Distribution of the monarch butterfly, Danaus plexippus (L.) (Lepidoptera: Nymphalidae), in western North America

The standard model for the migration of the monarch butterfly in western North America has hitherto been movement in the autumn to overwintering sites in coastal California, followed by a return inland by most individuals in the spring. This model is based largely on observational and limited tagging and recovery data. In this paper we test the model by plotting many years of museum and collection records on a monthly basis on a map of the region. Our plots suggest a movement of Oregon, Washington and other north-western populations of summer butterflies to California in the autumn, but movement of more north-easterly populations (e.g. from Idaho and Montana) along two pathways through Nevada, Utah and Arizona to Mexico. The more westerly of these two pathways may follow the Colorado River south as indicated by museum records and seasonal temperature data. The eastern pathway may enter northern Utah along the western scarp of the Wasatch Mountains and run south through Utah and Arizona. Further analysis of distributions suggests that monarch butterflies in the American West occur primarily along rivers, and there are observations indicating that autumn migrants often follow riparian corridors. More data are needed to test our new model; we suggest the nature of the data required.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 491–500.     

Spring remigration of the monarch butterfly, Danaus plexippus (Lepidoptera: Nymphalidae) in north-central Florida: estimating population parameters using mark-recapture

Monarch butterflies [Danaus plexippus) of the eastern North American population migrate each fall from die northern U.S.A. and southern Canada to overwintering sites in Mexico and return the following spring to the southeastern U.S.A. where they lay eggs and then die. The spring remigration is the least studied phase in the annual migration cycle. We therefore conducted a mark-recapture study and examined population recolonization dynamics and residence time in a north-central Florida pasture where the monarch's milkweed host plant (Asclepias humistrata) was abundant. Beginning in late March 1995 two waves of monarchs arrived, their numbers peaked at 71 individuals by mid-April, and the butterflies disappeared in early May. After arriving, the adults remained for 3–5 days, laid eggs and then continued to migrate. We also compared population sizes and arrival times in 1994 and 1996. We found no evidence of a second spring generation, which was also consistent with the deteriorating quality of the A. humistrata plants. Individuals of the new spring generation disappear shordy after eclosion. The arriving population was approximately nine times greater in 1995 than in 1996. Our findings support two recent hypodieses: (1) the bird-like migration of the monarch butterfly in North America evolved with the northward expansion and phenology of milkweeds; and (2) monarchs appear to be migratory throughout their annual cycle of several generations. By lingering for only a short time at each milkweed patch they encounter, the old monarchs returning from Mexico locate the resurgent milkweed flora over an extensive area in the southern states. Then, within less than a month, their fresh offspring continue the migration and exploit the unfolding cornucopia of milkweeds as the spring advances northward. The more we discover about the biology of this insect, the more remarkable is its annual migratory, breeding and overwintering cycle.     

Differences in phenotypic traits and migratory strategies between eastern North American monarch butterflies,Danaus plexippus (L.)

The eastern North American population of the monarch butterfly (Danaus plexippus plexippus) has different migratory routes. The majority fly to overwintering colonies in Mexico and others take an eastern route through Florida and Cuba. Monarchs migrating through Florida–Cuba do not overwinter and are mostly found nectaring and flying close to vegetation. This present study explores whether Florida–Cuba versus Mexican migrants differ in (1) phenotypic traits important for migration (e.g. wing size and condition, lipid and lean mass content, and reproductive status) and (2) migratory strategies. The monarch natal grounds (e.g. migrants versus residents) were determined through thin‐layer chromatography cardenolide fingerprint and stable isotopes (hydrogen δ²H and carbon δ¹³C). In addition, wing size and condition, lipid and lean mass, and reproductive status were determined. The results suggest that Mexican migrants are better suited for longer sustained flights and successful overwinter periods as a result of larger wings in better condition, reproductive diapause, and significant fat content. By contrast, Florida–Cuba migrants are more suited for shorter flights and opportunistic migratory strategies, given that their wings were in poor condition, as well as the active reproductive status of > 50% of these butterflies and their significantly low fat content. Eastern monarch migration is more complex and diverse than previously assumed. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Thoracic temperature,shivering, and flight in the monarch butterfly,Danaus plexippus (L.)

