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James DG. Monarch Butterflies in Western North America: A Holistic Review of Population Trends, Ecology, Stressors, Resilience and Adaptation. INSECTS 2024; 15:40. [PMID: 38249046 PMCID: PMC10817040 DOI: 10.3390/insects15010040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 01/04/2024] [Accepted: 01/05/2024] [Indexed: 01/23/2024]
Abstract
Monarch butterfly populations in western North America suffered a substantial decline, from millions of butterflies overwintering in California in the 1980s to less than 400,000 at the beginning of the 21st century. The introduction of neonicotinoid insecticides in the mid-1990s and their subsequent widespread use appears to be the most likely major factor behind this sudden decline. Habitat loss and unfavorable climates (high temperatures, aridity, and winter storms) have also played important and ongoing roles. These factors kept overwintering populations stable but below 300,000 during 2001-2017. Late winter storm mortality and consequent poor spring reproduction drove winter populations to less than 30,000 butterflies during 2018-2019. Record high temperatures in California during the fall of 2020 appeared to prematurely terminate monarch migration, resulting in the lowest overwintering population (1899) ever recorded. Many migrants formed winter-breeding populations in urban areas. Normal seasonal temperatures in the autumns of 2021 and 2022 enabled overwintering populations to return to around the 300,000 level, characteristic of the previous two decades. Natural enemies (predators, parasitoids, parasites, and pathogens) may be important regional or local drivers at times but they are a consistent and fundamental part of monarch ecology. Human interference (capture, rearing) likely has the least impact on monarch populations. The rearing of monarch caterpillars, particularly by children, is an important human link to nature that has positive ramifications for insect conservation beyond monarch butterflies and should be encouraged.
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Affiliation(s)
- David G James
- Department of Entomology, Washington State University, Irrigated Agriculture Research and Extension Center, Prosser, WA 99350, USA
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Kendzel MJ, Altizer SM, de Roode JC. Interactions between parasitism and migration in monarch butterflies. CURRENT OPINION IN INSECT SCIENCE 2023; 59:101089. [PMID: 37506879 DOI: 10.1016/j.cois.2023.101089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 07/12/2023] [Accepted: 07/23/2023] [Indexed: 07/30/2023]
Abstract
In many species, migration can increase parasite burdens or diversity as hosts move between diverse habitats with different parasite assemblages. On the other hand, migration can reduce parasite prevalence by letting animals escape infested habitats, or by exacerbating the costs of parasitism, leading to culling or dropout. How the balance between these negative and positive interactions is maintained or how they will change under anthropogenic pressure remains poorly understood. Here, we summarize the relationship between migration and infectious disease in monarch butterflies, finding that migration can reduce parasite prevalence through a combination of migratory culling and dropout. Because parasite prevalence has risen in recent decades, these processes are now resulting in the loss of tens of millions of monarchs. We highlight the remaining questions, asking how migration influences population genetics and virulence, how the establishment of resident populations interferes with migration, and whether infection can interfere with migratory cognition.
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Affiliation(s)
| | - Sonia M Altizer
- Odum School of Ecology, University of Georgia, Athens, GA 30602, USA
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Tenger-Trolander A. Environmental and genetic effects of captivity - are there lessons for monarch butterfly conservation? CURRENT OPINION IN INSECT SCIENCE 2023; 59:101088. [PMID: 37500011 DOI: 10.1016/j.cois.2023.101088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 07/17/2023] [Accepted: 07/17/2023] [Indexed: 07/29/2023]
Abstract
Rearing monarch butterflies in captivity for later release is a popular but contentious activity due to concerns about its potential negative effects on the wild population. In this review, I discuss how captive rearing and breeding could impact monarch fitness in the wild, the current evidence for such impacts in monarchs and other captive-reared/released organisms, and how this should inform our efforts to conserve monarchs and other species.
