Environmental drivers of carry-over effects in a pond-breeding amphibian, the Wood Frog (Rana sylvatica)

Abstract

Breeding animals confront a complex environment when deciding where to oviposit, and this decision may depend on fine-scale variation in environmental conditions that have the potential to affect not only embryos but also subsequent larvae. I evaluated the influences of two variables, light and temperature, at oviposition sites of Wood Frogs (Rana sylvatica LeConte, 1825). First, in four ponds varying in canopy cover, I moved a subset of egg masses from the original oviposition site to an alternative site in the same pond and monitored embryos until hatching commenced. I found that embryos in the alternative site experienced delays in hatching a mean of 2.5 days. Second, in each of the four ponds, I placed hatchlings from the two sites in enclosures throughout the pond. After 2 weeks, larval performance was assessed with respect to development and growth. Larvae from the alternative oviposition site gained less mass (on average, 15% less) and developed more slowly (up to two Gosner stages) than larvae from the original oviposition site. Collectively, these results show that in selecting oviposition sites, Wood Frogs can use local cues to support high performance of their offspring and that those positive effects can carry over well into the larval period.