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Brackley A, Lill J, Weiss M. Ecological Predictors of Pupal Survival in a Common North American Butterfly. ENVIRONMENTAL ENTOMOLOGY 2022; 51:1030-1039. [PMID: 35866523 DOI: 10.1093/ee/nvac055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Indexed: 06/15/2023]
Abstract
All holometabolous insects undergo a pupal life stage, a transformative period during which the insects are immobile and thus particularly vulnerable to both natural enemies and harmful abiotic conditions. For multivoltine species like the silver-spotted skipper [Epargyreus clarus (Cramer) (Lepidoptera: Hesperiidae)], which produces both diapausing and nondiapausing generations throughout much of its range, both the duration of the pupal stage and the ecological challenges faced by pupae can differ among generations. We conducted a set of field experiments to investigate the seasonal and annual variation in pupal mortality for E. clarus pupae experiencing different biotic and abiotic conditions. We also examined the behavioral and ecological factors influencing the construction and persistence of pupal shelters by prepupal larvae. Surprisingly, measures of both cumulative and daily pupal predation were significantly higher during the relatively short (10-14 d) nondiapausing (summer) generations, compared with the diapausing (winter) generations, despite a nearly 20-fold longer pupal duration recorded for the latter. Indirect evidence from field censuses suggested that this intergenerational difference in mortality was due to seasonal variation in consumption of pupae by generalist vertebrate predators. The presence of a shelter increased survival in summer, though not in winter, perhaps because winter pupae were likely to be buried under autumnal leaf litter, regardless of initial shelter status. When constructing their shelters, prepupal E. clarus larvae did not prefer host leaves over nonhost leaves, suggesting that induced preferences are unlikely to play an important role in this process. Despite finding marked differences in the decomposition rates of shelter leaves derived from host vs. nonhost plants, several lines of evidence suggest that these differences are unlikely to impact E. clarus pupal mortality during either the summer or winter generations.
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Affiliation(s)
- Allison Brackley
- Department of Biology, Georgetown University, 406 Reiss Building, 37th & O Street NW, Washington, DC, 20057, USA
| | - John Lill
- Department of Biological Sciences, George Washington University, 800 22nd Street, Suite 6000, NW, Washington, DC, 20052, USA
| | - Martha Weiss
- Department of Biology, Georgetown University, 406 Reiss Building, 37th & O Street NW, Washington, DC, 20057, USA
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Berasategui A, Breitenbach N, García-Lozano M, Pons I, Sailer B, Lanz C, Rodríguez V, Hipp K, Ziemert N, Windsor D, Salem H. The leaf beetle Chelymorpha alternans propagates a plant pathogen in exchange for pupal protection. Curr Biol 2022; 32:4114-4127.e6. [PMID: 35987210 DOI: 10.1016/j.cub.2022.07.065] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 07/21/2022] [Accepted: 07/22/2022] [Indexed: 12/14/2022]
Abstract
Many insects rely on microbial protection in the early stages of their development. However, in contrast to symbiont-mediated defense of eggs and young instars, the role of microbes in safeguarding pupae remains relatively unexplored, despite the susceptibility of the immobile stage to antagonistic challenges. Here, we outline the importance of symbiosis in ensuring pupal protection by describing a mutualistic partnership between the ascomycete Fusarium oxysporum and Chelymorpha alternans, a leaf beetle. The symbiont rapidly proliferates at the onset of pupation, extensively and conspicuously coating C. alternans during metamorphosis. The fungus confers defense against predation as symbiont elimination results in reduced pupal survivorship. In exchange, eclosing beetles vector F. oxysporum to their host plants, resulting in a systemic infection. By causing wilt disease, the fungus retained its phytopathogenic capacity in light of its symbiosis with C. alternans. Despite possessing a relatively reduced genome, F. oxysporum encodes metabolic pathways that reflect its dual lifestyle as a plant pathogen and a defensive insect symbiont. These include virulence factors underlying plant colonization, along with mycotoxins that may contribute to the defensive biochemistry of the insect host. Collectively, our findings shed light on a mutualism predicated on pupal protection of an herbivorous beetle in exchange for symbiont dissemination and propagation.
