Hormonal control of seasonal-morph determination in the small copper butterfly, Lycaena phlaeas daimio Seitz.

Spring and summer morphs of Lycaena phlaeas daimio Seitz. are characterized by a wing colour of red and reddish brown, respectively.When newly ecdysed pupae destined to be summer or intermediate morphs (90 or 10%) by larval exposure to long days (long-day pupae) were decapitated or decerebrated, more than half of the operated pupae developed into intermediate and spring morphs (48 and 7%). But, in pupae destined to be spring, intermediate, or summer morphs (72, 22 or 4%) (short-day pupae) these operations did not produce any significant changes in the seasonal morph.Brains excised from newly ecdysed long-day pupae were transplanted into the abdomen of decapitated short-day pupae of the same age. The implants changed most recipients into summer and intermediate morphs (46 and 36%). However, when the brains of short-day pupae were used, no significant changes occurred in the seasonal morph.When long-day or short-day pupae were treated with 20-hydroxyecdysone just after pupation, they produced more reddish wings than those of the untreated or saline-treated controls. When the application was followed by chilling, already known to induce the reddish morph, the effects of both treatments are cumulative so that more reddish adults developed.The results indicate that the brain of long-day pupae secretes a factor causing the wing to be brownish. In the absence (or low titre) of the factor, most short-day pupae develop into spring or intermediate morphs. Furthermore, ecdysteroids make the wing more reddish, when applied to newly ecdysed pupae.     

Environmental factors controlling seasonal morph determination in the small copper butterfly, Lycaena phlaeas daimio Seitz.

Environmental factors controlling seasonal morph determination and extension of the larval stages in Lycaena phlaeas daimio were studied in field observations and laboratory experiments, using criteria based on the numbers of red scales in the wing spots. Photoperiod and temperature conditions applied during the larval period and a low-temperature (5°C) introduced in pupal period were expected to be factors affecting the seasonal morph determination: the effects were confirmed by laboratory experiments. Furthermore, the length of the larval period extended by exposure to short days at 20°C, but not at 25°C, were found to show a clear correlation with the spring morph determination, but the correlation coefficient was negative in marked contrast to the situation in Polygonia and Papilio.     

The distribution and decline of a widespread butterfly Lycaena phlaeas in a pastoral landscape

1. Ecological specialists are often regarded as most likely to be threatened by anthropogenic habitat changes but few relevant data are available on changes in the status of widespread species. 2. Grid square distribution maps have been used widely to measure rates of decline and target conservation resources but it is known that coarse grain mapping is not appropriate to identify declines in widespread species that initially contain numerous local populations per grid cell. Changes in the status of widespread species need to be quantified. 3. Present‐day habitat associations, determined from over 2000 transect counts, combined with data on historical and present‐day habitat distributions, reveal that the area of occupancy and population‐level rate of decline of the Small Copper butterfly Lycaena phlaeas is likely to have been of the order of 92 and 89% respectively, in 35 km² of North Wales. Similar data on the species' major host plants Rumex acetosa and R. acetosella indicate possible declines in area occupied of 48 and 91%. If a 1‐km² grid was applied to the landscape, and if L. phlaeas, R. acetosa, and R. acetosella had occupied all 1‐km² cells in the study area in 1901 (non‐limestone cells for R. acetosella only), their declines would only have been recorded as 15, 9, and 35% respectively. 4. Many declining ecological specialists are threatened with extinction because of their initial rarity. At a population level, however, they may or may not be declining faster than less specialised species. The results presented here illustrate that some widespread species may have declined as much as many of Britain's rarities.     

Altitudinal life-history variation and thermal adaptation in the copper butterfly Lycaena tityrus

Understanding how organisms adapt to complex environments lies at the very heart of ecology and evolutionary biology. Clinal variation in traits related to fitness suggests a contribution of directional selection, and analyzing such variation has consequently become a key element in investigating adaptive evolution. In this study we examine climatic adaptation in the temperate-zone butterfly Lycaena tityrus across replicated populations from low-, (mid-) and high-altitudes, each reared at two different temperatures. In common garden experiments, high- compared to low-altitude populations showed a longer development time accompanied by reduced larval growth rates, increased cold- but decreased heat-stress resistance, and increased flight duration across a range of ambient temperatures. In contrast, differences in morphological traits such as pupal mass or wing size were negligible, suggesting that morphology is not necessarily indicative of flight performance. While patterns in stress resistance traits suggest adaptation to local temperatures, development times between populations were associated with differences in season length (enabling a second generation at lower altitudes, while high-altitude populations are monovoltine) rather than with temperature per se. Mid-altitude populations showed either intermediate patterns or patterns resembling low-altitude populations. Plastic responses to different rearing temperatures resulted, as expected, in reduced larval and pupal development times at higher temperatures accompanied by higher growth rates and decreased pupal mass. Further, butterflies reared at a lower temperature showed reduced chill-coma recovery times and decreased heat knock-down resistance as compared to those reared at a higher temperature. In summary, this study demonstrates local adaptations to regional climates, and that environmentally-induced plasticity can be as important as genetic factors in mediating adaptive responses.     

