Host plant use by the Heath fritillary butterfly, Melitaea athalia: plant habitat, species and chemistry

We present a study of habitat use, oviposition plant choice, and food plant suitability for the checkerspot butterfly Melitaea athalia Rottemburg (Lepidoptera: Nymphalidae) in Åland, Finland. We found that in Åland, unlike in the mainland of Finland and many parts of its range, M. athalia flies mainly in open meadows. When offered an array of plants in a large (32 × 26 m) field cage, they predominately oviposited upon Veronica chamaedrys L., V. spicata L. and Plantago lanceolata L. (Plantaginaceae), which grow in open meadows. The relative abundance of the butterfly in Åland, and its habitat and host plant use there, may reflect local adaptation to land use practices and geology that maintain clusters of small open meadows with little successional change. At the scale of a plant patch, preferred species were used as frequently in mixed species patches as in mono-specific patches, and more oviposition occurred in open than in grassy patches. All of the host plants used by M. athalia are defended by iridoid glycosides (IGs). However, oviposition choice among species and among individual plants within species was largely independent of IG concentration. This contrast with the more discerning congener, M. cinxia, supports the idea that host discrimination decreases with increasing host range. Finally, although the adult butterflies chose specific plant species for oviposition, as larvae they performed well on twelve out of thirteen species of plants, including both known hosts and related novel plants that occur in Åland, indicating a much wider range of larval food plant species than adult oviposition species.     

Three amino acid substitutions contributing to thermostability of phosphoglucose isomerase in the Glanville fritillary butterfly

Temperature is one of the most important environmental factors that affect organisms, especially ectotherms, due to its effects on protein stability. Understanding the general rules that govern thermostability changes in proteins to adapt high-temperature environments is crucial. Here, we report the amino acid substitutions of phosphoglucose isomerase (PGI) related to thermostability in the Glanville fritillary butterfly (Melitaea cinxia, Lepidoptera: Nymphalidae). The PGI encoded by the most common allele in M. cinxia in the Chinese population (G3-PGI), which is more thermal tolerant, is more stable under heat stress than that in the Finnish population (D1-PGI). There are 5 amino acid substitutions between G3-PGI and D1-PGI. Site-directed mutagenesis revealed that the combination of amino acid substitutions of H35Q, M49T, and I64V may increase PGI thermostability. These substitutions alter the 3D structure to increase the interaction between 2 monomers of PGI. Through molecular dynamics simulations, it was found that the amino acid at site 421 is more stable in G3-PGI, confining the motion of the α-helix 420–441 and stabilizing the interaction between 2 PGI monomers. The strategy for high-temperature adaptation through these 3 amino acid substitutions is also adopted by other butterfly species (Boloria eunomia, Aglais urticae, Colias erate, and Polycaena lua) concurrent with M. cinxia in the Tianshan Mountains of China, i.e., convergent evolution in butterflies.     

新疆东部天山蝶类多样性及其垂直分布

2006-2008年研究了新疆东部天山蝶类多样性和垂直分布.结果表明:研究区域内共记录蝴蝶7科43属63种,占新疆已记录蝶类种数的24.80％,区系组成主要是古北种,占73％;其次是广布种,占27％,没有发现东洋种.其中蛱蝶科的物种数最多,为11属19种,蚬蝶科的物种数最少,只有1属1种.按海拔将生境分为5个垂直自然带,包括低山灌木草原带、山地森林草原带、亚高山草甸带、高山草甸带、垫状植被带.蝶类物种数和个体数排序为亚高山草甸带＞山地森林草原带＞低山灌木草原带＞高山草甸带＞垫状植被带.采用Shannon-Wiener指数和G-F指数对蝶类物种和科、属的多样性进行了分析评价,结果显示亚高山草甸带的蝶类多样性最为丰富,其次是山地森林草原带和低山灌木草原带,而高山草甸带和垫状植被带的蝶类多样性相对较低,物种和科、属多样性分析结果均一致.蝶类垂直分布明显,物种数和个体数随海拔变化的趋势类似,均为先增加后下降.蝶类区系成分随着海拔升高发生改变,广布种的比例逐渐降低,高山草甸带和垫状植被带只有古北种分布.研究结果显示,生境改变对蝴蝶群落影响明显,保护生境是保护蝴蝶生存的最主要措施.     

