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Jacobus C De Roode - One of the best experts on this subject based on the ideXlab platform.
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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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Occurrence and host specificity of a neogregarine protozoan in four milkweed butterfly hosts (Danaus spp.)
2016Co-Authors: Paola Barriga, Jacobus C De Roode, Eleanore Sternberg, Thierry Lefèvre, Sonia AltizerAbstract:Occurrence and host specificity of a neogregarine protozoan in four milkweed butterfly hosts (Danaus spp.) Paola A. Barriga1*, Eleanore D. Sternberg2,3 Thierry Lefèvre2, 4, Jacobus C. de Roode2, Sonia Altizer1 1 Odum School of Ecology, University of Georgia, Athens, GA 30602, USA 2 Biology Department, Emory University, 1510 Clifton road, Atlanta, GA 30322, USA 3 Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, PA 16802, USA 4 MIVEGEC lab (Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle), CNRS-IRD, 911, Av. Agropolis 34394 Montpellier France *Corresponding author: E-mail address: paobarriga@gmail.com Metadata The “complete survey” file compiles information about prevalence of Ophryocystis elektroscirrha (OE) infection in wild populations of four butterfly species in the family Danainae (Danaus plexippus, D. gilippus, D. eresimus, and D. petila). To collect these butterflies, milkweed and other flowering plants attractive to Danaus spp. were identified and butterflies were collected using an aerial net during nectar feeding or active flight in all the locations mentioned. Butterfly abdomens were sampled non-destructively to obtain scales and parasite spores to determine infection status. Spore load was determined by counting all of the spores in a 2.5 cm diameter transparent adhesive tape pressed against monarch abdomens and transferred to index cards as described in Altizer et al. (2000). Spore samples were identified as OE or OE-like parasites based on amber coloration and shaped as ovals with tapered ends, and, with dimensions of 10-14 mm length and 7-10 mm width (Leong et al., 1997; Sander et al., 2013). Since molecular analyses have not yet been performed to test whether OE parasites found on monarchs belong to the same species as those found on queens or other species, we categorized parasites as OE parasites when found on monarchs, and as OE-like parasites when found on other butterfly species. Samples with more than 100 spores per adhesive tape were considered heavily infected, as previous monarch experiments demonstrated that these butterflies likely ingested spores as larvae (Altizer et al., 2000). Heavily infected butterflies were marked in the infected column of the dataset as “1.” In contrast, spore loads of less than 100 spores can result from passive spore transfer between adult butterflies (De Roode et al., 2009, 2007), and we refer to butterflies with these lower numbers of spores as exposed, but not necessarily infected. Therefore, those samples were marked as no infected and represent the “0s” in the database. Data columns represent: Species: Butterfly species collected Year: Year when butterflies were collected Population: Location where the butterflies were collected Infected: 0 = no infected and 1= infected The other four files compile the results of five experiments performed in laboratory conditions to test the specificity of OE or OE-like parasites infection in D. plexippus (monarchs) and D. gilippus (queens). Specifically, Experiments 1 and 2 focused on monarch and queen hosts, challenging each species with monarch parasite strains; the first experiment used a parasite dose of 10 spores and the second experiment used a dose of 100 spores per larva. Experiments 3 and 4 focused on a fully reciprocal cross-infection design challenging monarchs and queens with parasites collected from each of the two host species. Results from Experiment 3 and 4 were pooled to analyze infection probability. For experiment 3, we further analyzed adult monarch lifespan (without pooling the data, as lifespan was not measured for experiment 4). This file is labeled as “Experiment 3 adult life span.” In Experiment 5, we challenged monarchs from each of two populations (Georgia/U.S. and Queensland/Australia) with parasites from each of three sources: monarch parasites from North Florida, monarch parasites from Australia and an OE-like parasite from the lesser wanderer (D. petilia) in Australia, to compare the specificity of parasites in relation to host species and source location. Data columns represent (on files Experiment 1 to 5, and Experiment 3 life span): Host: Butterfly species studied Treatment: Treated to emphasize that only treated butterflies were analyzed Infection: 0 = no infected and 1= infected Dose: Number of parasite spores inoculated Year: When experiments were performed Monarchp: Explains the population where monarchs were collected (Georgia, US, or Australia). Parasite: Origin of the parasite. In Experiments 3 and 4 it refers to if those were collected from monarch or queen butterflies. In Experiment 5 it refers to if collected from monarchs in Australia, Florida or from “Other butterfly” and in that case comes from Danaus petilia. Sex: whether the butterfly was male (M) or female (F) Life_span: number of days that butterflies lived.
