达尔文将化石记录中没有物种过渡归因于他的假设,即物种形成发生在孤立的栖息地斑块内,地理上过于限制,无法被化石序列捕获。Mayr'sperpatricspeciationmodeladdedthatsuchspeciationwouldberapid,进一步解释缺乏多样化的证据。的确,Eldredge和Gould的原始标点平衡模型结合了达尔文的猜想,迈尔的模型和124年未成功采样化石记录的过渡。观察到这种分歧,然而,可以说明早期物种形成过程中的进化节奏和模式。这里,我们研究了在一个上新世的棘鱼周围的分歧,Gasterosteusdoryssus.这个血统出现了,大约8000代以上,进化出与装甲相关的16个性状中的12个显著减少,游泳和饮食,相对于其祖先人口。这比我们观察到的繁殖分离之间的形态差异更大,现存的Gasterosteusaculeatus的底栖生态型。因此,我们推断生殖隔离正在演变。然而,G.dorysus谱系的局部灭绝表明,孤立的,物种种群经常消失,支持达尔文对缺失证据的解释,并揭示了形态停滞背后的机制。灭绝也可能解释了stickleback物种复合体内有限的持续差异,并有助于调和跨时间尺度观察到的物种形成率变化。
Darwin attributed the absence of species transitions in the fossil record to his hypothesis that speciation occurs within isolated habitat patches too geographically restricted to be captured by fossil sequences. Mayr\'s peripatric speciation model added that such speciation would be rapid, further explaining missing evidence of diversification. Indeed, Eldredge and Gould\'s original punctuated equilibrium model combined Darwin\'s conjecture, Mayr\'s model and 124 years of unsuccessfully sampling the fossil record for transitions. Observing such divergence, however, could illustrate the tempo and mode of evolution during early speciation. Here, we investigate peripatric divergence in a Miocene stickleback fish, Gasterosteus doryssus. This lineage appeared and, over approximately 8000 generations, evolved significant reduction of 12 of 16 traits related to armour, swimming and diet, relative to its ancestral population. This was greater morphological divergence than we observed between reproductively isolated, benthic-limnetic ecotypes of extant Gasterosteus aculeatus. Therefore, we infer that reproductive isolation was evolving. However, local extinction of G. doryssus lineages shows how young, isolated, speciating populations often disappear, supporting Darwin\'s explanation for missing evidence and revealing a mechanism behind morphological stasis. Extinction may also account for limited sustained divergence within the stickleback species complex and help reconcile speciation rate variation observed across time scales.