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Christensen T, Dyer LA, Forister ML, Bowers MD, Carper A, Teglas MB, Hurtado P, Smilanich AM. Host plant-mediation of viral transmission and its consequences for a native butterfly. Ecology 2024; 105:e4282. [PMID: 38483138 DOI: 10.1002/ecy.4282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 11/11/2023] [Accepted: 01/18/2024] [Indexed: 04/04/2024]
Abstract
Pathogens play a key role in insect population dynamics, contributing to short-term fluctuations in abundance as well as long-term demographic trends. Two key factors that influence the effects of entomopathogens on herbivorous insect populations are modes of pathogen transmission and larval host plants. In this study, we examined tritrophic interactions between a sequestering specialist lepidopteran, Euphydryas phaeton, and a viral pathogen, Junonia coenia densovirus, on its native host plant, Chelone glabra, and a novel host plant, Plantago lanceolata, to explore whether host plant mediates viral transmission, survival, and viral loads. A two-factor factorial experiment was conducted in the laboratory with natal larval clusters randomly assigned to either the native or novel host plant and crossed with either uninoculated controls or viral inoculation (20% of individuals in the cluster inoculated). Diapausing clusters were overwintered in the laboratory and checked weekly for mortality. At the end of diapause, all surviving individuals were reared to adulthood to estimate survivorship. All individuals were screened to quantify viral loads, and estimate horizontal transmission postmortem. To test for vertical transmission, adults were mated, and the progeny were screened for viral presence. Within virus-treated groups, we found evidence for both horizontal and vertical transmission. Larval clusters reared on the native host plant had slightly higher horizontal transmission. Survival probability was lower in clusters feeding on the native host plant, with inoculated groups reared on the native host plant experiencing complete mortality. Viral loads did not differ by the host plant, although viral loads decreased with increased sequestration of secondary compounds on both host plants. Our results indicate that the use of a novel host plant may confer fitness benefits in terms of survival and reduced viral transmission when larvae feeding on it are infected with this pathogen, supporting hypotheses of potential evolutionary advantages of a host range expansion in the context of tritrophic interactions.
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Affiliation(s)
- Tara Christensen
- Program in Ecology, Evolution, and Conservation Biology, University of Nevada, Reno, Nevada, USA
- Department of Biology, University of Nevada, Reno, Nevada, USA
| | - Lee A Dyer
- Program in Ecology, Evolution, and Conservation Biology, University of Nevada, Reno, Nevada, USA
- Department of Biology, University of Nevada, Reno, Nevada, USA
| | - Matthew L Forister
- Program in Ecology, Evolution, and Conservation Biology, University of Nevada, Reno, Nevada, USA
- Department of Biology, University of Nevada, Reno, Nevada, USA
| | - M Deane Bowers
- Department of Ecology and Evolutionary Biology and Museum of Natural History, University of Colorado, Boulder, Boulder, Colorado, USA
| | - Adrian Carper
- Department of Ecology and Evolutionary Biology and Museum of Natural History, University of Colorado, Boulder, Boulder, Colorado, USA
| | - Mike B Teglas
- Program in Ecology, Evolution, and Conservation Biology, University of Nevada, Reno, Nevada, USA
- Department of Agriculture, Veterinary and Rangeland Sciences, University of Nevada, Reno, Nevada, USA
| | - Paul Hurtado
- Program in Ecology, Evolution, and Conservation Biology, University of Nevada, Reno, Nevada, USA
- Department of Mathematics and Statistics, University of Nevada, Reno, Nevada, USA
| | - Angela M Smilanich
- Program in Ecology, Evolution, and Conservation Biology, University of Nevada, Reno, Nevada, USA
- Department of Biology, University of Nevada, Reno, Nevada, USA
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Felden A, Dobelmann J, Baty JW, McCormick J, Haywood J, Lester PJ. Can immune gene silencing via dsRNA feeding promote pathogenic viruses to control the globally invasive Argentine ant? ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2023; 33:e2755. [PMID: 36196505 DOI: 10.1002/eap.2755] [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: 03/17/2022] [Revised: 06/27/2022] [Accepted: 08/03/2022] [Indexed: 06/16/2023]
Abstract
