Fueling the fall migration of the monarch butterfly

Monarch butterflies in eastern North America accumulate lipidsduring their fall migration to central Mexico, and use themas their energy source during a 5 month overwintering period.When and where along their migratory journey the butterfliesaccumulate these lipids has implications for the importanceof fall nectar sources in North America. We analyzed the lipidcontent of 765 summer breeding and fall migrant monarch butterfliescollected at 1 nectaring site in central Virginia over 4 years(1998–2001), and compared them with 16 additional publishedand unpublished datasets from other sites, dating back to 1941.Virginia migrants store significantly more lipid than summerbutterflies, and show significant intraseason and between-yearvariation. None of the Virginia samples, and none of the historicalsamples, with one exception, had lipid levels comparable withthose found in migrants that had reached Texas and northernMexico. This evidence suggests that upon reaching Texas, thebutterflies undergo a behavioral shift and spend more time nectaring.The one exceptional sample led us to the discovery that monarchsthat form roosts along their migratory routes have higher lipidcontents than monarchs collected while nectaring at flowers.We propose that for much of their journey monarchs are opportunisticmigrants, and the variation within and between samples reflectsbutterflies' individual experiences. The stored lipids appearto be of less importance as fuel for the butterflies' migrationthan for their survival during their overwintering period, inpart because soaring on favorable winds reduces the energeticcost of flying. The conservation of nectar plants in Texas andnorthern Mexico is crucial to sustaining the monarch's migratoryspectacle, and nectar abundance throughout eastern North Americais also important. As generalists in their selection of nectarsources and nectaring habitats, monarchs are unlikely to beaffected by small changes in plant communities. Agriculturaltransformations of natural communities in the eastern UnitedStates and Great Plains, however, and especially the extensiveplanting of genetically modified herbicide-resistant soybeansand corn, may be changing the availability of nectar for monarchsand other pollinators. This new technology is eliminating virtuallyall forbs in and surrounding agricultural fields, includingthe monarch's larval hostplants (milkweeds) and native and nonnativenectar sources. To evaluate whether changes in nectar availabilityare altering the butterflies' ability to accumulate energy,we recommend that monarchs' lipid contents be assayed annuallyat sites throughout eastern North America.     

The monarch butterfly controversy: scientific interpretations of a phenomenon

The future development and use of agricultural biotechnology has been challenged by two preliminary studies indicating potential risk to monarch butterfly populations by pollen from corn engineered to express proteins from Bacillus thuringiensis. Likewise, these studies have also challenged the way in which science should be performed, published in scientific journals and communicated to the public at large. Herein, we provide a history of the monarch controversy to date. We believe a retrospective view may be useful for providing insights into the proper roles and responsibilities of scientists, the media and public agencies and the consequences when they go awry.     

A genome befitting a monarch

The monarch butterfly is famous for its annual fall migration from eastern North America to central Mexico, but it has also been an important model for studies in long-distance migration. Now, Zhan et al. present the genome of the monarch, opening up the detailed characterization of the butterfly's navigational system and unique social life.     

Tracking climate impacts on the migratory monarch butterfly

Understanding the impacts of climate on migratory species is complicated by the fact that these species travel through several climates that may be changing in diverse ways throughout their complete migratory cycle. Most studies are not designed to tease out the direct and indirect effects of climate at various stages along the migration route. We assess the impacts of spring and summer climate conditions on breeding monarch butterflies, a species that completes its annual migration cycle over several generations. No single, broad‐scale climate metric can explain summer breeding phenology or the substantial year‐to‐year fluctuations observed in population abundances. As such, we built a Poisson regression model to help explain annual arrival times and abundances in the Midwestern United States. We incorporated the climate conditions experienced both during a spring migration/breeding phase in Texas as well as during subsequent arrival and breeding during the main recruitment period in Ohio. Using data from a state‐wide butterfly monitoring network in Ohio, our results suggest that climate acts in conflicting ways during the spring and summer seasons. High spring precipitation in Texas is associated with the largest annual population growth in Ohio and the earliest arrival to the summer breeding ground, as are intermediate spring temperatures in Texas. On the other hand, the timing of monarch arrivals to the summer breeding grounds is not affected by climate conditions within Ohio. Once in Ohio for summer breeding, precipitation has minimal impacts on overall abundances, whereas warmer summer temperatures are generally associated with the highest expected abundances, yet this effect is mitigated by the average seasonal temperature of each location in that the warmest sites receive no benefit of above average summer temperatures. Our results highlight the complex relationship between climate and performance for a migrating species and suggest that attempts to understand how monarchs will be affected by future climate conditions will be challenging.     

