Dissertations / Theses on the topic 'Monarch butterfly'

The presence of inhabitants in protected areas, a common occurrence in developing countries, represents a major challenge for conservation. This MA thesis questions the state's strategy in the case of the Monarch Butterfly Biosphere Reserve, in Mexico, a strategy which is officially based on the implementation of sustainable development through the participation of local communities. Working with the assumption that sustainable development is a political concept that implies a competition between different actors in order to define what has to be sustained, for whom, by whom, why, and how, I first analyze the factors that, until now, have impeded local inhabitants' participation. I argue that the subordination of civil society by the state during the last century is a historical burden that has debilitated civil society's capacity for effective participation. Second, I discuss the state's vision of sustainable development and the weight given to the two conflicting visions held, on the one hand, by local inhabitants and, on the other, by the environmentalists and biologists. I conclude that the state's appeal for the participation of local communities is not in recognition of the fact that local inhabitants have the right to greater input in the definition of sustainable development in the region, but needs to be understood as a strategy to achieve rule compliance. Unfortunately, then, while the Monarch Butterfly Biosphere Reserve may be managed according to a vision of sustainable development, this is not a vision that has emerged from a dialogue between the state and civil society. Local support is thus unlikely since transforming local communities into allies would rather require achieving a compromise based upon genuine dialogue.

Thesis (S.M. in Science Writing)--Massachusetts Institute of Technology, Dept. of Humanities, Graduate Program in Science Writing, 2007.
Includes bibliographical references (leaf 45).
Each fall, the entire monarch butterfly population of the Eastern United States and Canada funnels into a handful of oyamel pine groves in Michoacan, Mexico, to weather the winter months. Each spring, the butterflies mate and fly north to repopulate the continent in short generational bursts. The monarchs flying south in the fall are three generations removed from those that made the trip the previous year. With no parents to guide its way, a migrating monarch has only its genes to steer it to its Mexican overwintering site. Monarchs orient using the sun as a guidepost. Because the sun appears to move across the sky throughout the day, the butterflies must keep track of time in order to correctly interpret the sun's position. Although this so-called "time-compensated sun compass" was demonstrated in 1997, little was known about how it worked. Steven Reppert, a neurobiologist at the University of Massachusetts Medical School in Worcester, MA, is working to change that. His lab seeks to understand the cellular and molecular mechanisms monarchs use to guide them on their remarkable yearly journey. Reppert and his colleagues believe they have pinpointed the sun compass, and the circadian clock that guides it, in the monarch brain. They have shown how the clock and compass might work together to allow the monarchs to find their way to Mexico. Their work has also uncovered some unexpected insights into the workings and evolution of circadian clocks in general. This thesis profiles these discoveries, exploring how circadian biology has illuminated monarch migration, and how monarchs, in turn, have illuminated circadian biology.
by Jocelyn Rice.
S.M.in Science Writing

The eastern migratory population of monarch butterflies (Danaus plexippus plexippus) has declined by >80% within the last two decades. One possible cause of this decline is the loss of >= 1.3 billion stems of milkweed (Asclepias spp.), which monarchs require for reproduction. In an effort to restore monarchs to a population goal established by the US Fish and Wildlife Service and adopted by Mexico, Canada, and the US, we developed scenarios for amending the Midwestern US landscape with milkweed. Scenarios for milkweed restoration were developed for protected area grasslands, Conservation Reserve Program land, powerline, rail and roadside rights of way, urban/suburban lands, and land in agricultural production. Agricultural land was further divided into productive and marginal cropland. We elicited expert opinion as to the biological potential (in stems per acre) for lands in these individual sectors to support milkweed restoration and the likely adoption (probability) of management practices necessary for affecting restoration. Sixteen of 218 scenarios we developed for restoring milkweed to the Midwestern US were at levels (>1.3 billion new stems) necessary to reach the monarch population goal. One of these scenarios would convert all marginal agriculture to conserved status. The other 15 scenarios converted half of marginal agriculture (730 million stems), with remaining stems contributed by other societal sectors. Scenarios without substantive agricultural participation were insufficient for attaining the population goal. Agricultural lands are essential to reaching restoration targets because they occupy 77% of all potential monarch habitat. Barring fundamental changes to policy, innovative application of economic tools such as habitat exchanges may provide sufficient resources to tip the balance of the agro-ecological landscape toward a setting conducive to both robust agricultural production and reduced imperilment of the migratory monarch butterfly.

