R code and data for the publication "Mismatches in thermal performance between ectothermic predators and prey alter interaction strength and top-down control"

<strong>Abstract</strong> Climate change can alter predator-prey interactions when predators and prey have different thermal preferences as temperature change can exacerbate thermal mismatches (also called thermal asymmetry) with population-level consequences. We tested this using microarthropod predators (<em>Stratiolaelaps scimitus</em>) and prey (<em>Folsomia candida</em>) that differ in their temperature optima to examine predator-prey interactions across two temperature ranges, a cool (12 and 20 °C) and warm (20 and 26 °C) range. We predict that the lower thermal preference and optimum in <em>F</em>. <em>candida</em> will alter top-down control (i.e., interaction strength) by predators with interaction strength being strongest at intermediate temperatures, coinciding with <em>F</em>. <em>candida</em> thermal optimum. Predators and prey were placed in mesocosms, whereafter we measured population (predator and prey abundance), trait-based (average predator and prey body mass, and prey body length distribution), and predator-prey indices (predator-prey mass ratio (PPMR), Dynamic Index, and Log Response Ratio) to determine how temperature affected their interactions. Prey populations were highest at intermediate temperatures (average temperature exposure: 16 – 23 °C) but declined at warmer temperatures (average temperature exposure: 24.5 – 26 °C). Predators consistently lowered prey abundances and average prey mass increased when predators were added. Top-down control was greatest at intermediate temperatures (indicated by Log Response Ratio) when temperatures were near or below the thermal optimum for both species. Temperature-related prey declines negated top-down control under the warmest conditions suggesting that mismatches in thermal performance between predators and their prey will alter the strength and dominance of top-down or bottom-up forces of predator-prey interactions in a warmer world.

**摘要** 当捕食者与猎物具有不同热偏好时，气候变化可改变二者的相互作用；温度变化会加剧热错配（thermal mismatch），该现象亦称热不对称（thermal asymmetry），并带来种群层面的生态后果。本研究以微节肢动物捕食者斯氏绥螨（<em>Stratiolaelaps scimitus</em>）与猎物白色符跳虫（<em>Folsomia candida</em>）为实验对象，二者的温度最适值存在差异，以此探究两种温度梯度下的捕食者-猎物相互作用：低温梯度（12 ℃与20 ℃）与高温梯度（20 ℃与26 ℃）。我们提出预测：白色符跳虫较低的热偏好与温度最适值会改变捕食者施加的下行控制（top-down control，即相互作用强度），且相互作用强度在中等温度下达到最强，此时温度恰好匹配白色符跳虫的热最适值。我们将捕食者与猎物放置于中型实验生态系统（mesocosms）中，随后从三个维度开展测量：种群层面（捕食者与猎物的丰度）、性状层面（捕食者与猎物的平均体重，以及猎物的体长分布）以及捕食者-猎物相关指数（捕食者-猎物质量比（PPMR）、动态指数（Dynamic Index）与对数响应比（Log Response Ratio）），以解析温度如何影响二者的相互作用。实验结果显示，猎物种群在中等温度下（平均暴露温度：16 ℃~23 ℃）达到丰度峰值，但在较高温度下（平均暴露温度：24.5 ℃~26 ℃）出现下降。捕食者始终会降低猎物种群丰度，且当引入捕食者后，猎物的平均体重有所上升。当温度接近或低于两个物种的热最适值时，下行控制强度在中等温度下达到最大（以对数响应比为指示指标）。在最高温条件下，与温度相关的猎物种群下降抵消了下行控制，这表明捕食者与猎物之间热生理性能的错配，会在变暖的全球环境中改变捕食者-猎物相互作用中下行控制（top-down control）或上行控制（bottom-up control）的强度与主导地位。