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Steele C, Ragonese IG, Majewska AA. Extent and impacts of winter breeding in the North American monarch butterfly. CURRENT OPINION IN INSECT SCIENCE 2023; 59:101077. [PMID: 37336490 DOI: 10.1016/j.cois.2023.101077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 06/09/2023] [Accepted: 06/13/2023] [Indexed: 06/21/2023]
Abstract
Since the 1960s, scientists have observed the North American monarch butterfly (Danaus plexippus) continuing reproductive activities past the fall migration and into the winter months when the climate is mild. Recent work suggests that small populations of winter breeding monarchs are present in western and southeastern USA, as well as northwestern Mexico, with new winter breeding populations forming in areas where non-native milkweeds are planted. The year-round presence of milkweed plants and temperatures suitable for immature monarch development are vital factors allowing for winter breeding. Non-native milkweeds, in conjunction with novel barriers to migration, are likely contributing to the rise in winter breeding behavior. Warmer climates are already impacting milkweed phenology and range, possibly favoring winter breeding behavior. Similar pressures but different implications are expected for eastern and western winter breeding monarchs given the differences in the migration ecology, milkweed species, and climate changes in the two regions.
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Affiliation(s)
- Christen Steele
- Department of Ecology and Evolutionary Biology, Tulane University, 1430 Annunciation St, New Orleans, LA 70130, USA
| | - Isabella G Ragonese
- Odum School of Ecology, University of Georgia, 140 E Green Street, Athens, GA 30602, USA
| | - Ania A Majewska
- Department of Physiology and Pharmacology College of Veterinary Medicine, University of Georgia, 501 D.W. Brooks Drive, Athens, GA 30602, USA.
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Deppisch P, Helfrich-Förster C, Senthilan PR. The Gain and Loss of Cryptochrome/Photolyase Family Members during Evolution. Genes (Basel) 2022; 13:1613. [PMID: 36140781 PMCID: PMC9498864 DOI: 10.3390/genes13091613] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 09/02/2022] [Accepted: 09/05/2022] [Indexed: 11/20/2022] Open
Abstract
The cryptochrome/photolyase (CRY/PL) family represents an ancient group of proteins fulfilling two fundamental functions. While photolyases repair UV-induced DNA damages, cryptochromes mainly influence the circadian clock. In this study, we took advantage of the large number of already sequenced and annotated genes available in databases and systematically searched for the protein sequences of CRY/PL family members in all taxonomic groups primarily focusing on metazoans and limiting the number of species per taxonomic order to five. Using BLASTP searches and subsequent phylogenetic tree and motif analyses, we identified five distinct photolyases (CPDI, CPDII, CPDIII, 6-4 photolyase, and the plant photolyase PPL) and six cryptochrome subfamilies (DASH-CRY, mammalian-type MCRY, Drosophila-type DCRY, cnidarian-specific ACRY, plant-specific PCRY, and the putative magnetoreceptor CRY4. Manually assigning the CRY/PL subfamilies to the species studied, we have noted that over evolutionary history, an initial increase of various CRY/PL subfamilies was followed by a decrease and specialization. Thus, in more primitive organisms (e.g., bacteria, archaea, simple eukaryotes, and in basal metazoans), we find relatively few CRY/PL members. As species become more evolved (e.g., cnidarians, mollusks, echinoderms, etc.), the CRY/PL repertoire also increases, whereas it appears to decrease again in more recent organisms (humans, fruit flies, etc.). Moreover, our study indicates that all cryptochromes, although largely active in the circadian clock, arose independently from different photolyases, explaining their different modes of action.