Given the rapid population decline and recent petition for listing of the monarch butterfly (Danaus plexippus L.) under the Endangered Species Act, an accurate estimate of the Eastern, migratory population size is needed. Because of difficulty in counting individual monarchs, the number of hectares occupied by monarchs in the overwintering area is commonly used as a proxy for population size, which is then multiplied by the density of individuals per hectare to estimate population size. There is, however, considerable variation in published estimates of overwintering density, ranging from 6.9-60.9 million ha(-1). We develop a probability distribution for overwinter density of monarch butterflies from six published density estimates. The mean density among the mixture of the six published estimates was similar to 27.9 million butterflies ha(-1) (95% CI [2.4-80.7] million ha(-1)); the mixture distribution is approximately log-normal, and as such is better represented by the median (21.1 million butterflies ha(-1)). Based upon assumptions regarding the number of milkweed needed to support monarchs, the amount of milkweed (Asciepias spp.) lost (0.86 billion stems) in the northern US plus the amount of milkweed remaining (1.34 billion stems), we estimate >1.8 billion stems is needed to return monarchs to an average population size of 6 ha. Considerable uncertainty exists in this required amount of milkweed because of the considerable uncertainty occurring in overwinter density estimates. Nevertheless, the estimate is on the same order as other published estimates, The studies included in our synthesis differ substantially by year, location, method, and measures of precision. A better understanding of the factors influencing overwintering density across space and time would be valuable for increasing the precision of conservation recommendations.

Every fall, Northeastern America monarch butterflies (Danaus plexippus) undergo an extraordinary migration to their overwintering site in Central Mexico. During their long migration, monarch migrants use sun compass to navigate. To maintain a southward flying direction, monarch migrants compensate for the continuously changing position of the sun by providing timing information to the compass using their circadian clock. Animal circadian clocks depend primarily on a negative transcriptional feedback loop to track time. I started my work to re-construct the monarch butterfly circadian clock negative feedback loop in cell culture, focusing on homologs of Drosophila clock genes. It turned out that in addition to a Drosophila-like cryptochrome (cry1) gene, a second mammalian-like cry2 gene exists in monarch butterflies and many other insects, except in Drosophila. The two CRYs showed distinct functions in our initial assays in cultured Drosophila Schneider 2 (S2) cells. CRY2 functions as a potent transcriptional repressor, while CRY1 is light sensitive but shows no obvious transcriptional activity. The existence of two cry genes in insects changed the Drosophila-centric view of insect circadian clock. During the course of my study, our lab obtained a monarch cell line called DpN1 cells. These cells possess a light-driven clock and contributed tremendously to the research on monarch circadian clock. Using this cell line, I provided strong evidence supporting monarch CRY2’s role as a major circadian clock repressor and identified a protein-protein protective interaction cascade underlying the CRY1-mediated resetting of the molecular oscillator in DpN1 cells. I continued my work trying to understand how insect CRY2 inhibits transcription. I provided evidence suggesting the involvement of monarch PER in promoting CRY2 nuclear entry in both S2 cells and DpN1 cells. Finally, I mapped CRY2’s transcriptional inhibitory activity onto its N-terminal domain. Collectively, my research helped to change our view of insect clocks from a Drosophila-centric standpoint to a much more diverse picture. My studies also advanced the understanding of monarch circadian clock mechanism, and provides a foundation for further studies.