Pest control methods that can target pest species with limited environmental impacts are a conservation and economic priority. Species-specific pest control using RNA interference is a challenging but promising avenue in developing the next generation of pest management. We investigate the feasibility of manipulating a biological invader's immune system using double-stranded RNA (dsRNA) in order to increase susceptibility to naturally occurring pathogens. We used the invasive Argentine ant as a model, targeting the immunity-associated genes Spaetzle and Dicer-1 with dsRNA. We show that feeding with Spaetzle dsRNA can result in partial target gene silencing for up to 28 days in the laboratory and 5 days in the field. Dicer-1 dsRNA only resulted in partial gene knockdown after 2 days in the laboratory. Double-stranded RNA treatments were associated with significant gene expression disruptions across immune pathways in the laboratory and to a lower extent in the field. In total, 12 viruses and four bacteria were found in these ant populations. Some changes in viral loads in dsRNA-treated groups were observed. For example, Linepithema humile Polycipivirus 2 (LhuPCV2) loads increased after 2 days of treatment with Spaetzle and Dicer-1 dsRNA treatments in the laboratory. After treatment with the dsRNA in the field, after 5 days the virus Linepithema humile toti-like virus 1 (LhuTLV1) was significantly more abundant. However, immune pathway disruption did not result in a consistent increase in microbial infections, nor did it alter ant abundance in the field. Some viruses even declined in abundance after dsRNA treatment. Our study explored the feasibility of lowering a pest's immunity as a control tool. We demonstrate that it is possible to alter immune gene expression of pest species and pathogen loads, although in our specific system the affected pathogens did not appear to influence pest abundance. We provide suggestions on future directions for dsRNA-mediated immune disruption in pest species, including potential avenues to improve dsRNA delivery as well as the importance of pest and pathogen biology. Double-stranded RNA targeting immune function might be especially useful for pest control in systems in which viruses or other microorganisms are prevalent and have the potential to be pathogenic.
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Affiliation(s)
- Antoine Felden
- Centre for Biodiversity and Restoration Ecology, School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
| | - Jana Dobelmann
- Centre for Biodiversity and Restoration Ecology, School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
- Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm, Germany
| | - James W Baty
- Centre for Biodiversity and Restoration Ecology, School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
| | - Joseph McCormick
- Centre for Biodiversity and Restoration Ecology, School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
| | - John Haywood
- School of Mathematics and Statistics, Victoria University of Wellington, Wellington, New Zealand
| | - Philip J Lester
- Centre for Biodiversity and Restoration Ecology, School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
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Bunn DC, Miller N. Natural Occurrence and Analysis of Nosema sp. Infection in the Adult Population of Western Bean Cutworm in Michigan. ENVIRONMENTAL ENTOMOLOGY 2023; 52:39-46. [PMID: 36469425 DOI: 10.1093/ee/nvac102] [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: 06/30/2022] [Indexed: 06/17/2023]
Abstract
An understanding of population dynamics and insect biology is important for effective crop management strategies. Biotic factors such as pathogens play a large role on the fitness and dynamics of insect populations. Microsporidia are obligate intracellular parasites that infect more than 150 insect species and range from sublethal and chronic to fast acting and deadly. The western bean cutworm, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), is a pest of both corn (Zea maize L. [Poales: Poaceae]) and dry beans (Phaseolus sp L. [Fabales: Fabaceae]) that is infected by a microsporidian parasite from the genus Nosema (Microsporidia: Nosematidae). Unfortunately, little is known about the interactions between the Nosema sp. (Microsporidia: Nosematidae) infecting the western bean cutworm and its prevalence and effects on the host population. This is especially true for the western bean cutworm population that has settled in the Great Lakes region over the last two decades. Using field caught samples and phase contrast microscopy, no consistent trends in pathogen load were observed over the course of the western bean cutworm flight season. A weak, but statistically significant relationship was observed between male body weight and pathogen load. Overall, we found a 100% prevalence of infection in the adult western bean cutworm population in Michigan.
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Affiliation(s)
- Dakota C Bunn
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Nicholas Miller
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
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