Summary Monarch butterflies, Danaus plexippus (L.), display a warm-up behavior characterized by wingstrokes of small amplitude. Thoracic temperature during this shivering and during fixed flight was measured by means of a smallbead thermistor inserted into the thorax. At ambient temperatures of 15–16°C, once shivering is initiated the thoracic temperature rises at a maximum rate of 1.3°C/min, and a thoracic temperature 4.0°C greater then ambient is produced (Table 1). Fixed flight at these low ambient temperatures results in a similar rate of increase in thoracic temperature, and a similar temperature excess is produced (Fig. 3). At ambient temperatures between 22 and 35°C the thoracic temperature of an animal starting to fly rises at a faster rate, 3.6°C/min, and reaches a greater excess, 7.9°C (Fig. 4). The wingbeat frequency of animals in fixed flight increases with increasing thoracic temperature (Fig. 2). In the absence of direct solar radiation, shivering typically occurs prior to flight at low ambient temperatures (13–17°C), and the resulting increase in thoracic temperature allows monarch butterflies to fly at these cool temperatures.I thank Miss Janice Ruppert and Mr. C. J. Doughty for their valuable technical assistance. The co-operation of the administrators of New Brighton Beach State Park in permitting me to collect in the park is appreciated. Financial support for this study was provided in part by a faculty research grant from the University of California.     

Migratory connectivity of the monarch butterfly (Danaus plexippus): patterns of spring re-colonization in eastern North America

Each year, millions of monarch butterflies (Danaus plexippus) migrate up to 3000 km from their overwintering grounds in central Mexico to breed in eastern North America. Malcolm et al. (1993) articulated two non-mutually exclusive hypotheses to explain how Monarchs re-colonize North America each spring. The 'successive brood' hypothesis proposes that monarchs migrate from Mexico to the Gulf Coast, lay eggs and die, leaving northern re-colonization of the breeding range to subsequent generations. The 'single sweep' hypothesis proposes that overwintering monarchs continue to migrate northward after arriving on the Gulf coast and may reach the northern portion of the breeding range, laying eggs along the way. To examine these hypotheses, we sampled monarchs throughout the northern breeding range and combined stable-hydrogen isotopes (δD) to estimate natal origin with wing wear scores to differentiate between individuals born in the current vs. previous year. Similar to Malcolm et al. (1993), we found that the majority of the northern breeding range was re-colonized by the first generation of monarchs (90%). We also estimated that a small number of individuals (10%) originated directly from Mexico and, therefore adopted a sweep strategy. Contrary to Malcolm et al. (1993), we found that 62% of monarchs sampled in the Great Lakes originated from the Central U.S., suggesting that this region is important for sustaining production in the northern breeding areas. Our results provide new evidence of re-colonization patterns in monarchs and contribute important information towards identifying productive breeding regions of this unique migratory insect.     

Population genetic structure of the butterfly Melitaea didyma (Nymphalidae) along a northern distribution range border

The population genetic structure of the butterfly Melitaea didyma was studied along the northern distribution range border in Central Germany by means of allozyme electrophoresis. Individuals were sampled from a total of 21 habitat patches from four regions, and two provinces. Sampling was designed to estimate local vs. regional differentiation. High levels of variability were found, H _e= 0.14–0.21. The mean expected sample heterozygosity from one region, Mosel, was significantly lower than from the Hammelburg region, H _e= 0.17 and 0.19, respectively. Two hierarchical levels of genetic differentiation were found. Within regions individuals sampled from different patches behaved as belonging to one population with high levels of gene flow (Hammelburg F _ST= 0.015, Mosel F _ST= 0.044), though local isolation barriers did create a substructuring of these populations. The inbreeding coefficients, F _IS, were constant over all sample levels, suggesting a similar distribution of habitat patches within regions. Between regions gene flow was limited. An isolation by distance analysis indicated that the hierarchical structure, at the provincial level, may be breaking down due to isolation of regional populations. A more general observation was that the sampling design may greatly have influenced the estimation of genetic differentiation. Depending on which samples were included, overall F _ST estimates ranged from 0.059–0.090.     

Reward Tracking and Memory Decay in the Monarch Butterfly,Danaus plexippus L. (Lepidoptera: Nymphalidae)