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do healthy monarchs migrate farther tracking natal origins of parasitized vs uninfected monarch butterflies overwintering in mexico
PLOS ONE, 2015Co-Authors: Sonia Altizer, Jacobus C De Roode, Keith A Hobson, Andrew K Davis, Leonard I. WassenaarAbstract:Long-distance migration can lower parasite prevalence if strenuous journeys remove infected animals from wild populations. We examined wild monarch butterflies (Danaus plexippus) to investigate the potential costs of the protozoan Ophryocystis elektroscirrha on migratory success. We collected monarchs from two wintering sites in central Mexico to compare infection status with hydrogen isotope (δ2H) measurements as an indicator of latitude of origin at the start of fall migration. On average, uninfected monarchs had lower δ2H values than parasitized butterflies, indicating that uninfected butterflies originated from more northerly latitudes and travelled farther distances to reach Mexico. Within the infected class, monarchs with higher quantitative spore loads originated from more southerly latitudes, indicating that heavily infected monarchs originating from farther north are less likely to reach Mexico. We ruled out the alternative explanation that lower latitudes give rise to more infected monarchs prior to the onset of migration using citizen science data to examine regional differences in parasite prevalence during the summer breeding season. We also found a positive association between monarch wing area and estimated distance flown. Collectively, these results emphasize that seasonal migrations can help lower infection levels in wild animal populations. Our findings, combined with recent declines in the numbers of migratory monarchs wintering in Mexico and observations of sedentary (winter breeding) monarch populations in the southern U.S., suggest that shifts from migratory to sedentary behavior will likely lead to greater infection prevalence for North American monarchs.
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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concerns that captive breeding affects the ability of monarch butterflies to migrate
Nature, 2019Co-Authors: Karen S OberhauserAbstract:Monarch butterflies’ ability to migrate over long distances is impressive. Evidence that some monarchs reared in captivity have impaired migratory skills compared with wild monarchs has conservation implications. Captive rearing over many generations impairs migratory behaviour.
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quantifying ecosystem service flows at multiple scales across the range of a long distance migratory species
Ecosystem services, 2018Co-Authors: Karen S Oberhauser, Leslie Ries, Ruscena Wiederholt, Brice X Semmens, John B LoomisAbstract:Abstract Migratory species provide ecosystem goods and services throughout their annual cycles, often over long distances. Designing effective conservation solutions for migratory species requires knowledge of both species ecology and the socioeconomic context of their migrations. We present a framework built around the concept that migratory species act as carriers, delivering benefit flows to people throughout their annual cycle that are supported by the network of ecosystems upon which the species depend. We apply this framework to the monarch butterfly (Danaus plexippus) migration of eastern North America by calculating their spatial subsidies. Spatial subsidies are the net ecosystem service flows throughout a species’ range and a quantitative measure of the spatial mismatch between the locations where people receive most benefits and the locations of habitats that most support the species. Results indicate cultural benefits provided by monarchs in the U.S. and Canada are subsidized by migration and overwintering habitat in Mexico. At a finer scale, throughout the monarch range, habitat in rural landscapes subsidizes urban residents. Understanding the spatial distribution of benefits derived from and ecological support provided to monarchs and other migratory species offers a promising means of understanding the costs and benefits associated with conservation across jurisdictional borders.
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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.
Andrew K Davis - One of the best experts on this subject based on the ideXlab platform.
