Number of frogs per pond per night per stimulus

In tropical regions, some anuran species "explosively breed", reproducing in massive and highly diverse aggregations during a brief window of time. These aggregations can serve as acoustic beacons, attracting other anurans towards seasonal ponds. We hypothesize that conspecific and heterospecific calls play a role in navigation towards ponds and synchronization of reproduction among species. We simulated a chorus of two species (Trachycephalus coriaceus and Chiasmocleis shudikarensis) with contrasting call characteristics (low-frequency vs. high-frequency) and reproductive strategies (strict pond breeder vs. opportunistic) near known explosive breeding sites and predicted that choruses of T. coriaceus are more attractive to heterospecifics than of C. shudikarensis because the first provides a more reliable indicator of a suitable breeding pond and a better long-distance signal. We found that both choruses attracted conspecific frogs to the playback outside a natural breeding event. As predicted, heterospecifics were attracted only by low-frequency calls of T. coriaceus that breeds exclusively in large ponds, but not by higher-frequency calls of C. shudikarensis that also breeds in small pools not suitable for other species. Our study presents the first experimental evidence that tropical explosive breeding anurans are attracted to conspecific and heterospecific choruses. The contrasting effect of the playback of the two species on heterospecifics suggests that the attractive effect of a chorus depends on the reproductive strategy of both the sender and the receiver. Given the abundance and diversity of communities in tropical ecosystems, the use of heterospecific acoustic cues may prove widespread and requires further investigation.

在热带区域，部分无尾两栖类（anuran）会采取“爆发式繁殖”策略，即在短暂的繁殖窗口期内，以规模庞大、组成高度多样的聚集群体开展繁殖活动。这类聚集群体可作为声学信标，将其他无尾两栖类吸引至季节性繁殖池塘。我们提出假说：同种个体（conspecific）与异种个体（heterospecific）的鸣唱信号，在个体向繁殖池塘导航以及不同物种间繁殖同步化的过程中发挥着重要作用。我们在已知的爆发式繁殖位点附近，模拟了由厚皮糙嘴雨蛙（Trachycephalus coriaceus）与舒迪卡狭口蛙（Chiasmocleis shudikarensis）两个物种组成的鸣唱集群，二者在鸣唱特征（低频 vs 高频）与繁殖策略（专性池塘繁殖者 vs 机会主义繁殖者）上存在显著差异。我们预测，厚皮糙嘴雨蛙的鸣唱集群相较于舒迪卡狭口蛙，对异种个体更具吸引力，原因在于前者能够更可靠地指示适宜的繁殖池塘，同时具备更优良的长距离信号传递能力。本研究发现，在自然繁殖事件之外的回放实验中，两种鸣唱集群均能吸引同种蛙类前来。正如预测所示，异种个体仅会被仅在大型池塘繁殖的厚皮糙嘴雨蛙的低频鸣唱所吸引，而不会被同样会在不适宜其他物种的小型水塘繁殖的舒迪卡狭口蛙的高频鸣唱所吸引。本研究首次通过实验证实：热带爆发式繁殖的无尾两栖类会被同种与异种的鸣唱集群所吸引。两个物种的回放鸣唱对异种个体产生的差异化影响表明，鸣唱集群的吸引效应取决于信号发送者与接收者双方的繁殖策略。鉴于热带生态系统中群落的丰富度与多样性，利用异种声学线索的现象可能广泛存在，有待后续开展更为深入的研究。