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Karen S Oberhauser - One of the best experts on this subject based on the ideXlab platform.
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adult monarch Danaus plexippus abundance is higher in burned sites than in grazed sites
Frontiers in Ecology and Evolution, 2019Co-Authors: Julia B Leone, Diane L Larson, Jennifer L Larson, Nora Pennarola, Karen S OberhauserAbstract:Much of the remaining suitable habitat for monarchs (Danaus plexippus) in Minnesota is found in tallgrass prairies. We studied the association of adult monarch abundance with use of fire or grazing to manage prairies. Sites (n=20) ranged in size from 1 to 145 hectares and included land owned and managed by the Minnesota DNR, U.S. Fish and Wildlife Service, The Nature Conservancy, and private landowners. We measured Asclepias spp. (milkweeds, monarch host plants) and forb frequency in 0.5 x 2-m plots located along randomly-placed transects that were stratified to sample wet, mesic, and dry prairie types at each site. Adult butterfly surveys took place three times at each site during the summers of 2016 and 2017, using a standardized Pollard Walk (400 meters). Data were analyzed using mixed effects models. Monarchs were more abundant at sites managed with prescribed fire than with grazing. We found no difference in milkweed and forb frequency between burned and grazed prairies. There was no relationship between monarch abundance and the other predictor variables tested: milkweed frequency, site area, forb frequency, and percent prairie in a 1.5 km buffer area surrounding each site. Monarch abundance was lowest at grazed sites with high stocking rates. Our findings suggest that milkweed and forb frequency do not vary between burned and grazed sites, although we only considered land management practices for the 12 years before the study and the most recent burns occurred in 2014, two years prior to the start of our study. They also suggest that heavy grazing may have negative impacts on monarchs.
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local and cross seasonal associations of climate and land use with abundance of monarch butterflies Danaus plexippus
Ecography, 2018Co-Authors: Sarah P Saunders, Karen S Oberhauser, Wayne E Thogmartin, Leslie Ries, Elise F ZipkinAbstract:Quantifying how climate and land use factors drive population dynamics at regional scales is complex because it depends on the extent of spatial and temporal synchrony among local populations, and the integration of population processes throughout a species’ annual cycle. We modeled weekly, site-specific summer abundance (1994–2013) of monarch butterflies Danaus plexippus at sites across Illinois, USA to assess relative associations of monarch abundance with climate and land use variables during the winter, spring, and summer stages of their annual cycle. We developed negative binomial regression models to estimate monarch abundance during recruitment in Illinois as a function of local climate, site-specific crop cover, and county-level herbicide (glyphosate) application. We also incorporated cross-seasonal covariates, including annual abundance of wintering monarchs in Mexico and climate conditions during spring migration and breeding in Texas, USA. We provide the first empirical evidence of a negative association between county-level glyphosate application and local abundance of adult monarchs, particularly in areas of concentrated agriculture. However, this association was only evident during the initial years of the adoption of herbicide-resistant crops (1994–2003). We also found that wetter and, to a lesser degree, cooler springs in Texas were associated with higher summer abundances in Illinois, as were relatively cool local summer temperatures in Illinois. Site-specific abundance of monarchs averaged approximately one fewer per site from 2004–2013 than during the previous decade, suggesting a recent decline in local abundance of monarch butterflies on their summer breeding grounds in Illinois. Our results demonstrate that seasonal climate and land use are associated with trends in adult monarch abundance, and our approach highlights the value of considering fine-resolution temporal fluctuations in population-level responses to environmental conditions when inferring the dynamics of migratory species.
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Tachinid Fly (Diptera: Tachinidae) Parasitoids of Danaus plexippus (Lepidoptera: Nymphalidae)
Annals of the Entomological Society of America, 2017Co-Authors: Karen S Oberhauser, Dane Elmquist, Juan Manuel Perilla-lopez, Ilse Gebhard, Laura Lukens, John O StiremanAbstract:Extensive rearing of monarch larvae (Danaus plexippus L.) through the citizen science Monarch Larva Monitoring Project (MLMP) revealed that monarchs' primary parasitoids are flies in the family Tachinidae and that these parasitoids result in appreciable larval mortality. We document the tachinid community that attacks monarchs in the United States, evaluate their relative frequency, and examine variation in their specificity, oviposition strategy, and use of host stages. Based on results of rearing >20,000 monarchs by MLMP volunteers, overall parasitism by tachinids across life stages was 9.8% (17% for monarchs collected as fifth instars). We identified the flies that emerged from 466 monarch hosts, and found seven Tachinidae species. In decreasing order of frequency, these included Lespesia archippivora (Riley), Hyphantrophaga virilis (Aldrich & Webber), Compsilura concinnata (Meigen), Leschenaultia n. sp., Madremyia saundersii (Williston), Lespesia sp., and Nilea erecta (Coquillett). Lespesia sp., Leschenaultia n. sp., and N. erecta had not been previously reported as monarch parasitoids, and Leschenaultia n. sp. is apparently undescribed. We include new state records (Texas and Iowa) for C. concinnata. Lespesia archippivora and C. concinnata were overrepresented as parasitoids of later instars and were absent from monarchs collected as eggs, but H. virilis and Leschenaultia sp., which lay their eggs on foliage, were reared from caterpillars collected as eggs. To our knowledge, we include the first report of multiparasitism of monarchs, in which more than one parasitoid species emerged from a host. The biology of the tachinid parasitoids we identified and their relationship with monarchs is examined.
