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Raynaud-Berton B, Gibert P, Suppo C, Pincebourde S, Colinet H. Modelling thermal reaction norms for development and viability in Drosophila suzukii under constant, fluctuating and field conditions. J Therm Biol 2024; 123:103891. [PMID: 38972154 DOI: 10.1016/j.jtherbio.2024.103891] [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: 12/24/2023] [Revised: 05/15/2024] [Accepted: 06/09/2024] [Indexed: 07/09/2024]
Abstract
Phenological models for insect pests often rely on knowledge of thermal reaction norms. These may differ in shape depending on developmental thermal conditions (e.g. constant vs. fluctuating) and other factors such as life-stages. Here, we conducted an extensive comparative study of the thermal reaction norms for development and viability in the invasive fly, Drosophila suzukii, under constant and fluctuating thermal regimes. Flies, were submitted to 15 different constant temperatures (CT) ranging from 8 to 35 °C. We compared responses under CT with patterns observed under 15 different fluctuating temperature (FT) regimes. We tested several equations for thermal performance curves and compared various models to obtain thermal limits and degree-day estimations. To validate the model's predictions, the phenology was monitored in two artificial field-like conditions and two natural conditions in outdoor cages during spring and winter. Thermal reaction norm for viability from egg to pupa was broader than that from egg to adult. FT conditions yielded a broader thermal breadth for viability than CT, with a performance extended towards the colder side, consistent with our field observations in winter. Models resulting from both CT and FT conditions made accurate predictions of degree-day as long as the temperature remained within the linear part of the developmental rate curve. Under cold artificial and natural winter conditions, a model based on FT data made more accurate predictions. Model based on CT failed to predict adult's emergence in winter. We also document the first record of development and adult emergence throughout winter in D. suzukii. Population dynamics models in D. suzukii are all based on summer phenotype and CT. Accounting for variations between seasonal phenotypes, stages, and thermal conditions (CT vs. FT) could improve the predictive power of the models.
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Affiliation(s)
- Bréa Raynaud-Berton
- University of Rennes, CNRS, ECOBIO [(Ecosystèmes, biodiversité, évolution)] - UMR 6553, Rennes, France
| | - Patricia Gibert
- Université Claude Bernard Lyon 1, CNRS, LBBE (Laboratoire de Biométrie et Biologie Évolutive), UMR 5558, Villeurbanne, F-69100
| | - Christelle Suppo
- Institut de Recherche sur la Biologie de l'Insecte, UMR7261, CNRS, Université de Tours, Tours, France
| | - Sylvain Pincebourde
- Institut de Recherche sur la Biologie de l'Insecte, UMR7261, CNRS, Université de Tours, Tours, France
| | - Hervé Colinet
- University of Rennes, CNRS, ECOBIO [(Ecosystèmes, biodiversité, évolution)] - UMR 6553, Rennes, France.
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Sario S, Melo-Ferreira J, Santos C. Winter Is (Not) Coming: Is Climate Change Helping Drosophila suzukii Overwintering? BIOLOGY 2023; 12:907. [PMID: 37508339 PMCID: PMC10376787 DOI: 10.3390/biology12070907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 06/19/2023] [Accepted: 06/23/2023] [Indexed: 07/30/2023]
Abstract
Anthropogenic challenges, particularly climate change-associated factors, are strongly impacting the behavior, distribution, and survival of insects. Yet how these changes affect pests such as Drosophila suzukii, a cosmopolitan pest of soft-skinned small fruits, remains poorly understood. This polyphagous pest is chill-susceptible, with cold temperatures causing multiple stresses, including desiccation and starvation, also challenging the immune system. Since the invasion of Europe and the United States of America in 2009, it has been rapidly spreading to several European and American countries (both North and South American) and North African and Asian countries. However, globalization and global warming are allowing an altitudinal and latitudinal expansion of the species, and thus the colonization of colder regions. This review explores how D. suzukii adapts to survive during cold seasons. We focus on overwintering strategies of behavioral adaptations such as migration or sheltering, seasonal polyphenism, reproductive adaptations, as well as metabolic and transcriptomic changes in response to cold. Finally, we discuss how the continuation of climate change may promote the ability of this species to survive and spread, and what mitigation measures could be employed to overcome cold-adapted D. suzukii.
