Data from: Behavioral changes in tadpoles after multi-generational 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.

遭受集团内捕食（intraguild predation）的猎物，其行为可能面临相互冲突的选择压力：种间竞争会促使其提升活动水平，而捕食压力则会驱动其降低活动频次。为探究该进化冲突的潜在解决路径，本研究对比了两类蝌蚪的行为：一类来自4个不同种群的家系，这些种群与一种已引入的集团内捕食者已共存演化长达90年；另一类则来自4个未接触过该捕食者的种群家系。本研究的集团内猎物为种群衰退的加州红腿蛙（Rana draytonii）的蝌蚪，而集团内捕食者则为入侵物种美洲牛蛙（Lithobates catesbeianus）——这是一种贪食性捕食者，同时也是其他无尾类动物（anurans）的强劲竞争者。现有有限研究证据表明，部分与入侵捕食者长期共存的本土两栖动物，会对捕食者释放的化学信号产生适应性行为响应。本研究旨在验证：与美洲牛蛙蝌蚪同域（syntopic）或异域（allotopic）共存的R. draytonii蝌蚪家系，是否会对越冬美洲牛蛙蝌蚪的化学信号产生行为响应。当存在该化学信号时，同域种群的早期发育阶段蝌蚪的活动量显著降低，这符合演化形成的先天性防御策略；而异域种群的蝌蚪则未表现出任何行为变化。而发育后期的同域种群蝌蚪，其活动水平整体高于异域种群蝌蚪，尤其是在无化学信号的环境下，这表明其可能对美洲牛蛙蝌蚪带来的种间竞争产生了适应性响应。这类活动水平的提升似乎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，两栖动物发育过程中的行为变化，可与引入的集团内捕食者带来的复杂选择压力相匹配。本研究结果对于濒危两栖动物的保护管理，以及广泛入侵的集团内捕食者的防控均具有重要参考价值。