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do healthy monarchs migrate farther tracking natal origins of parasitized vs uninfected monarch butterflies overwintering in mexico
PLOS ONE, 2015Co-Authors: Sonia Altizer, Jacobus C De Roode, Keith A Hobson, Andrew K Davis, Leonard I. WassenaarAbstract:Long-distance migration can lower parasite prevalence if strenuous journeys remove infected animals from wild populations. We examined wild monarch butterflies (Danaus plexippus) to investigate the potential costs of the protozoan Ophryocystis elektroscirrha on migratory success. We collected monarchs from two wintering sites in central Mexico to compare infection status with hydrogen isotope (δ2H) measurements as an indicator of latitude of origin at the start of fall migration. On average, uninfected monarchs had lower δ2H values than parasitized butterflies, indicating that uninfected butterflies originated from more northerly latitudes and travelled farther distances to reach Mexico. Within the infected class, monarchs with higher quantitative spore loads originated from more southerly latitudes, indicating that heavily infected monarchs originating from farther north are less likely to reach Mexico. We ruled out the alternative explanation that lower latitudes give rise to more infected monarchs prior to the onset of migration using citizen science data to examine regional differences in parasite prevalence during the summer breeding season. We also found a positive association between monarch wing area and estimated distance flown. Collectively, these results emphasize that seasonal migrations can help lower infection levels in wild animal populations. Our findings, combined with recent declines in the numbers of migratory monarchs wintering in Mexico and observations of sedentary (winter breeding) monarch populations in the southern U.S., suggest that shifts from migratory to sedentary behavior will likely lead to greater infection prevalence for North American monarchs.
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measuring intraspecific variation in flight related morphology of monarch butterflies danaus plexippus which sex has the best flying gear
Journal of Insects, 2015Co-Authors: Andrew K Davis, Michael T HoldenAbstract:Optimal flight in butterflies depends on structural features of the wings and body, including wing size, flight muscle size, and wing loading. Arguably, there is no butterfly for which flight is more important than the monarch (Danaus plexippus), which undergoes long-distance migrations in North America. We examined morphological features of monarchs that would explain the apparent higher migratory success and flight ability of females over males. We examined 47 male and 45 female monarch specimens from a project where monarchs were reared under uniform conditions. We weighed individual body parts, including the thorax (flight muscle) and wings, and computed wing loading and wing thickness for all specimens. When we compared each morphological trait between sexes, we found that females did not differ from males in terms of relative thorax (wing muscle) size. Females were generally smaller than males, but females had relatively thicker wings than males for their size, which suggests greater mechanical strength. Importantly, females had significantly lower wing loading than males (7% lower). This would translate to more efficient flight, which may explain their higher migratory success. Results of this work should be useful for interpreting flight behavior and/or migration success in this and other Lepidopteran species.
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opinion conservation of monarch butterflies danaus plexippus could be enhanced with analyses and publication of citizen science tagging data
Insect Conservation and Diversity, 2015Co-Authors: Andrew K DavisAbstract:Recent declines in the size of overwintering colonies of monarch butterflies (Danaus plexippus) in eastern North America have stimulated calls for greater conservation efforts of the migratory phenomenon. Conservation decisions, however, should be guided by sound science, and the migratory phase of this population is the least-studied part of its life cycle. 2. Data from large-scale citizen science programs can help address this knowledge gap. For over 20 years, volunteers have been tagging migrating monarchs with numbered stickers from MonarchWatch (www.monarchwatch. org), who oversees the management of tagging and recovery records. These data have the potential to vastly improve scientific understanding of the migratory phase (such as identifying spatial and temporal trends in mortality) and help target conservation efforts, but this potential has not yet been fully realised, based on a review of published studies in the last 20 years. 3. Since citizen science programs are often understaffed and operate on mini- mal budgets, data analysis may not be a high priority for project staff. To stim- ulate scientific investigations using tagging data, there are alternative solutions that could be implemented including making data publicly available or soliciting assistance from external scientists. Such efforts would not only benefit research into monarch biology, but would lend scientific credibility to tagging activities. 4. Tagging monarchs is a popular activity with clear educational value. In my opinion these data could be, however, better utilised to improve the conser- vation of the migratory phenomenon itself.
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genetic factors and host traits predict spore morphology for a butterfly pathogen
Insects, 2013Co-Authors: Sarah E Sander, Sonia Altizer, Jacobus C De Roode, Andrew K DavisAbstract:Monarch butterflies (Danaus plexippus) throughout the world are commonly infected by the specialist pathogen Ophryocystis elektroscirrha (OE). This protozoan is transmitted when larvae ingest infectious stages (spores) scattered onto host plant leaves by infected adults. Parasites replicate internally during larval and pupal stages, and adult monarchs emerge covered with millions of dormant spores on the outsides of their bodies. Across multiple monarch populations, OE varies in prevalence and virulence. Here, we examined geographic and genetic variation in OE spore morphology using clonal parasite lineages derived from each of four host populations (eastern and western North America, South Florida and Hawaii). Spores were harvested from experimentally inoculated, captive-reared adult monarchs. Using light microscopy and digital image analysis, we measured the size, shape and color of 30 replicate spores per host. Analyses examined predictors of spore morphology, including parasite source population and clone, parasite load, and the following host traits: family line, sex, wing area, and wing color (orange and black pigmentation). Results showed significant differences in spore size and shape among parasite clones, suggesting genetic determinants of morphological variation. Spore size also increased with monarch wing size, and monarchs with larger and darker orange wings tended to have darker colored spores, consistent with the idea that parasite development depends on variation in host quality and resources. We found no evidence for effects of source population on variation in spore morphology. Collectively, these results provide support for heritable variation in spore morphology and a role for host traits in affecting parasite development.
