Inter-annual weather variability can drive the outcome of predator prey match in ponds

The matching of life-history-events to the availability of prey is essential for the growth and development of predators. Mismatches can constrain individuals to complete life-cycle steps in time and in ephemeral habitats it can lead to mortality unless compensation mechanisms exist. Here we measured the performance of a population of European fire-salamanders (<em>Salamandra salamandra</em>) and their prey in ephemeral ponds. We analysed how short time inter-annual variability of yearly rainfall and temperature (two consecutive years, 2011 and 2012) affects matching of predator and prey and how two different weather scenarios influenced the predator’s population structure. A single species (larvae of the mosquito <em>Aedes vexans</em>) dominates the prey community here, which occurs in high quantities only in the beginning of the season. When the occurrence of prey and predator matched during a period of sufficiently high temperatures (as in 2011), initial growth of the salamander larvae was high and population size development homogeneous. At low temperatures during matching of predatory and prey (as in 2012), the initial growth was low but the salamander larvae developed into two distinctly different sizes. Further, some individuals in the large cohort became cannibalistic and initial size differences increased. As a result, the latest (smallest) cohort disappeared completely. Temperature measurements and estimation of maximal growth rates revealed that temperature differences alone could explain the different early development between years. Our data show that weather conditions (rainfall; temperature during early growth phase) strongly determined the performance of salamander larvae in ponds. Our data also add to the match-mismatch concept that abiotic growth conditions (here: low temperature) could prevent efficient conversion of prey- into predator-biomass despite high prey availability.

生活史事件与猎物可获得性的匹配，对于捕食者的生长与发育至关重要。匹配失败则会制约个体按时完成生活史各阶段；在短暂生境中，若无补偿机制存在，甚至会导致个体死亡。本研究测定了短暂池塘内欧洲火蝾螈（*Salamandra salamandra*）种群及其猎物的生存表现。我们分析了2011与2012这两个连续年份的年降雨量与气温的短期年际波动如何影响捕食者与猎物的匹配关系，以及两种不同天气情景如何改变捕食者的种群结构。该生境的猎物群落由单一物种主导，即骚扰伊蚊（*Aedes vexans*）的幼虫，该猎物仅在季节初期大量出现。当猎物与捕食者的出现时段在充足高温条件下（如2011年）实现匹配时，蝾螈幼虫的初始生长速率较高，种群规模发展均匀一致。而当捕食者与猎物的匹配时段处于低温环境中（如2012年），蝾螈幼虫的初始生长速率较低，但会发育为两种截然不同的体型类群。此外，大型同龄组中的部分个体出现同类相食行为，初始体型差异进一步扩大。最终，最晚出现的（体型最小的）同龄组完全消亡。体温测定与最大生长速率估算结果显示，仅气温差异即可解释两年间早期发育的差异。本研究数据表明，天气条件（降雨量；生长初期的气温）极大地决定了池塘内蝾螈幼虫的生存表现。本研究数据还补充了匹配-失配假说：即便猎物可获得性较高，非生物生长条件（此处为低温）仍可能阻碍猎物生物量向捕食者生物量的高效转化。