Data from: A morphospace of planktonic marine diatoms, parts I and II

NOTE: PLEASE ALSO SEE Kotrc B, Knoll AH (2015) A morphospace of planktonic marine diatoms. II. Sampling standardization and spatial disparity partitioning. Paleobiology 41(1): 68-88. http://dx.doi.org/10.1017/pab.2014.5. Both molecular clocks and the first appearances of major groups in the fossil record suggest that most of the range of diatom morphologies observed today had evolved by the end of the Cretaceous Period. Despite this, a canonical reading of the Cenozoic fossil record suggests a dramatic rise in taxonomic diversity that can be interpreted as an explosion of morphological variety. We investigated this apparent discrepancy by using a discrete-character-based, empirical diatom morphospace, resolved by molecular phylogeny and by fossil occurrences through time. The morphospace shows little correspondence to phylogeny and little Cenozoic change in disparity as measured by mean pairwise distance. There is, however, an increase in the total volume of morphospace occupied. Although the increase in occupied volume through time ostensibly supports a conclusion of increasing morphological variety, sampling biases and other data suggest an underlying stationary pattern more consistent with molecular clock data.注：另请参阅 Kotrc B、Knoll AH（2015）《浮游海洋硅藻的形态空间（第二部分：采样标准化与空间差异分区）》，刊载于《古生物学（Paleobiology）》41(1): 68-88，DOI: 10.1017/pab.2014.5。分子钟（molecular clock）与化石记录中主要类群的首次出现均表明，现今所见的绝大多数硅藻形态多样性，已于白垩纪（Cretaceous Period）末期演化形成。尽管如此，新生代（Cenozoic）化石记录的经典解读却显示分类多样性出现急剧上升，这可被解释为形态多样性的爆发式增长。我们依托基于离散性状的经验硅藻形态空间（morphospace），结合分子系统发育（molecular phylogeny）与跨时间尺度的化石产出记录，对这一明显矛盾展开研究。该形态空间与系统发育的相关性极低，且以平均成对距离（mean pairwise distance）衡量的形态差异在新生代几乎未发生变化。然而，其所占据的形态空间总体积却有所增加。尽管随时间推移的占据体积增长表面上支持了形态多样性不断增加的结论，但采样偏差（sampling biases）与其他数据表明，其背后实则存在更符合分子钟数据的静态模式。