more central ones for a number of mutually non-exclusive reasons. Specific selection pressures may operate in environments that are more marginal for the species. Genetic drift may also have a strong effect in these populations if they are small, isolated and/or have experienced significant bottlenecks during the colonisation phase. The question if peripheral populations are special, and if yes then how and why, is of obvious relevance for speciation theory, as well as for conservation biology. To evaluate the uniqueness of populations at range margins and the influence of gene flow and selection, we performed a morphometric study of two grassland butterfly species: Coenonympha arcania and C. hero (Lepidoptera: Nymphalidae). The samples were collected from Swedish populations that are peripheral and isolated from the main area of the species distributions and from populations in the Baltic states that are peripheral but connected to the main area of the species distributions. These samples were compared to those from central parts of the species distributions. The isolated populations in both species differed consistently from both peripheral and central populations in their wing size and shape. We interpret this as a result of selection caused by differences in population structure in these isolated locations, presumably favoring different dispersal propensity of these butterflies. Alternative explanations based on colonisation history, latitudinal effects, inbreeding or phenotypic plasticity appear less plausible. As a contrast, the much weaker and seemingly random among-region differences in wing patterns are more likely to be ascribed to weaker selection pressures allowing genetic drift to be influential. In conclusion, both morphological data and results from neutral genetic markers in earlier studies of the same system provide congruent evidence of both adaptation and genetic drift in the isolated Swedish populations of both species. [ABSTRACT FROM AUTHOR]

Aim Climatic changes and fluctuations in the past have strongly influenced the distribution of animal and plant species. Such fluctuations are also reflected in the patterns of genetic diversity on both local and global scales. The genetic pattern of the pearly heath butterfly, Coenonympha arcania, was used to evaluate the genetic differentiation of isolated (in north-western Europe), peripheral (in north-eastern Europe) and central (in southern Europe) populations in the context of post-glacial distributional changes of the species. Location Europe (Sweden, Germany, the Baltic states, Italy, Slovenia, Hungary, Romania, Bulgaria). Thus, samples were collected from large parts of the species’ distribution representing the three categories mentioned above. Methods We analysed 18 loci of 569 individuals from 28 populations by allozyme electrophoresis. We used both individual-based and population-based analyses, including F-statistics, various clustering methods and Markov chain Monte Carlo simulations. Results All loci, except Fum, were polymorphic. The mean FST for all samples was 0.18. The mean genetic distance among populations was 0.046. Two major genetic lineages were distinguished. Populations from the centre of the distributional range in southern Europe and the northern periphery of the distributional range differed significantly in their level of genetic variability. The central populations of south-eastern Europe showed high levels of genetic diversity and no differentiation among populations. Main conclusions Most probably the two major genetic lineages evolved during glacial isolation in two disjunct Mediterranean refugia. The lack of genetic differentiation across south-eastern Europe implies a continuous Würm ice age distribution in this area, thus supporting the functional existence of steppe forests throughout this region. The peripheral-isolated populations in Sweden seem to have suffered from one or more severe bottlenecks, resulting in substantial genetic impoverishment. The peripheral-connected eastern Baltic populations, on the other hand, are affected by post-glacial and possibly recurrent gene flow from more central parts of the distribution. [ABSTRACT FROM AUTHOR]

The recent "overhead threshold" model for optimal age and body size at maturity (Day and Rowe 2002) predicts that phenotypic variability in adult body size will be low under inferior environmental quality and will increase with improving conditions. The model is, however, based on a potentially restrictive assumption of a monotone increase of fecundity with increasing body size. On the basis of a numerical model, we show that introducing the concept of maximum adult body size changes the predictions of the model. The dependence of variability in adult body size on environmental quality becomes a concave function with a maximum at intermediate values. Depending on the range of environmental conditions considered, one may therefore expect to observe both increasing and decreasing functions. We test the predictions of our model on a literature-based database of 131 insect species covering all major orders. We demonstrate that, in most species, relative phenotypic variation in body size decreases when environment-specific average of adult body size increases. In the majority of cases at least, such a relationship can be interpreted as a decreased relative variation in better growing conditions. With some potentially meaningful exceptions (e.g., females of capital-breeding insects), the general pattern was largely invariable across different taxa, ecological subdivisions, and sexes. [ABSTRACT FROM AUTHOR]