Phylogeography, genetic diversity and conservation of the large copper butterfly Lycaena dispar in Europe

We argue that insect species conservation at large scales should take account of the distribution of genetic diversity among populations. Maintenance of genetic diversity may be vital in retaining a species' adaptive capacity and evolutionary potential. We illustrate the concept using the example of the large copper butterfly Lycaena dispar in Europe. This species has become extinct in parts of its range and is declining rapidly in others, whilst conversely, increasing in many areas. The latter has recently reduced its conservation status. Mitochondrial DNA analysis is used to construct a phylogeography from a preliminary sample set obtained from across Europe. A cytochrome b fragment of 402 base pairs was sequenced and 10 haplotypes were found. Relatedness among populations suggest that those from northern and central Europe are closely related and probably form one evolutionary significant unit (ESU) reflecting post-glacial colonization from southeast Europe. In contrast, the sample from Italy is divergent and should be considered a separate ESU. Our results, combined with ecological data, suggest that conservation action for this species should be targeted on specific regions and populations.     

Larval survival in populations of the large copper butterfly Lycaena dispar batavus

Lycaena dispar is recorded as an early case of extinction and subsequent re-introduction in the UK. However, repeated establishment attempts have not resulted in self-sustaining populations, including those having taken place at Woodwalton Fen (Cambridgeshire, UK).
Earlier studies at Woodwalton Fen showed that the highest mortalities occurred between the egg stage and resumption of larval feeding in spring.
This study was designed; firstly, to investigate factors causing field mortality during different larval stages; secondly, to compare survival on Rumex hydrolapathum foodplants in different habitat situations; and thirdly, to compare survival in a natural population (Weerribben, The Netherlands) with the introduced Woodwalton Fen population. Experiments employed exclusion cages in order to examine the relative roles of vertebrate and invertebrate natural enemies, and survival on food-plants in open fen and waterside situations was compared.
Results suggest invertebrate predation to be the dominant mortality factor acting upon pre-diapause larvae. Over the winter diapause natural enemies do not have a significant role. However during both these stages losses still occur that are unaccounted for. Extensive winter flooding appears to increase overwintering losses. Vertebrate predators cause significant mortality of post-diapause larvae.
No significant difference was found between larval survival on open fen versus waterside plants.
Comparison of introduced and native populations reveal that overwintering survival was significantly higher in the latter; potential reasons for this difference are discussed.     

The contributions of larval growth and pupal duration to protandry in the black swallowtail butterfly,Papilio polyxenes

Summary Shorter male larval and pupal durations were sufficient to produce the protandrous emergence pattern of the black swallowtail butterfly. In 9 broods observed under natural conditions, the first male was seen 7.1±6.5 days before the first female, although the peak of captures relative to the first capture was similar in both sexes. The field data supported only weakly the predictions of the Wiklund-Fagerstrom model for protandry. Some prereproductive period was necessary for males, and they were limited in how frequently they could mate. A third of the females mated more than once.Males were significantly smaller in size and weight than females in both diapausing and non-diapausing broods. Feeding experiments indicated that male larvae ate less and converted their food into biomass more efficiently than females. Female pupae contained higher proportions of fat and protein than male pupae. Differential body composition may be involved in sexual dimorphism differences in both larval and pual developmental rates. Thus, in addition to size, chemical differences in composition or metabolism may contribute to the observed natural protandry.     

