Responses to nitrate pollution, warming and density in common frog tadpoles (Rana temporaria)

Amphibians face a variety of anthropogenic
environmental perturbations that could act alone or in combination to influence
population size. We investigated interactive effects of warming conditions, a
moderate pulse of nitrogen pollution, and conspecific density on larvae of the
common frog, Rana temporaria. The 16-day experiment had a 2 × 2 × 2 factorial design
implemented in 80-l
Ecology outdoor mesocosms. High density and warm
temperature both resulted in reduced activity and visibility; tadpoles grew and
developed more quickly at low density and high temperature. The high-nitrogen
treatment did not influence behavior, growth, or development rate. We attribute
this to several realistic features of our study, including a pulsed treatment
application and natural denitrification within the mesocosms. There was only a
single interaction among the three factors: higher temperature exacerbated
density-dependence in growth rate. These results illustrate that climate
warming may benefit temperate amphibians, although the benefits may be
counteracted by enhanced larval crowding.