Effects of meadow suitability on female behaviour in the alpine butterfly Parnassius smintheus

Abstract  1. Many butterfly populations persist in networks of naturally fragmented habitat patches. Movement and reproductive decisions made by adult females are critical to the persistence of these populations because colonisation of extinct habitat patches in the network requires emigration of fecund adult females from their natal meadow and their subsequent establishment in the extinct patch.
2. Movement and oviposition behaviours of mated Parnassius smintheus females released in suitable meadows (a good- and a poor-quality meadow) and an unsuitable meadow were compared, to determine whether adult females consider meadow suitability for their offspring despite frequent oviposition events off the larval host plant.
3. Bootstrap and correlated random walk analyses of female step lengths and turn angles demonstrated that females flew more randomly in the unsuitable meadow than in the suitable meadows. Although females tended to turn the sharpest angle between landing sites in the good-quality meadow, and fly the smallest distance between landing sites and displace the smallest distance from the release site in the suitable meadows, no significant differences were detected in turn angle, step length, and dispersal rates between suitable and unsuitable meadows.
4. Results from female flight observations and a caged oviposition study suggest that females lay significantly more eggs in suitable habitat than in unsuitable habitat despite not ovipositing on the host plant, and support the above findings.
5. Movement and oviposition behaviours of adult female P. smintheus promote their retention within meadows that can support their offspring.     

Land-use,environment, and their impact on butterfly populations in a mountainous pastoral landscape: species richness and family-level abundance

Extensive grasslands are considered to be of high biodiversity value, but are under threat from intensification and abandonment. We studied butterfly species richness and abundance in 47 hay and grazing meadows in the Picos de Europa, northern Spain in 2004. Nine transects were walked around the perimeter of the meadows from the 1 June to 28 July with butterflies recorded to species or species-group. Land-use, abiotic, and sward variables were also recorded. Change in meadow extent was estimated by comparing a digital map of open meadows with a cadastral map with 1950s provenance. We found: A decrease in open area, mostly attributable to reduction in grazing meadows. 75 or more butterfly species with species richness principally, and positively, influenced by altitude and presence of scrub in the body of the meadow. Hay meadow management was a positive influence on richness of satyrids. When all butterflies were considered together, the only significant factor influencing abundance was Plantago lanceolata (−ve). For sub-groups of the butterfly community there was no consistent pattern, although P. lanceolata was identified as a (−ve) factor in relation to hesperiid, nymphalid, satyrid, and Viola-feeding fritillary groups. Several regression models included components that could be linked to abiotic influences (water, aspect, altitude) but many were indicative of abandonment or relaxation of management intensity (scrub, Pteridium aquilinum, Asphodelus albus), sward components, fragmentation (distance to nearest meadow, number of meadows within 100 m), and land use (hay management, summer grazing). The results are discussed in relation to changing socio-economics, including the potential impact of tourism, and the need for financial instruments to support extensive farming.     

N equals two (times five). Exploring the effects of horse rewilding on five congeneric adult butterflies

