Implications of a fossil stickleback assemblage for Darwinian gradualism
Implications of a fossil stickleback assemblage for Darwinian gradualism
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DOI：
10.1111/j.1095-8649.2009.02416.x
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发表时间：
2009-11-01
影响因子：
2
通讯作者：
Bell, M. A.
中科院分区：
文献类型：
--
作者：
Bell, M. A.
达尔文假设，一个完整的化石记录将包含祖先和后代物种之间的许多逐渐过渡，但在《物种起源》出版150年后，很少有这样的过渡实现。棘鱼Gasterosteus doryssus的化石和它所在的存款为检测这种转变提供了极好的条件。丰富的，保存完好的化石出现在一个具有良好的时间分辨率的地层环境。对G. doryssus类似于现代湖泊的生态，这些湖泊拥有表型相似的三刺棘鱼Gasterosteus aculeatus。Gasterosteus aculeatus的盔甲非常厚，但G。doryssus由两个同期的生物物种组成，盔甲相对较弱，包括近岸底栖食虫动物（底栖）和近海食虫动物（湖沼）。底栖物种将其范围扩大到湖泊的湖沼区，在那里它显然转向了食肉，并在c. 5000年来，定向选择的反应。虽然平均表型发生了逐渐的进化，但一个单一的主基因引起了骨盆骨骼的大部分进化变化。因此，达尔文关于化石记录中物种之间的过渡是渐进的预期在一个很好的时间尺度上得到了满足，但是对于骨盆结构，一个被充分研究的特征，他关于渐进变化完全取决于个体之间大量的、微小的、可遗传的差异的预期是不正确的。
Darwin postulated that a complete fossil record would contain numerous gradual transitions between ancestral and descendant species, but 150 years after publication of The Origin of Species, few such transitions have materialized. The fossil stickleback Gasterosteus doryssus and the deposit in which it occurs provide excellent conditions to detect such transitions. Abundant, well-preserved fossils occur in a stratigraphic setting with fine temporal resolution. The paleoecology of G. doryssus resembles the ecology of modern lakes that harbour the phenotypically similar three-spined stickleback Gasterosteus aculeatus. Gasterosteus aculeatus are primitively highly armoured, but G. doryssus comprised two contemporaneous biological species with relatively weak armour, including a near-shore, benthic feeder (benthic) and an offshore planktivore (limnetic). The benthic species expanded its range into the limnetic zone of the lake, where it apparently switched to planktivory and evolved reduced armour within c. 5000 years in response to directional selection. Although gradual evolution of mean phenotypes occurred, a single major gene caused much of evolutionary change of the pelvic skeleton. Thus, Darwin's expectation that transitions between species in the fossil record would be gradual was met at a fine time scale, but for pelvic structure, a well-studied trait, his expectation that gradual change would depend entirely on numerous, small, heritable differences among individuals was incorrect.