Iterative adaptive radiations of fossil canids show no evidence for diversity-dependent trait evolution
Iterative adaptive radiations of fossil canids show no evidence for diversity-dependent trait evolution
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DOI：
10.1073/pnas.1403666111
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发表时间：
2015-04-21
影响因子：
11.1
通讯作者：
Slater, Graham J.
中科院分区：
文献类型：
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作者：
Slater, Graham J.
适应性辐射理论中一个长期存在的假设是，生态机会限制了表型进化的速度，在支系历史的早期就产生了形态差异的爆发。然而，在比较数据中，对早期爆发模型的经验支持很少。缺乏支持的一个可能原因是，大多数系统发育测试都集中在现存的支系上，而忽视了化石分类群的信息。在这里，我使用北美犬科动物的40年化石记录来测试适应性辐射的预期特征。对于磨牙的身体大小和磨牙面积这两个生态上重要的特征，暗示形态进化速度依赖于时间和多样性的模型被强烈拒绝。相反，Ornstein-Uhlenbeck过程意味着重复的，有时是快速的，对不同的饮食适应高峰的吸引得到了实质性的支持。依赖多样性的形态进化速率在表现出复制的适应性辐射模式的分支中似乎并不常见，例如犬科。相反，这些分支可能最好被认为是在一个主要适应带的受限辛普森子带中的确定性辐射。对自适应峰值模型的支持可能是对亚纬向辐射的诊断。早期爆发或生态机遇模型是否能解释更广泛的适应性辐射，如高等类群的进化，还有待观察。
A long-standing hypothesis in adaptive radiation theory is that ecological opportunity constrains rates of phenotypic evolution, generating a burst of morphological disparity early in clade history. Empirical support for the early burst model is rare in comparative data, however. One possible reason for this lack of support is that most phylogenetic tests have focused on extant clades, neglecting information from fossil taxa. Here, I test for the expected signature of adaptive radiation using the outstanding 40-My fossil record of North American canids. Models implying time-and diversity-dependent rates of morphological evolution are strongly rejected for two ecologically important traits, body size and grinding area of the molar teeth. Instead, Ornstein-Uhlenbeck processes implying repeated, and sometimes rapid, attraction to distinct dietary adaptive peaks receive substantial support. Diversity-dependent rates of morphological evolution seem uncommon in clades, such as canids, that exhibit a pattern of replicated adaptive radiation. Instead, these clades might best be thought of as deterministic radiations in constrained Simpsonian subzones of a major adaptive zone. Support for adaptive peak models may be diagnostic of subzonal radiations. It remains to be seen whether early burst or ecological opportunity models can explain broader adaptive radiations, such as the evolution of higher taxa.