Rewilding incomplete ecosystems by using ungulate megaherbivores represents a significant potential for sustainable management of habitats of declining species. Two xeric grasslands patches in the Podyjí National Park, Czech Republic, were rewilded by a feral horse breed, the Exmoor pony, in 2018. Before this in 2017, demography, mobility, and adult habitat use of five congeneric Melitaea butterflies co-occurring at the grasslands were investigated (Vodickova et al., J. Nature Conserv. 2019). In 2021, four seasons after the rewilding, we replicated the survey to assess the effects of the horse on the butterflies. Here, we compare the results of the two surveys and investigate changes in spatial patterns of adult distribution using Ripley’s K-functions.Total numbers of captures, and estimated population sizes, were consistently lower in 2021, with the largest drop for spring-flying M. cinxia. We cannot discern whether this was due to the cold 2021 spring, or due to reduction of grasses by the horse, possibly contributing to desiccation of M. cinxia host plants. Demographic parameters such as residency/longevity and capture probability changed only little. Mobility ranking among species remained identical, but within species, some mobility characteristics changed among years. Among early summer species, M. britomartis, second most abundant in 2017, switched to the first position with M. aurelia, and these two species displayed the most notable shift in adult habitat use between the two seasons. Short thorny shrubs avoided by the horse protect M. britomartis host plants; this threatened butterfly thus did not suffer from horse presence. M. athalia, a species of woodland edges, profited from decay of conifers caused by a series of dry years; and M. didyma, forming multiple generations, from increase of its host plant. Contrary to expectations, spatial distribution of most butterflies became more aggregated within rewilded pastures, probably due to regularities in home ranges use by the horses, which restructured the vegetation in a zonal, rather than patchy, way. A considerably larger areas should be rewilded by the herbivores to fully achieve the desired beneficial effects.     

An experimental examination of the effects of habitat quality on the dispersal and local abundance of the butterfly Parnassius smintheus

Abstract 1. Nectar flower abundance was manipulated through flower removal, and sex ratio was manipulated by moving individual butterflies within a series of nine alpine meadows. The movement and abundance of the butterfly Parnassius smintheus in the meadows were monitored using mark–release–recapture methods.
2. A total of 937 butterflies, 698 males and 239 females, was captured. There were 223 observed between-meadow movements. Fifty-two per cent of males and 35% of females moved among meadows.
3. The immigration of male butterflies was related positively to nectar flowers, host plant abundance, and female butterflies. Male emigration was not affected by any of the treatments. The number of males captured was related positively to nectar flowers and host plants but not affected by sex ratio. The number of resident male butterflies was greater in meadows containing flowers and was related positively to host plant abundance, but unaffected by sex ratio.
4. Flower removal, sex ratio, and abundance of Sedum had no significant effect on the abundance, movement, or residence time for female butterflies, in part due to small sample size.
5. The fact that males immigrate to higher quality meadows suggests that male butterflies are assessing meadow quality, either by sampling meadows or potentially from a distance using olfactory cues.     

Population level correlation between pre-alighting and post-alighting host plant preference in the Glanville fritillary butterfly

1. In many populations of the Glanville fritillary butterfly Melitaea cinxia, ovipositing females exhibit a post‐alighting preference for one of the potential host plant species available. The work reported here aimed to establish whether females with different post‐alighting preferences can discriminate between their host plant species prior to alighting, and whether pre‐alighting and post‐alighting preferences are correlated at the population level. 2. Alighting and oviposition events were recorded for groups of females from six populations in greenhouse and field experiments. 3. Landing frequencies did not change with experience, indicating that M. cinxia females did not learn from previous encounters with host plants. 4. Females from populations exhibiting post‐alighting preference searched efficiently for their host plants in the sense that they landed mainly on the species on which they oviposited predominantly. Pre‐alighting and post‐alighting preferences were correlated at the population level. 5. The correlation between pre‐alighting and post‐alighting preferences helps to explain why in nature, where the host plants often occur in distinct patches, females are more likely to colonise habitat patches in which their preferred host plant is abundant.     

Resource use of specialist butterflies in agricultural landscapes: conservation lessons from the butterfly Phengaris (Maculinea) nausithous