Photoperiod- and temperature-dependent induction of larval diapause in a multivoltine bruchid, Bruchidius dorsalis

The wild bruchid beetle, Bruchidius dorsalis Fahraeus (Coleoptera: Bruchidae), has a multivoltine life cycle and overwinters in several developmental stages in the middle part of Japan. We investigated the incidence of diapause under different conditions of photoperiod (from L8:D16 to L16:D8) and temperature (at 20 °C and 24 °C). Our experiments revealed the following results: (1) B. dorsalis entered diapause at the final (late fourth) instar larva under short photoperiods, (2) the larval diapause incidence was dependent on temperature (critical photoperiods were 12.5 h at 20 °C and 12 h at 24 °C), (3) some individuals did not enter diapause under short-photoperiod conditions at 24 °C, and (4) the sensitive stages to the photoperiod were from the late egg stage to the early first instar larva. Based on these results, we discuss not only the evolution of a complex overwintering strategy inB. dorsalis but also the domestication process of stored-bean pests.     

Egg weight variation in the butterfly Lycaena hippothoe: more small or fewer large eggs?

Fecundity, egg weight, hatching success of eggs, and adult (offspring) weight were compared between three geographically separated populations (i.e., subspecies) of the butterfly Lycaena hippothoe. All these traits differed substantially between populations. Our data suggest that, on an interpopulational level, egg size is traded off against egg number, egg size varies independent of adult size, and there is (given equal egg size) a positive relationship between adult weight (body size) and fecundity. The significantly heavier eggs of the alpine population Lycaena hippothoe eurydame showed strikingly increased hatchability, especially at high temperatures, as compared to the other populations. However, the ultimate reasons favoring large egg size in the alpine population, whether as a result of direct selection on egg size, as a correlated response based on other selective pressures, or reflecting relaxed selection for maximized fecundity, remain to be discovered. Received: November 10, 2000 / Accepted: February 5, 2001     

Altitudinal and environmental variation in lifespan in the Copper butterfly Lycaena tityrus

1.  Variation in longevity within and between natural populations is widespread, and understanding the relative importance of environmental and genetic factors as well as their interactions in mediating such variation is crucial in longevity research.
2.  In this study lifespan of adult copper butterflies was examined in relation to altitude, temperature (20 and 27 °C), sex and adult feeding.
3.  As expected, longevity increased with decreasing temperature, and sucrose-fed butterflies had longer lifespans compared to water-fed and finally non-fed individuals. The impact of feeding, especially of having access to water or not, was larger at the higher compared to the lower temperature.
4.  Regarding altitudinal patterns, increased lifespan in high-altitude populations was largely restricted to beneficial feeding conditions, while under carbohydrate deprivation low-altitude animals lived longer, suggesting that low-altitude butterflies do better under food stress.
5.  Differences in longevity between sexes were small at 20 °C, while females lived substantially longer than males at the higher temperature. Consequently, females may be less susceptible to high temperature stress than males. Further, males suffered more from food stress than females, suggesting that females are generally more stress resistant than males.
6.  Using a full factorial design, this study demonstrates that variation in longevity is caused by several factors, and additionally by substantial interactive effects. Consequently, patterns of variation in longevity are complex, and one needs to be cautious when neglecting this source of variation, by focussing on individual factors only.     

HSP70 expression in the Copper butterfly Lycaena tityrus across altitudes and temperatures

The ability to express heat‐shock proteins (HSP) under thermal stress is an essential mechanism for ectotherms to cope with unfavourable conditions. In this study, we investigate if Copper butterflies originating from different altitudes and/or being exposed to different rearing and induction temperatures show differences in HSP70 expression. HSP70 expression increased substantially at the higher rearing temperature in low‐altitude butterflies, which might represent an adaptation to occasionally occurring heat spells. On the other hand, high‐altitude butterflies showed much less plasticity in response to rearing temperatures, and overall seem to rely more on genetically fixed thermal stress resistance. Whether the latter indicates a higher vulnerability of high‐altitude populations to global warming needs further investigation. HSP70 expression increased with both colder and warmer induction temperatures.     

Dynamic landscapes shape post‐wildfire recolonisation and genetic structure of the endangered Hermes copper (Lycaena hermes) butterfly