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Affiliation(s)
- Aileen Berasategui
- Max Planck Institute for Biology, Mutualisms Research Group, Max-Planck-Ring 5, Tübingen 72076, Germany; University of Tübingen, Cluster of Excellence 'Controlling Microbes to Fight Infections', Auf der Morgenstelle 28, Tübingen 72076, Germany.
| | - Noa Breitenbach
- Max Planck Institute for Biology, Mutualisms Research Group, Max-Planck-Ring 5, Tübingen 72076, Germany
| | - Marleny García-Lozano
- Max Planck Institute for Biology, Mutualisms Research Group, Max-Planck-Ring 5, Tübingen 72076, Germany
| | - Inès Pons
- Max Planck Institute for Biology, Mutualisms Research Group, Max-Planck-Ring 5, Tübingen 72076, Germany
| | - Brigitte Sailer
- Max Planck Institute for Biology, Electron Microscopy Facility, Max-Planck-Ring 5, Tübingen 72076, Germany
| | - Christa Lanz
- Max Planck Institute for Biology, Genome Center, Max-Planck-Ring 5, Tübingen 72076, Germany
| | - Viterbo Rodríguez
- Centro Regional Universitario de Veraguas, Centro de Capacitación, Investigación y Monitoreo de la Biodiversidad en Coiba, Calle Décima, vía San Francisco, Santiago 08001, Republic of Panama
| | - Katharina Hipp
- Max Planck Institute for Biology, Electron Microscopy Facility, Max-Planck-Ring 5, Tübingen 72076, Germany
| | - Nadine Ziemert
- University of Tübingen, Cluster of Excellence 'Controlling Microbes to Fight Infections', Auf der Morgenstelle 28, Tübingen 72076, Germany
| | - Donald Windsor
- Smithsonian Tropical Research Institute, Luis Clement Avenue, Bldg. 401 Tupper, Panama City 0843-03092, Republic of Panama
| | - Hassan Salem
- Max Planck Institute for Biology, Mutualisms Research Group, Max-Planck-Ring 5, Tübingen 72076, Germany.
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Abarca M, Lill JT, Weiss MR. Host Plant and Thermal Stress Induce Supernumerary Instars in Caterpillars. ENVIRONMENTAL ENTOMOLOGY 2020; 49:123-131. [PMID: 31758687 DOI: 10.1093/ee/nvz136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Indexed: 06/10/2023]
Abstract
Environmental stressors may induce variation in the number of larval instars of holometabolous insects. Host plant quality and ambient temperature can both induce this life history shift in the silver-spotted skipper, Epargyreus clarus (Cramer 1775) (Lepidoptera: Hesperiidae). To better understand this phenomenon, we raised larvae on high-quality (kudzu) or low-quality (wisteria) host plants in growth chambers under three temperature regimes (20, 26, and 32°C) that were either constant or diurnally fluctuating (T ± 5°C), and recorded survival and incidence of supernumerary instars. Larvae feeding on the low-quality host and/or experiencing thermal stress were more likely to show supernumerary development (SD). A subset of treatments yielded a mix of SD and TD (typical development) individuals, allowing for comparisons between phenotypes. Under the most stressful treatment (20 ± 5°C, wisteria), development time was 9 days longer in SD than in TD individuals; by contrast, at typical summer temperatures (26 ± 5°C), also on wisteria, total development time did not differ between these two phenotypes. Head capsules of both second and third instars were smaller in SD individuals. A retrospective logistic regression analysis indicated that third-instar head capsule size could be used to predict expression of the SD phenotype. By the ultimate instar, however, there were no detectable differences in head capsule size, and SD and TD individuals did not differ in pupal mass, strongly suggesting that the SD phenotype functions as a compensatory mechanism allowing E. clarus larvae to achieve the same size at metamorphosis (a strong fitness correlate) as TD larvae.