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Affiliation(s)
| | | | - Pingkalai R. Senthilan
- Neurobiology & Genetics, Theodor-Boveri Institute, Biocenter, Julius-Maximilians-University Würzburg, 97074 Wurzburg, Germany
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Monarchs Reared in Winter in California Are Not Large Enough to Be Migrants. Comment on James et al. First Population Study on Winter Breeding Monarch Butterflies, Danaus plexippus (Lepidoptera: Nymphalidae) in the Urban South Bay of San Francisco, California. Insects 2021, 12, 946. INSECTS 2022; 13:insects13010063. [PMID: 35055906 PMCID: PMC8778705 DOI: 10.3390/insects13010063] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 12/01/2021] [Accepted: 01/01/2022] [Indexed: 01/19/2023]
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First Population Study on Winter Breeding Monarch Butterflies, Danaus plexippus (Lepidoptera: Nymphalidae) in the Urban South Bay of San Francisco, California. INSECTS 2021; 12:insects12100946. [PMID: 34680715 PMCID: PMC8537757 DOI: 10.3390/insects12100946] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 10/14/2021] [Accepted: 10/15/2021] [Indexed: 12/02/2022]
Abstract
Simple Summary Populations of western monarch butterflies, which formerly populated coastal overwintering sites in California in numbers exceeding one million, dwindled to less than 2000 in 2020/21. In the same winter, breeding populations of monarchs occurred commonly in the San Francisco Bay urban area for the first time. The urgent conservation need to understand this possible shift in overwintering strategy prompted this first study of the viability and ecology of monarch breeding populations in the South Bay urban area of San Francisco during January–June 2021. Adult monarchs along with eggs and larvae were common during winter and most of spring, utilizing non-native ornamental milkweed and multiple nectar sources from native and ornamental plants. Evidence from weekly counts and tagged butterflies indicated increased dispersal to the north and east during late April-mid-May, possibly representing spring migration to the Pacific Northwest and eastern California. Infection of reared adult monarchs with a protozoan parasite was high. Winter breeding of monarchs in the San Francisco urban area as an alternative and sustainable overwintering strategy for the western US population will likely depend on the continued presence of ornamental milkweeds, sustainable co-existence of monarchs and protozoan parasites, and successful migration to the greater western US during spring. Abstract The western North American monarch butterfly population assessed by counts of non-reproductive overwintering butterflies at coastal sites in California declined to less than 2000 in 2020/21. Simultaneously, reports of reproductive monarchs increased in San Francisco urban areas, perhaps representing a shift in overwintering strategy. To better understand monarch winter breeding in the Bay area, we studied adult and immature populations in Santa Clara County during January–June 2021. Adult monarchs were common with numbers ranging from 0.23–1.54/min during ~30 min weekly surveys at one site, with lowest numbers late April to mid-May. Eggs and larvae, primarily on ornamental milkweeds, were found on nearly all survey dates with lowest numbers mid-late April to mid-May. Levels of infection of adults by the parasite Ophryocystis elektroscirrha were consistently high during the study (69.3–77.5%). From 499 monarchs tagged post-eclosion, recovery rates of 19.2–23.6% occurred from releases in January-February and May-June but only 11.9–13.0% from March-April releases. Although distances were small, butterflies tagged in April were recovered from greater distances than other months. Tagged monarchs flew primarily north or east. There were reduced numbers of adult monarchs during late April-mid-May with some evidence of northerly and easterly emigration at the same time from tagged butterflies, suggesting some movement out of the South Bay area, perhaps representing spring migration. We conclude that monarchs can successfully breed and maintain populations on ornamental milkweeds during winter at urban sites in the South Bay of San Francisco and may still migrate during spring to remain part of the wider western population.