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Biological Observations of Monarch Butterfly Behavior at a Migratory Stopover Site: Results from a Long-term Tagging Study in Coastal South Carolina
Journal of Insect Behavior, 2010Co-Authors: John W. Mccord, Andrew K DavisAbstract:Like most migratory species, monarch butterflies ( Danaus plexippus ) must stop frequently during their long southward migration to rest and refuel, and the places where they stop are important for the success of the migration. The behavior of monarch butterflies at migratory stopover sites has never been examined in detail. Here we present results of a long-term study of monarchs at one stopover site in coastal South Carolina where over 12,000 monarchs have been captured, measured and tagged (with numbered stickers to track recovery rates) over 13 years. Only 3 monarchs (0.023%) were recovered at the monarchs’ overwintering sites in Mexico, which is consistent with other tagging studies on the eastern coast. The migration season was longer at this site than at inland locations and monarchs continued to be captured in November and December, when most monarchs had already arrived at the overwintering areas in Mexico. In addition, there were 94 monarchs captured between Jan 1 and Mar 15, indicating that some monarchs overwinter at this site. Of all monarchs captured during the migration season, 80% were captured while nectaring and 10% while roosting. Others were basking, resting, flying and even mating. The sex ratio was male biased by three to one in all behavior categories except those captured mating. Roosting and nectaring monarchs had fresher wings than those in other behavior categories, suggesting that these are younger individuals. There were 13 observations of females ovipositing on non-native Asclepias curassavica during the fall months, which speaks to the potential for this plant to pull monarchs out of the migratory pool. Aside from these insights, this study also serves as an example of the potential that monarch tagging studies have to advance scientific understanding of monarch migration.
Keith A Hobson - One of the best experts on this subject based on the ideXlab platform.
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isotopic δ2h analysis of stored lipids in migratory and overwintering monarch butterflies danaus plexippus evidence for southern critical late stage nectaring sites
Frontiers in Ecology and Evolution, 2020Co-Authors: Keith A Hobson, Oscar R Garciarubio, Rogelio Carreratrevino, Libesha Anparasan, Kevin J Kardynal, Jeremy N Mcneil, Eligio Garciaserrano, Blanca Xiomara Mora AlvarezAbstract:Monarch butterflies (Danaus plexippus) fuel their migration and overwinter energy needs through accumulated fat stores derived from plant nectars. Determining origins of these fuels is crucial to effective conservation programs. We used stable-hydrogen (δ2H) and carbon (δ13C) isotope measurements in stored lipids of monarchs raised under laboratory conditions as a proof of principle for the isotopic spatial sourcing of stored lipids. We then applied this approach to wild specimens collected from 2015 to 2018 to infer spatial information on nectaring by fall migrants through northeast Mexico and at the Mexican overwinter sites. Migrating monarchs derived from wide geographic natal origins but lipid δ2H values from migratory cohorts were not related to natal origin. Instead, migrants exploited isotopically similar nectar sources. Distributions of lipid δ2H values in overwintering monarchs were broader and more negative by ~40‰ suggesting more transport of lipids from higher latitudes or additional nectaring while migrating at higher elevations though northeastern to central Mexico. Our work establishes a new isotopic technique for tracking origins of stored lipids in monarchs and other migratory animals and emphasizes the importance of nectar availability in the southern portion of the range, and especially the nectar corridor through central Mexico.