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Affiliation(s)
- Sara Sario
- Biology Department, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal
- LAQV-REQUIMTE, Faculty of Sciences, University of Porto, 4050-453 Porto, Portugal
| | - José Melo-Ferreira
- Biology Department, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal
- CIBIO-Research Centre in Biodiversity and Genetic Resources, InBIO Associate Laboratory, 4485-661 Vairão, Portugal
- BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, 4485-661 Vairão, Portugal
| | - Conceição Santos
- Biology Department, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal
- LAQV-REQUIMTE, Faculty of Sciences, University of Porto, 4050-453 Porto, Portugal
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3
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Shope J, Polk D, Mansue C, Rodriguez-Saona C. The contrasting role of climate variation on the population dynamics of a native and an invasive insect pest. PLoS One 2023; 18:e0284600. [PMID: 37115782 PMCID: PMC10146567 DOI: 10.1371/journal.pone.0284600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 04/04/2023] [Indexed: 04/29/2023] Open
Abstract
Since 2008, spotted-wing drosophila, Drosophila suzukii, has become a major pest of soft, thin-skinned fruits in the USA, causing significant annual yield losses. Historically, the native blueberry maggot fly, Rhagoletis mendax, has been a key blueberry pest in eastern North America and a driver of insecticide usage. After its invasion in 2011 into New Jersey (USA), D. suzukii has supplanted R. mendax as the main target of insecticide applications in the state. However, the impact of D. suzukii on the native R. mendax has not been documented, particularly in relation to local climate. Historical monitoring data from New Jersey blueberry farms were used to assess the role of climate on R. mendax and D. suzukii populations. Seasonal trap captures of R. mendax adults have decreased after D. suzukii invasion, while D. suzukii trap captures have increased. Similarly, D. suzukii first captures have occurred earlier each year, while R. mendax has been captured later in the growing season. Winter freezing and summer growing degree days were found to significantly correlate with D. suzukii activity. Using downscaled climate simulations, we projected that D. suzukii will arrive in New Jersey blueberry fields up to 5 days earlier on average by 2030 and 2 weeks earlier by 2050 with warming temperatures, exacerbating yield losses and insecticide usage. As regional temperatures are projected to warm and the invasive range continues to expand, we predict the rate of phenological development of the invasive D. suzukii and its impact on native insects to change noticeably, bringing new challenges for pest management strategies.
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Affiliation(s)
- James Shope
- Department of Environmental Sciences, New Jersey Climate Change Resource Center, Rutgers University, New Brunswick, New Jersey, United States of America
| | - Dean Polk
- Rutgers Specialty Crop Research and Extension Center, Rutgers University, Cream Ridge, New Jersey, United States of America
| | - Carrie Mansue
- Cooperative Extension of Atlantic County, Rutgers University, Mays Landing, New Jersey, United States of America
| | - Cesar Rodriguez-Saona
- P.E. Marucci Center, Rutgers University, Chatsworth, New Jersey, United States of America
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Jones R, Eady PE, Goddard MR, Fountain MT. The Efficacy of Yeast Phagostimulant Baits in Attract-and-Kill Strategies Varies between Summer- and Winter-Morphs of Drosophila suzukii. INSECTS 2022; 13:995. [PMID: 36354819 PMCID: PMC9696471 DOI: 10.3390/insects13110995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 10/27/2022] [Accepted: 10/28/2022] [Indexed: 06/16/2023]
Abstract
Drosophila suzukii (Matsumura), is a globally invasive pest of soft and stone fruit. To survive winter in temperate zones it enters a reproductive diapause in a morphologically distinct phenotype. Phagostimulant baits can be combined with insecticides in attract-and-kill strategies for control. We investigated the effectiveness of single yeast species and combinations of co-fermented yeast phagostimulant baits when combined with insecticides in laboratory assays against both summer- and winter-morph D. suzukii. Candida zemplininia or Hanseniaspora uvarum + C. zemplininia combined with lambda-cyhalothrin or cyantraniliprole, and H. uvarum combined with cyantraniliprole caused significantly higher mortality in winter- compared to summer-morph D. suzukii. Additionally, lambda-cyhalothrin combined with M. pulcherrima + H. uvarum resulted in greater mortality compared to single yeasts, H. uvarum for both summer- and winter-morphs and C. zemplininia for summer-morphs. M. pulcherrima + H. uvarum with spinosad significantly reduced the time-to-kill (50%) of summer-morphs compared to insecticide alone. Most yeast-based baits were comparable in terms of attract-and-kill efficacy to Combi-protec, a commercially available bait, although M. pulcherrima or H. uvarum + C. zemplininia in with cyantraniliprole were less effective. Our study suggests that yeast phagostimulants in attract-and-kill strategies should be adjusted for summer- and winter-morph D. suzukii for more effective control.