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Species distribution models for natural enemies of monarch butterfly (Danaus plexippus) larvae and pupae: distribution patterns and implications for conservation
Journal of Insect Conservation, 2016Co-Authors: Shaun M. Mccoshum, Karen S Oberhauser, Shannon L. Andreoli, Carl M. Stenoien, Kristen A. BaumAbstract:Prey populations can be strongly influenced by predators and parasitoids, and migratory prey whose distributions vary geographically throughout their breeding seasons encounter different combinations of predators and parasitoids throughout their range. North American monarch butterflies ( Danaus plexippus ) are susceptible to a wide variety of natural enemies, but the distribution of these natural enemies has not been quantified. We developed ecological niche models using environmental data to identify areas with suitable abiotic conditions for eight known natural enemies of monarchs, including six predators: Arilus cristatus, Harmonia axyridis, Monomorium minimum, Podisus maculiventris, Polistes spp., and Solenopsis geminata ; and two parasitoids: Lespesia archippivora and Pteromalus cassotis . We combined correlated suitable areas for individual predators and parasitoids to identify regions with the most predator and parasitoid species potential. The Gulf Coast, West Coast, Florida, and parts of the eastern United States are predicted to have the most natural enemy species. We suggest that future research should assess monarch mortality rates in these areas, and that monarch conservation strategies consider pressure from natural enemies.
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quasi extinction risk and population targets for the eastern migratory population of monarch butterflies Danaus plexippus
Scientific Reports, 2016Co-Authors: Brice X Semmens, Karen S Oberhauser, Darius J Semmens, Wayne E Thogmartin, Ruscena Wiederholt, Laura Lopezhoffman, James E Diffendorfer, John M Pleasants, Orley R. TaylorAbstract:The Eastern, migratory population of monarch butterflies (Danaus plexippus), an iconic North American insect, has declined by ~80% over the last decade. The monarch’s multi-generational migration between overwintering grounds in central Mexico and the summer breeding grounds in the northern U.S. and southern Canada is celebrated in all three countries and creates shared management responsibilities across North America. Here we present a novel Bayesian multivariate auto-regressive state-space model to assess quasi-extinction risk and aid in the establishment of a target population size for monarch conservation planning. We find that, given a range of plausible quasi-extinction thresholds, the population has a substantial probability of quasi-extinction, from 11–57% over 20 years, although uncertainty in these estimates is large. Exceptionally high population stochasticity, declining numbers and a small current population size act in concert to drive this risk. An approximately 5-fold increase of the monarch population size (relative to the winter of 2014–15) is necessary to halve the current risk of quasi-extinction across all thresholds considered. Conserving the monarch migration thus requires active management to reverse population declines and the establishment of an ambitious target population size goal to buffer against future environmentally driven variability.
James R. Walters - One of the best experts on this subject based on the ideXlab platform.