1. The coastal sage scrub vegetation community experiences frequent fires, so the long‐term survival of species depends on the rate of recolonisations exceeding the rate of local extinctions. Recolonisation of these post‐wildfire habitats probably requires long‐distance dispersal events. These movements can also counter detrimental impacts associated with inbreeding. 2. The Hermes copper (Lycaena hermes) is an extremely rare butterfly inhabiting coastal sage scrub adjacent to San Diego, California, USA. Habitat loss due to urbanisation and impacts of recent wildfires has greatly restricted its range, prompting the United States Fish and Wildlife Service to list the Hermes copper as a Candidate Species in 2011. 3. Surveys for Hermes copper butterflies in 2010–2013 documented only two recolonisation events following wildfires in 2003 and 2007. Larger populations were readily detected each year, but detection of smaller populations was inconsistent. 4. Amplified fragment length polymorphism was used to identify potential genetic discontinuities within this species across the landscape. Results indicated that movements across much of the landscape were possible historically. However, individuals from three peripheral populations exhibited a higher degree of differentiation, suggesting more restricted dispersal in these regions. 5. From the results, it can be concluded that historically Hermes copper butterflies were able to move among habitat patches prior to recent changes in the landscape. However, low post‐fire recolonisation rates suggest limited contemporary dispersal, probably due to recent habitat fragmentation. This fragmentation is a relatively new event, as the human population in San Diego County experienced substantial growth in the late 20th Century.     

Hormonal control of pupal coloration in the painted lady butterfly Vanessa cardui

Pupae of the painted lady butterfly Vanessa cardui exhibit pupal color polyphenism consisting of white, dark and intermediate types. We investigated environmental factors affecting pupal coloration and the physiological mechanisms underlying the control of pupal color polyphenism in this species. Over 80% of larvae reared at 16 °C developed into pupae of dark types, whereas over 82% of larvae at 32 °C developed into pupae of white types irrespective of long/short-day photoperiod conditions. When mature larvae reared at 32 °C were ligatured between thoracic and abdominal parts at three different pharate pupal stages, all of the head-thoracic parts developed into white pupae regardless of pupal stage, but all abdominal parts ligatured at the early pharate pupal stage only developed into dark pupae. These results indicate that temperature during larval stages is an important element affecting pupal coloration as an environmental cue in V. cardui, and that a factor(s) inducing white pupae is released from head-thoracic parts under conditions of high temperature. Additionally, when ligatured abdomens destined to develop into dark pupae were treated with crude extracts prepared from the central nervous system, all of the ligatured abdomens developed into white pupae at a level dependent on dose and pupal stage. These results suggest that the factor inducing white pupae is a key molecule controlling pupal color polyphenism in V. cardui.     

Response of the copper butterfly Lycaena tityrus to increased leaf nitrogen in natural food plants: evidence against the nitrogen limitation hypothesis

This study examined the effects of increased leaf N in natural food plants on oviposition, preimaginal survival, growth, and adult size of the butterfly Lycaena tityrus. Female butterflies did not discriminate between leaves of high and low N content. In accordance with previous studies, we found higher growth rates and concomitantly decreased development times at a high N level. However, because of high pupal (and larval) mortality (overall 73.0%) as well as a reduction in adult size (by ca. 8%) this was, overall, not beneficial to the butterflies. Thus, our results were not consistent with the broad interspecific trend that insect herbivore performance is positively correlated with leaf N. These findings undermine the general applicability of the N limitation hypothesis. As the detrimental effects were largely confined to the pupal and adult stages, results obtained from the larval phase only may not yield reliable results and must therefore be interpreted with caution. If negative effects of N enrichment are found more frequently in declining species inhabiting nutrient poor grassland, this will have major implications for the conservation of these species. Received: 30 November 1999 / Accepted: 14 February 2000     

Hormonal control of lutein incorporation into pupal cuticle of the butterfly Inachis and the pupal melanization reducing factor

Abstract. . Morphological colour adaptation of pupae of the butterfly Inachis io L. (Lepidoptera: Nymphalidae) is controlled by a factor which reduces cuticular melanization (Biickmann & Maisch, 1987). This so-called pupal melanization reducing factor (PMRF) is located throughout the entire central nervous system of prepupae (Stamecker et al. , 1994).
Extracts of abdominal ganglia also stimulated dose-dependently lutein incorporation into pupal cuticle. In the bioassay higher doses were required to increase cuticular lutein content than to reduce melanization. Ligatures during the prepupal stage demonstrated two different critical periods for these pigmentation effects: an early one for melanization reduction and a late one for lutein incorporation.
An initial chromatographic purification yielded only two adjacent fractions which contained both the PMRF and the stimulation of lutein incorporation activity. Therefore it is assumed that only one hormone with a dual function may be responsible for pupal pigmentation.
Lutein content was found in gut, fat body, epidermis and haemolymph of I.io. Lutein incorporation into cuticle occurred within 1.5 days of the pupal moult when the cuticle was not yet fully sclerotized. Lutein content is significantly higher in cuticle of yellow pupae than of black ones.     