Most of the European grassland butterfly species are dependent on species rich grasslands shaped by low intensity farming. Conservation of these specialist species in agricultural landscapes relies on knowledge of their essential resources and the spatial distribution of these resources. In The Netherlands, the dusky large blue Phengaris (Maculinea) nausithous butterflies were extinct until their reintroduction in 1990. In addition, a spontaneous recolonization of road verges in an agricultural landscape occurred in 2001 in the southern part of The Netherlands. We analyzed the use of the essential resources, both host plants and host ants, of the latter population during the summers of 2003 and 2005. First we tested whether the distribution of the butterflies during several years could be explained by both the presence of host plants as well as host ants, as we expected that the resource that limits the distribution of this species can differ between locations and over time. We found that oviposition site selection was related to the most abundant resource. While in 2003, site selection was best explained by the presence of the host ant Myrmica scabrinodis, in 2005 it was more strongly related to flowerhead availability of the host plant. We secondly compared the net displacement of individuals between the road verge population and the reintroduced population in the Moerputten meadows, since we expected that movement of individuals depends on the structure of their habitat. On the road verges, butterflies moved significantly shorter distances than on meadows, which limits the butterflies in finding their essential resources. Finally we analyzed the availability of the two essential resources in the surroundings of the road verge population. Given the short net displacement distances and the adverse landscape features for long-distance dispersal, this landscape analysis suggests that the Phengaris population at the Posterholt site is trapped on the recently recolonized road verges. These results highlight the importance of assessing the availability of essential resources across different years and locations relative to the movement of the butterflies, and the necessity to careful manage these resources for the conservation of specialist species in agricultural landscapes, such as this butterfly species.     

Life history of the Glanville fritillary butterfly in fragmented versus continuous landscapes

Habitat loss and fragmentation threaten the long‐term viability of innumerable species of plants and animals. At the same time, habitat fragmentation may impose strong natural selection and lead to evolution of life histories with possible consequences for demographic dynamics. The Baltic populations of the Glanville fritillary butterfly (Melitaea cinxia) inhabit regions with highly fragmented habitat (networks of small dry meadows) as well as regions with extensive continuous habitat (calcareous alvar grasslands). Here, we report the results of common garden studies on butterflies originating from two highly fragmented landscapes (FL) in Finland and Sweden and from two continuous landscapes (CL) in Sweden and Estonia, conducted in a large outdoor cage (32 by 26 m) and in the laboratory. We investigated a comprehensive set of 51 life‐history traits, including measures of larval growth and development, flight performance, and adult reproductive behavior. Seventeen of the 51 traits showed a significant difference between fragmented versus CL. Most notably, the growth rate of postdiapause larvae and several measures of flight capacity, including flight metabolic rate, were higher in butterflies from fragmented than CL. Females from CL had shorter intervals between consecutive egg clutches and somewhat higher life‐time egg production, but shorter longevity, than females from FL. These results are likely to reflect the constant opportunities for oviposition in females living in continuous habitats, while the more dispersive females from FL allocate more resources to dispersal capacity at the cost of egg maturation rate. This study supports theoretical predictions about small population sizes and high rate of population turnover in fragmented habitats selecting for increased rate of dispersal, but the results also indicate that many other life‐history traits apart from dispersal are affected by the degree of habitat fragmentation.     

What can sown wildflower strips contribute to butterfly conservation?: an example from a Swiss lowland agricultural landscape

The objective of this study was to compare butterfly abundances and diversity between wildflower strips and extensively used meadows to identify which butterfly species can be supported by establishing wildflower strips. Butterflies were recorded along transects during one season in twenty-five sown wildflower strips and eleven extensively used meadows in a Swiss lowland agricultural landscape (600 ha). In total 1,669 butterflies of 25 species were observed (25 in the strips, 18 in meadows). This can be related to 38 species recorded in the region (lowland part of Kanton Fribourg) within the Swiss Biodiversity Monitoring Programme. In wildflower strips the number of butterflies per transect meter was significantly higher than in the meadows, but there was no significant difference in species richness. Butterfly communities, though, were quite different between the two habitat types. Habitat type, abundances of flowering plants and presence of forest within 50 m were identified as factors influencing butterfly species richness. Butterfly abundances were affected by habitat type and abundance of flowering plants. In wildflower strips, 65% of all flower visits by butterflies were observed on Origanum. It can be concluded that sown wildflower strips can support a substantial part of a regions species pool. This is mostly true for common species, but can apply to rare species when, for example, larval food plant requirements are met.     