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population genomics reveals variable patterns of immune gene evolution in monarch butterflies Danaus plexippus
Molecular Ecology, 2021Co-Authors: Wenhao Tan, Jacobus C De Roode, Andrew J. Mongue, Nicole M Gerardo, Venkat Talla, James R. WaltersAbstract:Humoral and cellular immune responses provide animals with major defences against harmful pathogens. While it is often assumed that immune genes undergo rapid diversifying selection, this assumption has not been tested in many species. Moreover, it is likely that different classes of immune genes experience different levels of evolutionary constraint, resulting in varying selection patterns. We examined the evolutionary patterns for a set of 91 canonical immune genes of North American monarch butterflies (Danaus plexippus), using as an outgroup the closely related soldier butterfly (Danaus eresimus). As a comparison to these immune genes, we selected a set of control genes that were paired with each immune for approximate size and genomic location. As a whole, these immune genes had a significant but modest reduction in Tajima's D relative to paired-control genes, but otherwise did not show distinct patterns of population genetic variation or evolutionary rates. When further partitioning these immune genes into four functional classes (recognition, signalling, modulation, and effector), we found distinct differences among these groups. Relative to control genes, recognition genes exhibit increased nonsynonymous diversity and divergence, suggesting reduced constraints on evolution, and supporting the notion that coevolution with pathogens results in diversifying selection. In contrast, signalling genes showed an opposite pattern of reduced diversity and divergence, suggesting evolutionary constraints and conservation. Modulator and effector genes showed no statistical differences from controls. These results are consistent with patterns found in immune genes in fruit flies and Pieris butterflies, suggesting that consistent selective pressures on different classes of immune genes broadly govern the evolution of innate immunity among insects.
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transcriptomics of monarch butterflies Danaus plexippus reveals that toxic host plants alter expression of detoxification genes and down regulate a small number of immune genes
Molecular Ecology, 2019Co-Authors: Wenhao Tan, James R. Walters, Mark D Hunter, Tarik Acevedo, Erica V Harris, Tiffanie Y Alcaide, Nicole M Gerardo, Jacobus C De RoodeAbstract:Herbivorous insects have evolved many mechanisms to overcome plant chemical defences, including detoxification and sequestration. Herbivores may also use toxic plants to reduce parasite infection. Plant toxins could directly interfere with parasites or could enhance endogenous immunity. Alternatively, plant toxins could favour down-regulation of endogenous immunity by providing an alternative (exogenous) defence against parasitism. However, studies on genomewide transcriptomic responses to plant defences and the interplay between plant toxicity and parasite infection remain rare. Monarch butterflies (Danaus plexippus) are specialist herbivores of milkweeds (Asclepias spp.), which contain toxic cardenolides. Monarchs have adapted to cardenolides through multiple resistance mechanisms and can sequester cardenolides to defend against bird predators. In addition, high-cardenolide milkweeds confer monarch resistance to a specialist protozoan parasite (Ophryocystis elektroscirrha). We used this system to study the interplay between the effects of plant toxicity and parasite infection on global gene expression. We compared transcriptional profiles between parasite-infected and uninfected monarch larvae reared on two milkweed species. Our results demonstrate that monarch differentially express several hundred genes when feeding on A. curassavica and A. incarnata, two species that differ substantially in cardenolide concentrations. These differentially expressed genes include genes within multiple families of canonical insect detoxification genes, suggesting that they play a role in monarch toxin resistance and sequestration. Interestingly, we found little transcriptional response to infection. However, parasite growth was reduced in monarchs reared on A. curassavica, and in these monarchs, several immune genes were down-regulated, consistent with the hypothesis that medicinal plants can reduce reliance on endogenous immunity.
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population genomics reveals complex patterns of immune gene evolution in monarch butterflies Danaus plexippus
bioRxiv, 2019Co-Authors: Wenhao Tan, Andrew J. Mongue, Nicole M Gerardo, J C De Roode, James R. WaltersAbstract:ABSTRACT Immune genes presumably rapidly evolve as pathogens exert strong selection pressures on host defense, but the evolution of immune genes is also constrained by trade-offs with other biological functions and shaped by the environmental context. Thus, immune genes may exhibit complex evolutionary patterns, particularly when organisms disperse to or live in variable environments. We examined the evolutionary patterns of the full set of known canonical immune genes within and among populations of monarch butterflies (Danaus plexippus), and relative to a closely related species (D. gilippus). Monarchs represent a system with a known evolutionary history, in which North American monarchs dispersed to form novel populations across the world, providing an opportunity to explore the evolution of immunity in the light of population expansion into novel environments. By analyzing a whole-genome resequencing dataset across populations, we found that immune genes as a whole do not exhibit consistent patterns of selection, differentiation, or genetic variation, but that patterns are specific to functional classes. Species comparisons between D. plexippus and D. gilippus and analyses of monarch populations both revealed consistently low levels of genetic variation in signaling genes, suggesting conservation of these genes over evolutionary time. Modulation genes showed the opposite pattern, with signatures of relaxed selection across populations. In contrast, recognition and effector genes exhibited less consistent patterns. When focusing on genes with exceptionally strong signatures of selection or differentiation, we also found population-specific patterns, consistent with the hypothesis that monarch populations do not face uniform selection pressures with respect to immune function.