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Affiliation(s)
- Rory Jones
- School of Life Sciences, University of Lincoln, Lincoln LN6 7DL, UK
- NIAB, East Malling, Kent ME19 6BJ, UK
| | - Paul E. Eady
- School of Life Sciences, University of Lincoln, Lincoln LN6 7DL, UK
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Feltman NR, Burkness EC, Ebbenga D, Hutchison WD, Smanski MJ. HUGE pipeline to measure temporal genetic variation in Drosophila suzukii populations for genetic biocontrol applications. FRONTIERS IN INSECT SCIENCE 2022; 2:981974. [PMID: 38468784 PMCID: PMC10926429 DOI: 10.3389/finsc.2022.981974] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 08/22/2022] [Indexed: 03/13/2024]
Abstract
Understanding the fine-scale genome sequence diversity that exists within natural populations is important for developing models of species migration, temporal stability, and range expansion. For invasive species, agricultural pests, and disease vectors, sequence diversity at specific loci in the genome can impact the efficacy of next-generation genetic biocontrol strategies. Here we describe a pipeline for haplotype-resolution genetic variant discovery and quantification from thousands of Spotted Wing Drosophila (Drosophila suzukii, SWD) isolated at two field sites in the North-Central United States (Minnesota) across two seasons. We observed highly similar single nucleotide polymorphism (SNP) frequencies at each genomic location at each field site and year. This supports the hypotheses that SWD overwinters in Minnesota, is annually populated by the same source populations or a combination of both theories. Also, the stable genetic structure of SWD populations allows for the rational design of genetic biocontrol technologies for population suppression.
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Affiliation(s)
- Nathan R. Feltman
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Saint Paul, MN, United States
- Biotechnology Institute, University of Minnesota, Saint Paul, MN, United States
| | - Eric C. Burkness
- Department of Entomology, University of Minnesota, Saint Paul, MN, United States
| | - Dominique N. Ebbenga
- Department of Entomology, University of Minnesota, Saint Paul, MN, United States
| | - William D. Hutchison
- Department of Entomology, University of Minnesota, Saint Paul, MN, United States
| | - Michael J. Smanski
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Saint Paul, MN, United States
- Biotechnology Institute, University of Minnesota, Saint Paul, MN, United States
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Field Suppression of Spotted Wing Drosophila (SWD) ( Drosophila suzukii Matsumura) Using the Sterile Insect Technique (SIT). INSECTS 2022; 13:insects13040328. [PMID: 35447770 PMCID: PMC9031279 DOI: 10.3390/insects13040328] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/22/2022] [Accepted: 03/23/2022] [Indexed: 12/04/2022]
Abstract
Drosophila suzukii (spotted wing drosophila—SWD) is an economically important pest of soft and stone fruit worldwide. Control relies on broad-spectrum insecticides, which are neither fully effective nor environmentally sustainable. The sterile insect technique (SIT) is a proven, effective and environmentally friendly pest-management tool. Here, we investigated, for the first time, the potential of using SIT to control D. suzukii in field conditions without physical barriers that limit insect invasion. A proprietary method of rearing and irradiation with X-rays was used to obtain males that were > 99% sterile. Sterile males were released twice per week from April to October 2021 on a site in Kent, UK, where everbearing strawberries were grown in open polytunnels. The infestation of wild female D. suzukii was monitored weekly using red sticky traps with dry lure at the treated site and at two similar control sites that did not receive sterile male releases. Releases of sterile males suppressed the wild female D. suzukii population by up to 91% in comparison with the control sites. We thus demonstrated the feasibility of SIT to achieve season-long control of D. suzukii using early, sustained and dynamically targeted releases of sterile males. This provides a promising environmentally friendly method to control this important pest.
