Adamowicz Sarah J, Purvis Andy, Wills Matthew A
Division of Biology, Imperial College London, Silwood Park Campus, Ascot SL5 7PY, United Kingdom.
Proc Natl Acad Sci U S A. 2008 Mar 25;105(12):4786-91. doi: 10.1073/pnas.0709378105. Epub 2008 Mar 17.
The prospect of finding macroevolutionary trends and rules in the history of life is tremendously appealing, but very few pervasive trends have been found. Here, we demonstrate a parallel increase in the morphological complexity of most of the deep lineages within a major clade. We focus on the Crustacea, measuring the morphological differentiation of limbs. First, we show a clear trend of increasing complexity among 66 free-living, ordinal-level taxa from the Phanerozoic fossil record. We next demonstrate that this trend is pervasive, occurring in 10 or 11 of 12 matched-pair comparisons (across five morphological diversity indices) between extinct Paleozoic and related Recent taxa. This clearly differentiates the pattern from the effects of lineage sorting. Furthermore, newly appearing taxa tend to have had more types of limbs and a higher degree of limb differentiation than the contemporaneous average, whereas those going extinct showed higher-than-average limb redundancy. Patterns of contemporary species diversity partially reflect the paleontological trend. These results provide a rare demonstration of a large-scale and probably driven trend occurring across multiple independent lineages and influencing both the form and number of species through deep time and in the present day.
在生命历史中寻找宏观进化趋势和规律的前景极具吸引力，但迄今发现的普遍趋势却寥寥无几。在此，我们证明了一个主要分支内大多数深层谱系的形态复杂性呈平行增加。我们聚焦于甲壳纲，测量附肢的形态分化。首先，我们从显生宙化石记录中66个自由生活的目级分类单元中发现了复杂性增加的明显趋势。接下来，我们证明这一趋势具有普遍性，在已灭绝的古生代类群与相关的现代类群之间的12组配对比较（涵盖五个形态多样性指数）中，有10组或11组呈现出该趋势。这明显将此模式与谱系分选效应区分开来。此外，新出现的分类单元往往比同时期的平均水平具有更多类型的附肢和更高程度的附肢分化，而那些走向灭绝的分类单元则表现出高于平均水平的附肢冗余。当代物种多样性模式部分反映了古生物学趋势。这些结果罕见地证明了一种大规模且可能受驱动的趋势，这种趋势跨越多个独立谱系，在漫长的时间里及当下都影响着物种的形态和数量。