1. The allometric relationship between growth rate and body mass has received considerable attention but different taxa have not been equally studied. In particular, a limited amount of information is available on growth allometry of insect larvae. 2. In life-history studies, it is often assumed that insect larvae grow exponentially. This leads one to expect that potential rewards of extending growth periods are high in terms of increased adult body masses and fecundities. Therefore, it has been a challenge to find costs of large size that counterbalance the fecundity advantage of attaining larger sizes. 3. This study examines the intraspecific growth allometry of lepidopteran larvae. Original methodology is proposed to address problems arising from the complexity of the insect growth curve, and the high sensitivity of growth rates to environmental conditions. To facilitate generalizations, larvae of 11 unrelated lepidopteran species were subjected to an identical study design. 4. Instantaneous absolute growth rates of larvae were related to body size by an intraspecific allometric exponent in the range between 0·41 and 0·88. There were significant differences between the species but values of the exponent as high as 1 (exponential growth), and as low as 0 (linear growth) could safely be excluded. 5. Instantaneous relative growth rates of larvae were typically 35% lower in their last instar when compared to the penultimate one. Using the exponential growth curve (i.e. assuming the constancy of relative growth rates) in modelling insect life-histories may therefore lead to substantially biased conclusions. [ABSTRACT FROM AUTHOR]

Optimal behavioural decisions are expected to depend on various state variables, such as physiological condition or age. In insects, empirical evidence of the effect of adult age on oviposition selectivity is mixed. Consistently, optimality models – which primarily incorporate the effects of egg load and senescence – fail to provide universal predictions. Here we propose that spatial variation in mortality rates creates an additional mechanism able to select for an increase in selectivity with age. Females can be selected to use the fact of having reached an advanced age as a cue of low mortality rates in their environment. Older females may thus be less time-limited, and can afford for more careful host selection. This is because variation in mortality rates can cause a positive correlation between individual age, and expected residual life span. We present a simulation model that formalises the verbal argument presented above, and discuss the findings in the more general context of the dependence of reproductive output on age. [ABSTRACT FROM AUTHOR]

We studied if the population density experienced during larval development affects the reproductive schedule ofYponomeuta evonymellusL. (Lepidoptera, Yponomeutidae), a moth species characterized by outbreak population dynamics. More specifically, we predicted that reproduction would be delayed to facilitate emigration from sites with suboptimally high densities of conspecifics. We manipulated larval densities in the laboratory, as well as in those pupae collected from the extremes of natural densities. As the response, we also recorded the timing and sizes of egg clutches laid. The results did not support our initial predictions: the timing of oviposition was not dependent on larval growth conditions. This apparent lack of adaptation might be related to the loss of‘memory’ during metamorphosis in holometabolous insects. However, oviposition schedules were also only minimally sensitive to elevated adult density. An inability to respond to high larval densities may contribute to the outbreak dynamics in this species. [ABSTRACT FROM AUTHOR]

Studies examining interspecific differences in sexual size dimorphism (SSD) typically assume that the degree of sexual differences in body size is invariable within species. This work was conducted to assess validity of this assumption. As a result of a systematic literature survey, datasets for 158 insect species were retrieved. Each dataset contained adult or pupal weights of males and females for two or more different subsets, typically originating from different conditions during immature development. For each species, an analysis was conducted to examine dependence of SSD on body size, the latter variable being used as a proxy of environmental quality. A considerable variation in SSD was revealed at the intraspecific level in insects. The results suggest that environmental conditions may strongly affect the degree, though not the direction of SSD within species. In most species, female size appeared to be more sensitive to environmental conditions than male size: with conditions improving, there was a larger relative increase in female than male size. As a consequence, sexual differences in size were shown to increase with increasing body size in species with female-biased SSD (females were the larger sex in more than 80% of the species examined). The results were consistent across different insect orders and ecological subdivisions. Mechanisms leading to intraspecific variation in SSD are discussed. This study underlines the need to consider intraspecific variation in SSD in comparative studies. [ABSTRACT FROM AUTHOR]