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transcriptomics of monarch butterflies Danaus plexippus reveals strong differential gene expression in response to host plant toxicity but weak response to parasite infection
bioRxiv, 2019Co-Authors: Wenhao Tan, James R. Walters, Mark D Hunter, Tarik Acevedo, Erica V Harris, Tiffanie Y Alcaide, Nicole M Gerardo, Jacobus C De RoodeAbstract:ABSTRACT Herbivorous insects have evolved many mechanisms to overcome plant chemical defenses, including detoxification and sequestration. Herbivores may also use toxic plants to reduce parasite infection. Plant toxins could directly interfere with parasites or could enhance endogenous immunity. Alternatively, plant toxins could favor down-regulation of endogenous immunity by providing an alternative (exogenous) defense against parasitism. However, studies on genome-wide transcriptomic responses to plant defenses and the interplay between host plant toxicity and parasite infection remain rare. Monarch butterflies (Danaus plexippus) are specialist herbivores that feed on milkweeds (Asclepias spp.), which contain toxic cardenolides. Monarchs have adapted to cardenolides through multiple resistance mechanisms and can sequester cardenolides to defend against bird predators. In addition, high-cardenolide milkweeds confer medicinal effects to monarchs against a specialist protozoan parasite (Ophryocystis elektroscirrha). We used this system to study the interplay between the effects of plant toxicity and parasite infection on global gene expression. Our results demonstrate that monarch larvae differentially express several hundred genes when feeding on A. curassavica and A. incarnata, two species that are similar in nutritional content but differ substantially in cardenolide concentrations. These differentially expressed genes include genes within multiple families of canonical insect detoxification genes, suggesting that they play a role in monarch toxin resistance and sequestration. Interestingly, we found little transcriptional response to infection. However, parasite growth was reduced in monarchs reared on A. curassavica, and in these monarchs, a small number of immune genes were down-regulated, consistent with the hypothesis that medicinal plants can reduce reliance on endogenous immunity.
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Neo-sex Chromosomes in the Monarch Butterfly, Danaus plexippus.
G3: Genes Genomes Genetics, 2017Co-Authors: Andrew J. Mongue, Petr Nguyen, Anna Voleníková, James R. WaltersAbstract:We report the discovery of a neo-sex chromosome in the monarch butterfly, Danaus plexippus, and several of its close relatives. Z-linked scaffolds in the D. plexippus genome assembly were identified via sex-specific differences in Illumina sequencing coverage. Additionally, a majority of the D. plexippus genome assembly was assigned to chromosomes based on counts of one-to-one orthologs relative to the butterfly Melitaea cinxia (with replication using two other lepidopteran species), in which genome scaffolds have been mapped to linkage groups. Sequencing coverage-based assessments of Z linkage combined with homology-based chromosomal assignments provided strong evidence for a Z-autosome fusion in the Danaus lineage, involving the autosome homologous to chromosome 21 in M. cinxia. Coverage analysis also identified three notable assembly errors resulting in chimeric Z-autosome scaffolds. Cytogenetic analysis further revealed a large W chromosome that is partially euchromatic, consistent with being a neo-W chromosome. The discovery of a neo-Z and the provisional assignment of chromosome linkage for >90% of D. plexippus genes lays the foundation for novel insights concerning sex chromosome evolution in this female-heterogametic model species for functional and evolutionary genomics.
Jacobus C De Roode - One of the best experts on this subject based on the ideXlab platform.
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population genomics reveals variable patterns of immune gene evolution in monarch butterflies Danaus plexippus
Molecular Ecology, 2021Co-Authors: Wenhao Tan, Jacobus C De Roode, Andrew J. Mongue, Nicole M Gerardo, Venkat Talla, James R. WaltersAbstract:Humoral and cellular immune responses provide animals with major defences against harmful pathogens. While it is often assumed that immune genes undergo rapid diversifying selection, this assumption has not been tested in many species. Moreover, it is likely that different classes of immune genes experience different levels of evolutionary constraint, resulting in varying selection patterns. We examined the evolutionary patterns for a set of 91 canonical immune genes of North American monarch butterflies (Danaus plexippus), using as an outgroup the closely related soldier butterfly (Danaus eresimus). As a comparison to these immune genes, we selected a set of control genes that were paired with each immune for approximate size and genomic location. As a whole, these immune genes had a significant but modest reduction in Tajima's D relative to paired-control genes, but otherwise did not show distinct patterns of population genetic variation or evolutionary rates. When further partitioning these immune genes into four functional classes (recognition, signalling, modulation, and effector), we found distinct differences among these groups. Relative to control genes, recognition genes exhibit increased nonsynonymous diversity and divergence, suggesting reduced constraints on evolution, and supporting the notion that coevolution with pathogens results in diversifying selection. In contrast, signalling genes showed an opposite pattern of reduced diversity and divergence, suggesting evolutionary constraints and conservation. Modulator and effector genes showed no statistical differences from controls. These results are consistent with patterns found in immune genes in fruit flies and Pieris butterflies, suggesting that consistent selective pressures on different classes of immune genes broadly govern the evolution of innate immunity among insects.