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Tarapacki P, Jørgensen LB, Sørensen JG, Andersen MK, Colinet H, Overgaard J. Acclimation, duration and intensity of cold exposure determine the rate of cold stress accumulation and mortality in Drosophila suzukii. JOURNAL OF INSECT PHYSIOLOGY 2021; 135:104323. [PMID: 34717940 DOI: 10.1016/j.jinsphys.2021.104323] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 10/18/2021] [Accepted: 10/21/2021] [Indexed: 06/13/2023]
Abstract
The spotted wing drosophila (SWD), Drosophila suzukii, is a major invasive fruit pest. There is strong consensus that low temperature is among the main drivers of SWD population distribution, and the invasion success of SWD is also linked to its thermal plasticity. Most studies on ectotherm cold tolerance focus on exposure to a single stressful temperature but here we investigated how cold stress intensity affected survival duration across a broad range of low temperatures (-7 to +3 °C). The analysis of Lt50 at different stressful temperatures (Thermal Death Time curve - TDT) is based on the suggestion that cold injury accumulation rate increases exponentially with the intensity of thermal stress. In accordance with the hypothesis, Lt50 of SWD decreased exponentially with temperature. Further, comparison of TDT curves from flies acclimated to 15, 19 and 23 °C, respectively, showed an almost full compensation with acclimation such that the temperature required to induce mortality over a fixed time decreased almost 1 °C per °C lowering of acclimation temperature. Importantly, this change in cold tolerance with acclimation was uniform across the range of moderate to intense cold stress exposures examined. To understand if cold stress at moderate and intense exposures affects the same physiological systems we examined how physiological markers/symptoms of chill injury developed at different intensities of the cold stress. Specifically, hsp23 expression and extracellular [K+] were measured in flies exposed to different intensities of cold stress (-6, -2 and +2 °C) and at various time points corresponding to the same progression of injury (equivalent to 1/3, 2/3 or 3/3 of Lt50). The different cold stress intensities all triggered hsp23 expression following 2 h of recovery, but patterns of expression differed. At the most intense cold stress (-6 and -2 °C) a gradual increase with time was found. In contrast, at +2 °C an initial increase was followed by a dissipating expression. A gradual perturbation of ion balance (hyperkalemia) was also found at all three cold stress intensities examined, with only slight dissimilarities between treatment temperatures. Despite some differences between the three cold intensities examined, the results generally support the hypothesis that intense and moderate cold stress induces the same physiological perturbation. This suggests that cold stress experienced during natural fluctuating conditions is additive and the results also illustrate that the rate of injury accumulation increases dramatically (exponentially) with decreasing temperature (increasing stress).
