Genotypic sex determination enabled adaptive radiations of extinct marine reptiles
Genotypic sex determination enabled adaptive radiations of extinct marine reptiles
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DOI：
10.1038/nature08350
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发表时间：
2009-09
期刊：
影响因子：
64.8
通讯作者：
C. Organ;D. Janes;A. Meade;M. Pagel
中科院分区：
文献类型：
--
作者：
C. Organ;D. Janes;A. Meade;M. Pagel
适应性辐射通常伴随着关键性状的进化，例如羊膜卵的起源和随后的陆生脊椎动物的辐射。一个物种决定其后代性别的机制与关键的生态和生活史特征有关，但与主要的适应性辐射无关，部分原因是性别决定机制并不重要。在这里，我们建立了一个以前未知的94个物种的性别决定机制之间的协同进化关系，一个物种是否生育年轻或产卵。我们使用这种关系来预测已灭绝的中生代海洋爬行动物（沧龙，蜥脚龙和鱼龙）的三个独立谱系的性别决定机制，其中每一个都是从化石中进化出来的活产。我们的研究结果表明，每个谱系在获得活产之前进化出基因型性别决定。这使得它们能够在远洋辐射，在那里，开放海洋相对稳定的温度限制了温度依赖性的性别决定。由于不再需要在陆地上移动和筑巢，每一个群体都进化出了适应远洋生活方式的极端身体适应性，例如鱼龙的尾部、背鳍和翼状四肢。包括鱼龙，沧龙和蜥脚类，基因型的性别决定是目前在所有已知的完全中上层类（海蛇，sirenians和鲸目动物），这表明这种模式的性别决定和随后的进化活产的海洋适应性辐射所需的关键特征在类谱系。
Adaptive radiations often follow the evolution of key traits, such as the origin of the amniotic egg and the subsequent radiation of terrestrial vertebrates. The mechanism by which a species determines the sex of its offspring has been linked to critical ecological and life-history traits,,but not to major adaptive radiations, in part because sex-determining mechanisms do not fossilize. Here we establish a previously unknown coevolutionary relationship in 94 amniote species between sex-determining mechanism and whether a species bears live young or lays eggs. We use that relationship to predict the sex-determining mechanism in three independent lineages of extinct Mesozoic marine reptiles (mosasaurs, sauropterygians and ichthyosaurs), each of which is known from fossils to have evolved live birth,,,. Our results indicate that each lineage evolved genotypic sex determination before acquiring live birth. This enabled their pelagic radiations, where the relatively stable temperatures of the open ocean constrain temperature-dependent sex determination in amniote species. Freed from the need to move and nest on land,,, extreme physical adaptations to a pelagic lifestyle evolved in each group, such as the fluked tails, dorsal fins and wing-shaped limbs of ichthyosaurs. With the inclusion of ichthyosaurs, mosasaurs and sauropterygians, genotypic sex determination is present in all known fully pelagic amniote groups (sea snakes, sirenians and cetaceans), suggesting that this mode of sex determination and the subsequent evolution of live birth are key traits required for marine adaptive radiations in amniote lineages.