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transcriptomics of monarch butterflies Danaus plexippus reveals that toxic host plants alter expression of detoxification genes and down regulate a small number of immune genes
Molecular Ecology, 2019Co-Authors: Wenhao Tan, James R. Walters, Mark D Hunter, Tarik Acevedo, Erica V Harris, Tiffanie Y Alcaide, Nicole M Gerardo, Jacobus C De RoodeAbstract:Herbivorous insects have evolved many mechanisms to overcome plant chemical defences, including detoxification and sequestration. Herbivores may also use toxic plants to reduce parasite infection. Plant toxins could directly interfere with parasites or could enhance endogenous immunity. Alternatively, plant toxins could favour down-regulation of endogenous immunity by providing an alternative (exogenous) defence against parasitism. However, studies on genomewide transcriptomic responses to plant defences and the interplay between plant toxicity and parasite infection remain rare. Monarch butterflies (Danaus plexippus) are specialist herbivores of milkweeds (Asclepias spp.), which contain toxic cardenolides. Monarchs have adapted to cardenolides through multiple resistance mechanisms and can sequester cardenolides to defend against bird predators. In addition, high-cardenolide milkweeds confer monarch resistance to a specialist protozoan parasite (Ophryocystis elektroscirrha). We used this system to study the interplay between the effects of plant toxicity and parasite infection on global gene expression. We compared transcriptional profiles between parasite-infected and uninfected monarch larvae reared on two milkweed species. Our results demonstrate that monarch differentially express several hundred genes when feeding on A. curassavica and A. incarnata, two species that differ substantially in cardenolide concentrations. These differentially expressed genes include genes within multiple families of canonical insect detoxification genes, suggesting that they play a role in monarch toxin resistance and sequestration. Interestingly, we found little transcriptional response to infection. However, parasite growth was reduced in monarchs reared on A. curassavica, and in these monarchs, several immune genes were down-regulated, consistent with the hypothesis that medicinal plants can reduce reliance on endogenous immunity.
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transcriptomics of monarch butterflies Danaus plexippus reveals strong differential gene expression in response to host plant toxicity but weak response to parasite infection
bioRxiv, 2019Co-Authors: Wenhao Tan, James R. Walters, Mark D Hunter, Tarik Acevedo, Erica V Harris, Tiffanie Y Alcaide, Nicole M Gerardo, Jacobus C De RoodeAbstract:ABSTRACT Herbivorous insects have evolved many mechanisms to overcome plant chemical defenses, including detoxification and sequestration. Herbivores may also use toxic plants to reduce parasite infection. Plant toxins could directly interfere with parasites or could enhance endogenous immunity. Alternatively, plant toxins could favor down-regulation of endogenous immunity by providing an alternative (exogenous) defense against parasitism. However, studies on genome-wide transcriptomic responses to plant defenses and the interplay between host plant toxicity and parasite infection remain rare. Monarch butterflies (Danaus plexippus) are specialist herbivores that feed on milkweeds (Asclepias spp.), which contain toxic cardenolides. Monarchs have adapted to cardenolides through multiple resistance mechanisms and can sequester cardenolides to defend against bird predators. In addition, high-cardenolide milkweeds confer medicinal effects to monarchs against a specialist protozoan parasite (Ophryocystis elektroscirrha). We used this system to study the interplay between the effects of plant toxicity and parasite infection on global gene expression. Our results demonstrate that monarch larvae differentially express several hundred genes when feeding on A. curassavica and A. incarnata, two species that are similar in nutritional content but differ substantially in cardenolide concentrations. These differentially expressed genes include genes within multiple families of canonical insect detoxification genes, suggesting that they play a role in monarch toxin resistance and sequestration. Interestingly, we found little transcriptional response to infection. However, parasite growth was reduced in monarchs reared on A. curassavica, and in these monarchs, a small number of immune genes were down-regulated, consistent with the hypothesis that medicinal plants can reduce reliance on endogenous immunity.