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Affiliation(s)
| | | | | | - Mads Kuhlmann Andersen
- Department of Biology, Aarhus University, 8000 Aarhus C, Denmark; Department of Biology, Carleton University, Ottawa K1S 5B6, Canada
| | - Hervé Colinet
- University of Rennes, CNRS, ECOBIO [(Ecosystèmes, biodiversité, évolution)] - UMR 6553, F-35000 Rennes, France
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8
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Panel ADC, Pen I, Pannebakker BA, Helsen HHM, Wertheim B. Seasonal morphotypes of Drosophila suzukii differ in key life-history traits during and after a prolonged period of cold exposure. Ecol Evol 2020; 10:9085-9099. [PMID: 32953048 PMCID: PMC7487234 DOI: 10.1002/ece3.6517] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Revised: 06/02/2020] [Accepted: 06/05/2020] [Indexed: 01/13/2023] Open
Abstract
Seasonal polyphenism in Drosophila suzukii manifests itself in two discrete adult morphotypes, the "winter morph" (WM) and the "summer morph" (SM). These morphotypes are known to differ in thermal stress tolerance, and they co-occur during parts of the year. In this study, we aimed to estimate morph-specific survival and fecundity in laboratory settings simulating field conditions. We specifically analyzed how WM and SM D. suzukii differed in mortality and reproduction during and after a period of cold exposure resembling winter and spring conditions in temperate climates. The median lifespan of D. suzukii varied around 5 months for the WM flies and around 7 months for the SM flies. WM flies showed higher survival during the cold-exposure period compared with SM flies, and especially SM males suffered high mortality under these conditions. In contrast, SM flies had lower mortality rates than WM flies under spring-like conditions. Intriguingly, reproductive status (virgin or mated) did not impact the fly survival, either during the cold exposure or during spring-like conditions. Even though the reproductive potential of WM flies was greatly reduced compared with SM flies, both WM and SM females that had mated before the cold exposure were able to continuously produce viable offspring for 5 months under spring-like conditions. Finally, the fertility of the overwintered WM males was almost zero, while the surviving SM males did not suffer reduced fertility. Combined with other studies on D. suzukii monitoring and overwintering behavior, these results suggest that overwintered flies of both morphotypes could live long enough to infest the first commercial crops of the season. The high mortality of SM males and the low fertility of WM males after prolonged cold exposure also highlight the necessity for females to store sperm over winter to be able to start reproducing early in the following spring.
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Affiliation(s)
- Aurore D. C. Panel
- Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningenThe Netherlands
| | - Ido Pen
- Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningenThe Netherlands
| | - Bart A. Pannebakker
- Laboratory of GeneticsWageningen University & ResearchWageningenThe Netherlands
| | | | - Bregje Wertheim
- Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningenThe Netherlands
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Stockton DG, Wallingford AK, Brind'amore G, Diepenbrock L, Burrack H, Leach H, Isaacs R, Iglesias LE, Liburd O, Drummond F, Ballman E, Guedot C, Van Zoeren J, Loeb GM. Seasonal polyphenism of spotted-wing Drosophila is affected by variation in local abiotic conditions within its invaded range, likely influencing survival and regional population dynamics. Ecol Evol 2020; 10:7669-7685. [PMID: 32760556 PMCID: PMC7391339 DOI: 10.1002/ece3.6491] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 05/20/2020] [Accepted: 05/21/2020] [Indexed: 12/14/2022] Open
Abstract
Overwintering Drosophila often display adaptive phenotypic differences beneficial for survival at low temperatures. However, it is unclear which morphological traits are the best estimators of abiotic conditions, how those traits are correlated with functional outcomes in cold tolerance, and whether there are regional differences in trait expression.We used a combination of controlled laboratory assays, and collaborative field collections of invasive Drosophila suzukii in different areas of the United States, to study the factors affecting phenotype variability of this temperate fruit pest now found globally.Laboratory studies demonstrated that winter morph (WM) trait expression is continuous within the developmental temperature niche of this species (10-25°C) and that wing length and abdominal melanization are the best predictors of the larval abiotic environment.However, the duration and timing of cold exposure also produced significant variation in development time, morphology, and survival at cold temperatures. During a stress test assay conducted at -5°C, although cold tolerance was greater among WM flies, long-term exposure to cold temperatures as adults significantly improved summer morph (SM) survival, indicating that these traits are not controlled by a single mechanism.Among wild D. suzukii populations, we found that regional variation in abiotic conditions differentially affects the expression of morphological traits, although further research is needed to determine whether these differences are genetic or environmental in origin and whether thermal susceptibility thresholds differ among populations within its invaded range.