Local and landscape effects on butterfly density in northern Idaho grasslands and forests

Understanding butterfly response to landscape context can inform conservation management and planning. We tested whether local-scale resources (host and nectar plants, canopy cover) or landscape context, measured at two scales, better explained the densities of four butterfly species. The density of Coenonympha tullia, which has host plants strongly associated with grassland habitats, was positively correlated with the amount of grassland in 0.5- and 1-km radius landscapes and only occurred in forests when they bordered grasslands. For the other species, Celastrina ladon, Cupido amyntula, and Vanessa cardui, local-scale resources better explained butterfly densities, emphasizing the importance of local habitat quality for butterflies. These three species also used host plants that were distributed more heterogeneously within and among habitat types. Our findings demonstrate the importance of host plant spatial distributions when determining the scale at which butterfly density relates to resources, and we recommend that both these distributions and landscape context be evaluated when developing butterfly monitoring programs, managing for species of concern, or modeling potential habitat.     

Interactions between habitat quality and connectivity affect immigration but not abundance or population growth of the butterfly, Parnassius smintheus

Habitat geometry has been a primary focus in studies of spatially structured systems. Recent studies have indicated that a more comprehensive approach including habitat quality may be needed, however most previous studies have neglected potential interactions between quality and geometry. We investigated the effects of habitat quality for the butterfly Parnassius smintheus among a series of 17 sub‐populations. Specifically, we examined how habitat connectivity and local nectar flower density affect dispersal, and local population abundance and growth. We first determined which flower species were potentially important by examining nectar flower electivity and then quantified nectar flower density in meadows over a five year period (2003–2007). These data along with meadow connectivity were compared to local population statistics derived from mark–recapture over the same time period. The number of immigrants to a meadow increased as meadow connectivity increased, but showed no direct relationship with nectar flower density; however, there was a significant interaction between meadow connectivity and nectar flower density such that meadows with high connectivity and a high density of nectar flowers received the greatest number of immigrants. The number of emigrants from a meadow increased with increasing habitat quality and connectivity, but showed no interactive effect. The abundance of butterflies increased with meadow connectivity, but showed no relationship with habitat quality or any interactive effect. Separate experiments showed that access to nectar flowers significantly increased female reproductive output, but not lifespan. Despite the effects on immigration and reproductive output, local population growth rates also showed no relationship to nectar flower density. Our results indicate that habitat quality can be important for immigration in spatially structured populations; however, effects of habitat quality may not necessarily translate into higher abundance or population growth. Additionally, habitat quality should not be considered independently from habitat isolation, particularly if it directly affects dispersal. Preserving or augmenting habitat quality will do little to bolster immigration or colonization without adequate connectivity.     

青海互助北山国家森林公园不同生境的蝶类多样性研究

为了进一步探讨高海拔地区蝴蝶种类和数量与生境结构之间的关系,1993–1997年每年的7月对互助北山国家森林公园不同生境类型(谷间平原、温性草原、针阔叶混交林、高寒灌丛草甸)中蝶类群落的结构、数量和多样性进行了调查。共获得蝴蝶标本4,745头,86种,隶属于8科57属。种类较丰富的类群主要有:粉蝶科豆粉蝶属(Colias)6种、菜粉蝶属(Pieris)5种、绢粉蝶属(Aporia)4种、云粉蝶属(Pontia)3种,蛱蝶科网蛱蝶属(Melitaea)3种;个体数量以粉蝶科和灰蝶科为最多。不同的生境蝶类在种类组成和个体数量上有明显差异,其中以针阔叶混交林物种数(44种)最多,谷间平原个体数量(1,969只)最多。物种多样性指数以针阔叶混交林中最高,高寒灌丛草甸最低;均匀度以针阔叶混交林最高,谷间平原最低;优势度以高寒灌丛草甸最高。从不同生境蝶类成分的特有性上分析,特有属和特有种含量高低依次为针阔叶混交林(20属24种)>高寒灌丛草甸(8属8种)>谷间平原(6属7种)>温性草原(5属6种)。不同生境类型间蝶类种类的相似性系数在0–0.4259之间。蝶类种类组成的聚类分析结果显示:谷间平原与温性草原最先聚为一类,然后与针阔叶混交林聚为一类,最后与高寒灌丛草甸聚为一类。为保护该地区的蝶类物种多样性,应加大宣传力度,建立自然保护区,继续加强本底资源调查。     

