Context-dependent effects of a cryptic virus on butterfly population dynamics
Brendan D Carson1,2, Colin M Orians1, Elizabeth E Crone1,3
1Department of Biology, Tufts University, Medford, Massachusetts, USA.
Ecology
|October 12, 2025
Summary
Cryptic viruses like Junonia coenia densovirus (JcDV) impact butterfly populations by reducing survival and reproduction. Environmental stressors, such as drought, can amplify JcDV
Area of Science:
- Ecology
- Virology
- Population Dynamics
Background:
- Virulent pathogens are well-studied, but the impact of ubiquitous "cryptic" viruses on animal populations remains largely unexplored.
- Insects, with short generation times and high reproductive rates, are ideal models for studying cryptic virus effects on population dynamics.
Purpose of the Study:
- To investigate the demographic impacts of a cryptic non-occluded densovirus (Junonia coenia DV, JcDV) on the Baltimore checkerspot butterfly (Euphydryas phaeton).
- To assess how JcDV influences butterfly survival, reproduction, and population growth rates under varying environmental conditions.
Main Methods:
- A two-year field mesocosm experiment (2021-2022) exposed Euphydryas phaeton to different levels of Junonia coenia densovirus (JcDV) exposure.
- Measured key demographic parameters including post-diapause larval survival, sex ratio, and female fecundity.
- Utilized vital rates to parameterize a demographic model for estimating population growth rates.
Main Results:
- JcDV significantly reduced E. phaeton post-diapause larval survival and female fecundity, while also causing a male-biased sex ratio.
- JcDV consistently reduced estimated population growth rates in both experimental years.
- Population decline occurred in 2022, coinciding with a regional drought, indicating an interaction between viral impact and climatic factors.
Conclusions:
- Cryptic viruses like JcDV can significantly influence butterfly population dynamics, affecting vital rates and overall growth.
- The impact of JcDV on E. phaeton populations is exacerbated by environmental stressors, such as drought.
- This study highlights the critical role of cryptic viruses in shaping insect population dynamics, particularly under challenging environmental conditions.
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