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Diffendorfer JE, Botello F, Drummond MA, Ancona ZH, Corro LM, Thogmartin WE, Ibsen PC, Moreno-Sanchez R, Lukens L, Sánchez-Cordero V. Changes in landscape and climate in Mexico and Texas reveal small effects on migratory habitat of monarch butterflies (Danaus plexippus). Sci Rep 2024; 14:6703. [PMID: 38509089 PMCID: PMC10954652 DOI: 10.1038/s41598-024-56693-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 03/09/2024] [Indexed: 03/22/2024] Open
Abstract
The decline of the iconic monarch butterfly (Danaus plexippus) in North America has motivated research on the impacts of land use and land cover (LULC) change and climate variability on monarch habitat and population dynamics. We investigated spring and fall trends in LULC, milkweed and nectar resources over a 20-year period, and ~ 30 years of climate variables in Mexico and Texas, U.S. This region supports spring breeding, and spring and fall migration during the annual life cycle of the monarch. We estimated a - 2.9% decline in milkweed in Texas, but little to no change in Mexico. Fall and spring nectar resources declined < 1% in both study extents. Vegetation greenness increased in the fall and spring in Mexico while the other climate variables did not change in both Mexico and Texas. Monarch habitat in Mexico and Texas appears relatively more intact than in the midwestern, agricultural landscapes of the U.S. Given the relatively modest observed changes in nectar and milkweed, the relatively stable climate conditions, and increased vegetation greenness in Mexico, it seems unlikely that habitat loss (quantity or quality) in Mexico and Texas has caused large declines in population size or survival during migration.
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Affiliation(s)
- Jay E Diffendorfer
- U.S. Geological Survey, Geosciences and Environmental Change Science Center, Lakewood, CO, USA.
| | - Francisco Botello
- Departamento de Zoología, Instituto de Biología, Universidad Nacional Autónoma de México, Mexico City, Mexico
- Departamento de Monitoreo Biológico y Planeación de Conservación, Conservación Biológica y Desarrollo Social, Mexico City, Mexico
| | - Mark A Drummond
- U.S. Geological Survey, Geosciences and Environmental Change Science Center, Lakewood, CO, USA
| | - Zach H Ancona
- U.S. Geological Survey, Geosciences and Environmental Change Science Center, Lakewood, CO, USA
| | - Lucila M Corro
- U.S. Geological Survey, Geosciences and Environmental Change Science Center, Lakewood, CO, USA
| | - Wayne E Thogmartin
- U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, WI, USA
| | - Peter C Ibsen
- U.S. Geological Survey, Geosciences and Environmental Change Science Center, Lakewood, CO, USA
| | - Rafael Moreno-Sanchez
- Department of Geography and Environmental Sciences, University of Colorado Denver, 1200 Larimer St, NC 3016-C, Denver, CO, 80204, USA
| | - Laura Lukens
- Monarch Joint Venture, 2233 University Ave W., Suite 426, St. Paul, MN, USA
- Department of Forestry & Rangeland Science, Colorado State University, 1472 Campus Delivery, Fort Collins, CO, USA
| | - Victor Sánchez-Cordero
- Departamento de Zoología, Instituto de Biología, Universidad Nacional Autónoma de México, Mexico City, Mexico
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2
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Donaldson JE, Ezenwa VO, Morrison TA, Holdo RM. Effects of migratory animals on resident parasite dynamics. Trends Ecol Evol 2024:S0169-5347(24)00019-3. [PMID: 38355367 DOI: 10.1016/j.tree.2024.01.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2023] [Revised: 01/08/2024] [Accepted: 01/16/2024] [Indexed: 02/16/2024]
Abstract
Migratory animals can bring parasites into resident animal (i.e., non-migratory) home ranges (transport effects) and exert trophic effects that either promote or reduce parasite exposure to resident hosts. Here, we examine the importance of these transport and trophic effects and their interactions for resident parasite dynamics. We propose that migrant transport and trophic effects are impacted by the number of migratory animals entering a resident's home range (migration intensity), the amount of time that migrants spend within a resident's home range (migration duration), and the timing of migrant-resident interactions. We then incorporate migration intensity, duration, and timing into a framework for exploring the net impact of migrant trophic and transport effects on resident animal parasite prevalence.