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Affiliation(s)
- Mariana Abarca
- Department of Biology, Georgetown University, Washington, DC
| | - John T Lill
- Department of Biological Sciences, George Washington University, Washington, DC
| | - Martha R Weiss
- Department of Biology, Georgetown University, Washington, DC
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Herbivore seasonality responds to conflicting cues: Untangling the effects of host, temperature, and photoperiod. PLoS One 2019; 14:e0222227. [PMID: 31487319 PMCID: PMC6728043 DOI: 10.1371/journal.pone.0222227] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 08/23/2019] [Indexed: 11/19/2022] Open
Abstract
Organisms from temperate ecosystems experience a cyclic alternation of favorable seasons, when they can grow and develop, and unfavorable periods, characterized by low temperatures and reduced resource availability. A common adaptation to these changing conditions is to undergo a state of metabolic arrest triggered by environmental cues (e.g. diapause) during the unfavorable periods. Altered environmental conditions resulting from global change can expose organisms to contradictory cues, potentially triggering maladaptive responses. Here, I compared the performance of an oligophagous butterfly when experiencing consistent vs contradictory environmental cues by manipulating temperature, daylength, and host plant in the laboratory. I implemented a fully factorial design with realistic temperature and photoperiodic regimes to resemble environmental conditions during mid-summer and the summer-autumn transition within the focal species’ range. To assess the role of host plant at mediating the effects of abiotic factors, larvae were fed foliage of either a high or a low-quality host species. Decreasing daylength was the primary cue inducing diapause; however, feeding on a low-quality host at low temperatures also induced diapause in larvae growing under constant summer daylength. Conversely, exposure to high temperatures while feeding on a high-quality host occasionally overruled the diapause-inducing effect of decreasing daylength. Feeding on a high-quality host mitigated the lethal effects of cold, but not of hot temperatures. In addition, exposure to cold temperatures resulted in a significant reduction of pupal mass only under decreasing daylength. These results indicate that responses to environmental stressors in this multivoltine butterfly differ across the growing season according to the eco-physiological state of individuals (whether they undergo direct development or diapause). Traits related to oligophagy, such as sensitivity to multiple cues for diapause induction, as well as some of its consequences, such as the occurrence of overlapping generations, are likely to mitigate some of the detrimental effects of global change.
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Lindstedt C, Murphy L, Mappes J. Antipredator strategies of pupae: how to avoid predation in an immobile life stage? Philos Trans R Soc Lond B Biol Sci 2019; 374:20190069. [PMID: 31438812 DOI: 10.1098/rstb.2019.0069] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Antipredator strategies of the pupal stage in insects have received little attention in comparison to larval or adult stages. This is despite the fact that predation risk can be high during the pupal stage, making it a critical stage for subsequent fitness. The immobile pupae are not, however, defenceless; a wide range of antipredator strategies have evolved against invertebrate and vertebrate predators. The most common strategy seems to be 'avoiding encounters with predators' by actively hiding in vegetation and soil or via cryptic coloration and masquerade. Pupae have also evolved behavioural and secondary defences such as defensive toxins, physical defences or deimatic movements and sounds. Interestingly, warning coloration used to advertise unprofitability has evolved very rarely, even though the pupal stage often contains defensive toxins in chemically defended species. In some species, pupae gain protection from conspecifics or mimic chemical and auditory signals and thereby manipulate other species to protect them. Our literature survey highlights the importance of studying selection pressures across an individual's life stages to predict how ontogenetic variation in selective environments shapes individual fitness and population dynamics in insects. Finally, we also suggest interesting avenues for future research to pursue. This article is part of the theme issue 'The evolution of complete metamorphosis'.