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the effects of milkweed induced defense on parasite resistance in monarch butterflies Danaus plexippus
Journal of Chemical Ecology, 2018Co-Authors: Wenhao Tan, Mark D Hunter, Leiling Tao, Kevin M Hoang, Jacobus C De RoodeAbstract:Many plants express induced defenses against herbivores through increasing the production of toxic secondary chemicals following damage. Phytochemical induction can directly or indirectly affect other organisms within the community. In tri-trophic systems, increased concentrations of plant toxins could be detrimental to plants if herbivores can sequester these toxins as protective chemicals for themselves. Thus, through trophic interactions, induction can lead to either positive or negative effects on plant fitness. We examined the effects of milkweed (Asclepias spp.) induced defenses on the resistance of monarch caterpillars (Danaus plexippus) to a protozoan parasite (Ophryocystis elektroscirrha). Milkweeds contain toxic secondary chemicals called cardenolides, higher concentrations of which are associated with reduced parasite growth. Previous work showed that declines in foliar cardenolides caused by aphid attack render monarch caterpillars more susceptible to infection. Here, we ask whether cardenolide induction by monarchs increases monarch resistance to disease. We subjected the high-cardenolide milkweed A. curassavica and the low-cardenolide A. syriaca to caterpillar grazing, and reared infected and uninfected caterpillars on these plants. As expected, monarchs suffered less parasite growth and disease when reared on A. curassavica than on A. syriaca. We also found that herbivory increased cardenolide concentrations in A. curassavica, but not A. syriaca. However, cardenolide induction in A. curassavica was insufficient to influence monarch resistance to the parasite. Our results suggest that interspecific variation in cardenolide concentration is a more important driver of parasite defense than plasticity via induced defenses in this tri-trophic system.
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strength in numbers high parasite burdens increase transmission of a protozoan parasite of monarch butterflies Danaus plexippus
Oecologia, 2009Co-Authors: Jacobus C De Roode, Jean Chi, Rachel M Rarick, Sonia AltizerAbstract:Parasites often produce large numbers of offspring within their hosts. High parasite burdens are thought to be important for parasite transmission, but can also lower host fitness. We studied the protozoan Ophryocystis elektroscirrha, a common parasite of monarch butterflies (Danaus plexippus), to quantify the benefits of high parasite burdens for parasite transmission. This parasite is transmitted vertically when females scatter spores onto eggs and host plant leaves during oviposition; spores can also be transmitted between mating adults. Monarch larvae were experimentally infected and emerging adult females were mated and monitored in individual outdoor field cages. We provided females with fresh host plant material daily and quantified their lifespan and lifetime fecundity. Parasite transmission was measured by counting the numbers of parasite spores transferred to eggs and host plant leaves. We also quantified spores transferred from infected females to their mating partners. Infected monarchs had shorter lifespans and lower lifetime fecundity than uninfected monarchs. Among infected females, those with higher parasite loads transmitted more parasite spores to their eggs and to host plant leaves. There was also a trend for females with greater parasite loads to transmit more spores to their mating partners. These results demonstrate that high parasite loads on infected butterflies confer a strong fitness advantage to the parasite by increasing between-host transmission.
Michelle J Solensky - One of the best experts on this subject based on the ideXlab platform.
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sperm precedence in monarch butterflies Danaus plexippus
Behavioral Ecology, 2009Co-Authors: Michelle J Solensky, Karen S OberhauserAbstract:We characterized sperm precedence in monarch butterflies (Danaus plexippus), using a series of experiments in which we manipulated male mating histories to vary spermatophore size and the number of sperm transferred. Several factors affected the outcome of sperm competition. There was a pattern of second-male sperm precedence, but second-male precedence was rarely complete, and several other factors had significant effects on paternity patterns. Larger males outcompeted smaller males when they were not matched for size. Phosphoglucose isomerase (PGI) genotype affected the outcome of sperm competition under very hot conditions. When sperm from the same pair of males competed in different females, males fared better when they transferred more sperm. These results demonstrate that sperm precedence within a species can be affected by many factors, including the circumstances under which it is measured. Key words: monarch butterflies, PGI genotype, sperm competition, sperm transfer. [Behav Ecol]
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male monarch butterflies Danaus plexippus adjust ejaculates in response to intensity of sperm competition
Animal Behaviour, 2009Co-Authors: Michelle J Solensky, Karen S OberhauserAbstract:During mating, male Lepidoptera transfer spermatophores that consist of accessory gland material, eupyrene (nucleated) sperm and apyrene sperm that is incapable of fertilizing eggs. Sexual selection theory predicts that males should allocate these materials strategically based on the risk and intensity of sperm competition. We studied the relationship between behavioural and physiological cues and material allocation by male monarch butterflies, Danaus plexippus. Males that had waited longer between matings transferred larger spermatophores and more apyrene and eupyrene sperm. Eupyrene sperm number was also correlated with female mating history, with males transferring more sperm to females that had larger amounts of spermatophore material stored from previous mates, regardless of whether this came from one or three mates. This result suggests that males use stored ejaculates to assess female mating history and increase eupyrene sperm investment under increased sperm competition intensity. Male monarchs appear to be capable of independently manipulating the different components of their ejaculates. Ejaculate allocation patterns suggest that males benefit by maximizing spermatophore size and apyrene sperm number, possibly to delay future female remating. However, males allocate more eupyrene sperm to females when sperm competition is more intense, which is consistent with predictions from recent sperm competition models.
