Adaptive radiations are characterized by extreme and/or iterative phenotypic divergence; however, such variation does not accumulate evenly across an organism. Instead, it is often partitioned into sub-units, or modules, which can differentially respond to selection. While it is recognized that changing the pattern of modularity or the strength of covariation (integration) can influence the range or rate of morphological evolution, the relationship between shape variation and covariation remains unclear. For example, it is possible that rapid phenotypic change requires concomitant changes to the underlying covariance structure. Alternatively, repeated shifts between phenotypic states may be facilitated by a conserved covariance structure. Distinguishing between these scenarios will contribute to a better understanding of the factors that shape biodiversity. Here, we explore these questions using a diverse Lake Malawi cichlid species complex, Tropheops, that appears to partition habitat by depth. We construct a phylogeny of Tropheops populations and use 3D geometric morphometrics to assess the shape of four bones involved in feeding (mandible, pharyngeal jaw, maxilla, pre-maxilla) in populations that inhabit deep versus shallow habitats. We next test numerous modularity hypotheses to understand whether fish at different depths are characterized by conserved or divergent patterns of modularity. We further examine rates of morphological evolution and disparity between habitats and among modules. Finally, we raise a single Tropheops species in environments mimicking deep or shallow habitats to discover whether plasticity can replicate the pattern of morphology, disparity, or modularity observed in natural populations. Our data support the hypothesis that conserved patterns of modularity permit the evolution of divergent morphologies and may facilitate the repeated transitions between habitats. In addition, we find the lab-reared populations replicate many trends in the natural populations, which suggests that plasticity may be an important force in initiating depth transitions, priming the feeding apparatus for evolutionary change.

中文翻译：

---

在丽鱼科动物饲养装置中强大的模块化模式下，生态形态差异和栖息地易感性。

适应性辐射的特征在于极端和/或反复的表型发散。但是，这种变化在整个生物体中并不是均匀累积的。取而代之的是，它通常被划分为多个子单元或模块，这些子单元或模块可以不同地响应选择。尽管人们认识到改变模块化的模式或协变（整合）的强度会影响形态演化的范围或速率，但形状变化和协变之间的关系仍然不清楚。例如，快速的表型改变可能需要对基础协方差结构进行相应的改变。备选地，可以通过保守的协方差结构来促进表型状态之间的重复移位。在这些情况之间进行区分将有助于更好地理解影响生物多样性的因素。在这里，我们使用多样化的马拉维丽鱼科鱼物种Tropheops探索这些问题，它似乎可以按深度划分栖息地。我们构建了Tropheops种群的系统发育系统，并使用3D几何形态计量学评估了居住在深深或浅层栖息地的种群中与进食有关的四块骨头（下颌骨，咽颌，上颌骨，上颌骨）的形状。接下来，我们测试大量的模块化假设，以了解不同深度的鱼类是否具有保守或不同的模块化特征。我们进一步研究了栖息地之间以及模块之间形态演化和差异的速率。最后，我们在模仿深浅栖息地的环境中饲养单个Tropheops物种，以发现可塑性是否可以复制自然种群中观察到的形态，差异或模块化模式。我们的数据支持以下假设，即模块化的保守模式允许演化不同的形态，并可能促进生境之间的反复过渡。此外，我们发现实验室饲养的种群在自然种群中复制了许多趋势，这表明可塑性可能是引发深度转变的重要力量，从而为进化变化提供了可能。我们的数据支持这样的假设，即模块化的保守模式允许不同形态的演变，并可能促进生境之间的反复过渡。此外，我们发现实验室饲养的种群在自然种群中复制了许多趋势，这表明可塑性可能是引发深度转变的重要力量，从而为进化变化提供了可能。我们的数据支持这样的假设，即模块化的保守模式允许不同形态的演变，并可能促进生境之间的反复过渡。此外，我们发现实验室饲养的种群在自然种群中复制了许多趋势，这表明可塑性可能是引发深度转变的重要力量，从而为进化变化提供了可能。