Marjanović David, Laurin Michel
Comparative Osteohistology, UMR CNRS 7179, Université Paris 6, Paris, France.
Syst Biol. 2007 Jun;56(3):369-88. doi: 10.1080/10635150701397635.
A review of the paleontological literature shows that the early dates of appearance of Lissamphibia recently inferred from molecular data do not favor an origin of extant amphibians from temnospondyls, contrary to recent claims. A supertree is assembled using new Mesquite modules that allow extinct taxa to be incorporated into a time-calibrated phylogeny with a user-defined geological time scale. The supertree incorporates 223 extinct species of lissamphibians and has a highly significant stratigraphic fit. Some divergences can even be dated with sufficient precision to serve as calibration points in molecular divergence date analyses. Fourteen combinations of minimal branch length settings and 10 random resolutions for each polytomy give much more recent minimal origination times of lissamphibian taxa than recent studies based on a phylogenetic analyses of molecular sequences. Attempts to replicate recent molecular date estimates show that these estimates depend strongly on the choice of calibration points, on the dating method, and on the chosen model of evolution; for instance, the estimate for the date of the origin of Lissamphibia can lie between 351 and 266 Mya. This range of values is generally compatible with our time-calibrated supertree and indicates that there is no unbridgeable gap between dates obtained using the fossil record and those using molecular evidence, contrary to previous suggestions.
古生物学文献综述表明，最近从分子数据推断出的滑体两栖类最早出现时间并不支持现存两栖动物起源于离片椎类的观点，这与近期的说法相反。利用新的Mesquite模块构建了一个超树，该模块允许将已灭绝的分类群纳入具有用户定义地质时间尺度的时间校准系统发育树中。这个超树纳入了223种已灭绝的滑体两栖动物物种，并且具有高度显著的地层拟合度。一些分歧甚至可以精确到足以作为分子分歧时间分析中的校准点。与基于分子序列系统发育分析的近期研究相比，14种最小分支长度设置组合以及每个多歧分支的10种随机分辨率给出了滑体两栖类分类群更近的最小起源时间。试图复制近期分子时间估计的结果表明，这些估计强烈依赖于校准点的选择、年代测定方法以及所选的进化模型；例如，滑体两栖类起源时间的估计值可能在3.51亿年至2.66亿年之间。这个值的范围通常与我们的时间校准超树相符，表明使用化石记录获得的时间与使用分子证据获得的时间之间不存在无法弥合的差距，这与之前的观点相反。