Managing Monarch butterfly overwintering groves: making room among the eucalyptus Proper management and conservation of the coastal California overwintering sites used by western Monarch butterflies (Danaus plexippus L.) is critical for continued use of these sites by monarchs. Many management efforts are currently concentrating on eucalyptus-only sites because of the prevailing notion that monarchs prefer eucalyptus over native tree species. Yet, whether a preference exists or not has never been tested. Herein, we test the “eucalyptus preference” hypothesis with data from five overwintering sites comprised of blue gum eucalyptus (Eucalyptus globulus) and at least one other native tree species from fall 2009 to spring 2012. We found that when monarchs clustered disproportionately on a tree species relative to its availability, they clustered significantly more than expected on native trees and significantly less than expected on eucalyptus. Also, in years when the overwintering population was highest, monarchs clustered disproportionately on native conifers, and they often switched from clustering on eucalyptus in the early winter to native conifers in the middle or late winter. Our results suggest that overwintering groves should be managed to include a mixture of tree species. We cannot recommend simply planting more eucalyptus. At overwintering sites in central coastal California, native conifers such as Monterey cypress (Hesperocyparis macrocarpa) and pitch canker-resistant Monterey pine (Pinus radiata) should be planted as replacements for blue gum eucalyptus in areas where trees are likely to fall, and around the perimeter of groves. Testing the Monarch butterfly eucalyptus preference hypothesis at California overwintering sites Western Monarch butterflies (Danaus plexippus L.) overwinter in groves of native and non-native trees along the California coast. Eucalyptus is abundant in coastal counties, and overwintering monarchs utilize this type of tree more than any other. This has led to the belief that monarchs prefer eucalyptus. Yet whether a preference exists has never been tested. We tested the “eucalyptus preference” hypothesis at five California overwintering sites with canopies comprised of eucalyptus and at least one native conifer species. We found that at no time over the course of three years did monarchs cluster on trees in proportion to their availability in the canopy. Overall, they did not cluster on one tree species significantly more frequently than another, indicating that monarchs do not prefer eucalyptus—or any tree species—all of the time. However, more often than not monarchs clustered significantly more than expected on native trees, particularly at midseason when the weather was most inclement. They also clustered disproportionately on native conifers when the overwintering population size was highest. At most sites monarchs exhibited tree switching, shifting from eucalyptus to native conifers in the middle or late winter. Based on these results, we reject the “eucalyptus preference” hypothesis. In its place, we propose the “conditional preference hypothesis”, wherein monarchs are predicted to prefer cluster trees according to microclimate conditions and prefer alternate trees within a site as climatic conditions change. Rejection of the eucalyptus preference hypothesis suggests that sites comprised exclusively of eucalyptus may not offer monarchs a suitable range of microhabitats, and further suggests we should rethink “eucalyptus-centric” management. Monarch butterflies overwintering in coastal California: low site fidelity and high intersite movement Western monarch butterflies (Danaus plexippus L.) overwinter in large aggregations at hundreds of sites along the California coast. Management plans and census methods are both founded on the assumption that individual monarchs arrive at an overwintering site in the fall and stay at that site for the winter. Though populations potentially coalesce en masse from autumnal sites onto climax overwintering sites, very little individual movement between sites is inferred. Monarch movement is therefore thought to be primarily into sites (as opposed to out of or among them). We refer to this assumption and inference as the accrual hypothesis. In light of previous studies that provide evidence for movement among sites, we propose that overwintering monarchs may belong to a superpopulation. The existence of a superpopulation comprised of individuals moving in and out of sites would force us to rethink our ideas of landscape-level resource use by monarchs, our site-centric (rather than landscape-level) management strategies, and our abundance estimation techniques, which employ closed population models. We tested the closed population model, the accrual hypothesis, and the superpopulation model at three California overwintering sites using a mark-resight study design. We found that a large proportion of the monarchs at a site moved among (into and out of) monitored sites, both while the population size increased in October and November, and while the population appeared to exhibit an equilibrium winter maximum. The pattern of abundance of both tagged and untagged monarchs at monitored sites leads us to reject the closed population model and the accrual hypothesis. We found that monarchs at all three study sites are part of a larger superpopulation, though the sites do not contribute to the superpopulation equally. We determined that mark-resight is a viable alternative to existing population estimation techniques, though mark-resight methods would need to be explored further before being applied routinely. Our results suggest we need to move away from site-based management and manage instead for landscape-level overwintering (superpopulation) dynamics.