It is often claimed that some organisms maximise individual growth rates (within limits set by physiological and environmental constraints) whereas others do not. Adequate experimental protocol to test for these hypotheses has not been available. We proceeded from the idea that a maximiser should be unable to further improve its growth performance, i.e. there should be no adaptive plasticity in relative growth rates. In the case of an insect larva always maximising its weight gain, we should thus expect no increase in growth rate following a short-term environmental perturbation. Another prediction is that initial and final weights of a larval instar should be highly correlated. We applied this approach to test for the growth rate maximiser status of the geometrid moth Epirrita autumnata. Based on various lines of ecological evidence it had previously been suggested that this spring-feeding species is strongly selected for high growth rates, and may be growing at its maximum physiological potential. Contrary to expectations, the larvae responded to starvation treatments by a subsequent compensatory increase in their relative growth rates. Such a plasticity may indicate that the rates of gaining weight are not maximised even in a `classical' example a time- constrained organism. This observation supports the idea that endogenous regulation of growth rates is widespread, and it remains to be shown if true maximisation ever exists in nature. In contrast, possibilities to compensate for adverse conditions experienced early in larval development appeared to be limited. This was indicated by the strong correlation between initial weight in the last instar, and pupal weight. Though consistent with our expectations, such an inability to compensate can hardly be ascribed to growth rate maximisation, as indicated by quantitatively similar patterns found in an unrelated species with different ecology, the butterfly Polygonia c-album. [ABSTRACT FROM AUTHOR]

Strong correlation between female body size and potential fecundity is often observed in insects. Directional selection favouring increased body sizes is thus predicted in the absence of opposing selection pressure. The evolutionary forces capable of counterbalancing such a 'fecundity advantage' are poorly documented. This study focuses on revealing the costs of large body size in the wingless females of Orgyia antiqua and O. leucostigma, two related species of lymantriid moths. Extreme behavioural simplicity of these animals allows systematic assessment of various fitness components in conditions that are close to natural. A linear relationship between pupal weight and potential fecundity was observed. This association was found to be independent of particular rearing conditions. There was no evidence that the relationship between fecundity and body mass becomes asymptotic when body sizes increases. No component of fitness showed a negative phenotypic correlation with body size; some displayed a weakly positive one. In particular, pupal mortality, adult longevity, mating and oviposition success, as well as egg hatching rate and egg size, were established as independent of body size in a series of field and laboratory experiments. There was a very high overall efficiency of converting resources accumulated during the larval stage to egg masses. With no costs of large adult size, selective forces balancing the fecundity advantage should operate in the course of immature development. The strong dependence of realized fecundity on body size is considered characteristic of the capital breeding strategy. [ABSTRACT FROM AUTHOR]

A comprehensive phylogeny of north European Geometridae is reconstructed using a two‐step analytical pipeline. First, a phylogenomic backbone tree was inferred using a 117‐species subset of geometrid moths and a 35‐species set of outgroup taxa from eight other macroheteroceran families. The data matrix totalled 209,499 bp from 648 protein‐coding loci obtained using anchored hybrid enrichment technique for sequencing. This backbone was used for constructing a larger phylogeny of Geometridae based on up to 11 'traditional' protein‐coding genes which were obtained for all 376 species of north European geometrids, complemented by 98 species from taxonomic key groups of Geometridae from other parts of the world. Our results largely corroborate earlier findings about higher classification of Geometridae, but new evidence nevertheless allows us to suggest several changes to the taxonomy. Lampropterygini Õunap & Nedumpally tribus nova and Pelurgini Õunap & Nedumpally tribus nova (both Larentiinae) are described. Epirranthini are regarded as a junior subjective synonym of Rumiini syn. n. Triphosini and Macariini are shown to be paraphyletic within their current limits. Costaconvexa Agenjo is transferred from Xanthorhoini to Epirrhoini new tribe association, Artiora Meyrick from Ennomini incertae sedis to Boarmiini new tribe association, Selenia Hübner from Ennominae incertae sedis to Epionini new tribe association and Epirranthis Hübner from Epirranthini to Rumiini new tribe association. Ochyria Hübner stat. rev. is revived from synonym of Xanthorhoe Hübner as a valid genus and Epelis Hulst stat. rev. and Speranza Curtis stat. rev. from synonyms of Macaria Curtis as valid genera, leading to the following new or revised combinations: Ochyria quadrifasiata (Clerck) rev. comb., Epelis carbonaria (Clerck) comb. n., Speranza fusca (Thunberg) comb. n., Speranza artesiaria (Denis & Schiffermüller) rev. comb., Speranza brunneata (Thunberg) rev. comb., Speranza wauaria (Linnaeus) rev. comb., Speranza loricaria (Eversmann) rev. comb.Perizoma saxicola Tikhonov rev. comb. is transferred back to its original genus from Gagitodes Warren. Hydrelia Hübner, Xanthorhoe and Heliomata Grote & Robinson are shown to be paraphyletic within their current limits. [ABSTRACT FROM AUTHOR]