Due to their long‐distance migration routes and high longevity, monarch butterflies (Danaus plexippus) are likely to benefit from learning how to discriminate and remember suitable feeding resources. In this study, we assessed monarchs’ abilities to track changing nectar sources over time and to retain learned information presented in two conditioning schedules. Non‐preferred (blue and red) and preferred (yellow) artificial flowers were concomitantly offered to monarchs in a three‐phase experiment. In each phase, flowers of only one color contained sucrose solution, while the others contained water. The rewarding color was changed in each phase. Instantaneous observations were made to assess butterfly visits to each color during each phase; continuous observations over the first 90 min of a new phase allowed us to look in more detail at the transition process. Overall, monarchs tracked sucrose availability, visiting the rewarding flowers more often than the unrewarding ones, regardless of innate preferences. However, butterflies reverted to innate color preferences when the newly rewarding color was different from the initial trained color. In a second experiment, memory decay was compared for butterflies trained according to two schedules: ‘single training’ (sucrose solution in red vs. water in blue artificial flowers in one 15‐min session per day) or ‘intermittent training’ (as above, but in two 7.5‐min sessions per day). Afterwards, butterflies were tested on alternate days for a week in arrays containing unrewarding models of both colors. Following either training schedule, memory persisted for at least 3 d after reinforcement ceased. Our findings reveal that monarchs are able to change their feeding responses according to the flowers’ reward status despite innate preferences, as well as to retain flower information for about half a week regardless of the conditioning dynamics.     

Variation in thermally induced melanism in monarch butterflies (Lepidoptera: Nymphalidae) from three North American populations

• 1.As ectotherms, insects often experience varying temperatures throughout their life cycle, and some respond by becoming more or less melanistic (dark coloring) during development to increase or decrease thermal energy absorption as larvae or adults.
• 2.Monarch butterflies (Danaus plexippus) breed in temperate and tropical environments worldwide and are exposed to different average and extreme temperatures in different parts of their geographic range. In this study, we compared variation in thermally induced melanism among monarch butterflies from eastern and western North America and from South Florida.
• 3.We raised the progeny of wild-captured adult butterflies from these populations in a common garden experiment, rearing individuals in cold (19 °C), moderate (26 °C), and hot (32 °C) temperatures to examine population variation in larval and adult pigmentation.
• 4.Across all populations, monarch larvae developed the darkest coloration in the cold treatment and were lightest when reared in hot temperatures. Similar results were observed for measures of adult wing melanism, with the exception of adult females, which developed darker colored wings in warmer temperatures.
• 5.Significant population-level differences in average measures of melanism among larvae and adult butterflies were observed. Larvae from the eastern population became substantially darker in colder temperatures than S. Florida or western larvae. Western larvae were lightest overall, which might be adaptive to high temperatures experienced throughout portions of their summer breeding range. S. Florida larvae showed a lower response to cold temperatures relative to monarchs from either migratory population.
• 6.Population level differences were also observed for thermal responses in wing melanism, particularly among adult females. Moreover, we found significant family level effects for each measure of larval and adult melanism, pointing to a genetic basis or strong maternal effects influencing these traits in monarch butterflies.

     

四种松毛虫不同地理种群遗传多样性的等位酶分析

【目的】采用等位酶电泳技术对中国松毛虫属Dendrolimus 4种共9个地理种群进行遗传多样性和遗传分化研究。【方法】对6种等位酶系统乳酸脱氢酶（LDH）、苹果酸脱氢酶（MDH）、苹果酸酶（ME）、乙醇脱氢酶（ADH）、甲酸脱氢酶（FDH）、谷氨酸脱氢酶（GDH）进行聚丙烯酰胺凝胶电泳分析。【结果】在4种松毛虫9个地理居群中共检测到10个基因位点,其中4个位点为多态位点,检测到17个等位基因; 种群总体水平多态位点比率P=40%,平均有效基因数A=1.700,平均期望杂合度He=0.151,种群平均遗传距离为0.001～0.285; 其中马尾松毛虫指名亚种Dendrolimu punctatus Walker 6个居群的遗传分化度Fst=0.265,基因流Nm=0.692。4种松毛虫之间遗传关系最近的是落叶松毛虫D. superans Butler和马尾松毛虫的地理亚种赤松毛虫D. punctatus spectabilis Butler,遗传关系最远的是落叶松毛虫D. superans Butler和云南松毛虫D. houi Lajonquiere。【结论】 马尾松毛虫居群间遗传分化程度较大,基因交流较少,遗传漂变已经成为导致该物种种群分化的主要原因之一;遗传距离与地理距离存在一定相关性。     

Genetic differentiation of Diplodus sargus (Pisces: Sparidae) populations in the south-west Mediterranean

Allozyme analysis of tissue samples of 1249 white sea bream Diplodus sargus from five localities of the south-west Mediterranean revealed a high degree of genetic polymorphism. The observed heterozygosity ranged from 0.4182 (Cape of Palos) to 0.3138 (Tabarca). Several populations were characterized by unique alleles. Examination of the spatial structure was performed using Nei's distances and F- statistics, and indicated genetic differences between groups. One group, which clustered Tabarca and Guardamar, could be explained by the small geographical distance between them. Mazarrón and Cape of Palos samples showed genetic divergence from other samples (Guardamar, Tabarca and Águilas) and this difference may be as a result of local current systems and larval dispersal.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 249–261.     