Plants play an important role in structuring ecological communities from the bottom up through interactions with herbivores, and environmental variation can affect these interactions. We use the interaction between common milkweed (Asclepias syriaca) and the monarch butterfly (Danaus plexippus) to examine 1) the role of environmental variation in dictating plants traits, and 2) how those variations affect herbivores. We quantified intraspecific trait variation in 53 natural common milkweed populations, then remeasured these traits when population representatives were regrown in a common garden to control for environmental variation. We then measured growth, performance, and survival of monarch larvae feeding on these same plants. Our findings indicate distinct spatial patterns in traits throughout the range of A. syriaca, but these patterns dissipate when genets are regrown in a common environment. When monarch larvae are raised on these milkweeds, those fed on plants from the Northeast gain more weight than those fed on plants from the Northcentral and Southcentral regions. These results can better inform monarch conservation efforts; current conservation efforts have been focused on milkweed restoration in the Midwest, but an increased focus on milkweed restoration in the Northeast may be beneficial. Furthermore, we demonstrated plasticity in specific plant traits in response to environmental change, which could have theoretical implications in light of current and projected changes in climate.

Species are experiencing shifts in their phenology (i.e., seasonal timing of recurring biological events) due to climate change, leading to disruptions in the relative timing of interacting species. These shifts can be detrimental to the fitness of the consumer (e.g., herbivore) in the interaction. In its larval form, the monarch butterfly (Danaus plexippus) is a specialist herbivore that feeds on milkweed plants (Asclepias spp.). Given that plants generally experience seasonal declines in quality, it is hypothesized that if climate change disrupts the timing of the larval stage relative to the availability of younger milkweed plants, monarch performance will be negatively affected. In this thesis, I explore the potential for negative consequences for the eastern monarch population due to potential shifts in the timing of their interaction with milkweed—due to phenological shifts in either species. I used field surveys around Ottawa, ON to determine monarch oviposition preference on common milkweed (Asclepias syriaca) plants and the seasonal availability of their preferred plants. To determine the potential consequences for monarch fitness where females oviposit on non-preferred plants, I conducted a field experiment to assess the effect of milkweed size on monarch larval performance. Based on field surveys, females preferentially oviposited on smaller milkweed plants in earlier developmental stages with low levels of discolouration. Plants in early developmental stages were consistently available in large proportion over the summer season. These results suggest that even if the relative timing of the monarch-milkweed interaction in the eastern population is shifted due to climate change, there will likely be suitable milkweed plants available for oviposition throughout the breeding season, which could act as a buffer to disruptions in the relative timing of the interaction. I found that bigger plants exuded more latex and had thicker leaves than smaller plants. However, larval performance was unaffected by these plant quality differences. While it is unclear how the relative timing of the monarch-milkweed interaction will change in the future, my results suggest that shifts in the relative timing of their interaction within the breeding season are unlikely to have negative consequences for larval performance in eastern Ontario. Future studies should determine how the relative timing of the interaction will change in the region and explore how climate change will affect the quality of milkweed plants.