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Davis AK. Captive-reared migratory monarchs fly in the wrong direction: a critique of Wilcox et al. CONSERVATION PHYSIOLOGY 2021; 9:coab063. [PMID: 34413978 PMCID: PMC8372217 DOI: 10.1093/conphys/coab063] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 06/30/2021] [Accepted: 07/31/2021] [Indexed: 06/13/2023]
Affiliation(s)
- Andrew K Davis
- Odum School of Ecology, University of Georgia, Athens, GA 30602, USA
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Freedman MG, Roode JC, Forister ML, Kronforst MR, Pierce AA, Schultz CB, Taylor OR, Crone EE. Are eastern and western monarch butterflies distinct populations? A review of evidence for ecological, phenotypic, and genetic differentiation and implications for conservation. CONSERVATION SCIENCE AND PRACTICE 2021. [DOI: 10.1111/csp2.432] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Affiliation(s)
- Micah G. Freedman
- Department of Ecology & Evolution University of Chicago Chicago Illinois USA
- Center for Population Biology University of California, Davis Davis California USA
| | | | | | - Marcus R. Kronforst
- Department of Ecology & Evolution University of Chicago Chicago Illinois USA
| | - Amanda A. Pierce
- United States Environmental Protection Agency Washington District of Columbia USA
| | - Cheryl B. Schultz
- School of Biological Sciences, Washington State University Vancouver Washington USA
| | - Orley R. Taylor
- Department of Ecology and Evolutionary Biology University of Kansas Lawrence Kansas USA
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James DG. Western North American Monarchs: Spiraling into Oblivion or Adapting to a Changing Environment? ANIMAL MIGRATION 2021. [DOI: 10.1515/ami-2021-0002] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Abstract
Monarch butterflies in western North America typically migrate each fall from the Pacific Northwest to overwintering sites in California. Winter 2020/21 saw the lowest number of overwintering western monarch butterflies ever recorded, but was also marked by a winter-breeding population in the San Francisco bay area that appeared to be the largest ever seen. Recoveries of monarchs with wing tags from the Pacific Northwest suggested that many non-reproductive migrants in fall 2020 became reproductive in the San Francisco bay area and did not reach coastal overwintering sites. Mean daily maximum temperatures for San Francisco during fall and winter increased by ~1 °C during the past decade and were 2.5 °C above the 30 year mean during September-October 2020. Warm fall and winter temperatures along with the availability of non-native milkweeds likely caused the increase in winter breeding in winter 2020/21. The outcome of continued winter-breeding in the San Francisco bay area is uncertain. Whether it becomes a sink or source will be dependent on whether winter-breeding monarchs can re-enter their migratory state during spring. However, endemic levels of infection by the protozoan parasite, Ophryocystis elektroscirrha (OE), are often high in winter-breeding monarchs which can limit migration success. The eventual co-existence of winter-breeding and non-breeding monarch populations in northern and central California is probable, with an optimistic view suggesting that the adaptability of the monarch butterfly will allow it to persist in a changed environment.
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Affiliation(s)
- David G James
- Department of Entomology, Irrigated Agriculture Research and Extension Center , Washington State University , 24106 North Bunn Road, Prosser, WA, 99350, USA
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Wilcox AAE, Newman AEM, Raine NE, Mitchell GW, Norris DR. Captive-reared migratory monarch butterflies show natural orientation when released in the wild. CONSERVATION PHYSIOLOGY 2021; 9:coab032. [PMID: 34386237 PMCID: PMC8355447 DOI: 10.1093/conphys/coab032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 01/27/2021] [Accepted: 04/14/2021] [Indexed: 05/08/2023]
Abstract
Eastern North American migratory monarch butterflies (Danaus plexippus) have faced sharp declines over the past two decades. Captive rearing of monarch butterflies is a popular and widely used approach for both public education and conservation. However, recent evidence suggests that captive-reared monarchs may lose their capacity to orient southward during fall migration to their Mexican overwintering sites, raising questions about the value and ethics of this activity undertaken by tens of thousands of North American citizens, educators, volunteers and conservationists each year. We raised offspring of wild-caught monarchs on swamp milkweed (Asclepias incarnata) indoors at 29°C during the day and 23°C at night (~77% RH, 18L:6D), and after eclosion, individuals were either tested in a flight simulator or radio tracked in the wild using an array of automated telemetry towers. While 26% (10/39) of monarchs tested in the flight simulator showed a weakly concentrated southward orientation, 97% (28/29) of the radio-tracked individuals that could be reliably detected by automated towers flew in a south to southeast direction from the release site and were detected at distances of up to 200 km away. Our results suggest that, although captive rearing of monarch butterflies may cause temporary disorientation, proper orientation is likely established after exposure to natural skylight cues.
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Affiliation(s)
- Alana A E Wilcox
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
- Corresponding author: Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
| | - Amy E M Newman
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | - Nigel E Raine
- School of Environmental Sciences, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | - Greg W Mitchell
- Wildlife Research Division, Environment and Climate Change Canada, National Wildlife Research Centre, 1125 Colonel By Drive, Ottawa, Ontario, K1S 5B6, Canada
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, K1S 5B6, Canada
| | - D Ryan Norris
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
- Nature Conservancy of Canada, 245 Eglington Avenue East, Toronto, Ontario, M4P 3J1, Canada
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