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Duration of the 4th and 5th instar of Araschnia levana larvae as explained by developmental pathway (direct vs. diapause development), temperature (17 vs. 20 • C), season (June vs. August), and sex; linear mixed models (SAS, Proc MIXED, type 3 sums of squares) with brood (progeny of one female) as a random effect.
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Seasonal polyphenisms are cases in which individuals representing generations occurring in different times of the year systematically differ in their morphological, physiological, and/or behavioral traits. Such differences are often assumed to constitute adaptive responses to seasonally varying environments, but the evidence for this is still scarc...
Contexts in source publication
Context 1
... investigate the influence of environmental factors on the lifehistory traits of the two developmental pathways, map butterfly larvae were reared in controlled conditions under a 2 × 2 × 2 crossed experimental design (Supplementary Table 1). The factors varied were (1) photoperiod-long (18L:6D, inducing direct development) or short day (12L:12D, inducing diapause development), (2) temperature (17 vs. 22 • C), and (3) host quality, manipulated by means of rearing the larvae in either early (June) or late season (August). ...Context 2
... particular, the time spent in both penultimate and final instar was 10-20% longer in individuals that developed through diapause pathway, compared to directly developing individuals. The magnitude of the difference varied, depending on temperature and season but invariably attained statistical significance ( Table 1 and Figures 1, 2). The alternative measure of development time, the period of active growth (from molting until achieving of peak body mass), was also longer in diapausing than in directly developing individuals ( Table 2). ...Context 3
... alternative measure of development time, the period of active growth (from molting until achieving of peak body mass), was also longer in diapausing than in directly developing individuals ( Table 2). Individuals reared at 17 • C had, on average, 50% longer penultimate and final instar durations and longer active growth phases than those reared at the higher temperature; late-season larvae had 5-10% longer instar durations than those reared in early season (Supplementary Table 2), and instar durations of females were 5-15% longer than in males (all differences statistically significant, Tables 1, 2). The differences in durations of the 4th and 5th instar between the developmental pathways were larger in early than in late season and at lower than at higher rearing temperatures (significant interaction terms, Tables 1, 2 and Supplementary Table 2). ...Context 4
... reared at 17 • C had, on average, 50% longer penultimate and final instar durations and longer active growth phases than those reared at the higher temperature; late-season larvae had 5-10% longer instar durations than those reared in early season (Supplementary Table 2), and instar durations of females were 5-15% longer than in males (all differences statistically significant, Tables 1, 2). The differences in durations of the 4th and 5th instar between the developmental pathways were larger in early than in late season and at lower than at higher rearing temperatures (significant interaction terms, Tables 1, 2 and Supplementary Table 2). However, when analyzed separately by rearing temperature and season, the differences between developmental pathways remained significant in all cases except in the 4th instar active growth phase of larvae reared at low temperature and in late season. ...Context 5
... when analyzed separately by rearing temperature and season, the differences between developmental pathways remained significant in all cases except in the 4th instar active growth phase of larvae reared at low temperature and in late season. In the final instar, the difference between the sexes was higher at lower than at higher rearing temperature and in late than in early season (significant interaction terms, Tables 1, 2). There was a consistent effect of photoperiod on larval growth rates (Figures 1, 2 and Supplementary Table 2). ...Similar publications
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Climate change allows species to expand polewards, but non‐changing environmental features may limit expansions. Daylength is unaffected by climate and drives life cycle timing in many animals and plants. Because daylength varies over latitudes, poleward‐expanding populations must adapt to new daylength conditions. We studied local adaptation to da...
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Citations
... Recently, a study by Esperk and Tammaru (2021) reported comparisons of various parameters of larval growth schedules in a 2 × 2 × 2 crossed design with photoperiod, temperature, and host plant quality as the varied factors [36]. Specifically (among other findings), they showed that levana larvae spent more time in both final and penultimate larval instars. ...
... Recently, a study by Esperk and Tammaru (2021) reported comparisons of various parameters of larval growth schedules in a 2 × 2 × 2 crossed design with photoperiod, temperature, and host plant quality as the varied factors [36]. Specifically (among other findings), they showed that levana larvae spent more time in both final and penultimate larval instars. ...
... The observed effects could also result directly from the diet quality, and this should be tested in future studies by co-varying light regimes and diets. In fact, a recent study by Esperk and Tammaru (2021) demonstrated that in terms of growth parameters, many between-generation differences have an adaptive nature and can, therefore, be considered part of the phenotypic response to seasonality. Similar study designs should be employed to scrutinize changes in body composition or life history traits reported in earlier studies. ...
The European map butterfly Araschnia levana is a well-known example of seasonal polyphenism. Spring and summer imagoes exhibit distinct morphological phenotypes. Key environmental factors responsible for the expression of different morphs are day length and temperature. Larval exposure to light for more than 16 h per day entails direct development and results in the adult f. prorsa summer phenotype. Less than 15.5 h per day increasingly promotes diapause and the adult f. levana spring phenotype. The phenotype depends on the timing of the release of 20-hydroxyecdysone in pupae. Release within the first days after pupation potentially inhibits the default “levana-gene-expression-profile” because pre-pupae destined for diapause or subitaneous development have unique transcriptomic programs. Moreover, multiple microRNAs and their targets are differentially regulated during the larval and pupal stages, and candidates for diapause maintenance, duration, and phenotype determination have been identified. However, the complete pathway from photoreception to timekeeping and diapause or subitaneous development remains unclear. Beside the wing polyphenism, the hormonal and epigenetic modifications of the two phenotypes also include differences in biomechanical design and immunocompetence. Here, we discuss research on the physiological and molecular basis of polyphenism in A. levana, including hormonal control, epigenetic regulation, and the effect of ecological parameters on developmental fate.
The population structure and behaviour of univoltine butterfly species have been studied intensively. However, much less is known about bivoltine species. In particular, in-depth studies of the differences in population structure, behaviour, and ecology between these two generations are largely lacking. Therefore, we here present a mark-release-recapture study of two successive generations of the fritillary butterfly Boloria selene performed in eastern Brandenburg (Germany). We revealed intersexual and intergenerational differences regarding behaviour, dispersal, population characteristics, and protandry. The observed population densities were higher in the second generation. The flight activity of females decreased in the second generation, but remained unchanged in males. This was further supported by the rate of wing decay. The first generation displayed a linear correlation between wing decay and passed time in both sexes, whereas the linear correlation was lost in second-generation females. The proportion of resting individuals in both sexes increased in the second generation, as well as the number of nectaring females. The choice of plant genera used for nectaring seems to be more specialised in the first and more opportunistic in the second generation. The average flight distances were generally higher for females than for males and overall higher in the first generation. Predictions of long-distance movements based on the inverse power function were also generally higher in females than in males but lower in the first generation. Additionally, we found protandry only in the first but not in the second generation, which might correlate with the different developmental pathways of the two generations. These remarkable differences between both generations might reflect an adaptation to the different ecological demands during the flight season and the different tasks they have, i.e. , growth in the spring season; dispersal and colonisation of new habitats during the summer season.
