Late to the Table: Diversification of Tetrapod Mandibular Biomechanics Lagged Behind the Evolution of Terrestriality
Late to the Table: Diversification of Tetrapod Mandibular Biomechanics Lagged Behind the Evolution of Terrestriality
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DOI：
10.1093/icb/ict006
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发表时间：
2013-08-01
影响因子：
2.6
通讯作者：
Ruta, Marcello
中科院分区：
文献类型：
--
作者：
Anderson, Philip S. L.;Friedman, Matt;Ruta, Marcello
中晚泥盆世（英语：Middle to Late Devonian）的四足动物（英语：figure-bearing tetrapods）的起源。393-360 Mya）及其随后的土地入侵代表了新生态机会驱动的重大进化辐射的经典案例。在这个和其他例子中，新的生态空间的探索被假设为与功能创新和适应性分化的表型。在所有形态功能系统的同时变化是罕见的主要进化过渡，可能是不存在的。在这里，我们重点关注早期四足动物及其亲属的下颌骨作为模型系统，以测试功能创新的转变是否与四足动物历史上的一些重大事件同时代。为此，我们量化的机械变化的tetrapodomorphs的下颌骨的年龄范围从早泥盆纪最早的二叠纪。从泥盆纪到宾夕法尼亚早期，生物力学的差异是稳定的，尽管负重的、趾状肢的起源和陆地殖民的初始阶段都发生在这段时间。一个明显的增加功能的变化是在最新的宾夕法尼亚州和最早的二叠纪，当茎和冠的mechanical morphospace开始探索新的领域，部分归因于草食动物的起源模式检测。我们没有发现之间的tetrapodomorph“鱼”和早期的指状四足动物的功能变化率的差异，虽然两个独立的转变之间检测到泥盆纪干四足动物更crownward比ostega。相反，最深刻的变化，在进化速度是嵌套在四足动物的冠，并与adapotes（特别是diadectomorphs和一些联会）。与陆生性相关的颅后特征的起源（例如具有能够承重的功能性肘/膝和腕/踝关节的四肢）与下颌生物力学的发散的开始之间的实质性时间间隙提供了一个在主要适应性辐射期间“功能模块化”的令人信服的例子。
The origin of digit-bearing tetrapods in the Middle to Late Devonian (ca. 393-360 Mya) and their subsequent invasion of land represent a classic case of a major evolutionary radiation driven by new ecological opportunities. In this and other examples, exploration of new eco-space is hypothesized to correlate with functional innovation and adaptive divergence of phenotypes. Simultaneous changes in all morphofunctional systems are rare in major evolutionary transitions and may be non-existent. Here, we focus on the mandibles of early tetrapods and their kin as a model system to test whether shifts in functional innovation were coeval with some major events in tetrapod history. To this end, we quantified mechanical variation in the mandibles of tetrapodomorphs ranging in age from Early Devonian to earliest Permian. Biomechanical disparity is stable from the Devonian to the Early Pennsylvanian, even though the origin of weight-bearing, digited limbs, and the initial phases of the colonization of land occurred during this interval. An appreciable increase in functional variation is detected in the latest Pennsylvanian and earliest Permian, when stem and crown amniotes began to explore new regions of mechanical morphospace, a pattern partly attributable to the origin of herbivory. We find no difference in the rate of functional change between tetrapodomorph "fish" and early digited tetrapods, although two independent shifts are detected among Devonian stem tetrapods more crownward than Acanthostega. Instead, the most profound shifts in evolutionary rate are nested well within the tetrapod crown and are associated with amniotes (particularly diadectomorphs and some synapsids). The substantial temporal gap between the origin of postcranial features associated with terrestriality, such as limbs with functional elbow/knee and wrist/ankle joints capable of weight-bearing, and the onset of divergence in jaw biomechanics provides a compelling example of "functional modularity" during a major adaptive radiation.