Data from: Behavioral changes in tadpoles after multigenerational exposure to an invasive intraguild predator

Prey subject to intraguild predation may face conflicting selective pressure on behavior, with competition favoring increased activity and predation favoring activity reduction. To discover how this evolutionary conflict might be resolved, we compared the behavior of tadpoles from four families drawn from different populations that had potentially co-evolved with an introduced intraguild predator for up to 90 years with the behavior of tadpoles from four families from unexposed populations. Intraguild prey were tadpoles of the declining California Red-legged Frog (Rana draytonii) and the intraguild predator was the invasive American Bullfrog (Lithobates catesbeianus), a voracious predator and strong competitor of other anurans. Limited evidence suggests that some native amphibians that have co-occurred with invasive predators for generations show adaptive behavioral responses to predator chemical cues. We tested whether R. draytonii larvae from families either allotopic or syntopic with bullfrogs would show responses to cues from overwintered bullfrog larvae. In the presence of cues, early-stage syntopic larvae decreased movement, consistent with an evolved innate defense, while allotopic larvae did not show behavioral changes. Later-stage syntopic larvae were generally more active than allotopic larvae, especially in the absence of cues, indicating a potential adaptive response to competition from bullfrog larvae. Increased activity appeared to be timed for when tadpoles became more resistant to predation. This is the first study to show changes in behavior across development consistent with complex selective pressure from an introduced intraguild predator. These findings have important implications for management of an endangered amphibian and a widely-introduced, invasive intraguild predator.面临集团内捕食（intraguild predation）的猎物，其行为可能承受相互冲突的选择压力：种间竞争会推动猎物提升活动水平，而捕食压力则会促使其降低活动水平。为探究这类进化冲突的解决机制，我们对比了两类蝌蚪的行为：一类为采自不同种群的4个家系的蝌蚪，其所在种群与一种引入的集团内捕食者共存了长达90年、并可能与之共同进化；另一类同样来自4个家系，但其所在种群从未接触过该捕食者。本研究中的集团内猎物为种群数量正在下降的加州红腿蛙（Rana draytonii）蝌蚪，集团内捕食者则为入侵物种美洲牛蛙（Lithobates catesbeianus）——这是一种贪婪的捕食者，同时也是其他无尾两栖类的强劲竞争者。现有有限证据表明，部分与入侵捕食者长期共存的本土两栖类，会对捕食者的化学信号产生适应性行为响应。我们测试了与牛蛙异域分布（allotopic）或同域分布（syntopic）的加州红腿蛙幼体，是否会对越冬牛蛙幼体的化学信号产生行为响应。当存在该信号时，早期发育阶段的同域分布幼体活动量下降，这与其进化形成的先天防御策略一致；而异域分布幼体则未表现出行为变化。在无信号的环境中，后期发育阶段的同域分布幼体通常比异域分布幼体更为活跃，这表明其可能对牛蛙带来的种间竞争产生了适应性响应。活动水平的提升似乎恰好与蝌蚪对捕食抗性增强的发育阶段相契合。本研究首次证实，跨发育阶段的行为变化与引入的集团内捕食者带来的复杂选择压力相一致。这些发现对于濒危两栖类的保护管理，以及广泛入侵的集团内捕食者的防控均具有重要意义。