Data from: An ancient origin for the enigmatic Flat-Headed Frogs (Bombinatoridae: Barbourula) from the islands of Southeast Asia

Background: The complex history of Southeast Asian islands has long been of interest to biogeographers. Dispersal and vicariance events in the Pleistocene have received the most attention, though recent studies suggest a potentially more ancient history to components of the terrestrial fauna. Among this fauna is the enigmatic archaeobatrachian frog genus Barbourula, which only occurs on the islands of Borneo and Palawan. We utilize this lineage to gain unique insight into the temporal history of lineage diversification in Southeast Asian islands. Methodology/Principal Findings: Using mitochondrial and nuclear genetic data, multiple fossil calibration points, and likelihood and Bayesian methods, we estimate phylogenetic relationships and divergence times for Barbourula. We determine the sensitivity of focal divergence times to specific calibration points by jackknife approach in which each calibration point is excluded from analysis. We find that relevant divergence time estimates are robust to the exclusion of specific calibration points. Barbourula is recovered as a monophyletic lineage nested within a monophyletic Costata. Barbourula diverged from its sister taxon Bombina in the Paleogene and the two species of Barbourula diverged in the Late Miocene. Conclusions/Significance: The divergences within Barbourula and between it and Bombina are surprisingly old and represent the oldest estimates for a cladogenetic event resulting in living taxa endemic to Southeast Asian islands. Moreover, these divergence time estimates are consistent with a new biogeographic scenario: the Palawan Ark Hypothesis. We suggest that components of Palawan's terrestrial fauna might have ''rafted'' on emergent portions of the North Palawan Block during its migration from the Asian mainland to its present-day position near Borneo. Further, dispersal from Palawan to Borneo (rather than Borneo to Palawan) may explain the current day disjunct distribution of this ancient lineage.背景：东南亚岛屿的复杂演化历史长期以来一直是生物地理学家的研究热点。既往研究多聚焦更新世（Pleistocene）时期的扩散与隔离分化事件，但近期研究表明，部分陆地动物类群的演化历史可能更为久远。在这些类群中，存在一类神秘的古蛙类（archaeobatrachian）蛙属——巴博蛙属（Barbourula），该属仅分布于婆罗洲（Borneo）与巴拉望岛（Palawan）。本研究以该演化支为对象，旨在深入解析东南亚岛屿类群分化的时间演化历程，这一视角具备独特研究价值。 方法/主要结果：本研究借助线粒体（mitochondrial）与核基因遗传数据、多组化石校准点，以及最大似然法与贝叶斯法，对巴博蛙属（Barbourula）的系统发育关系与分化时间进行估算。通过刀切法（jackknife）检验目标分化时间对特定校准点的敏感性：具体操作为逐一排除单个校准点后开展分析。研究发现，相关分化时间估算结果对单个校准点的排除具有稳健性。巴博蛙属（Barbourula）被鉴定为单系演化支，且嵌套于单系的肋突类（Costata）支系内。巴博蛙属与其姐妹类群铃蟾属（Bombina）的分化发生于古近纪（Paleogene），而巴博蛙属内两个物种的分化则发生于晚中新世（Late Miocene）。 结论与意义：巴博蛙属（Barbourula）内部及其与铃蟾属（Bombina）的分化时间出乎意料地古老，这代表了目前针对东南亚岛屿特有现生类群的分支演化（cladogenetic）事件的最古老估算结果。此外，本次分化时间估算结果与全新的生物地理学情景——巴拉望方舟假说（Palawan Ark Hypothesis）——相吻合。我们提出，巴拉望岛的部分陆地类群可能在北巴拉望地块（North Palawan Block）从亚洲大陆迁移至现今靠近婆罗洲的位置期间，依托该地块出露的区域进行了“浮运”扩散。此外，从巴拉望岛向婆罗洲的扩散（而非反之），或可解释该古老演化支现今的间断分布格局。