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Affiliation(s)
| | - Vanessa O Ezenwa
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
| | - Thomas A Morrison
- School of Biodiversity, Animal Health, and Comparative Medicine, University of Glasgow, Glasgow, UK
| | - Ricardo M Holdo
- Odum School of Ecology, University of Georgia, Athens, GA, USA
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3
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Ragonese IG, Sarkar MR, Hall RJ, Altizer S. Extreme heat reduces host and parasite performance in a butterfly-parasite interaction. Proc Biol Sci 2024; 291:20232305. [PMID: 38228180 DOI: 10.1098/rspb.2023.2305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 12/12/2023] [Indexed: 01/18/2024] Open
Abstract
Environmental temperature fundamentally shapes insect physiology, fitness and interactions with parasites. Differential climate warming effects on host versus parasite biology could exacerbate or inhibit parasite transmission, with far-reaching implications for pollination services, biocontrol and human health. Here, we experimentally test how controlled temperatures influence multiple components of host and parasite fitness in monarch butterflies (Danaus plexippus) and their protozoan parasites Ophryocystis elektroscirrha. Using five constant-temperature treatments spanning 18-34°C, we measured monarch development, survival, size, immune function and parasite infection status and intensity. Monarch size and survival declined sharply at the hottest temperature (34°C), as did infection probability, suggesting that extreme heat decreases both host and parasite performance. The lack of infection at 34°C was not due to greater host immunity or faster host development but could instead reflect the thermal limits of parasite invasion and within-host replication. In the context of ongoing climate change, temperature increases above current thermal maxima could reduce the fitness of both monarchs and their parasites, with lower infection rates potentially balancing negative impacts of extreme heat on future monarch abundance and distribution.
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Affiliation(s)
- Isabella G Ragonese
- Odum School of Ecology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
- Center for the Ecology of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
| | - Maya R Sarkar
- College of Biological Sciences, University of Minnesota, St Paul, MN 5455, USA
| | - Richard J Hall
- Odum School of Ecology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
- Center for the Ecology of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
| | - Sonia Altizer
- Odum School of Ecology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
- Center for the Ecology of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
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4
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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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5
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Hobson KA, Taylor O, Ramírez MI, Carrera-Treviño R, Pleasants J, Bitzer R, Baum KA, Mora Alvarez BX, Kastens J, McNeil JN. Dynamics of stored lipids in fall migratory monarch butterflies ( Danaus plexippus): Nectaring in northern Mexico allows recovery from droughts at higher latitudes. CONSERVATION PHYSIOLOGY 2023; 11:coad087. [PMID: 38026803 PMCID: PMC10673816 DOI: 10.1093/conphys/coad087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 10/10/2023] [Accepted: 10/25/2023] [Indexed: 12/01/2023]
Abstract
The eastern population of the North American monarch butterfly (Danaus plexippus) overwinters from November through March in the high-altitude (3000 m+) forests of central Mexico during which time they rely largely on stored lipids. These are acquired during larval development and the conversion of sugars from floral nectar by adults. We sampled fall migrant monarchs from southern Canada through the migratory route to two overwintering sites in 2019 (n = 10 locations), 2020 (n = 8 locations) and 2021 (n = 7 locations). Moderate to extreme droughts along the migratory route were expected to result in low lipid levels in overwintering monarchs but our analysis of lipid levels of monarchs collected at overwintering sites indicated that in all years most had high levels of lipids prior to winter. Clearly, a significant proportion of lipids were consistently acquired in Mexico during the last portion of the migration. Drought conditions in Oklahoma, Texas and northern Mexico in 2019 resulted in the lowest levels of lipid mass and wing loading observed in that year but with higher levels at locations southward in Mexico to the overwintering sites. Compared with 2019, lipid levels increased during the 2020 and 2021 fall migrations but were again higher during the Mexican portion of the migration than for Oklahoma and Texas samples, emphasizing a recovery of lipids as monarchs advanced toward the overwintering locations. In all 3 years, body water was highest during the Canada-USA phase of migration but then declined during the nectar foraging phase in Mexico before recovering again at the overwintering sites. The increase in mass and lipids from those in Texas to the overwintering sites in Mexico indicates that nectar availability in Mexico can compensate for poor conditions experienced further north. Our work emphasizes the need to maintain the floral and therefore nectar resources that fuel both the migration and storage of lipids throughout the entire migratory route.
