Finkel Z V, Sebbo J, Feist-Burkhardt S, Irwin A J, Katz M E, Schofield O M E, Young J R, Falkowski P G
Environmental Science Program and Mathematics and Computer Science Department, Mount Allison University, Sackville, NB, Canada.
Proc Natl Acad Sci U S A. 2007 Dec 18;104(51):20416-20. doi: 10.1073/pnas.0709381104. Epub 2007 Dec 12.
The size structure of phytoplankton assemblages strongly influences energy transfer through the food web and carbon cycling in the ocean. We determined the macroevolutionary trajectory in the median size of dinoflagellate cysts to compare with the macroevolutionary size change in other plankton groups. We found the median size of the dinoflagellate cysts generally decreases through the Cenozoic. Diatoms exhibit an extremely similar pattern in their median size over time, even though species diversity of the two groups has opposing trends, indicating that the macroevolutionary size change is an active response to selection pressure rather than a passive response to changes in diversity. The changes in the median size of dinoflagellate cysts are highly correlated with both deep ocean temperatures and the thermal gradient between the surface and deep waters, indicating the magnitude and frequency of nutrient availability may have acted as a selective factor in the macroevolution of cell size in the plankton. Our results suggest that climate, because it affects stratification in the ocean, is a universal abiotic driver that has been responsible for macroevolutionary changes in the size structure of marine planktonic communities over the past 65 million years of Earth's history.
浮游植物群落的大小结构强烈影响着海洋食物网中的能量传递和碳循环。我们确定了甲藻孢囊的中位大小的宏观进化轨迹，以便与其他浮游生物类群的宏观进化大小变化进行比较。我们发现，甲藻孢囊的中位大小在整个新生代总体上呈下降趋势。硅藻在其随时间变化的中位大小上表现出极其相似的模式，尽管这两个类群的物种多样性趋势相反，这表明宏观进化的大小变化是对选择压力的积极响应，而不是对多样性变化的被动响应。甲藻孢囊中位大小的变化与深海温度以及表层与深层水域之间的热梯度高度相关，这表明营养物质可利用性的大小和频率可能在浮游生物细胞大小的宏观进化中起到了选择因素的作用。我们的研究结果表明，由于气候会影响海洋中的分层现象，它是一个普遍的非生物驱动因素，在地球历史上过去的6500万年里，一直导致海洋浮游生物群落大小结构的宏观进化变化。
