Spatial and temporal patterns of Ambystoma tigrinum virus (ATV) prevalence in tiger salamanders Ambystoma tigrinum nebulosum.

Amphibian ranaviruses have been documented as causes of mass mortality in amphibian populations throughout the world. The temporal and spatial dynamics of ranavirus infections when epidemics are not apparent remains unclear. To address this question, we collected tissue samples from 2003 to 2006 in 4 geographically separated tiger salamander Ambystoma tigrinum nebulosum host populations on the Kaibab Plateau in northern Arizona. We tested for Ambystoma tigrinum virus (ATV), a lethal ranavirus of tiger salamanders, calculated ATV prevalence for each sampling date, and examined temporal and spatial patterns by quantifying the annual level of ATV synchrony among populations using the intraclass correlation coefficient. Salamander populations were commonly infected with ATV. We observed no morbidity or mortality in these populations even as ATV prevalence values varied from 0 to 57%. Infection prevalence across the landscape was more similar within a given year than between years. There was no statistically significant spatial pattern in prevalence across the landscape. Our findings highlight the need to explore new hypotheses regarding the population level impact of these pathogens on amphibian communities.