This dissertation describes the purification and partial characterization of CBP from the epidermis of the monarch butterfly larvae (Danaus plexippus). A yellow protein-carotenoid complex was extracted from the yellow pigmented epidermal tissue from monarch butterfly larvae by homogenization. Additional steps in the purification process included differential precipitation with ammonium sulfate, cation and anion chromatography, and lastly size exclusion chromatography. Polyacrylamide gel electrophoresis demonstrates that a single protein was isolated (M-LBP) having a ~60 kDa molecular weight, the value has subsequently been confirmed by HR-tandem MS. Lutein is the sole carotenoid bound by M-LBP with a stoichiometry of the binding of 2: 1. Immunohistochemistry results show that M-LBP has no cross-reactivity to antibodies for silk worm CBP (Bombix mori) but does have cross-reactivity with antibodies for horn worm epidermal CBP (Agrius convolvuli). Binding affinities were determined using surface plasmon resonance for the carotenoids lutein (KD = 18.6 ± 0.7), R,R-zeaxanthin (KD = 990 ± 60), R,S-zeaxanthin (KD = 60 ± 2). Tryptophyphan fluorescence lifetimes were determined for the apoprotein and compared to those of the native M-LBP. Tryptophan fluorescence lifetimes were found to be 3.9 ns and 3.0 ns, respectively for these two forms of the protein, indicating that upon dissociation of the carotenoid from the protein the tryptophan fluorophore adopts a position where it has less interaction with the polar surface environment.

archives@tulane.edu
The Eastern migratory monarch butterfly undertakes one of the longest annual migrations known among animal taxa, journeying from as far north as Canada down to central Mexico. A small subpopulation of monarchs has been found dropping out of migration in favor of breeding year-round along the U.S. Gulf Coast. The majority of these dropouts, known as winter-breeders, are feeding and breeding on a non-native milkweed species called tropical milkweed (Asclepias curassavica) that has greater concentrations of toxic cardenolides. The effects of tropical milkweed on monarchs are not yet fully understood, but it is correlated to breakage of reproductive diapause and migratory drop-out. The drop-out phenomenon is concerning due to the increased prevalence of infection by the monarch’s specialized protozoan parasite, Ophryocystis elektroscirrha (OE). OE is often physically damaging and can be lethal to monarchs. Here, we investigate the effects of a colder climate that winter-breeders experience on the Gulf Coast in the winter, exposure to OE, and a diet of exclusively tropical milkweed on larval development and adult wing morphology and pigmentation. Morphology and pigmentation are often functional traits that enhance fitness; thus, we use these measures as proxies for fitness components such as flight performance and immune function. In the first chapter, we found that monarchs reared on tropical milkweed developed faster and had larger wings and higher aspect ratios than monarchs reared on a low-cardenolide native milkweed species, swamp milkweed (Asclepias incarnata). In the second chapter, we found that monarchs reared in a suboptimal temperature developed slower and emerged with smaller, darker (redder and more melanized) wings than monarchs reared in a warmer or ‘normal’ temperature. Additionally, exposure to OE affected wing shape such that exposed monarchs had rounder wings with a slightly lower aspect ratio than unexposed monarchs. Lower temperature did not significantly affect melanism in monarch wings, but monarchs exposed to OE had less melanin deposited onto their wings than unexposed monarchs. Together, the findings from both chapters suggest that the conditions experienced by winter-breeders on the Gulf Coast are detrimental to monarch morphology. Smaller, rounder wings with lower aspect ratios are not conducive to migratory success, and paler color or less melanin are potential negative responses to exposure or infection by OE. While monarchs reared on tropical milkweed were larger and slightly redder which is a seemingly positive result, it may be limited to nonmigratory monarchs or winter breeders who may be adapted to tropical milkweed. Thus, it remains unclear how tropical milkweed is affecting the biology of migratory monarchs versus winter-breeders, but we suggest that the colder winter and increased risk of OE infection are negatively affecting winter-breeding populations and possibly migratory behavior. Migratory monarchs are already of conservation concern, and further monitoring and studying of the winter-breeding population and migrant populations are necessary to ensure the stability of monarch populations if and when they encounter tropical milkweed and whether the milkweed is driving population-level shifts in migratory behavior.
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Caitlin Ducat