Male monarch butterfly spermatophore mass and mating strategies

Male monarch butterflies, Danaus plexippus, produce a spermatophore which can represent approximately 10% of their body mass. Spermatophore mass increased with age in virgin males, and with the time since last mating in non-virgin males. Male monarchs did not delay re-mating until they were able to produce a large spermatophore. Recently mated males were as likely as virgins to copulate with both virgin and non-virgin females. Monarchs provide an example of Bateman's principle, mating whenever possible, despite the non-trivial cost involved.     

The case of the monarch butterfly: a verdict is returned

A publication reporting the harmful effects on the monarch butterfly of maize genetically modified to express insecticidal delta-endotoxins from the soil bacterium Bacillus thuringiensis (Bt) caused much public interest. A series of ecologically based studies were subsequently carried out to evaluate rigorously the impact of pollen from such crops and to quantify the risks. The results demonstrated that the commercial large-scale cultivation of current Bt-maize hybrids did not pose a significant risk to the monarch population. Further studies also demonstrated that Bt-expressing crops posed little risk to other nontarget insects, including beneficial insects such as pollinators and natural enemies.     

The Larix kaempferi genome reveals new insights into wood properties

Here, through single-molecule real-time sequencing,we present a high-quality genome sequence of the Japanese larch(Larix kaempferi), a conifer species with great value for wood production and ecological afforestation. The assembled genome is 10.97 Gb in size, harboring 45,828 protein-coding genes. Of the genome, 66.8% consists of repeat sequences, of which long terminal repeat retrotransposons are dominant and make up 69.86%. We find that tandem duplications have been responsible for the expansi...     

Flight-induced compass representation in the monarch butterfly heading network

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Host plant species affects virulence in monarch butterfly parasites

1. Studies have considered how intrinsic host and parasite properties determine parasite virulence, but have largely ignored the role of extrinsic ecological factors in its expression. 2. We studied how parasite genotype and host plant species interact to determine virulence of the protozoan parasite Ophryocystis elektroscirrha (McLaughlin & Myers 1970) in the monarch butterfly Danaus plexippus L. We infected monarch larvae with one of four parasite genotypes and reared them on two milkweed species that differed in their levels of cardenolides: toxic chemicals involved in predator defence. 3. Parasite infection, replication and virulence were affected strongly by host plant species. While uninfected monarchs lived equally long on both plant species, infected monarchs suffered a greater reduction in their life spans (55% vs. 30%) on the low-cardenolide vs. the high-cardenolide host plant. These life span differences resulted from different levels of parasite replication in monarchs reared on the two plant species. 4. The virulence rank order of parasite genotypes was unaffected by host plant species, suggesting that host plant species affected parasite genotypes similarly, rather than through complex plant species-parasite genotype interactions. 5. Our results demonstrate that host ecology importantly affects parasite virulence, with implications for host-parasite dynamics in natural populations.     

Thoughts of a travelling ecologist 12.The plight of the monarch butterfly

<正>Nature conservation needs people who care about nature,and the efforts to convince people to care about the fate of nature has extensively relied on selected charismatic species,theconservation icons.One famous example is the great panda,Ailuropoda melanoleuca,well known as the World Wide Fund for Nature(WWF)logo.When it comes to invertebrates,the     