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Affiliation(s)
- Dara G Stockton
- Department of Entomology Cornell AgriTech Cornell University Geneva New York USA
| | - Anna K Wallingford
- University of New Hampshire Cooperative Extension Durham New Hampshire USA
| | | | - Lauren Diepenbrock
- Department of Entomology and Nematology University of Florida Lake Alfred Florida USA
| | - Hannah Burrack
- Department of Entomology and Plant Pathology North Carolina State University Raleigh North Carolina USA
| | - Heather Leach
- Department of Entomology The Pennsylvania State University University Park Pennsylvania USA
| | - Rufus Isaacs
- Department of Entomology Michigan State University East Lansing Michigan USA
| | - Lindsy E Iglesias
- Department of Entomology Cornell AgriTech Cornell University Geneva New York USA
| | - Oscar Liburd
- Department of Entomology and Nematology University of Florida Gainesville Florida USA
| | - Francis Drummond
- School of Biology and Ecology University of Maine Orono Maine USA
- Cooperative Extension University of Maine Orono Maine USA
| | - Elissa Ballman
- School of Biology and Ecology University of Maine Orono Maine USA
| | - Christelle Guedot
- Department of Entomology University of Wisconsin Madison Wisconsin USA
| | - Janet Van Zoeren
- Department of Entomology University of Wisconsin Madison Wisconsin USA
| | - Greg M Loeb
- Department of Entomology Cornell AgriTech Cornell University Geneva New York USA
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10
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Tran AK, Hutchison WD, Asplen MK. Morphometric criteria to differentiate Drosophila suzukii (Diptera: Drosophilidae) seasonal morphs. PLoS One 2020; 15:e0228780. [PMID: 32027732 PMCID: PMC7004555 DOI: 10.1371/journal.pone.0228780] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 01/23/2020] [Indexed: 11/21/2022] Open
Abstract
Temperate insect species often enter diapause in preparation for overwintering. One such species is the invasive vinegar fly, Drosophila suzukii (Matsumura), which has seasonal polymorphisms, considered winter and summer morphs. To date, the morphs have been differentiated by color and size with winter morphs typically being darker and larger compared to summer morphs. ‘Dark’ and ‘large’ are subjective, however, and standardizing an identification process can ensure that the morph of interest is being accurately characterized. The goal of our research was to investigate a quantitative method to distinguish between D. suzukii morphs based on body and wing size. We reared winter and summer morph D. suzukii in the laboratory using standard procedures, and measured wing length, wing width, and hind tibia length. Additionally, we collected field D. suzukii to document the seasonal phenology of the morphs in Minnesota based on our model’s cutoff criteria. A classification and regression tree analysis were used to determine which metrics would be best for predicting field-caught D. suzukii morphs. Using laboratory-reared flies as our known morphs for the training data in the classification model we developed classification trees based on wing length and the ratio of wing length to hind tibia length. The frequency of winter and summer morphs present in the field varied based on which classification tree was used. Nevertheless, we suggest ratio of wing length to hind tibia length as the most robust criteria for differentiating D. suzukii morphs because the ratio accounts for the size variability between laboratory-reared and field-caught flies and the error rate of misclassification is reduced to 0.01 for males. The results from this work can aid in future D. suzukii research by allowing scientists to objectively differentiate the morphs, and thereby improve our understanding of the biology and phenology of seasonal morph dynamics.
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Affiliation(s)
- Anh K. Tran
- Department of Entomology, University of Minnesota, Saint Paul, Minnesota, United States of America
- * E-mail:
| | - W. D. Hutchison
- Department of Entomology, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Mark K. Asplen
- Natural Sciences Department, Metropolitan State University, Saint Paul, Minnesota, United States of America
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