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mortality of monarch butterflies danaus plexippus at two highway crossing hotspots during autumn migration in northeast mexico
Frontiers in Ecology and Evolution, 2019Co-Authors: Blanca Xiomara Mora Alvarez, Rogelio Carreratrevino, Keith A HobsonAbstract:The contribution to annual mortality of migrating monarch butterflies (Danaus plexippus) due to collisions with vehicles is poorly understood but likely significant. Recent estimates based on a study in Texas suggests that mortality during autumn migration may be of the order of 2 million per year or about 3% of the population. However, MaxEnt models used in that study are not well suited to quantifying mortality at hotspots where monarchs are concentrated by topography such as canyons when crossing highways. Potentially catastrophic mortality could occur at such sites if timing of migration and weather conditions conspire to force a large proportion of the migrating population across highways at low altitude. We investigated monarch mortality 15 October to 11 November, 2018 at two highway crossings in northeastern Mexico known for their frequent and extensive collisions (La Muralla and Santa Catarina). During a 15-19 day period of migration, we collected dead and injured monarchs along a series of 500 m roadside transects. We estimated a minimum total mortality during fall migration at just these sites of about 196,560 individuals. Monarchs exhibited a diurnal pattern of passage at Santa Catarina of peaks in late morning and late afternoon. Average vehicle speeds exceeded posted 60 km/h limits designed to protect monarchs, ranging from 75.1 to 99.6 km/h at La Muralla and 86.6 to 106.8 km/h at Santa Catarina. We recommend finer-scale documentation of migration pathways and an inventory of significant highway crossing hotspots for monarchs during fall migration in northeast Mexico. Mitigative measures could include better enforced vehicle speeds at least during the short period of migration, deflection structures to raise the height of crossing monarchs and/or manipulation of habitat to lower the potential for monarchs descending to roost near key crossing points.
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expanding the isotopic toolbox to track monarch butterfly danaus plexippus origins and migration on the utility of stable oxygen isotope δ18o measurements
Frontiers in Ecology and Evolution, 2019Co-Authors: Keith A Hobson, Kevin J Kardynal, Geoff KoehlerAbstract:The measurement of naturally occurring stable hydrogen (δ2H) and carbon (δ13C) isotopes in wings of the eastern North American monarch butterflies (Danaus plexippus) have proven useful to infer natal origins of individuals overwintering in Mexico. This approach has provided a breakthrough for monarch conservation because it is the only viable means of inferring origins at continental scales. Recently, routine simultaneous analyses of tissue δ2H and δ18O of organic materials has emerged leading to questions of whether the dual measurement of these isotopes could be used to more accurately infer spatial origins even though the two isotopes are expected to be coupled due to the meteoric relationship. Such refinement would potentially increase the accuracy of isotopic assignment of wintering monarchs to natal origin. We measured a sample of 150 known natal-origin monarchs from throughout their eastern range simultaneously for both δ2H and δ18O wing values. Wing δ2H and δ18O values were correlated (r2=0.42). We found that wing δ2H values were more closely correlated with amount-weighted growing season average precipitation δ2H values predicted for natal sites (r2=0.61) compared to the relationship between wing δ18O values and amount-weighted growing season average precipitation δ18O values (r2=0.30). This suggests that monarch wing δ2H values will be generally more useful in natal assignments than δ18O values. Spatial information related to the use of deuterium excess in environmental waters was similarly found to be not useful when applied to monarch wings likely due to the considerable variance in wing δ18O values. Nonetheless, we recommend further testing of monarch wing δ2H and δ18O values from known natal sites with an emphasis on field data across a strong gradient in precipitation deuterium excess.
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patterns of parasitism in monarch butterflies during the breeding season in eastern north america
Ecological Entomology, 2018Co-Authors: D Tyler T Flockhart, Keith A Hobson, Leonard I. Wassenaar, Dara A Satterfield, Anjuli Dabydeen, Ryan D NorrisAbstract:1. Migratory behaviour can result in reduced prevalence of pathogens in host populations. Two hypotheses have been proposed to explain this relationship: (i) ‘migratory escape’, where migrants benefit from escaping pathogen accumulation in contaminated environments; and (ii) ‘migratory culling’, where the selective removal of infected individuals occurs during migration. 2. In the host–parasite system between the monarch butterfly (Danaus plexippus Linn.) and its obligate protozoan parasite Ophryocystis elektroscirrha (OE), there is evidence to support both hypotheses, particularly during the monarchs' autumn migration. However, these processes can operate simultaneously and could vary throughout the monarchs' annual migratory cycle. Assessing the relative strength for each hypothesis has not previously been done. 3. To evaluate both hypotheses, parasite infection prevalence was examined in monarchs sampled in eastern North America during April–September, and stable isotopes (δ²H, δ¹³C) were used to estimate natal origin and infer migration distance. There was stronger support for the migratory escape hypothesis, wherein infection prevalence increased over the breeding season and was higher at southern latitudes, where the breeding season tends to be longer compared with northern latitudes. Little support was found for the migratory culling hypothesis, as infection prevalence was similar whether monarchs travelled shorter or longer distances. 4. These results suggest that migration allows individuals to escape parasites not only during the autumn, as shown in previous work, but during the monarchs' spring and summer movements when they recolonise the breeding range. These results imply a potential fitness advantage to monarchs that migrate further north to exploit parasite‐free habitats.