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Affiliation(s)
- Keith A Hobson
- Department of Biology, University of Western Ontario, 1151 Richmond St, London, ON, N6A 5B7, Canada
- Environment and Climate Change Canada, 11 Innovation Blvd, Saskatoon, SK, S7N 3H5, Canada
| | - Orley Taylor
- Department of Ecology and Evolutionary Biology and Kansas Biological Survey and Center for Ecological Research, University of Kansas, 1450 Jayhawk Blvd, Lawrence, KS 66045, USA
| | - M Isabel Ramírez
- Centro de Investigaciones en Geografia Ambiental, Universidad Nacional Autónoma de Mexico, Antigua Carretera A Patzcuaro 8701, Ex hacienda San Jose de la Huerta, 58190, Morelia, Michoacán, Mexico
| | - Rogelio Carrera-Treviño
- Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Nuevo León, C. Francisco Villa 20, Escobedo, Nuevo León, México
| | - John Pleasants
- Department of Ecology, Evolution, and Organismal Biology, 2200 Osborne Dr, Iowa State University, Ames, IA 5011, USA
| | - Royce Bitzer
- Department of Plant Pathology, Entomology, and Microbiology, 2213 Pammel Dr., Iowa State University, Ames, IA 50011, USA
| | - Kristen A Baum
- Department of Integrative Biology, Oklahoma State University, 501 Life Sciences E, Stillwater, OK 74078, USA
| | - Blanca X Mora Alvarez
- Department of Biology, University of Western Ontario, 1151 Richmond St, London, ON, N6A 5B7, Canada
| | - Jude Kastens
- Kansas Biological Survey & Center for Ecological Research, University of Kansas, 2101 Constant Ave., Lawrence, KS 66047, USA
| | - Jeremy N McNeil
- Department of Biology, University of Western Ontario, 1151 Richmond St, London, ON, N6A 5B7, Canada
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6
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Shaw AK, Levet M, Binning SA. A unified evolutionary framework for understanding parasite infection and host migratory behaviour. Ecol Lett 2023; 26:1987-2002. [PMID: 37706582 DOI: 10.1111/ele.14301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 08/09/2023] [Accepted: 08/12/2023] [Indexed: 09/15/2023]
Abstract
Animal migration impacts organismal health and parasite transmission: migrants are simultaneously exposed to parasites and able to reduce infection for both individuals and populations. However, these dynamics are difficult to study; empirical studies reveal disparate results while existing theory makes assumptions that simplify natural complexity. Here, we systematically review empirical studies of migration and infection across taxa, highlighting key gaps in our understanding. Next, we develop a unified evolutionary framework incorporating different selective pressures of parasite-migration interactions while accounting for ecological complexity that goes beyond previous theory. Our framework generates diverse migration-infection patterns paralleling those seen in empirical systems, including partial and differential migration. Finally, we generate predictions about which mechanisms dominate which empirical systems to guide future studies. Our framework provides an overarching understanding of selective pressures shaping migration patterns in the context of animal health and disease, which is critical for predicting how environmental change may threaten migration.
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Affiliation(s)
- Allison K Shaw
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, Minnesota, USA
| | - Marie Levet
- Département de Sciences Biologiques, Université de Montréal, Montréal, Québec, Canada
| | - Sandra A Binning
- Département de Sciences Biologiques, Université de Montréal, Montréal, Québec, Canada
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7
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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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8
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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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9
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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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10
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Yang LH. Complexity, humility, and action: a current perspective on monarchs in Western North America. CURRENT OPINION IN INSECT SCIENCE 2023; 59:101078. [PMID: 37380104 DOI: 10.1016/j.cois.2023.101078] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 06/16/2023] [Accepted: 06/19/2023] [Indexed: 06/30/2023]
Abstract
Recent studies have continued to shed light on the ecology of monarch butterflies (Danaus plexippus) in western North America. These studies have documented a declining overwintering population over several decades, punctuated by unexpected variability in recent years. Understanding this variability will require grappling with the spatial and temporal heterogeneity of resources and risks presented to western monarchs throughout their annual life cycle. Recent changes in the western monarch population further illustrate how interacting global change drivers can create complex causes and consequences in this system. The complexity of this system should inspire humility. However, even recognizing the limits of our current understanding, there is enough scientific common ground to take some conservation actions now.
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Affiliation(s)
- Louie H Yang
- Department of Entomology and Nematology, University of California, Davis, CA 95616, USA.