Temporal and spatial variation of mortality in field populations of Danaus plexippus L. and D. chrysippus L. Larvae (Lepidoptera: Nymphalidae)

Summary Mortality estimates for the immature stages of two butterfly species, Danaus plexippus and D. chrysippus, were obtained by observing the survival of egg cohorts on different sized patches of food plants (Asclepias spp.), over a one-year period. Losses were variable (0–100%) but usually high (90% and over) throughout the year for both species. Most of the losses in both species occurred in the early stages. The mortality by the third instar accounts for 86–100% of the total losses by instar V. Accordingly both species fall into Price's (1975) type A survivorship category. The size of patches of host plants affected losses. The trend was for increasing losses with increasing patch size. A full life-budget is presented for D. plexippus and implications of the observed mortality levels for competition between the two butterfly species is discussed.     

Spatial metabolomics reveal divergent cardenolide processing in the monarch (Danaus plexippus) and the common crow butterfly (Euploea core)

Although being famous for sequestering milkweed cardenolides, the mechanism of sequestration and where cardenolides are localized in caterpillars of the monarch butterfly (Danaus plexippus, Lepidoptera: Danaini) is still unknown. While monarchs tolerate cardenolides by a resistant Na⁺/K⁺-ATPase, it is unclear how closely related species such as the nonsequestering common crow butterfly (Euploea core, Lepidoptera: Danaini) cope with these toxins. Using novel atmospheric-pressure scanning microprobe matrix-assisted laser/desorption ionization mass spectrometry imaging, we compared the distribution of cardenolides in caterpillars of D. plexippus and E. core. Specifically, we tested at which physiological scale quantitative differences between both species are mediated and how cardenolides distribute across body tissues. Whereas D. plexippus sequestered most cardenolides from milkweed (Asclepias curassavica), no cardenolides were found in the tissues of E. core. Remarkably, quantitative differences already manifest in the gut lumen: while monarchs retain and accumulate cardenolides above plant concentrations, the toxins are degraded in the gut lumen of crows. We visualized cardenolide transport over the monarch midgut epithelium and identified integument cells as the final site of storage where defences might be perceived by predators. Our study provides molecular insight into cardenolide sequestration and highlights the great potential of mass spectrometry imaging for understanding the kinetics of multiple compounds including endogenous metabolites, plant toxins, or insecticides in insects.     

Genetic relationships between Mt. Halla and Mongolian populations of Hipparchia autonoe (Lepidoptera: Nymphalidae)

Hipparchia autonoe belongs to the family Nymphalidae (Lepidoptera) and is designated as an endangered insect and national monument in Korea. It only inhabits a very restricted area on Mt. Halla but is widely distributed in several Asian countries including Mongolia. A previous study conducted to understand the genetic relationship between Mt. Halla and Mongolian H. autonoe for conservation purposes suffered from a limited number of samples. Therefore, we sequenced the DNA barcode region of an additional 36 H. autonoe individuals, combined them with previous data from 19 individuals, and performed phylogenetic and population genetic analyses. Furthermore, the internal transcribed spacer 2 (ITS2) region was also sequenced from the 36 samples as a nuclear DNA marker. The existence of independent haplotypes, sequence types, and significant F_ST estimates (P < 0.05) between Mt. Halla and Mongolian populations indicated hampered gene flow between the populations. Nevertheless, an absence of a reciprocal monophyletic group in Mt. Halla and Mongolian populations by cytochrome oxidase subunit I gene‐ and ITS2‐based phylogeny suggests that the genetic isolation of the Mt. Halla population from the Mongolian populations seemed not large enough to consider them independent genetic entities.     