Early succession of butterfly and plant communities on set-aside fields

 Hypotheses on secondary succession of butterfly and plant communities were tested using naturally developed 1- to 4-year-old set-aside fields (n = 16), sown fields (n = 8) and old meadows (n = 4) in 1992 in South Germany. Pioneer successional fields (1st and 2nd year of succession, dominated by annuals) and early successional fields (3rd and 4th year of succession where perennials, especially grasses became dominant) had fewer plant species than mid-successional fields (old meadows). In contrast to established hypotheses, mean number of plant species decreased from 1- to 4-year-old set-aside fields. Species richness of butterfly communities did not change during the first four years of succession, but species composition changed greatly. Pioneer successional fields were characterized by (1) specialized butterflies depending on annual pioneer foodplants (e.g. Issoria lathonia), and (2) species preferring the pioneer successions despite their host plants being more abundant on early and mid-successional fields (e.g. Papilio machaon). The variability in butterfly species richness was best explained by flower abundance which was closely correlated with plant species richness. Species whose abundance was correlated with habitat connectivity were significantly smaller than species which correlated with flower abundance. Numbers of caterpillar species were correlated with numbers of adult butterfly species. Life-history features of butterflies changed significantly from pioneer to early and mid-successional fields. We found decreasing body size and migrational ability, decreasing numbers of species hibernating as imago, decreasing numbers of generations and increasing larval stage duration with age of succession, but, contrary to expectation, host plant specialization, numbers of egg-cluster laying species and egg diameter did not change with successional age. Received 18 September 1995 / Accepted: 17 July 1996     

Habitat utilization by ovipositing females and larvae of the Marsh fritillary (Euphydryas aurinia) in a mosaic of meadows and croplands

The butterfly Euphydryas aurinia occurs as a classical metapopulation in Yanjiaping village, Heibei province, China. In the patch network under study there were 38 habitat patches. Most patches were uncultivated, consisting of meadows and fallows, while others had been cultivated, i.e., used as small croplands. In the cultivated patches, the habitat for the butterfly can be classified into two types: meadow type (MTH) and cropland type (CTH). In contrast, the uncultivated habitat patches consists only of MTH. We examined the habitat utilization of ovipositing females and larvae of E. aurinia to assess the effect of mixed land use on the butterfly’s occurrence. More egg clusters and pre-hibernating larval groups were distributed throughout CTH than MTH. This dependence on CTH may be due to the preference of egg-laying females for large-sized host plants, which were mainly concentrated in CTH. Compared to the MTH, the mortality rate in CTH was lower. Therefore, for both eggs and pre-hibernating larvae, the quality of CTH was higher than that of MTH. The conditions in MTH, on the other hand, were important for the development of post-hibernation larvae. A combination of extensive farming and animal husbandry has created a mosaic of meadows and croplands in the habitats studied here, which is typical of rural areas in some developing countries. This study implies that patchy land use typical of traditional agriculture facilitates the long-term persistence of E. aurinia.     

Conserving a wetland butterfly: quantifying early lifestage survival through seasonal flooding, adult nectar, and habitat preference

Conservation of once thought extinct populations of Lycaena xanthoides in western Oregon will require specific information of how the butterfly interacts with its now rare wetland habitat. Three experiments were conducted to yield information directly applicable to wetland restoration work: (1) to quantify the survival of L. xanthoides eggs laid on inundated plants, (2) to quantify adult nectar preferences, (3) to investigate the role of adult resources and how butterflies assess habitat quality. Survival of eggs laid on inundated plants was nearly seven times lower than the survival of eggs laid on uninundated plants, indicating that eggs laid on plants that are seasonally flooded are a population sink. Adult L. xanthoides preferred an endemic native nectar plant, Grindelia integrifolia × nana, as an adult resource and used it approximately 88% of the time while other butterfly species preferred to nectar on the non-native Mentha pulegium. Adult L. xanthoides had a significantly greater short-term recapture rate in two restored study sites that had a high relative amount of Grindelia integrifolia × nana compared to a degraded site that lacked the preferred nectar source. Based on the results from the three small experiments, restoration of wetlands for L. xanthoides should concentrate plantings of host plant in non-flooded areas and propagate conspicuous patches of the preferred nectar plant.     