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Affiliation(s)
- Carita Lindstedt
- Department of Biological and Environmental Sciences, P.O. Box 35, FI-40014 University of Jyväskylä, Jyväskylä, Finland
| | - Liam Murphy
- Department of Biological and Environmental Sciences, P.O. Box 35, FI-40014 University of Jyväskylä, Jyväskylä, Finland
| | - Johanna Mappes
- Department of Biological and Environmental Sciences, P.O. Box 35, FI-40014 University of Jyväskylä, Jyväskylä, Finland
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Wheelwright NT, Taylor LU, West BM, Voss ER, Berzins SY, Villeneuve AR, LeBlanc HR, Leos VB, Mayne SJ, McCarthy SA, Nagar SJ, Watling JS. Pupation Site Selection and Enemy Avoidance in the Introduced Pine Sawfly ( Diprion similis). Northeast Nat (Steuben) 2017. [DOI: 10.1656/045.024.s705] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
| | - Liam U. Taylor
- Department of Biology, Bowdoin College, Brunswick, ME 04011
| | | | - Erin R. Voss
- Department of Biology, Bowdoin College, Brunswick, ME 04011
| | | | | | | | - Victor B. Leos
- Department of Biology, Bowdoin College, Brunswick, ME 04011
| | | | | | - Shan J. Nagar
- Department of Biology, Bowdoin College, Brunswick, ME 04011
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Grof-Tisza P, Holyoak M, Antell E, Karban R. Predation and associational refuge drive ontogenetic niche shifts in an arctiid caterpillar. Ecology 2015; 96:80-9. [DOI: 10.1890/14-1092.1] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Patrick Grof-Tisza
- Ecology Graduate Group, University of California, 1 Shields Ave., Davis, California 95616 USA
| | - Marcel Holyoak
- Department of Environmental Science and Policy, University of California, 1 Shields Ave., Davis, California 95616 USA
| | - Edward Antell
- Romberg Tiburon Center for Environmental Studies, San Francisco State University, San Francisco, California 94132 USA
| | - Richard Karban
- Department of Entomology, University of California, 1 Shields Ave., Davis, California 95616 USA
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Fiorentino VL, Murphy SM, Stoepler TM, Lill JT. Facilitative effects of group feeding on performance of the saddleback caterpillar (Lepidoptera: Limacodidae). ENVIRONMENTAL ENTOMOLOGY 2014; 43:131-138. [PMID: 24472205 DOI: 10.1603/en13144] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Gregarious feeding by insect herbivores is a widely observed, yet poorly understood, behavioral adaptation. Previous research has tested the importance of group feeding for predator deterrence, noting the ubiquity of aposematism among group-feeding insects, but few studies have examined the role of feeding facilitation for aggregates of insect herbivores. We tested the hypothesis that group feeding has facilitative effects on performance of the saddleback caterpillar, Acharia stimulea Clemens, a generalist herbivore of deciduous trees. In an understory forest setting, we reared caterpillars alone or in groups on two different host plants, white oak (Quercus alba L.) and American beech (Fagus grandifolia Ehrlich), and recorded multiple measures of insect performance during regular field censuses. As predicted, A. stimulea caterpillars feeding in groups on white oak had increased relative growth rates compared with caterpillars feeding alone, and the magnitude of this facilitative effect varied among censuses, conferring benefits both early and late in development. By contrast, no facilitative effects of group feeding were detected on beech, suggesting that the benefits of facilitative feeding may be host specific. On both hosts, caterpillar development time was slightly faster for group-feeding cohorts compared with their solitary counterparts. Because early instar caterpillars are particularly vulnerable to predation and parasitism, even modest increases in growth rates and reductions in development time may decrease exposure time to enemies during these vulnerable stages. On both hosts, group feeding also reduced the trade-off between individual development time and cocoon mass, suggesting that feeding efficiency is improved in group feeders relative to solitary caterpillars.
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Affiliation(s)
- Victoria L Fiorentino
- Department of Biological Sciences, George Washington University, 2023 G Street NW, Suite 340, Washington, DC 20052, USA
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