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，均聚焦于相对晚近且地理分布受限的演化支系。目前学界尚未明确：横跨完整大陆的古老演化支系的多样化过程，是否符合适应辐射的理论范式。本研究采用全新的化石校准方案，构建了新热带丽鱼科鱼类的时间树（Chronogram），并以此检验南美与中美的谱系分化及形态多样化模式，是否与两地所提出的适应辐射假说相符。研究发现，新热带丽鱼科整体以及物种多样性极高的地纹丽鱼族（Geophagini）的多样化过程，均符合依赖多样性的演化模式：即早期出现爆发式分化，随后谱系积累速率逐步降低。南美地纹丽鱼族在演化早期经历了快速的体型形态分化，开拓出以长体型捕食者为典型特征的全新形态空间；在所有新热带丽鱼类群中，与营养特化相关的头部形态特征分化，均受到强烈的适应性选择约束。南美丽体鱼族（Cichlasomatini）的形态分化速率则始终保持恒定。尽管南美慈鲷族（Heroini）的形态多样化程度有限，但在始新世（Eocene）入侵中美洲生境后，其演化出的趋同分化模式与地纹丽鱼族的形态变异特征高度相似。新热带丽鱼科的多样化过程，受到地纹丽鱼族早期适应辐射的显著影响，这一过程可能抑制了其他慈鲷类群的演化分化。