Assesses the genetic and environmental components of within- and among-population variance in pupal period in a moth species in several common-environment rearings. Genetic basis of the latitudinal among-population differences in pupal period; Flat fitness profiles in relation to eclosion date; Genetic variance in variance of pupil period.

Larval density, size of pheromone­trapped adult males, and survival and parasitism rates in the laboratory of field­collected larvae of Epirrita autumnata were investigated along three pollution gradients: the surrounding of smelters at Monchegorsk and Nikel in north­western Russia and a factory complex at Harjavalta, south­western Finland. Along the gradients, the emissions are qualitatively similar, consisting mainly of Cu, Ni and SO2, but the amounts emitted vary. Cu and Ni concentrations in birch (Betula pubescens) leaves, a common diet of E. autumnata larvae, were monitored and used as general indices of pollution. High Cu and/or Ni concentrations in birch foliage, and/or associated changes in other pollutants, were associated with detrimental effects on E. autumnata performance. They occurred when concentrations of foliage Cu and/or Ni exceeded 20–30 µg g&sup-1; In the Harjavalta and Monchegorsk gradients, crossing the above threshold values in heavy metal concentrations in the foliage, larval density and survival increased significantly with distance from the smelters. No pollution­related trends with distance were found either for male size or for larval parameters in that section of the Nikel gradient where foliage heavy metals were below this threshold value. Parasitism rates were not associated with pollution, indicating that parasitoids were not differently sensitive to pollutants than their herbivorous host. No indication was found of a positive effect of moderate pollution on E. autumnata and heavy pollution had detrimental effects. The results do not suggests that the species might become a severe pest in polluted areas outside its natural outbreak range. [ABSTRACT FROM AUTHOR]

Examines induced resistance of birch tree foliage during and after a natural insect outbreak in Finland. Measurement on the effects of quality of the host tree; Defoliation of experimental trees by wild larvae; Importance of terminating agents for different individual outbreak peaks.

