Desert anurans use short-term ephemeral pools to breed and are faced with the challenge of completing metamorphosis before pools desiccate. Most anurans can reach metamorphosis in less than a month, and some, like Scaphiopus couchii, can develop and leave the pools in less than two weeks. Others have demonstrated that S. couchii is adapted to using smaller pools in arid regions in which other species (Anaxyrus sp.) cannot complete metamorphosis. Density dependant delays in growth and development in larger ephemeral pools can prevent the smaller S. couchii from ever reaching metamorphosis. Hence, S. couchii have presumably adapted to using the pools with the shortest hydroperiods by metamorphosing faster and at smaller sizes than other desert anurans. Developmental rates for anurans are likely influenced by pool temperature, food availability and larval density. Increased seasonal temperatures due to global climate change may reduce the advantage of S. couchii in short-term pools due to increased pool desiccation rates. Short-term ephemeral pools in the Sonoran Desert are monitored for surface areas, volumes, pool and ambient temperatures, and relative humidity. Evaporation rates for variable pool sizes and ambient temperature scenarios are modeled to evaluate time lost for metamorphosis and potential effects on larval fitness.
Results/Conclusions
We present the relationship between pool size, pool desiccation rate, time lost for development and developmental rates to present the likelihood that S. couchii will be able to respond to projected changes in climate. The combination of stress effects on tadpole physiology in conjunction with decreased dissolved oxygen concentration lengthen time to metamorphosis. This increases the probability of catastrophic mortality of entire cohorts in the smaller pools that the S. couchii tadpoles use and leads to fewer pools producing offspring in any given rainy season. A reduction in the number of pools producing tadpoles as a result of these physiological changes has long term implications on the ability of the species to survive with projected changes in climate.
