Data from: Testing for ancient adaptive radiations in Neotropical cichlid fishes

Most contemporary studies of adaptive radiation focus on relatively recent and geographically restricted clades. It is less clear whether diversification of ancient clades spanning entire continents is consistent with adaptive radiation. We used novel fossil calibrations to generate a chronogram of Neotropical cichlid fishes and to test whether patterns of lineage and morphological diversification are congruent with hypothesized adaptive radiations in South and Central America. We found that diversification in the Neotropical cichlid clade and the highly diverse tribe Geophagini was consistent with diversity-dependent, early bursts of divergence followed by decreased rates of lineage accumulation. South American Geophagini underwent early rapid differentiation in body shape, expanding into novel morphological space characterized by elongate-bodied predators. Divergence in head-shape attributes associated with trophic specialization evolved under strong adaptive constraints in all Neotropical cichlid clades. The South American Cichlasomatini followed patterns consistent with constant rates of morphological divergence. Although morphological diversification in South American Heroini was limited, Eocene invasion of Central American habitats was followed by convergent diversification mirroring variation observed in Geophagini. Diversification in Neotropical cichlids was influenced by the early adaptive radiation of Geophagini, which potentially limited differentiation in other cichlid clades.

当前绝大多数关于适应辐射（adaptive radiation）的研究，均聚焦于形成时间较晚、地理分布局限的演化支（clade）。针对横跨整个大陆的古老演化支，其物种分化是否符合适应辐射模式，目前尚无明确定论。
本研究采用全新的化石校准方法，构建了新热带界慈鲷鱼类（Neotropical cichlid fishes）的时间演化树（chronogram），并检验了中南美洲地区假说中的适应辐射模式，是否与该类群的谱系分化及形态分化模式相一致。
研究结果显示：新热带界慈鲷演化支及其物种多样性极高的土鲷族（Geophagini）的物种分化模式，符合依赖多样性的分化规律——早期出现分化爆发，随后谱系积累速率逐步降低。
南美土鲷族的体型在早期发生了快速分化，开拓出以长体型捕食者为特征的全新形态空间。
所有新热带界慈鲷演化支中，与食性特化相关的头部形态特征分化，均处于较强的适应性约束之下。
南美丽体鱼族（Cichlasomatini）的形态分化速率则保持恒定。
尽管南美海丽鱼族（Heroini）的形态分化程度有限，但在始新世（Eocene）侵入中美洲生境后，该类群发生了趋同分化，其形态变异模式与土鲷族中观测到的变异特征高度吻合。
新热带界慈鲷的物种分化受到土鲷族早期适应辐射的影响，该过程可能抑制了其他慈鲷演化支的分化。