Natural enemies play a key role in population dynamics of insects and exert significant selective pressures on various traits of these animals. Although there is a wealth of empirical and theoretical research on predators and parasitoids, the ecological role of pathogens (other than viruses) remains less understood. Entomopathogenic fungi (EPF), encompassing over 1000 known species from 11 phyla, have primarily been studied in the context of biocontrol in agroecosystems, while their role in natural ecosystems is poorly known. In this paper, we synthesize case studies reporting the prevalence of EPF infections in field populations of insects. We examine differences in this variable among major host taxa and those of the pathogens. From 79 case studies that met our selection criteria, we retrieved data on 122 species of fungi infecting 104 insect species. The meta‐analytic median prevalence of fungal infections was 8.2%; even if likely inflated by publication bias, this suggests that EPF‐induced mortality levels are lower than those attributable to predators and parasitoids. We found no substantial differences in fungal prevalence among major insect taxa and only a moderate difference among fungal orders, with Neozygitales showing the highest prevalence and Eurotiales the lowest. Our analysis revealed no significant differences in overall EPF prevalence between tropical and temperate studies, although different fungal taxa showed different geographical patterns. In temperate areas, there is some evidence of increasing infection prevalence toward the end of the growing season. Although quantitative data on the effect of EPF on insect populations are still scarce, evidence is consistent with the emerging generalization that insect populations commonly harbor species‐rich assemblages of pathogenic fungi, but infections rarely reach epidemic levels. Further studies on multi‐species assemblages of EPF associated with natural insect populations are needed to better understand the ecological role of fungal infections. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. Graphical Abstract [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Dry body mass (DBM) is perhaps the most biologically informative variable describing body size in invertebrates. Unfortunately, obtaining species-specific indices of DBM is problematic because body mass inevitably changes during the course of the life of an individual. Here, we present a phylogenetically informed analysis of allometric relationships between body size and various linear measurements in the moth family Geometridae, which relies on DBM recorded at a fixed time point of adult life. We demonstrate that all measurements of wing size predict DBM with reasonable accuracy, with the distance between the most distal ends of the two forewings in traditionally mounted moths showing the best performance. Abdomen width provides independent morphometric information and can be used as a proxy of body plan, i.e. a measurement of shape that is not dependent on size. Incorporating abdomen width into the regression models considerably increases their predictive ability. We also show that the allometric relationships are reasonably consistent between the two sexes, between monophyletic clades of Geometridae and between the two geographical regions involved in the study (northern Europe and equatorial Africa). The derived equations thus appear to be general enough to be applied in various studies, from comparative phylogenetic analyses to applied projects monitoring insect biomass. [ABSTRACT FROM AUTHOR]

Creating multiyear cycles in population density demands, in traditional models, causal factors that operate on local populations in a density-dependent way with time lags. However, cycles of the geometrid Epirrita autumnata in northern Europe may be regional, not local; i.e., successive outbreaks occur in different localities. We review possible causes of cycles of E. autumnata under both local and regional scenarios, including large-scale synchrony. Assuming cyclicity is a local phenomenon, individual populations of E. autumnata display peaks but populations all over the outbreak range fluctuate in synchrony. This concept assumes that the peaks at most localities are so low that they do not lead to visible defoliation and easily remain unnoticed. In this scenario, populations are able to start recovery a few years after the crash, i.e., at the time of the mitigation of detrimental delayed density-dependent factors, such as delayed inducible resistance of the host plant or parasitism. In that case, the same factors that lead to crashes also explain the periodicity of cyclic fluctuations. According to the regional cyclicity scenario, different factors canbe important in different phases of the cycle. The key is to identify the factors that tend to produce outbreaks with a periodicity of about 10 years. Initiation of the increase phase seems to coincide withmaxima in sunspot activity, but causal connections remain unclear. Climatic factor(s) associated with the solar cycle could contribute tothe large-scale geographic synchrony. [ABSTRACT FROM AUTHOR]

Populations of herbivorous insects are considered to be primarily regulated by natural enemies. However, little is known about the ecological role of entomopathogenic fungi. There is very little data on the diversity and prevalence of fungal pathogens in natural insect populations. In this study, the percentage mortality attributable to fungal pathogens for the immature stages of three noctuid moths feeding inside the stems of the herbaceous plant, Typha latifolia, were determined. The average percentage mortality caused by fungal pathogens was around 8%, with the value never exceeding 20% at any of the studied sites. As many as ten species of fungi were identified in the 52 infected larvae/pupae collected, this high diversity is consistent with the results of comparable studies. The prevalence of fungal infections did not correlate with host population density or performance of the host insects. This study contributes to the emerging generalisation that populations of insects commonly harbour diverse assemblages of pathogenic fungi, but with low overall prevalence. A significant contribution of these antagonists to regulating insect populations is unlikely. [ABSTRACT FROM AUTHOR]

