Effects of Salinity and Density on Tadpoles of Two Anurans from the Río Salado, Puebla, Mexico

Abstract

Abstract Numerous studies have explored environmental factors that drive the distributions of anuran larvae. However, the causal links between physical or chemical factors and tadpole distributions often remain untested. The Rio Salado is an intermittent, naturally saline river in Puebla, Mexico, that is increasingly being impacted by removal of water for commercial salt production. Using tadpoles of Exerodonta xera (Hylidae; Puebla Treefrog) and Incilius occidentalis (Bufonidae; Pine Toad), we experimentally examined the hypothesis that the distribution of tadpoles along the Rio Salado results from the effects of salinity on tadpole survivorship, growth, and metamorphosis. We also examined the effect of tadpole density and the interaction of tadpole density and salinity, because pool size likely affects tadpole density. Increased salinity did not affect survivorship in I. occidentalis but reduced survivorship in E. xera by approximately 20% at both 0.4 parts per thousand (ppt) (0.4 g L−1) and 0.8 ppt (0....