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Pepi A, Pan V, Grof-Tisza P, Holyoak M, Ballman A, Laws-McNeil A, Mase V, Moseley C, Karban R. Spatial habitat heterogeneity influences host-pathogen dynamics in a patchy population of Ranchman's tiger moth. Ecology 2023; 104:e4144. [PMID: 37471147 DOI: 10.1002/ecy.4144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 05/12/2023] [Accepted: 06/16/2023] [Indexed: 07/22/2023]
Abstract
Host-pathogen dynamics are influenced by many factors that vary locally, but models of disease rarely consider dynamics across spatially heterogeneous environments. In addition, theory predicts that dispersal will influence host-pathogen dynamics of populations that are linked, although this has not been examined empirically in natural systems. We examined the spatial dynamics of a patchy population of tiger moths and its baculovirus pathogen, in which habitat type and weather influence dynamics. Theoretical models of host-baculovirus dynamics predict that such variation in dynamics between habitat types could be driven by a range of factors, of which we predict two are likely to be operating in this system: (1) differences in the environmental persistence of pathogens or (2) differences in host intrinsic rates of increase. We used time series models and monitored infection rates of hosts to characterize population and disease dynamics and distinguish between these possibilities. We also examined the role of host dispersal (connectivity) and weather as important contributors to dynamics, using time series models and experiments. We found that the population growth rate was higher, delayed density dependence was weaker, and long-period oscillations had lower amplitudes in high-quality habitat patches. The infection rate was higher on average in high-quality habitat, and this was likely to have been driven by higher mean population densities and no differences in pathogen persistence in different habitats (delayed density dependence). Time series modeling and experiments also showed an interactive effect of temperature and precipitation on moth population growth rates (likely caused by variation in host plant quality and quantity), and an effect of connectivity. Our results showed that spatial heterogeneity, connectivity, climate, and their interactions were important in driving host-baculovirus dynamics. In particular, our study found that connected patches and spatial heterogeneity generated differences in dynamics that only partially aligned with theoretical predictions.
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Affiliation(s)
- Adam Pepi
- Department of Entomology and Nematology, University of California, Davis, Davis, California, USA
- Department of Biology, Tufts University, Medford, Massachusetts, USA
| | - Vincent Pan
- Ecology, Evolution and Behavior, Michigan State University, East Lansing, Michigan, USA
| | | | - Marcel Holyoak
- Department of Environmental Science and Policy, University of California, Davis, Davis, California, USA
| | - Alexis Ballman
- Department of Entomology and Nematology, University of California, Davis, Davis, California, USA
| | - Aiyanna Laws-McNeil
- Department of Entomology and Nematology, University of California, Davis, Davis, California, USA
| | - Vinay Mase
- Department of Entomology and Nematology, University of California, Davis, Davis, California, USA
| | - Cameron Moseley
- Department of Entomology and Nematology, University of California, Davis, Davis, California, USA
| | - Richard Karban
- Department of Entomology and Nematology, University of California, Davis, Davis, California, USA
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Lin PA, Kansman J, Chuang WP, Robert C, Erb M, Felton GW. Water availability and plant-herbivore interactions. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:2811-2828. [PMID: 36477789 DOI: 10.1093/jxb/erac481] [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: 07/28/2022] [Accepted: 12/04/2022] [Indexed: 06/06/2023]
Abstract
Water is essential to plant growth and drives plant evolution and interactions with other organisms such as herbivores. However, water availability fluctuates, and these fluctuations are intensified by climate change. How plant water availability influences plant-herbivore interactions in the future is an important question in basic and applied ecology. Here we summarize and synthesize the recent discoveries on the impact of water availability on plant antiherbivore defense ecology and the underlying physiological processes. Water deficit tends to enhance plant resistance and escape traits (i.e. early phenology) against herbivory but negatively affects other defense strategies, including indirect defense and tolerance. However, exceptions are sometimes observed in specific plant-herbivore species pairs. We discuss the effect of water availability on species interactions associated with plants and herbivores from individual to community levels and how these interactions drive plant evolution. Although water stress and many other abiotic stresses are predicted to increase in intensity and frequency due to climate change, we identify a significant lack of study on the interactive impact of additional abiotic stressors on water-plant-herbivore interactions. This review summarizes critical knowledge gaps and informs possible future research directions in water-plant-herbivore interactions.