The degree of ecological specialization plays a crucial role in shaping the structure and functioning of communities. However, comparing specialization within and among groups of organisms is complicated by both methodological issues and conceptual and terminological inconsistencies. Environmental predictability has been considered a key determinant of specialization though empirical evidence is still limited. Fungi and their insect consumers provide a poorly studied but promising system to measure host specialization and test the predictability hypothesis. In this study, we systematically sampled mushrooms in North European boreal forest, and reared total samples of fungivores colonizing the fruitbodies. Due to the unpredictable nature of mushrooms as a resource, low levels of host specialization can be predicted for these insects, which have indeed widely been considered polyphagous. Contrary to expectations, the majority of the studied fungus gnats were found not to exploit their host taxa indiscriminately. Not only were some mushroom taxa never colonized, the infestation rate of acceptable hosts also differed in most of these fungivores. Gnat species themselves formed continua with respect to the estimates of the degree of specialization, derived from parametric individual-based analyses of presence-absence data. In most cases, host use was best explained by models in which the hosts were classified at genus level, with limited support to specialization to particular host species, families, or orders. Indeed, most of the common fungivores appeared to preferentially use various species from one or a few mushroom genera while occasionally feeding on members of other host taxa. This pattern has likely evolved as a compromise between selective forces stemming from host unpredictability and taxon-specific chemical profiles of the mushrooms. Our study highlights the multidimensional nature of ecological specialization: a high number of acceptable hosts does not preclude considerable discrimination among members of the available resource pool. Such situations can only be revealed by individual-based analyses capable of capturing differences in partner-to-partner interaction intensities. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Simple Summary: Sugar baits are not only used to attract butterflies; they are also used to attract nocturnal moths. Similarly to most sampling techniques, the results of bait trapping are influenced by ambient conditions. In order to understand how bait trap catches depend on weather parameters, we performed a study in the north European forest zone using portable weather stations placed next to the traps. We found that the number of moths caught was strongly positively dependent on temperature and negatively dependent on air humidity. Diversity showed a similar dependence on temperature and humidity but was also negatively affected by air pressure and positively affected by the change of pressure during the night. Our findings help to interpret the results of quantitative insect trapping projects as they allow one to properly account for variability in weather conditions. 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. [ABSTRACT FROM AUTHOR]

Optimality models predict that diet-induced bivariate reaction norms for age and size at maturity can have diverse shapes, with the slope varying from negative to positive. To evaluate these predictions, we perform a quantitative review of relevant data, using a literature-derived database of body sizes and development times for over 200 insect species. We show that bivariate reaction norms with a negative slope prevail in nearly all taxonomic and ecological categories of insects as well as in some other ectotherm taxa with comparable life histories (arachnids and amphibians). In insects, positive slopes are largely limited to species, which feed on discrete resource items, parasitoids in particular. By contrast, with virtually no meaningful exceptions, herbivorous and predatory insects display reaction norms with a negative slope. This is consistent with the idea that predictable resource depletion, a scenario selecting for positively sloped reaction norms, is not frequent for these insects. Another source of such selection-a positive correlation between resource levels and juvenile mortality rates-should similarly be rare among insects. Positive slopes can also be predicted by models which integrate life-history evolution and population dynamics. As bottom-up regulation is not common in most insect groups, such models may not be most appropriate for insects. [ABSTRACT FROM AUTHOR]

