1. A fundamental goal of disease ecology is to determine the landscape and environmental
processes that drive disease dynamics at different biological levels to
guide management and conservation. Although ranaviruses (family Iridoviridae)
are emerging amphibian pathogens, few studies have conducted comprehensive
field surveys to assess potential drivers of ranavirus disease dynamics.
2. We examined the factors underlying patterns in site-level ranavirus presence and
individual-level ranavirus infection in 76 ponds and 1,088 individuals representing
five amphibian species within the East Bay region of California.
3. Based on a competing-model approach followed by variance partitioning, landscape
and biotic variables explained the most variation in site-level presence. However, biotic
and individual-level variables explained the most variation in individual-level infection.
4. Distance to nearest ranavirus-infected pond (the landscape factor) was more important
than biotic factors at the site level; however, biotic factors were most influential
at the individual level. At the site level, the probability of ranavirus presence
correlated negatively with distance to nearest ranavirus-positive pond, suggesting
that the movement of water or mobile taxa (e.g., adult amphibians, birds, reptiles)
may facilitate the movement of ranavirus between ponds and across the landscape.
5. Taxonomic richness associated positively with ranavirus presence at the site
level, but vertebrate richness associated negatively with infection prevalence in
the host population. This might reflect the contrasting influences of diversity on
pathogen colonisation versus transmission among hosts.
6. Amphibian host species differed in their likelihood of ranavirus infection: American
bullfrogs (Rana catesbeiana) had the weakest association with infection while roughskinned
newts (Taricha granulosa) had the strongest. After accounting for host species
effects, hostswith greater snout–vent length had a lower probability of infection.
7. Our study demonstrates the array of landscape, environmental, and individual level
factors associated with ranavirus epidemiology. Moreover, our study helps
illustrate that the importance of these factors varies with biological level.
Cite this work
Researchers should cite this work as follows:
- Tornabene, B. J., Hoverman, J. T. (2018). The influence of landscape and environmental factors on ranavirus epidemiology in a California amphibian assemblage. Purdue University Research Repository. doi:10.4231/R7MW2FBT