The ecology of a continental evolutionary radiation: Is the radiation of sigmodontine rodents adaptive?

Evolutionary radiations on continents are less well-understood and appreciated than those occurring on islands. The extent of ecological influence on species divergence can be evaluated to determine whether a radiation was ultimately the outcome of divergent natural selection or else arose mainly by nonecological divergence. Here, we used phylogenetic comparative methods to test distinct hypotheses corresponding to adaptive and nonadaptive evolutionary scenarios for the morphological evolution of sigmodontine rodents. Results showed that ecological variables (diet and life-mode) explain little of the shape and size variation of sigmodontine skulls and mandibles. A Brownian model with varying rates for insectivory versus all other diets was the most likely evolutionary model. The insectivorous sigmodontines have a faster rate of morphological evolution than mice feeding on other diets, possibly due to stronger selection for features that aid insectivory. We also demonstrate that rapid ea...相较于岛屿上发生的演化辐射（evolutionary radiation），大陆上的演化辐射的相关研究认知与重视程度均相对更低。我们可通过评估生态作用对物种分化的影响程度，判断某一演化辐射最终究竟是趋异自然选择的结果，还是主要源自非生态性分化。本研究采用系统发育比较方法（phylogenetic comparative methods），针对棉鼠亚科啮齿类（sigmodontine rodents）的形态演化，检验对应适应性与非适应性演化情景的不同假说。研究结果显示，生态变量（食性与生活模式）仅能解释棉鼠亚科啮齿类颅骨与下颌骨的形态及大小变异中的极小部分。以食虫性类群与其他所有食性类群的演化速率差异为特征的布朗模型（Brownian model），是最符合数据的演化模型。食虫性棉鼠亚科啮齿类的形态演化速率快于其他食性的啮齿类，这可能源于针对有助于食虫适应性的特征的更强选择压力。本研究同时证实，快速的ea……