Aquatic tail size carries over to the terrestrial phase without impairing locomotion in adult Eastern Red-Spotted Newts (Notophthalmus viridescens viridescens)

Many species have evolved phenotypic flexibility to adjust to seasonal changes in their environment, including seasonal breeding phenotypes that increase reproductive success. If there are limits to this flexibility, such that traits carry over across seasons, there may be costs incurred as a result of trade-offs in optimal performance. Male and female Eastern Red-spotted Newts (Notophthalmus viridescens viridescens (Rafinesque, 1820)) increase tail size for the aquatic breeding season, and reduce their tail size as they return to the terrestrial environment after reproducing. We tested whether large aquatic tails (which should increase swim performance) carry over to become larger tails in the terrestrial phase (relative to body size), and whether this incurs a cost of decreased walking speed on land. We found a strong correlation between tail size in both phases, suggesting that this trait does carry-over between seasons and environments. Tail size was positively related to locomotor speed in the aquatic phase, but we found no evidence of a locomotor trade-off associated with tail size in the terrestrial phase. Further research that tests for alternative costs of developing large aquatic tails that are then carried over to the terrestrial environment would help to clarify the evolution of this life-cycle staging trait.