The draft genome of Actinia tenebrosa reveals insights into toxin evolution

Sea anemones have a wide array of toxic compounds (peptide toxins found in their venom) which have potential uses as therapeutics. To date, the majority of studies characterizing toxins in sea anemones have been restricted to species from the superfamily, Actinioidea. No highly complete draft genomes are currently available for this superfamily, however, highlighting our limited understanding of the genes encoding toxins in this important group. Here we have sequenced, assembled, and annotated a draft genome for Actinia tenebrosa. The genome is estimated to be approximately 255 megabases, with 31,556 protein‐coding genes. Quality metrics revealed that this draft genome matches the quality and completeness of other model cnidarian genomes, including Nematostella, Hydra, and Acropora. Phylogenomic analyses revealed strong conservation of the Cnidaria and Hexacorallia core‐gene set. However, we found that lineage‐specific gene families have undergone significant expansion events compared with shared gene families. Enrichment analysis performed for both gene ontologies, and protein domains revealed that genes encoding toxins contribute to a significant proportion of the lineage‐specific genes and gene families. The results make clear that the draft genome of A. tenebrosa will provide insight into the evolution of toxins and lineage‐specific genes, and provide an important resource for the discovery of novel biological compounds.     

Behavioural resistance against a protozoan parasite in the monarch butterfly

1. As parasites can dramatically reduce the fitness of their hosts, there should be strong selection for hosts to evolve and maintain defence mechanisms against their parasites. One way in which hosts may protect themselves against parasitism is through altered behaviours, but such defences have been much less studied than other forms of parasite resistance. 2. We studied whether monarch butterflies (Danaus plexippus L.) use altered behaviours to protect themselves and their offspring against the protozoan parasite Ophryocystis elektroscirrha (McLaughlin & Myers (1970), Journal of Protozoology, 17, p. 300). In particular, we studied whether (i) monarch larvae can avoid contact with infectious parasite spores; (ii) infected larvae preferentially consume therapeutic food plants when given a choice or increase the intake of such plants in the absence of choice; and (iii) infected female butterflies preferentially lay their eggs on medicinal plants that make their offspring less sick. 3. We found that monarch larvae were unable to avoid infectious parasite spores. Larvae were also not able to preferentially feed on therapeutic food plants or increase the ingestion of such plants. However, infected female butterflies preferentially laid their eggs on food plants that reduce parasite growth in their offspring. 4. Our results suggest that animals may use altered behaviours as a protection against parasites and that such behaviours may be limited to a single stage in the host-parasite life cycle. Our results also suggest that animals may use altered behaviours to protect their offspring instead of themselves. Thus, our study indicates that an inclusive fitness approach should be adopted to study behavioural defences against parasites.     

Nestedness in island faunas: novel insights into island biogeography through butterfly community profiles of colonization ability and migration capacity

Aim To relate variation in the migration capacity and colonization ability of island communities to island geography and species island occupancy. Location Islands off mainland Britain and Ireland. Methods Mean migration (transfer) capacity and colonization (establishment) ability (ecological indices), indexed from 12 ecological variables for 56 butterfly species living on 103 islands, were related to species nestedness, island and mainland source geography and indices using linear regression models, RLQ analysis and fourth‐corner analysis. Random creation of faunas from source species, rank correlation and rank regression were used to examine differences between island and source ecological indices, and relationships to island geography. Results Island butterfly faunas are highly nested. The two ecological indices related closely to island occupancy, nestedness rank of species, island richness and geography. The key variables related to migration capacity were island area and isolation; for colonization ability they were area, isolation and longitude. Compared with colonization ability, migration capacity was found to correlate more strongly with island species occupancy and species richness. For island faunas, the means for both ecological indices decreased, and variation increased, with increasing island species richness. Mean colonization ability and migration capacity values were significantly higher for island faunas than for mainland source faunas, but these differences decreased with island latitude. Main conclusions The nested pattern of butterfly species on islands off mainland Britain and Ireland relates strongly to colonization ability but especially to migration capacity. Differences in colonization ability among species are most obvious for large, topographically varied islands. Generalists with abundant multiple resources and greater migration capacity are found on all islands, whereas specialists are restricted to large islands with varied and long‐lived biotopes, and islands close to shore. The inference is that source–sink dynamics dominate butterfly distributions on British and Irish islands; species are capable of dispersing to new areas, but, with the exception of large and northern islands, facilities (resources) for permanent colonization are limited. The pattern of colonization ability and migration capacity is likely to be repeated for mainland areas, where such indices should provide useful independent measures for assessing the conservation status of faunas within spatial units.