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In seasonal environments, phenotypic plasticity in response to gradual changes in environmental variables may result in the production of discrete seasonal morphs. Production of the appropriate seasonal morph at the correct time relies on individuals interpreting environmental cues during their development. The speckled wood butterfly Pararge aegeria (L.) has previously been shown to have developmental and phenotypic plasticity across seasons and space (habitats). Here, we examine the developmental sensitivity of different seasonal cohorts of female P. aegeria to changes in local weather conditions over time (1989-1999) and determine how such temporal climatic variation affects adult phenotype development. We observed trait- and cohort-specific changes of adult phenotype development in response to local temporal changes in temperature and rainfall levels. We discuss our findings using current life-history theory and consider the potential for changes in local weather conditions to influence population variability in butterfly morphology and performance. [ABSTRACT FROM AUTHOR]

Butterfly wing characteristics are extensively used as model system in studies of development, quantitative genetics and phenotypic plasticity. In spite of its evolutionary relevance, however, the effect of stress on the expression of genetic variation itself has only rarely been studied. In this paper, we explore genetic variation of wing characteristics of the Speckled wood Pararge aegeria along a host plant drought stress gradient. Forewing area, basal and distal degree of melanization and the area of five yellow wing spots were measured. We found an increase in (additive) genetic variation in degree of melanization at higher drought stress, and a similar, yet non-significant, relationship for forewing size. As a result, both the upper limits of the narrow-sense heritability and the coefficient of additive genetic variation of wing size and melanization increased with drought stress. Patterns for the different yellow wing spots were less consistent, suggesting trait-specificity in the relationships between genetic variation and environmental stress. [ABSTRACT FROM AUTHOR]

1. Active time budgets of flying ectotherms depend on body temperature. Knowledge of flight ability and performance is currently heavily biased towards the range of temperatures favourable for voluntary flight activity. Flight under suboptimal temperature conditions may also be important, however, in terms of fitness. 2. Here we study the ability of organisms to fly at body temperatures colder than those at which flight is initiated voluntarily, and the duration of such flights. Laboratory-reared Pararge aegeria (L.) butterflies that originated from woodland and agricultural landscape were tested at five temperatures (range: 10–21 °C) in a common-garden set-up. 3. We predict that males are able to fly at lower temperatures than females as males have lower wing loading (i.e. body mass/wing area). Since woodland is on average cooler than agricultural landscape we also predict that flight ability at low temperature is better developed in woodland individuals. 4. Individuals showed an ability to fly at all tested temperatures and flights were longer with increasing temperature. Males flew for longer than females. There was no difference in flight duration between sexes at the lowest temperature, but an increasing difference with increasing temperature. We showed that woodland butterflies flew for longer and had higher wing loading than agricultural landscape butterflies. 5. Our results shed new light on the thermal ecology of flight at suboptimal temperatures and are discussed from both proximate and ultimate points of view. [ABSTRACT FROM AUTHOR]

Although contemporary animal contest theory emphasises the importance of physical asymmetries in resolving disputes, such asymmetries do not obviously settle fights in all groups. Territorial male butterflies, for example, compete via elaborate non-contact aerial interactions in which success is determined by relative persistence. Prior research suggests that the resolution of these contests is not clearly related to physical variables such as body size or energy reserves. However, given that the contests involve elaborate aerial manoeuvres, one long-standing suggestion is that asymmetries in flight performance, and thus flight morphology, may be important. We addressed this hypothesis via a manipulative investigation into the biophysical correlates of contest success in the speckled wood butterfly, Pararge aegeria. This species possesses the ability for significant adaptive phenotypic plasticity in relevant flight morphological parameters. We took advantage of this plasticity to rear 90 individuals of markedly varying flight morphologies, which we then pitted against each other in a semi-controlled experimental fashion. Multiple logistic and lognormal analyses provided little evidence for the relevance of morphological parameters, including relative flight musculature, wing loading and wing aspect ratio (wing length relative to area), to the outcome and/or duration of experimental contests. Instead, we found a positive effect of age upon contest success. Given that ability for high acceleration is strongly linked to variation in these morphological parameters, our findings suggest that flight performance is not a strong determinant of resource-holding potential in this notably territorial butterfly. [ABSTRACT FROM AUTHOR]

