Colonization of a novel habitat is often followed by phenotypic diversification in the wake of ecological opportunity. However, some habitats should be inherently more constraining than others if the challenges of that environment offer few evolutionary solutions. We examined this push-and-pull on macroevolutionary diversification following habitat transitions in the anglerfishes (Lophiiformes). We constructed a phylogeny with extensive sampling (1,092 loci and ~38% of species), combined with three-dimensional phenotypic data from museum specimens. We used these datasets to examine the tempo and mode of phenotypic diversification. The deep-sea pelagic anglerfishes originated from a benthic ancestor and shortly after experienced rapid lineage diversification rates. This transition incurred shifts towards larger jaws, smaller eyes and a more laterally compressed body plan. Despite these directional trends, this lineage still evolved high phenotypic disparity in body, skull and jaw shapes. In particular, bathypelagic anglerfishes show high variability in body elongation, while benthic anglerfishes are constrained around optimal shapes. Within this radiation, phenotypic evolution was concentrated among recently diverged lineages, notably those that deviated from the archetypical globose body plan. Taken together, these results demonstrate that spectacular evolutionary radiations can unfold even within environments with few ecological resources and demanding physiological challenges.

新栖息地的定殖之后，通常会在生态机会之后出现表型多样化。然而，如果环境的挑战几乎没有提供进化解决方案，那么某些栖息地本质上应该比其他栖息地更具限制性。我们研究了琵琶鱼 （Lophiiformes） 栖息地转变后对宏观进化多样性的这种推拉。我们构建了一个系统发育，其中包含大量采样 （1,092 个基因座和 ~38% 的物种），并结合了来自博物馆标本的三维表型数据。我们使用这些数据集来检查表型多样化的速度和模式。深海中上层琵琶鱼起源于底栖动物的祖先，不久之后经历了快速的谱系多样化。这种转变导致了向更大的下巴、更小的眼睛和更横向压缩的身体计划的转变。尽管有这些方向性趋势，该谱系在身体、头骨和下巴形状方面仍然进化出高度的表型差异。特别是，深海琵琶鱼的身体伸长率表现出高度可变性，而底栖琵琶鱼则受到最佳形状的限制。在这种辐射中，表型进化集中在最近分化的谱系中，特别是那些偏离原型球体计划的谱系。综上所述，这些结果表明，即使在生态资源匮乏和苛刻的生理挑战的环境中，壮观的进化辐射也可以展开。