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Affiliation(s)
- Po-An Lin
- Department of Entomology, National Taiwan University, Taipei, Taiwan
| | - Jessica Kansman
- Department of Entomology, the Pennsylvania State University, University Park, PA, USA
| | - Wen-Po Chuang
- Department of Agronomy, National Taiwan University, Taipei, Taiwan
| | | | - Matthias Erb
- Institute of Plant Science, University of Bern, Bern, Switzerland
| | - Gary W Felton
- Department of Entomology, the Pennsylvania State University, University Park, PA, USA
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Pepi A, Hayes T, Lyberger K. Thermal asymmetries influence effects of warming on stage and size-dependent predator–prey interactions. THEOR ECOL-NETH 2023. [DOI: 10.1007/s12080-023-00555-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
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Pan VS, Pepi A, LoPresti EF, Karban R. The consequence of leaf life span to virus infection of herbivorous insects. Oecologia 2023; 201:449-459. [PMID: 36692690 DOI: 10.1007/s00442-023-05325-w] [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: 01/15/2023] [Accepted: 01/17/2023] [Indexed: 01/25/2023]
Abstract
Many herbivorous insects die of pathogen infections, though the role of plant traits in promoting the persistence of these pathogens as an indirect interaction is poorly understood. We tested whether winter leaf retention of bush lupines (Lupinus arboreus) promotes the persistence of a nucleopolyhedroviruses, thereby increasing the infection risk of caterpillars (Arctia virginalis) feeding on the foliage during spring. We also investigated whether winter leaf retention reduces viral exposure of younger caterpillars that live on the ground, as leaf retention prevents contaminated leaves from reaching the ground. We surveyed winter leaf retention of 248 lupine bush canopies across twelve sites and examined how it related to caterpillar infection risk, herbivory, and inflorescence density. We also manipulated the amount of lupine litter available to young caterpillars in a feeding experiment to emulate litterfall exposure in the field. Greater retention of contaminated leaves from the previous season increased infection rates of caterpillars in early spring. Higher infection rates reduced herbivory and increased plant inflorescence density by summer. Young caterpillars exposed to less litterfall were more likely to starve to death but less likely to die from infection, further suggesting foliage mediated exposure to viruses. We speculate that longer leaf life span may be an unrecognized trait that indirectly mediates top-down control of herbivores by facilitating epizootics.
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Affiliation(s)
- Vincent S Pan
- Department of Integrative Biology, Michigan State University, 288 Farm Lane, East Lansing, MI, 48824, USA.
| | - Adam Pepi
- Department of Entomology and Nematology, University of California-Davis, Briggs Hall, One Shields Avenue, Davis, CA, 95616, USA
| | - Eric F LoPresti
- Department of Biological Sciences, University of South Carolina, 700 Sumter St #401, Columbia, SC, 29208, USA
| | - Richard Karban
- Department of Entomology and Nematology, University of California-Davis, Briggs Hall, One Shields Avenue, Davis, CA, 95616, USA
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Pepi A, Pan V, Rutkowski D, Mase V, Karban R. Influence of delayed density and ultraviolet radiation on caterpillar baculovirus infection and mortality. J Anim Ecol 2022; 91:2192-2202. [DOI: 10.1111/1365-2656.13803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 07/26/2022] [Indexed: 11/27/2022]
Affiliation(s)
- Adam Pepi
- Department of Biology Tufts University Medford MA USA
| | - Vincent Pan
- Department of Integrative Biology Michigan State University East Lansing MI USA
| | - Danielle Rutkowski
- Department of Entomology & Nematology University of California Davis CA USA
| | - Vinay Mase
- Department of Entomology & Nematology University of California Davis CA USA
| | - Richard Karban
- Department of Entomology & Nematology University of California Davis CA USA
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Pepi A, Grof-Tisza P, Holyoak M, Karban R. Hilltopping influences spatial dynamics in a patchy population of tiger moths. Proc Biol Sci 2022; 289:20220505. [PMID: 35673863 PMCID: PMC9174710 DOI: 10.1098/rspb.2022.0505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Dispersal is a key driver of spatial population dynamics. Dispersal behaviour may be shaped by many factors, such as mate-finding, the spatial distribution of resources, or wind and currents, yet most models of spatial dynamics assume random dispersal. We examined the spatial dynamics of a day-flying moth species (Arctia virginalis) that forms mating aggregations on hilltops (hilltopping) based on long-term adult and larval population censuses. Using time-series models, we compared spatial population dynamics resulting from empirically founded hilltop-based connectivity indices and modelled the interactive effects of temperature, precipitation and density dependence. Model comparisons supported hilltop-based connectivity metrics including hilltop elevation over random connectivity, suggesting an effect of hilltopping behaviour on dynamics. We also found strong interactive effects of temperature and precipitation on dynamics. Simulations based on fitted time-series models showed lower patch occupancy and regional synchrony, and higher colonization and extinction rates when hilltopping was included, with potential implications for the probability of persistence of the patch network. Overall, our results show the potential for dispersal behaviour to have important effects on spatial population dynamics and persistence, and we advocate the inclusion of such non-random dispersal in metapopulation models.
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Affiliation(s)
- Adam Pepi
- Department of Entomology and Nematology, University of California Davis, CA, USA,Department of Biology, Tufts University, MA, USA
| | | | - Marcel Holyoak
- Department of Environmental Science and Policy, University of California Davis, CA, USA
| | - Richard Karban
- Department of Entomology and Nematology, University of California Davis, CA, USA
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