Indirect interaction between butterfly species mediated by a shared pupal parasitoid

Indirect interactions among species can greatly affect their abundances and the structure of the community they live in. Using a field experiment, we tested the hypothesis that congeneric butterfly species interact indirectly through a shared pupal parasitoid. We predicted that symmetrical apparent competition would lead to high parasitism of both species, and the effect would increase with regional butterfly abundance. Instead, parasitism of one host, Melitaea cinxia, was reduced in the presence of the second host, M. athalia. Parasitism of M. athalia did not differ whether or not M. cinxia was present. This pattern did not vary with regional butterfly abundance, though overall rate of parasitism did. Details of the experiment suggest that the apparent commensalism occurred because M. cinxia pupae are protected by silk tents whereas M. athalia are exposed, causing locally foraging parasitoids to favour the more accessible host where the two are present together. The local short-term apparent commensalism favouring M. cinxia opposes the landscape scale trend, in which parasitism increases where butterfly density is high. The outcome of this study illustrates short-term apparent commensalism, that host suitability can depend on relative accessibility, and that indirect interactions occurring at different scales may be in opposition.     

Habitat exploration in butterflies – an outdoor cage experiment

A large outdoor cage, measuring 7 × 30 m, was used to study the willingness of butterflies to move through unsuitable habitat in search of neighbouring patches. The area inside the cage was divided into two grassland parts by a 7 m long shady part of unsuitable habitat that the butterflies had to fly through to move between the grassland parts. In 1999 and 2000 we performed experiments on three Melitaeini species (Melitaea cinxia and Mellicta athalia were used both years and Euphydryas aurinia in 2000) and three additional species (Brenthis ino and Aphantopus hyperantus in 1999 and Clossiana euphrosyne in 2000). In both years the Melitaeini species moved at considerably lower rates through the shady part than the other species. Among the Melitaeini species Mell. athalia moved most frequently through the shady part while E. aurinia and M. cinxia moved at lower rates. The distribution of these butterflies differ from widespread to localized and the results are discussed in the context of their habitat preferences and distribution patterns.     

Stable isotopes (δD and δ13C) are geographic indicators of natal origins of monarch butterflies in eastern North America

Wing membranes of laboratory and field-reared monarch butterflies (Danaus plexippus) were analyzed for their stable-hydrogen (δD) and carbon (δ¹³C) isotope ratios to determine whether this technique could be used to identify their natal origins. We hypothesized that the hydrogen isotopic composition of monarch butterfly wing keratin would reflect the hydrogen isotope patterns of rainfall in areas of natal origin where wings were formed. Monarchs were reared in the laboratory on milkweed plants (Asclepias sp.) grown with water of known deuterium content, and, with the assistance of volunteers, on native milkweeds throughout eastern North America. The results show that the stable hydrogen isotopic composition of monarch butterflies is highly correlated with the isotopic composition of the milkweed host plants, which in turn corresponds closely with the long-term geographic patterns of deuterium in rainfall. Stable-carbon isotope values in milkweed host plants were similarly correlated with those values in monarch butterflies and showed a general pattern of enrichment along a southwest to northeast gradient bisecting the Great Lakes. These findings indicate that natal origins of migratory and wintering monarchs in Mexico can be inferred from the combined δD and δ¹³C isotopic signatures in their wings. This relationship establishes that analysis of hydrogen and carbon isotopes can be used to answer questions concerning the biology of migratory monarch butterflies and provides a new approach to tracking similar migratory movements of other organisms. Received: 1 July 1998 / Accepted: 11 November 1998