The degree to which variation in adult food availability affects the population dynamics of a species depends on its position on the capital‐income breeding continuum. The long‐lived butterflies that feed on fruits as adults constitute an example of Lepidoptera with a high degree of income breeding.For three species of fruit‐feeding butterflies in Uganda, we assessed the contribution of income to breeding in the wild, and the consequences of variation in fruit availability for body mass and population dynamics. We interpreted body‐mass loss within individuals as well as younger individuals having higher body mass than older ones as evidence for the depletion of capital reserves.Despite large sample sizes, we were able to show only modest body‐mass loss in one species, indicating that large‐bodied fruit‐feeding butterflies are functionally income breeders in the wild. Butterfly body mass was sensitive to environmental factors, although the responses to fruit availability and weather parameters were dominated by interactive effects. In all three species, periods of higher availability of fruit were followed by periods of higher adult abundance three to five months later, fitting the egg‐to‐adult time.Our results suggest that adult food is rapidly used for reproduction so that body mass remains stable and population size responds to adult food availability.For these income breeding species, the frequent periods of low adult food availability may select for extended adult longevity for the purpose of postponing reproduction to the onset of more favourable conditions. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In litter-bearing mammals, the environment and social interactions during early life often have a substantial effect on future behaviour of the animal. Most information though derives from lab rodents, pets or farm animals while comparable data are scarce for non-domesticated species, and endangered carnivores in particular. In this study, we focused on social behaviour of juvenile European mink, with the practical aim to provide information for enhancing the ex-situ breeding programme of this critically endangered species. As the first step, we compiled a detailed ethogram of social behaviour observed among the European mink cubs. For the 13 captive born litters available, we then systematically recorded the relative duration of different types of behaviour during a two months period. The behaviour of the captive cubs was found to be diverse, containing all elements characteristic of congeneric mustelids, with no indication of litters deviating from the typical pattern. In all broods, a considerable and approximately equal share of time was allocated to social play, a suggested indicator of positive welfare. Aggressive behaviour of the mother towards her offspring was minimal when the cubs were young and, increased only with the litter dispersal period approaching. Bites between the cubs during play fighting did not increase with the age of the juveniles. We found no evidence that captive environment adversely affects the behaviour of the juveniles during the first months of their life. [ABSTRACT FROM AUTHOR]

Predictive classifications of life histories are essential for evolutionary ecology. While attempts to apply a single approach to all organisms may be overambitious, recent advances suggest that more narrow ordination schemes can be useful. However, these schemes mostly lack easily observable proxies of the position of a species on respective axes. It has been proposed that, in insects, the degree of capital (vs. income) breeding, reflecting the importance of adult feeding for reproduction, correlates with various ecological traits at the level of among-species comparison. We sought to prove these ideas via rigorous phylogenetic comparative analyses. We used experimentally derived life-history data for 57 species of European Geometridae (Lepidoptera), and an original phylogenetic reconstruction. The degree of capital breeding was estimated based on morphological proxies, including relative abdomen size of females. Applying Brownian-motion-based comparative analyses (with an original update to include error estimates), we demonstrated the associations between the degree of capital breeding and larval diet breadth, sexual size dimorphism, and reproductive season. Ornstein-Uhlenbeck model based phylogenetic analysis suggested a causal relationship between the degree of capital breeding and diet breadth. Our study indicates that the gradation from capital to income breeding is an informative axis to ordinate life-history strategies in flying insects which are affected by the fecundity vs. mobility trade off, with the availability of easy to record proxies contributing to its predictive power in practical contexts. [ABSTRACT FROM AUTHOR]

Spatiotemporal variation in the degree of melanism is often considered in the context of thermal adaptation, melanism being advantageous under suboptimal thermal conditions. Yet, other mutually nonexclusive explanations exist. Analysis of geographical patterns combined with laboratory experiments on the mechanisms of morph induction helps to unveil the adaptive value of particular cases of polyphenism., In the context of the thermal melanism hypothesis and seasonal adaptations, we explored an array of environmental factors that may affect the expression and performance of nonmelanic vs. melanic larval morphs in different latitudinal populations of the facultatively bivoltine moth Chiasmia clathrata (Lepidoptera: Geometridae)., Geographical variation in larval coloration was independent of average temperatures experienced by the populations in the wild. The melanic morph was, however, more abundant in dry than in mesic habitats. In the laboratory, the melanic morph was induced especially under a high level of incident radiation but also at relatively high temperatures, but independently of photoperiod. Melanic larvae had higher growth rates and shorter development times than the nonmelanic ones when both temperature and the level of incident radiation were high., Our results that melanism is induced and advantageous in warm desiccating conditions contradict the thermal melanism hypothesis for this species. Neither has melanism evolved to compensate time constraints due to forthcoming autumn. Instead, larvae solve seasonal variation in the time available for growth by an elevated growth rate and a shortened larval period in the face of autumnal photoperiods. The phenotypic response to the level of incident radiation and a lack of adaptive adjustment of larval growth trajectories in univoltine populations underpin the role of deterministic environmental variation in the evolution of irreversible adaptive plasticity and seasonal polyphenism. [ABSTRACT FROM AUTHOR]