High levels of allozyme variation within populations and low allozyme divergence within and among species of Hemerocallis (Liliaceae)

Thirty populations from five species of Hemerocallis in Korea were analyzed by starch gel electrophoresis to measure genetic diversity and to determine genetic population structure and the amount of genetic divergence within and between species at 12 isozyme loci. In addition, Moran's I spatial autocorrelation statistics were used to examine the spatial distribution of allozyme polymorphisms in populations of H. thunbergii and H. hakuunensis. Populations of five Korean species maintain high levels of genetic variation and little differentiation among populations and species. Mean expected heterozygosities range from 0.165 in H. hongdoensis, an island endemic, to 0.265 in H. taeanensis, and a total of 81 alleles across the 12 loci were detected in the five species. G(ST) values for each of the five species were low, ranging from 0.051 in H. taeanensis to 0.078 in H. hakuunensis. Mean intraspecific Nei's genetic identities (I) between populations of the five species were all above 0.97. However, a considerable level of heterozygote deficiencies within populations was detected, ranging from 0.242 to 0.411 measured as F(IS) statistics. This deficiencies may be due to inbreeding, limited pollen and seed dispersal, or from the pooling of subpopulations that differ in allele frequencies. A small spatial scale population substructuring (<12 m) was found in H. thunbergii and H. hakuunensis. A group of populations from each of the five previously designated Hemerocallis species (based on their morphology, ecology, and phenology) agrees with our allozyme data, though pairwise comparisons among species had high I values (from 0.862, H. middendorffii vs. H. hongdoensis, to 0.969, H. thunbergii vs. H. taeanensis). This is attributed to the presence of the same high-frequency alleles in different species at seven loci. In addition, no "diagnostic allele" that appears in all populations of one species, but is absent in other species, was detected at the 12 isozyme loci. These all suggest that species of Hemerocallis in Korea may have recently derived from an ancestor or progenitor harboring high levels of genetic diversity.     

Immature stages of the butterfly Magneuptychia libye (L.) (Lepidoptera: Nymphalidae, Satyrinae)

The immature stages of the butterfly Magneuptychia libye (L.) are described, and their morphology is compared with other Neotropical Satyrinae.     

Genetic differentiation in Hippocrepis emerus (Leguminosae): allozyme and DNA fingerprint variation in disjunct Scandinavian populations

The structure of genetic variation in disjunct Scandinavian populations of Hippocrepis emerus was studied using allozymes and DNA fingerprinting. Variation in the three native regional populations in Scandinavia was compared with that in a recently introduced population in Sweden. In contrast to the recently introduced population, the native Scandinavian isolates of H. emerus showed high levels of allozyme fixation and low levels of DNA diversity. Variation in allozymes and at DNA fingerprint loci showed closely congruent patterns of geographic variation, with pronounced differentiation between the native Norwegian and Swedish isolates of the species. The structure of genetic variation in native Scandinavian H. emerus is interpreted in terms of historical population bottlenecks and founder events during the species' postglacial immigration into Scandinavia.     

Adult movements between populations in the specialist butterfly Proclossiana eunomia (Lepidoptera, Nymphalidae)

Abstract.

• 1 The structure of local populations of a monophagous butterfly, the bog fritillary Proclossiana eunomia, was studied in a complex of suitable habitat patches separated by spruce plantations or fertilized pasture.
• 2 An unexpected high level of adult movements between habitat patches was detected by a mark—release—recapture technique. Local populations were connected by adult movements across unsuitable habitats, leading to a meta-population structure.
• 3 This evidence of the metapopulation structure of a specialist butterfly challenges the supposed relationship between habitat specialization and closed, isolated populations.
• 4 Males and females of P.eunomia exhibited different spatial behaviours; females were more likely to emigrate and dispersed further than males. These differences in spatial behaviour are related to the mating system.

     

The effect of ant association on the population genetics of the Australian butterfly Jalmenus evagoras (Lepidoptera: Lycaenidae)

Populations of the myrmecophilous lycaenid Jalmenus evagoras Donovan were assessed for genetic structure at three hierarchical spatial scales: sites, geographically-defined subpopulations, and subpopulations defined by species of mutualistic ant-associate. Estimates of Wright's FST generated from multilocus electrophoretic data revealed low, though significant, amounts of genetic structure. Most structure was observed at the level of geographic subpopulations, suggesting that adult butterflies do not exhibit preferential mating and oviposition along the lines of ant associate. The genetic structure data, together with estimates of Nei's genetic distance (D) for pairwise site and subpopulation comparisons, suggest that J. evagoras populations are spatially and temporally dynamic. These patterns are considered in the context of extinction and recolonization models. The extreme patchiness of J. evagoras populations stems from the stringent requirements of both host plant and host ant, contributing to an extinction/ recolonization process. We discuss the key parameters influencing genetic cohesion versus differentiation under an extinction/recolonization regime, including mode of butterfly dispersal, site turnover rate, and the effects of host dispersal and phenology. This system provides a model of population-level consequences of certain mutualistic interactions as well as of a class of patterns arising from an extinction/recolonization process.