Iterative Evolution of Depth Stratification in Neogene Planktonic Foraminifera

尽管试验很少，但人们普遍认为， 生物通过侵入未被占据的部分来形成物种并多样化 水柱。 辐射被认为是当人口 在海洋前沿或海洋边界之间变得孤立 垂直分层的水团 广泛趋同进化 在浮游有孔虫和其他浮游类群中， 同样的栖息地会被不同的血统反复入侵 在地质时期。 例如，球状的，多刺的 有孔虫不断地产生压缩的光滑壁 种具一个周边脊或龙骨。 我们提出 来测试解释迭代进化的流行模型， 龙骨状浮游有孔虫的入侵 逐渐深入到水柱的深处 我们的研究将产生物种的del 18 O同位素排名 在两组独立进化的globorotaliids中， keel：Fohsella和Menardella/Globoconella早期成员 进化枝 地表生活的异长岩 有孔虫，底栖有孔虫，以及这两个 谱系将用于估计深度生境的变化。 以来 这些谱系独立地从球状祖先进化而来，我们 可以观察到类似的深度栖息地变化是否发生在 这与两个谱系中相似的形态学变化一致。 这些结果将使我们能够检验以下假设： 表面居住的物种通过入侵更深的部分辐射 水柱 我们的研究结果将表明，如果重复收敛 有孔虫的演化可以用 栖息地的深度。 我们还可以确定， 形态进化与生态进化无关 在这些海洋浮游生物中。 此外，本研究将记录 一个主要的辐射展开的生态背景。

It has been widely assumed, despite few tests, that pelagic organisms speciate and diversify by invading unoccupied parts of the water column. Radiation is thought to occur when populations become isolated across oceanic fronts or across boundaries between vertically stratified water masses. Extensive convergent evolution in planktonic foraminifera and other planktonic groups suggests that the same habitats are repeatedly invaded by different lineages over geologic time. For example, globular, spiny-walled planktonic foraminifera repeatedly give rise to compressed, smooth-walled species ornamented with a peripheral carina or keel. We propose to test the popular model that explains the iterative evolution of keeled planktonic foraminifera in terms of invasion of progressively deeper parts of the water column. Our study will produce del 18 O isotopic rankings for species in two groups of globorotaliids that independently evolved the keel: Fohsella and early members of the Menardella/Globoconella clade. Isotopic differences between surface-dwelling planktonic foraminifera, benthic foraminifera, and members of these two lineages will be used to estimate changes in depth habitats. Since these lineages independently evolved from globular ancestors, we can observe whether similar changes in depth habitat occurred in concert with similar morphological changes in both lineages. These results will permit us to test the hypothesis that surface-dwelling species radiated by invading deeper parts of the water column. Our findings will show if the repeated convergent evolution of foraminifera can be explained in terms of changes of depth habitat within lineages. We can also determine whether or not morphological evolution is correlated with ecological evolution in these marine plankton. In addition, this study will document the ecological context in which a major radiation unfolded.