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do healthy monarchs migrate farther tracking natal origins of parasitized vs uninfected monarch butterflies overwintering in mexico
PLOS ONE, 2015Co-Authors: Sonia Altizer, Jacobus C De Roode, Keith A Hobson, Andrew K Davis, Leonard I. WassenaarAbstract:Long-distance migration can lower parasite prevalence if strenuous journeys remove infected animals from wild populations. We examined wild monarch butterflies (Danaus plexippus) to investigate the potential costs of the protozoan Ophryocystis elektroscirrha on migratory success. We collected monarchs from two wintering sites in central Mexico to compare infection status with hydrogen isotope (δ2H) measurements as an indicator of latitude of origin at the start of fall migration. On average, uninfected monarchs had lower δ2H values than parasitized butterflies, indicating that uninfected butterflies originated from more northerly latitudes and travelled farther distances to reach Mexico. Within the infected class, monarchs with higher quantitative spore loads originated from more southerly latitudes, indicating that heavily infected monarchs originating from farther north are less likely to reach Mexico. We ruled out the alternative explanation that lower latitudes give rise to more infected monarchs prior to the onset of migration using citizen science data to examine regional differences in parasite prevalence during the summer breeding season. We also found a positive association between monarch wing area and estimated distance flown. Collectively, these results emphasize that seasonal migrations can help lower infection levels in wild animal populations. Our findings, combined with recent declines in the numbers of migratory monarchs wintering in Mexico and observations of sedentary (winter breeding) monarch populations in the southern U.S., suggest that shifts from migratory to sedentary behavior will likely lead to greater infection prevalence for North American monarchs.
Nathan P. Lemoine - One of the best experts on this subject based on the ideXlab platform.
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Effects of [i]in situ[i] climate warming on monarch caterpillar ([i]Danaus plexippus[i]) development
2020Co-Authors: Nathan P. Lemoine, Jillian N Capdevielle, John D ParkerAbstract:Climate warming will fundamentally alter basic life history strategies of many ectothermic insects. In the lab, rising temperatures increase growth rates of lepidopteran larvae, but also reduce final pupal mass and increase mortality. Using in situ field warming experiments on their natural host plants, we assessed the impact of climate warming on development of monarch (Danaus plexippus) larvae. Monarchs were reared on Asclepias tuberosa grown under 'Ambient' and 'Warmed' conditions. We quantified time to pupation, final pupal mass, and survivorship. Warming significantly decreased time to pupation, such that an increase of 1˚ C corresponded to a 0.5 day decrease in pupation time. In contrast, survivorship and pupal mass were not affected by warming. Our results indicate that climate warming will speed the developmental rate of monarchs, influencing their ecological and evolutionary dynamics. However, the effects of climate warming on larval development in other monarch populations and at different times of year should be 32 'Ambient' and 'Warmed' conditions. We quantified time to pupation, final pupal mass, and 33 survivorship. Warming significantly decreased time to pupation, such that an increase of 1˚ C 34 corresponded to a 0.5 day decrease in pupation time. In contrast, survivorship and pupal mass 35 were not affected by warming. Our results indicate that climate warming will speed the 36 developmental rate of monarchs, influencing their ecological and evolutionary dynamics. 37 However, the effects of climate warming on larval development in other monarch populations 38 and at different times of year should be investigated. Here, we report results from an in situ warming experiment designed to assess how 81 climate warming influences growth, survival, and development of monarch larvae. We 82 hypothesized that warming would reduce larval development time, as has commonly been 83 reported for monarch larvae , but would also decrease pupal mass and 84 survivorship (Zalucki 1982, York and Oberhauser 2002). In August 2014, monarch eggs and larvae were gathered from A. syriaca within nearby 109 old-growth fields. Eggs and larvae were reared in mesh cages and fed fresh A. syriaca leaves 110 daily until they reached the third instar. Larval development was checked continuously 111 throughout the day. Immediately after molting to the third instar, larvae were randomly assigned 112 to a temperature treatment ('Ambient', 'Warmed') and placed on a single A. tuberosa within a 113 randomly chosen plot (n = 15, n = 18 for 'Ambient' and 'Warmed' treatments, respectively). A 114 mesh bag was placed over the plant to retain the monarch. First or second instar larvae escaped 115 the mesh bags easily and thus were not used. If the monarch consumed the entire host plant, they 116 were transferred to another plant within the same subplot. Time to pupation