Oh Dogeun, Kim Yongsu, Yoo Sohee, Kang Changku
Department of Biosciences, Mokpo National University, Muan, Jeollanamdo, South Korea.
PeerJ. 2021 Sep 13;9:e12172. doi: 10.7717/peerj.12172. eCollection 2021.
Ephemeral streams are challenging environments for tadpoles; thus, adaptive features that increase the survival of these larvae should be favored by natural selection. In this study, we compared the adaptive growth strategies of (the oriental fire-bellied toad) tadpoles from ephemeral streams with those of such tadpoles from non-ephemeral streams. Using a common garden experiment, we tested the interactive effects of location (ephemeral non-ephemeral), food availability, and growing density on larval period, weight at metamorphosis, and cannibalism. We found that tadpoles from ephemeral streams underwent a shorter larval period compared with those from non-ephemeral streams but that this difference was contingent on food availability. The observed faster growth is likely to be an adaptive response because tadpoles in ephemeral streams experience more biotic/abiotic stressors, such as desiccation risk and limited resources, compared with those in non-ephemeral streams, with their earlier metamorphosis potentially resulting in survival benefits. As a trade-off for their faster growth, tadpoles from ephemeral streams generally had a lower body weight at metamorphosis compared with those from non-ephemeral streams. We also found lower cannibalism rates among tadpoles from ephemeral streams, which can be attributed to the indirect fitness costs of cannibalizing their kin. Our study demonstrates how ephemeral habitats have affected the evolutionary change in cannibalistic behaviors in anurans and provides additional evidence that natural selection has mediated the evolution of growth strategies of tadpoles in ephemeral streams.
季节性溪流对于蝌蚪来说是具有挑战性的生存环境；因此，那些能提高这些幼体存活率的适应性特征应该会受到自然选择的青睐。在本研究中，我们比较了来自季节性溪流的东方铃蟾蝌蚪与来自非季节性溪流的同类蝌蚪的适应性生长策略。通过一个共同花园实验，我们测试了地点（季节性/非季节性）、食物可获得性和生长密度对幼体期、变态时体重以及同类相食现象的交互作用。我们发现，与来自非季节性溪流的蝌蚪相比，来自季节性溪流的蝌蚪幼体期更短，但这种差异取决于食物可获得性。观察到的更快生长可能是一种适应性反应，因为与非季节性溪流中的蝌蚪相比，季节性溪流中的蝌蚪面临更多的生物/非生物压力源，如干涸风险和资源有限，它们更早变态可能会带来生存优势。作为更快生长的一种权衡，来自季节性溪流的蝌蚪在变态时的体重通常比来自非季节性溪流的蝌蚪低。我们还发现来自季节性溪流的蝌蚪之间同类相食的发生率较低，这可以归因于同类相食其亲属所带来的间接适合度成本。我们的研究展示了季节性栖息地如何影响无尾目动物同类相食行为的进化变化，并提供了额外的证据，证明自然选择介导了季节性溪流中蝌蚪生长策略的进化。
