Disease dynamics of red-spotted newts and their anuran prey in a montane pond community

Abstract

Long-term monitoring of amphibians is needed to clarify population-level effects of ranaviruses (Rv) and the fungal pathogen Batrachochytrium dendrobatidis (Bd). We investigated disease dynamics of co-occurring amphibian species and potential demographic consequences of Rv and Bd infections at a montane site in the Southern Appalachians, Georgia, USA. Our 3-yr study was unique in combining disease surveillance with intensive population monitoring at a site where both pathogens are present. We detected sub-clinical Bd infections in larval and adult redspotted newts Notophthalmus viridescens viridescens, but found no effect of Bd on body condition of adult newts. Bd infections also occurred in larvae of 5 anuran species that bred in our fishless study pond, and we detected co-infections with Bd and Rv in adult newts and larval green frogs Lithobates clamitans. However, all mortality and clinical signs in adult newts and larval anurans were most consistent with ranaviral disease, including a die-off of larval wood frogs Lithobates sylvaticus in small fish ponds located near our main study pond. During 2 yr of drift fence monitoring, we documented high juvenile production in newts, green frogs and American bullfrogs L. catesbeianus, but saw no evidence of juvenile recruitment in wood frogs. Larvae of this susceptible species may have suffered high mortality in the presence of both Rv and predators. Our findings were generally consistent with results of Rv-exposure experiments and support the purported role of red-spotted newts, green frogs, and American bullfrogs as common reservoirs for Bd and/or Rv in permanent and semi-permanent wetlands.

Host–pathogen metapopulation dynamics suggest high elevation refugia for boreal toads

“…, Rothermel et al. ). Mechanisms underlying disease emergence are often poorly understood because populations may decline before sampling can occur, pathogens may be newly described, and static patterns of disease metrics (e.g., occurrence or prevalence) are not informative (Hastings , Yackulic et al.…”

“…Emerging infectious diseases (EIDs) can increase species extinction rates, shape community dynamics, and fundamentally alter how ecosystems function (Whiles et al 2012, Langwig et al 2016, Rothermel et al 2016. Mechanisms underlying disease emergence are often poorly understood because populations may decline before sampling can occur, pathogens may be newly described, and static patterns of disease metrics (e.g., occurrence or prevalence) are not informative (Hastings 2001, Yackulic et al 2015.…”

Out in the cold and sick: Low temperatures and fungal infections impair a frog's skin defenses

“…Southern leopard frogs, Rana (Lithobates) sphenocephala, are listed as 'least concern' on the IUCN red list, and although Bd was detected in this species as early as 1900-1920 and more recently (Talley et al, 2015;Peterson et al, 2007), there have been no reported declines due to chytridiomycosis. However, Bd appears to be a particular threat to vulnerable newly metamorphosed juveniles, possibly leading to lower yearly recruitment of young of the year into adult populations (Rachowicz et al, 2006;Wise et al, 2014;Rothermel et al, 2016;Clare et al, 2016).…”

The impacts of overwintered green frog larvae on wood frog embryo mortality under a wetter climate

“…The hydroperiod, or number of days a wetland contains water, is one of the most important factors in determining where particular amphibian species will successfully reproduce (Welborn, Skelly, & Werner, 1996). In addition, indirect effects can also occur because hydroperiod impacts predator density (Skelly, 1996) and disease dynamics (Richter et al, 2013;Rothermel et al, 2016). The length of the wetland hydroperiod can have direct and indirect impacts on amphibian reproductive success.…”

“…The direct effects include larvae mortality if the hydroperiod is shorter than the minimum time required for a species to complete metamorphosis (Pechmann, Scott, Whitfield, & Semlitsch, 1989) and reduced terrestrial survival associated with early metamorphosis at a small size (Altwegg & Reyer, 2003). In addition, indirect effects can also occur because hydroperiod impacts predator density (Skelly, 1996) and disease dynamics (Richter et al, 2013;Rothermel et al, 2016). Most species have an optimal hydroperiod range that balances their developmental needs with the risks associated with predation, terrestrial survival and disease (Skelly, 1996;Snodgrass, Bryan, & Burger, 2000;Werner et al, 2007).…”