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The Effect of Behavior and Ecology on Male Mating Success in Overwintering Monarch Butterflies (Danaus plexippus)
Journal of Insect Behavior, 2004Co-Authors: Michelle J SolenskyAbstract:Monarch butterflies (Danaus plexippus) appear to forego the chemical courtship that is typical of other danaid butterflies, and instead employ a coercive mating system. Females have been described as using resistance behaviors in response to male coercion. Much of our understanding of sexual selection in monarchs is based on observations of mating attempts that occur on the ground, but recent studies report frequent mating attempts in the tree canopy. I compared mating activity on the ground to that in the tree canopy and found that, among heterosexual mating attempts, location did not affect the likelihood of ending in copulation. This suggests that the more easily obtained data on ground attempts may reasonably approximate mating activity in the canopy. The outcome of ground attempts was influenced by vegetation structure and the position of the male relative to the female and the ground at the start of the ground phase of the mating attempt. My observations suggest that butterfly position may be correlated with male search strategy. It remains unclear whether described resistance behaviors represent female or male control. However, the data do demonstrate that attempt outcome is influenced by both behavior and ecology: male search and capture strategies may influence copulatory success, and human-induced changes to the habitat can influence monarch mating activity at overwintering sites.
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temperature induced variation in larval coloration in Danaus plexippus lepidoptera nymphalidae
Annals of The Entomological Society of America, 2003Co-Authors: Michelle J Solensky, Elizabeth LarkinAbstract:Abstract Color variation has been reported within many species of Lepidoptera, and may be important in larval thermoregulation. Researchers have reported seasonal melanization and lack of yellow pigmentation in monarch larvae (Danaus plexippus L.). While the latter results from a recessive autosomal mutation, the source of variation in larval melanization is unclear. We measured the proportion of black, white, and yellow coloration on monarch fifth instars when larvae were reared in warm (32–22°C), control (27–17°C), or cold (20–10°C) temperature treatments. We found that temperature had a significant effect on monarch larval coloration. Larvae reared in a cold environment had more black and less white and yellow pigment than those reared in a warm environment. Because coloration affects absorption of radiant energy, color variation in response to temperature may be an ectothermic adaptation to suboptimal thermal conditions.
Ryan D Norris - One of the best experts on this subject based on the ideXlab platform.
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effects of early life exposure to sublethal levels of a common neonicotinoid insecticide on the orientation and migration of monarch butterflies Danaus plexippus
The Journal of Experimental Biology, 2020Co-Authors: Alana A E Wilcox, Ryan D Norris, Amy E M Newman, Nigel E Raine, Greg W MitchellAbstract:Migratory insects use a variety of innate mechanisms to determine their orientation and maintain correct bearing. For long-distance migrants, like the monarch butterfly (Danaus plexippus), these journeys could be affected by exposure to environmental contaminants. Neonicotinoids are synthetic insecticides that work by affecting the nervous system of insects resulting in impairment of their mobility, cognitive performance and other physiological and behavioural functions. To examine how neonicotinoids might affect the ability of monarch butterflies to maintain a proper directional orientation on their ∼4,000 km migration, we grew swamp milkweed (Asclepias incarnata) in soil that was either untreated (0 ng/g: control) or mixed with low (15 ng/g of soil), or high (25 ng/g of soil) levels of the neonicotinoid clothianidin. Monarch caterpillars were raised on control or clothianidin-treated milkweed and, after pupation, either tested for orientation in a static flight simulator or radio-tracked in the wild during the fall migration period. Despite clothianidin being detectable in milkweed tissue consumed by caterpillars, there was no evidence that clothianidin influenced the orientation, vector strength (i.e., concentration of direction data around the mean), or the rate of travel of adult butterflies and nor was there evidence that morphological traits (i.e., mass and forewing length), testing time, wind speed, or temperature impacted directionality. While samples sizes for both flight simulator and radio-tracking tests were limited, our preliminary results suggest that clothianidin exposure during early caterpillar development does not affect the directed flight of adult migratory monarch butterflies or influence their orientation at the beginning of migration.