Dimorphic growth patterns and sex‐specific reaction norms in the butterfly Lycaena hippothoe sumadiensis

Directly developing larvae of the butterfly Lycaena hippothoe sumadiensis exhibited two growth strategies with one cohort passing four larval instars at high growth rates, and the other five instars at lower growth rates. The 4‐instar‐cohort displayed decreased development times, in combination with slightly reduced pupal and adult weights. In addition to adjustment of growth rate, omitting a larval instar may comprise a further mechanism to decrease development time when needed. Using the 4‐instar‐cohort, sex‐related differences in reaction norms were investigated over a temperature gradient. At high temperatures, protandrous males showed early emergence at a reduced size, whereas weight of females remained similar throughout. These differences suggest that large size is more important for female than for male fitness. The pattern is similar to that previously reported for alpine L. tityrus, indicating that sex‐specific reaction norms might be widespread in species living under severe time constraints.     

Programmed cell death at the periphery of the pupal wing of the butterfly,Pieris rapae

The outline of the adult wing of lepidopteran insects (butterflies and moths) emerges as a result of disappearance of a group of cells at the periphery of the pupal wing. Histological observation of the pupal wing of Pieris rapae showed that, just after apolysis of the wing epithelium from the pupal cuticle, there occurs a rapid and localized decrease of the number of cells at the periphery of the wing. This decrease occurs through cell death, which lasts 1–1.5 days at 20°C. Dying cells lose contact with the neighbouring cells and show condensation of chromatin and cytoplasm. They then appear to be phagocytosed by neighbouring epithelial cells or discharged through the basal surface of the epithelium into the lumen within the wing and taken up by phagocytes. Fragmentation of DNA in the nuclei was detected in the dead cells or their debris. These results indicate that programmed cell death in the lepidopteran wing proceeds through a mechanism closely similar to that of apoptosis in the vertebrate.     

Temporal occurrence of the pupal melanization reducing factor during development of the butterfly, Inachis io

Abstract. . In prepupae of Inachis io L. (Lepidoptera: Nymphalidae), a pupal melanization reducing factor (PMRF) which controls morphological colour adaptation (Bückmann & Maisch, 1987) is located in the brain, suboesophageal ganglion, thoracic ganglia, and all abdominal ganglia and their closely associated neurohaemal organs (Stamecker et al , 1994)
In animals adapted to a yellow background, PMRF content decreased in all these ganglia complexes during the prepupal stage which may be due to a release of the hormone at the critical period of the melanization reducing effect. The release of PMRF apparently occurs in a slow, but continuous, manner and may be superimposed by an incessant PMRF production at the same time recognizable by reincreasing melanization scores towards the end of prepupal and beginning of pupal stage. Therefore PMRF content in ganglia were not completely exhausted. When animals were kept on a black background, such a decline of PMRF content did not occur in both posterior ganglia complexes, whereas values from brain-suboesophageal ganglion complexes were too variable.
The target cells seem to be sensitive to PMRF treatment over a wide time range of nearly 20 h from the early stage of spinning a silk mat to 13-h-old prepupae for the melanization reducing effect.
PMRF activity was also detected in first-instar larvae and in the nervous system of third-instar larvae as well as in pupae which had completed their pigmentation. Furthermore, all three parts of the adult body still contained PMRF. Possibly PMRF may have functions in larval and adult stages in addition to its effect on morphological colour adaptation.     

Sexual differences in life-history traits in the butterfly Lycaena tityrus: a comparison between direct and diapause development

During direct development the butterfly Lycaena tityrus was previously found to display sex-related reaction norms in response to temperature. Based on selection for protandry in males and fecundity selection for larger females, males favoured early emergence over large size, leading to a dramatic weight loss at higher temperatures, whereas females maintained similar weights throughout. Because males were able to avoid a weight reduction relative to females in spite of their shorter development at lower temperatures, sexual size dimorphism existed at higher temperatures only. In the present paper we compare sexual differences in life-history traits in L. tityrus between direct and diapause development at 25 °C. We demonstrate that, regardless of developmental pathway, protandry persisted and relative sexual size dimorphism, with females being larger, remained unchanged. Although diapausing individuals were less time-constrained, allowing them to grow to considerably higher final weights in both sexes, males were not able to reduce their weight loss relative to females. This is explained by the pressure to gain a developmental advantage solely during post-diapause development, whereas direct developing males may spread the burden over the whole larval period. Our results highlight the importance of considering sexual differences in selective pressures, which may influence central life-history traits in manifold ways.