was recorded as the 117 number of hours between experiment initiation and onset of chrysalis formation, and this number 118 was converted to number of days (development hour / 24). Dead individuals were recorded and 119 removed from the host plant. Chrysalids were carefully transported back to the lab and weighed 120 to obtain final pupal mass. 121 We measured three plant traits (specific leaf area (SLA), water content, and latex 122 production) to determine whether warming effects on monarch development might be mediated 123 through warming effects on plant traits. At the end of the experiment, two newly expanded 124 leaves were collected from each plant. For one leaf, we measured leaf area, obtained a fresh wet 125 mass, and then dried the leaf to obtain a dry mass. We calculated specific leaf area (SLA) as area 126 / dry mass and percent water content as (1 -dry mass (g) / fresh mass (g))*100. Using the second 127 leaf, we determined latex production by cutting the tip of the leaf and blotting all latex onto a 128 dry, pre-weighed piece of filter paper. The filter paper was dried again and latex concentration Although heaters raised temperatures of 'Warmed' plots by ~4˚ C on average, plots 132 varied considerably in temperature due to different light levels across the experimental garden 133 and varying plant biomass within each plot. We therefore measured temperature with a handheld 134 infrared thermometer in each subplot during the night at the end of the experiment. For 135 consistency, we recorded temperature of a white plastic sphere mounted 0.5 m from the ground 136 in the middle of each subplot. We then treated temperature as a quantitative, rather than 137 categorical, variable in all analyses. Note that these measures reflect relative differences in 138 temperature among plots that should be relatively constant over the experiment. 139 We regressed all response variables against night-time temperatures as measured by the 140 IR gun using OLS regressions. We regressed mortality against temperature using logistic 141 regression, where the response variable was dichotomous with survival = 0 and dead = 1. 142 Although monarchs experience mortality as pupae, brief exposure to prolonged temperatures did 143 not alter pupal mortality rates and third instar individuals were the most sensitive to temperature 144 increases (York and Oberhauser 2002). Thus, our experiment likely captured most of the 145 influence of temperature on larval survival. 146 Model assumptions were verified with residual plots where appropriate. All analyses 147 were conducted using Python v2.7 with the 'numpy', 'pandas', and 'statsmodels' modules 148 (McKinney 2010, Seabold and Perktold 2010 151 Time to pupation declined rapidly with increasing temperature (p < 0.001, R 2 = 0.57) 152 169 Warming had no effect on any measured plant trait. SLA (p = 0.940, R 2 = 0), percent 170 water content (p = 0.313, R 2 = 0.05), and latex concentration (p = 0.739, R 2 = 0.01) all did not 171 vary with temperature. Thus, any effects of warming on monarch development time were direct 172 effects of temperature on monarch physiology rather than being mediated through the plant traits 173 we measured. 189 temperatures above 28˚ C induced high mortality rates in monarch larvae (Zalucki 1982, York 190 and Oberhauser 2002). However, these studies used either pulses of extremely high temperatures 191 (i.e. 36˚ C) or held monarchs at a constant temperature (i.e. 28˚ C). Ambient, maximum daytime 192 temperatures averaged 30 ˚C during our experiment; warming increased this maximum to 32-34˚ 193 C. Although these temperatures are above the thermal optimum of monarch survival, we found 194 no effect of in situ warming on either pupal mass or survival. As temperatures exceeded 28˚ C 195 for less than 20% of the full 24 hour day, it is likely that diel and daily temperature fluctuations 196 mitigated the lethality of high temperatures
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effects of in situ climate warming on monarch caterpillar danaus plexippus development
PeerJ, 2015Co-Authors: Nathan P. Lemoine, Jillian N Capdevielle, John D ParkerAbstract:Climate warming will fundamentally alter basic life history strategies of many ectothermic insects. In the lab, rising temperatures increase growth rates of lepidopteran larvae but also reduce final pupal mass and increase mortality. Using in situ field warming experiments on their natural host plants, we assessed the impact of climate warming on development of monarch (Danaus plexippus) larvae. Monarchs were reared on Asclepias tuberosa grown under 'Ambient' and 'Warmed' conditions. We quantified time to pupation, final pupal mass, and survivorship. Warming significantly decreased time to pupation, such that an increase of 1 °C corresponded to a 0.5 day decrease in pupation time. In contrast, survivorship and pupal mass were not affected by warming. Our results indicate that climate warming will speed the developmental rate of monarchs, influencing their ecological and evolutionary dynamics. However, the effects of climate warming on larval development in other monarch populations and at different times of year should be investigated.