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

Summary 1. The relationship between maximal acceleration capacity and flight morphology was tested experimentally in the butterfly Pararge aegeria . Such relations are often assumed but seldom tested. 2. In both sexes acceleration capacity was positively correlated with total body mass, thorax mass, forewing area, forewing length, wing loading, aspect ratio and centre of forewing area (centroid). Relationships with total body mass, forewing area, forewing length and wing loading were stronger in males. This can be explained by different mass allocation: males allocate proportionally more mass to the thorax, females more to the abdomen. 3. Evidence for the combined effect of morphological traits on acceleration capacity was found by multivariate analysis. In males and females, a more distant relative centroid and higher relative thorax mass were related to a higher flight capacity. In addition, aspect ratio was positively related to acceleration capacity in males only. 4. Our results support the assumed mechanism behind the relationship between flight morphology and mate-locating behaviour. [ABSTRACT FROM AUTHOR]

The temperate-zone butterfly Pararge aegeria can use three developmental pathways corresponding to different seasonal cohorts: (1) development with a pupal winter diapause resulting in early spring adults; (2) development with a larval winter diapause resulting in late-spring adults and (3) direct development resulting in summer or second generation adults. In order to test adaptive predictions, we compared variation in flight- and thermoregulation-related morphology among adult males and females from the three pathways using both field data (i.e. wild-caught butterflies) and experimental breeding data (i.e. reared under different photoperiod regimes). Morphological patterns among the pathways were largely similar in the field and rearing data. Seasonal patterns differed between the sexes for most traits, including (relative) size measures and wing colour. Our results suggest sex-related, adaptive seasonal plasticity for morphological traits related to flight behaviour in a multivoltine insect. [ABSTRACT FROM AUTHOR]

Sixty agoraphobics were treated by behavioural therapy (self-exposure in vivo) either with their partner involved in all aspects of treatment or without their partner. The two treatment formats were about equally effective. Behavioural treatment directed at the agoraphobia resulted in improvement irrespective of marital quality and partner involvement in the therapy. The effects of treatment led neither to a deterioration of the marriage nor to adjustment problems in the partner. Avoidance behaviour, intropunitivity and overprotection were found to predict treatment response. The partners of agoraphobics were not found to have psychological problems themselves. [ABSTRACT FROM AUTHOR]

Males of the speckled wood butterfly Pararge aegeria L. (Satyrinae), actively search for females (“patrolling”) or wait for them at particular places (“perching”). Darker males are more likely to patrol than pale ones, which are mainly territorial perchers. We studied whether this morphological variation relates to thermoregulatory differences. The relationship between thoracic temperature and ambient temperature differed between the colour types under natural conditions: darker males had on average lower body temperatures than paler males. Different activities (e.g. resting, flying) and behavioural strategies (perching or patrolling) were associated with differences in thoracic temperature: patrolling males which mainly engaged in long flights and periods of basking afterwards, had lower thoracic temperatures than perching males which engaged in very short flights, fights and basking. When resting for a while thoracic temperatures did not differ between males practising different strategies. Under laboratory conditions, darker males heated up faster than pale males but there was no difference in the thoracic temperature at which they started to fly. These results indicate that thermal requirements (or general conditions) differ between the behavioural strategies, and that behavioural differences between phenotypes (colour types) relate to differences in thermal ecology. This supports the idea that darker males are better adapted to patrolling. There is no evidence that one mate-locating strategy is always superior to the other, which coincides with the observation that both strategies co-exist. More generally, this study shows that relatively small differences in colour can have a considerable effect on thermoregulation and hence on the behavioural strategies a heliothermic insect will adopt. [ABSTRACT FROM AUTHOR]