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an evaluation of studies on the potential threats contributing to the decline of eastern migratory north american monarch butterflies Danaus plexippus
Frontiers in Ecology and Evolution, 2019Co-Authors: Alana A E Wilcox, D Tyler T Flockhart, Amy E M Newman, Ryan D NorrisAbstract:The migratory monarch butterflies (Danaus plexippus) of eastern North America have undergone large-scale declines, which may be attributable to a variety of underlying causes. The uncertainty about the primary cause of declines and whether individual threats are likely to increase in the future presents challenges for developing effective conservation management and policy initiatives that aim to improve population viability. This paper identifies five potential threats and classifies these threats according to the types of studies (observational, experimental, simulation/models) and their current impact and anticipated risk. Broadly, the threats can be classified into five categories: (1) change in suitable abiotic environmental conditions; (2) deforestation in the overwintering range; (3) exposure to contaminants including the bacteria Bacillus thuringiensis, herbicides, and insecticides; (4) loss of breeding habitat; and (5) predation, parasitism, and species-specific pathogens. The vast distribution of the monarch butterfly makes it likely that population declines are attributed to a suite of interacting factors that vary spatially and temporally in their contribution. Nonetheless, the published papers we reviewed suggest the decline in suitable environmental conditions in addition to overwintering (i.e., deforestation) and breeding habitat loss are the most likely threats to continue to affect the population viability of monarch butterflies.
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Table_1_An Evaluation of Studies on the Potential Threats Contributing to the Decline of Eastern Migratory North American Monarch Butterflies (Danaus plexippus).docx
2019Co-Authors: Alana A E Wilcox, D Tyler T Flockhart, Amy E M Newman, Ryan D NorrisAbstract:The migratory monarch butterflies (Danaus plexippus) of eastern North America have undergone large-scale declines, which may be attributable to a variety of underlying causes. The uncertainty about the primary cause of declines and whether individual threats are likely to increase in the future presents challenges for developing effective conservation management and policy initiatives that aim to improve population viability. This paper identifies five potential threats and classifies these threats according to the types of studies (observational, experimental, simulation/models) and their current impact and anticipated risk. Broadly, the threats can be classified into five categories: (1) change in suitable abiotic environmental conditions; (2) deforestation in the overwintering range; (3) exposure to contaminants including the bacteria Bacillus thuringiensis, herbicides, and insecticides; (4) loss of breeding habitat; and (5) predation, parasitism, and species-specific pathogens. The vast distribution of the monarch butterfly makes it likely that population declines are attributed to a suite of interacting factors that vary spatially and temporally in their contribution. Nonetheless, the published papers we reviewed suggest the decline in suitable environmental conditions in addition to overwintering (i.e., deforestation) and breeding habitat loss are the most likely threats to continue to affect the population viability of monarch butterflies.
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experimental examination of intraspecific density dependent competition during the breeding period in monarch butterflies Danaus plexippus
PLOS ONE, 2012Co-Authors: D Tyler T Flockhart, Tara G Martin, Ryan D NorrisAbstract:A central goal of population ecology is to identify the factors that regulate population growth. Monarch butterflies (Danaus plexippus) in eastern North America re-colonize the breeding range over several generations that result in population densities that vary across space and time during the breeding season. We used laboratory experiments to measure the strength of density-dependent intraspecific competition on egg laying rate and larval survival and then applied our results to density estimates of wild monarch populations to model the strength of density dependence during the breeding season. Egg laying rates did not change with density but larvae at high densities were smaller, had lower survival, and weighed less as adults compared to lower densities. Using mean larval densities from field surveys resulted in conservative estimates of density-dependent population reduction that varied between breeding regions and different phases of the breeding season. Our results suggest the highest levels of population reduction due to density-dependent intraspecific competition occur early in the breeding season in the southern portion of the breeding range. However, we also found that the strength of density dependence could be almost five times higher depending on how many life-stages were used as part of field estimates. Our study is the first to link experimental results of a density-dependent reduction in vital rates to observed monarch densities in the wild and show that the effects of density dependent competition in monarchs varies across space and time, providing valuable information for developing robust, year-round population models in this migratory organism.
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migratory connectivity of the monarch butterfly Danaus plexippus patterns of spring re colonization in eastern north america
PLOS ONE, 2012Co-Authors: Nathan G Miller, Keith A Hobson, Leonard I Wassenaar, Ryan D NorrisAbstract: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.
