Ranavirus Effects on Metamorphic Salamander Body Condition and Growth in Created Wetlands

Ranaviruses are infectious pathogens which contribute to global amphibian declines. We happened upon a natural field experiment in which a ranavirus outbreak occurred in two of four fenced ephemeral wetlands. We monitored constructed wetlands in east-central Illinois, detecting ~90% of amphibian movement from February 21 to July 7, 2017. In April and May, a ranavirus outbreak removed 100% of Wood Frog (Rana sylvatica) and >90% of Silvery Salamander (Ambystoma platineum) larvae from two wetlands, creating an “exposed” group of individuals which survived, and an “unexposed” group of individuals from wetlands where there was no outbreak. We held up to twelve Silvery Salamander metamorphs from each pond in growth chambers to monitor the body condition index (BCI), survival, and daily growth rates. These parameters were then compared between the exposed and unexposed groups with a Student’s t-test. The exposed group had significantly better BCI scores than the unexposed group (PP=0.468). We propose that complete removal of Wood Frogs via ranavirus infections removed the interspecific competition between Wood Frog and Chorus Frog tadpoles (Pseudacris maculata) allowing the latter species to increase in size and abundance relative to those in unexposed wetlands. The increased prey availability (Chorus Frogs) likely benefited the predatory Silvery Salamanders by decreasing intraspecific competition for prey. These findings highlight the need to understand long-term effects of ranavirus on community composition, as recurring outbreaks will affect recruitment differently among amphibian species within a community.