Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan.
Graduate School of Global Environmental Studies, Kyoto University, Kyoto, Japan.
PeerJ. 2022 Jun 8;10:e13452. doi: 10.7717/peerj.13452. eCollection 2022.
The Quaternary climate affected the present species richness and geographic distribution patterns of amphibians by limiting their activities during the glacial period. The present study examined the phylogenetic relationships of Japanese toads ( and ) and the demography of each lineage from the past to the present based on mitochondrial sequences and ecological niche models. Japanese toads are a monophyletic group with two main clades (clades A and B). Clade A represents , including three clades (clades A1, A2, and A3). Clade B contains three clades, two of which corresponded to (clades B1 and B2) and the other to . Clade B2 and made a sister group, and, thus, is paraphyletic. Clades A and B diverged in the late Miocene 5.7 million years ago (Mya) during the period when the Japanese archipelago was constructed. The earliest divergence between the three clades of clade A was estimated at 1.8 Mya. Clades A1 and A2 may have diverged at 0.8 Mya, resulting from the isolation in the multiple different refugia; however, the effects of the glacial climate on the divergence events of clade A3 are unclear. Divergences within clade B occurred from the late Pliocene to the early Pleistocene (3.2-2.2 Mya). Niche similarity between the parapatric clade in clade B (clades B1 and B2) indicated their allopatric divergence. It was suggested that niche segregation between and contributed to a rapid adaptation of for lotic breeding. All clade of Japanese toads retreated to each refugium at a low elevation in the glacial period, and effective population sizes increased to construct the current populations after the Last Glacial Maximum. Furthermore, we highlight the areas of climate stability from the last glacial maximum to the present that have served as the refugia of Japanese toads and, thus, affected their present distribution patterns.
第四纪气候通过限制两栖动物在冰川期的活动，影响了它们的现生物种丰富度和地理分布格局。本研究基于线粒体序列和生态位模型，探讨了日本蟾蜍（Bufo japonicus）及其各谱系从过去到现在的系统发育关系和种群动态。日本蟾蜍是一个单系群，包含两个主要分支（分支 A 和 B）。分支 A 代表，包括三个分支（分支 A1、A2 和 A3）。分支 B 包含三个分支，其中两个与（分支 B1 和 B2）相对应，另一个与相对应。分支 B2 和 形成姐妹群，因此是并系的。分支 A 和 B 于 570 万年前的中新世晚期（Mya）分化，当时日本群岛正在形成。分支 A 的三个分支最早的分化发生在 180 万年前。分支 A1 和 A2 可能在 80 万年前分化，这是由于在多个不同的避难所中隔离所致；然而，冰川气候对分支 A3 分化事件的影响尚不清楚。分支 B 内的分化发生在上新世晚期到更新世早期（320-220 万年前）。分支 B 中的并系分支（分支 B1 和 B2）之间的生态位相似性表明它们是异域分化的。这表明 与 之间的生态位隔离有助于 对流水繁殖的快速适应。在冰川期，所有日本蟾蜍分支都退缩到低海拔的避难所，在末次冰盛期后种群数量增加，形成了现在的种群。此外，我们强调了从末次冰盛期到现在气候稳定的区域，这些区域是日本蟾蜍的避难所，影响了它们现有的分布模式。
