Data for: Photoperiod effects in a freshwater community: amphibian larvae develop faster and zooplankton abundance increases under an early-season photoperiod

Organisms that shift their phenologies in response to global warming will experience novel photic environments, as photoperiod (daylength) continues to follow the same annual cycle. How different organisms respond to novel photoperiods could result in phenological mismatches and altered interspecific interactions. We conducted an outdoor mesocosm experiment exposing green frog (Rana clamitans) larvae, gray treefrog (Hyla versicolor) larvae, phytoplankton, periphyton, and zooplankton to a three-month shift in photoperiod: an early-season photoperiod (simulating April) and a late-season photoperiod (simulating July). We manipulated photoperiod by covering and uncovering tanks with clear or light-blocking lids to mimic realistic changes in daylength. We assessed amphibian life history traits and measured phytoplankton, periphyton, and zooplankton abundances. Green frog larvae and gray treefrog metamorphs were more developed under the early-season photoperiod. Gray treefrog total length was also reduced, but photoperiod did not affect green frog total length. Although phytoplankton and periphyton abundances were not affected by photoperiod, copepod nauplii were in greater abundance under the early-season photoperiod. Overall, this simplified aquatic community did not exhibit significant changes to structure when exposed to a three-month shift in photoperiod. Temperate amphibians that breed earlier in the year may develop faster, which may have long-term costs to post-metamorphic growth and performance. Asynchronous shifts in zooplankton abundances in response to altered photoperiods could subsequently affect freshwater community structure. While photoperiod has been shown to individually affect freshwater organisms, our study using replicated outdoor wetland communities shows that the comprehensive effects of photoperiod may be less important than other cues such as temperature and precipitation.

受全球变暖影响而调整物候的生物将面临全新的光环境，尽管光周期（photoperiod，即日长）仍遵循原有的年度循环。不同生物对新型光周期的响应差异，可能引发物候失配与种间相互作用的改变。本研究开展了一项室外中型生态系统（mesocosm）实验，将绿蛙（Rana clamitans）蝌蚪、灰树蛙（Hyla versicolor）蝌蚪、浮游植物、周丛生物以及浮游动物暴露于为期三个月的光周期偏移处理，设置两种光周期条件：早季光周期（模拟四月）与晚季光周期（模拟七月）。我们通过使用透光或遮光盖板覆盖或掀开养殖缸，模拟自然日长的真实变化，以此调控光周期。我们评估了两栖动物的生活史特征，并测定了浮游植物、周丛生物及浮游动物的丰度。早季光周期处理下，绿蛙蝌蚪与灰树蛙幼蛙的发育程度更高；灰树蛙的总长度也有所缩短，但光周期并未对绿蛙的总长度产生影响。尽管浮游植物与周丛生物的丰度未受光周期影响，但早季光周期下桡足类无节幼体（copepod nauplii）的丰度更高。总体而言，该简化水生群落在经历三个月的光周期偏移后，群落结构未出现显著变化。温带两栖动物若提前繁殖，其发育速度可能更快，但这可能对变态后的生长与适合度带来长期代价。浮游动物丰度随光周期改变出现异步变化，后续可能影响淡水群落结构。尽管已有研究表明光周期会单独影响淡水生物，但本研究通过设置重复室外湿地群落开展实验发现，光周期的综合效应可能弱于温度、降水等其他环境因子。