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 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.

两栖动物面临着多种由人类活动引起的环境扰动，这些扰动可能单独作用或相互结合，从而影响种群数量。本研究调查了升温条件、适度的氮污染脉冲以及同种密度对普通青蛙（Rana temporaria）幼体的交互作用。该16天的实验采用2×2×2的析因设计，在80升的户外中宇宙中进行。高密度和高温均导致活动性和可见性降低；在低密度和高温条件下，蝌蚪的生长和发育速度更快。高氮处理对行为、生长或发育速率没有影响。我们将其归因于本研究的一些现实特征，包括脉冲式处理的应用和中宇宙内的自然反硝化作用。三个因素之间仅存在一个交互作用：高温加剧了密度对生长速率的依赖性。这些结果说明，气候变暖可能对温带两栖动物有益，尽管这种益处可能因幼体拥挤程度的增加而被抵消。