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11
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Davis AK, Nibbelink N, Deneka CJ. Revisiting geographic variation in melanism of monarch butterfly larvae in North America using iNaturalist photos. J Therm Biol 2022; 110:103374. [DOI: 10.1016/j.jtherbio.2022.103374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 10/11/2022] [Accepted: 10/18/2022] [Indexed: 11/07/2022]
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12
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Crossley MS, Meehan TD, Moran MD, Glassberg J, Snyder WE, Davis AK. Opposing global change drivers counterbalance trends in breeding North American monarch butterflies. GLOBAL CHANGE BIOLOGY 2022; 28:4726-4735. [PMID: 35686571 PMCID: PMC9542617 DOI: 10.1111/gcb.16282] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 05/21/2022] [Indexed: 05/26/2023]
Abstract
Many insects are in clear decline, with monarch butterflies (Danaus plexippus) drawing particular attention as a flagship species. It is well documented that, among migratory populations, numbers of overwintering monarchs have been falling across several decades, but trends among breeding monarchs are less clear. Here, we compile >135,000 monarch observations between 1993 and 2018 from the North American Butterfly Association's annual butterfly count to examine spatiotemporal patterns and potential drivers of adult monarch relative abundance trends across the entire breeding range in eastern and western North America. While the data revealed declines at some sites, particularly the US Northeast and parts of the Midwest, numbers in other areas, notably the US Southeast and Northwest, were unchanged or increasing, yielding a slightly positive overall trend across the species range. Negative impacts of agricultural glyphosate use appeared to be counterbalanced by positive effects of annual temperature, particularly in the US Midwest. Overall, our results suggest that population growth in summer is compensating for losses during the winter and that changing environmental variables have offsetting effects on mortality and/or reproduction. We suggest that density-dependent reproductive compensation when lower numbers arrive each spring is currently able to maintain relatively stable breeding monarch numbers. However, we caution against complacency since accelerating climate change may bring growing threats. In addition, increases of summer monarchs in some regions, especially in California and in the south, may reflect replacement of migratory with resident populations. Nonetheless, it is perhaps reassuring that ubiquitous downward trends in summer monarch abundance are not evident.
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Affiliation(s)
- Michael S. Crossley
- Department of Entomology and Wildlife EcologyUniversity of DelawareNewarkDelawareUSA
| | | | - Matthew D. Moran
- Department of Biology and Health SciencesHendrix CollegeConwayArkansasUSA
| | - Jeffrey Glassberg
- North American Butterfly AssociationMorristownNew JerseyUSA
- Rice UniversityHoustonTexasUSA
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13
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Niitepõld K, Parry HA, Harris NR, Appel AG, de Roode JC, Kavazis AN, Hood WR. Flying on empty: Reduced mitochondrial function and flight capacity in food-deprived monarch butterflies. J Exp Biol 2022; 225:275693. [PMID: 35694960 DOI: 10.1242/jeb.244431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 06/07/2022] [Indexed: 11/20/2022]
Abstract
Mitochondrial function is fundamental to organismal performance, health, and fitness - especially during energetically challenging events, such as migration. With this investigation, we evaluated mitochondrial sensitivity to ecologically relevant stressors. We focused on an iconic migrant, the North American monarch butterfly (Danaus plexippus), and examined the effects of two stressors: seven days of food deprivation, and infection by the protozoan parasite Ophryocystis elektroscirrha (known to reduce survival and flight performance). We measured whole-animal resting (RMR) and peak flight metabolic rate, and mitochondrial respiration of isolated mitochondria from the flight muscles. Food deprivation reduced mass-independent RMR and peak flight metabolic rate, whereas infection did not. Fed monarchs used mainly lipids in flight (respiratory quotient 0.73), but the respiratory quotient dropped in food-deprived individuals, possibly indicating switching to alternative energy sources, such as ketone bodies. Food deprivation decreased mitochondrial maximum oxygen consumption but not basal respiration, resulting in lower respiratory control ratio (RCR). Furthermore, food deprivation decreased mitochondrial complex III activity, but increased complex IV activity. Infection did not result in any changes in these mitochondrial variables. Mitochondrial maximum respiration rate correlated positively with mass-independent RMR and flight metabolic rate, suggesting a link between mitochondria and whole-animal performance. In conclusion, low food availability negatively affects mitochondrial function and flight performance, with potential implications on migration, fitness, and population dynamics. Although previous studies have reported poor flight performance in infected monarchs, we found no differences in physiological performance, suggesting that reduced flight capacity may be due to structural differences or low energy stores.
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Affiliation(s)
- Kristjan Niitepõld
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA.,The Finnish Science Centre Heureka, 01300 Vantaa, Finland
| | - Hailey A Parry
- School of Kinesiology, Auburn University, Auburn, AL 36849, USA
| | - Natalie R Harris
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA
| | - Arthur G Appel
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849, USA
| | | | | | - Wendy R Hood
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA
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