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climate change may alter breeding ground distributions of eastern migratory monarchs danaus plexippus via range expansion of asclepias host plants
PLOS ONE, 2015Co-Authors: Nathan P. LemoineAbstract:Climate change can profoundly alter species’ distributions due to changes in temperature, precipitation, or seasonality. Migratory monarch butterflies (Danaus plexippus) may be particularly susceptible to climate-driven changes in host plant abundance or reduced overwintering habitat. For example, climate change may significantly reduce the availability of overwintering habitat by restricting the amount of area with suitable microclimate conditions. However, potential effects of climate change on monarch northward migrations remain largely unknown, particularly with respect to their milkweed (Asclepias spp.) host plants. Given that monarchs largely depend on the genus Asclepias as larval host plants, the effects of climate change on monarch northward migrations will most likely be mediated by climate change effects on Asclepias. Here, I used MaxEnt species distribution modeling to assess potential changes in Asclepias and monarch distributions under moderate and severe climate change scenarios. First, Asclepias distributions were projected to extend northward throughout much of Canada despite considerable variability in the environmental drivers of each individual species. Second, Asclepias distributions were an important predictor of current monarch distributions, indicating that monarchs may be constrained as much by the availability of Asclepias host plants as environmental variables per se. Accordingly, modeling future distributions of monarchs, and indeed any tightly coupled plant-insect system, should incorporate the effects of climate change on host plant distributions. Finally, MaxEnt predictions of Asclepias and monarch distributions were remarkably consistent among general circulation models. Nearly all models predicted that the current monarch summer breeding range will become slightly less suitable for Asclepias and monarchs in the future. Asclepias, and consequently monarchs, should therefore undergo expanded northern range limits in summer months while encountering reduced habitat suitability throughout the northern migration.
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climate change may alter breeding ground distributions of eastern migratory monarchs danaus plexippus via range expansion of asclepias host plants
PLOS ONE, 2015Co-Authors: Nathan P. LemoineAbstract:Climate change can profoundly alter species’ distributions due to changes in temperature, precipitation, or seasonality. Migratory monarch butterflies (Danaus plexippus) may be particularly susceptible to climate-driven changes in host plant abundance or reduced overwintering habitat. For example, climate change may significantly reduce the availability of overwintering habitat by restricting the amount of area with suitable microclimate conditions. However, potential effects of climate change on monarch northward migrations remain largely unknown, particularly with respect to their milkweed (Asclepias spp.) host plants. Given that monarchs largely depend on the genus Asclepias as larval host plants, the effects of climate change on monarch northward migrations will most likely be mediated by climate change effects on Asclepias. Here, I used MaxEnt species distribution modeling to assess potential changes in Asclepias and monarch distributions under moderate and severe climate change scenarios. First, Asclepias distributions were projected to extend northward throughout much of Canada despite considerable variability in the environmental drivers of each individual species. Second, Asclepias distributions were an important predictor of current monarch distributions, indicating that monarchs may be constrained as much by the availability of Asclepias host plants as environmental variables per se. Accordingly, modeling future distributions of monarchs, and indeed any tightly coupled plant-insect system, should incorporate the effects of climate change on host plant distributions. Finally, MaxEnt predictions of Asclepias and monarch distributions were remarkably consistent among general circulation models. Nearly all models predicted that the current monarch summer breeding range will become slightly less suitable for Asclepias and monarchs in the future. Asclepias, and consequently monarchs, should therefore undergo expanded northern range limits in summer months while encountering reduced habitat suitability throughout the northern migration.
