Data from: Rates of anagenetic evolution and selection intensity in Middle and Upper Ordovician species of the bryozoan genus Peronopora

Evolutionary rates and selection intensities in eight cladistically defined species-level evolutionary sequences of the Middle and Upper Ordovician bryozoan genus Peronopora were calculated for comparison with values published for fossil and living taxa. Calculations were restricted to statistically significant unidirectional segments of anagenetic series to minimize the mixing of different modes, directions, and rates of evolutionary change. Rates and selection intensities ranged from 10^−7 to 10^−6 darwins and from 10^−6 to 10^−5 haldanes. Across characters, the weighted mean evolutionary rate equaled 5.86 × 10^−7 darwins and the mean selection intensity was 6.44 × 10^−7. Mean rates of 2.15 × 10^−6, 4.31 × 10^−6, and 8.61 × 10^−6 haldanes, and corresponding mean selection intensities equaling 2.39 × 10^−6, 4.78 × 10^−6, and 9.56 × 10^−6, were calculated for generation lengths of 0.5, 1, and 2 years, respectively. The magnitudes of positive and negative evolutionary rates and selection intensities do not differ statistically, individual characters display no consistent pattern of positive or negative values, and no character complexes were detectable. A mosaic pattern of change occurs across characters in evolutionary sequences. Eighty percent of analyzed evolutionary series were multispecies lineages. Both individual and mean values provide direct estimates of the rates of evolution within those lineages at the moment of speciation. Rates of anagenetic evolution in Peronopora were low and similar to published rates for a variety of fossil protists, invertebrates, and vertebrates. However, earlier rate calculations did not isolate the effect of unidirectional anagenesis from that of stasis, random walks, trend reversals, or rate variations. Eight percent of characters in Peronopora produced anagenetic series that were statistically significant, a percentage similar to the 5% calculated in a study of 251 sequences of evolving traits in 53 fossil lineages (Hunt 2007). Stasis and mutation-drift are the most common patterns detectable in the fossil record, although anagenesis remains a potentially important force in shaping the course of both micro- and macroevolution.

本研究针对中奥陶世至晚奥陶世柱苔藓虫属（Peronopora）的8个经分支系统学定义的物种级演化序列，计算了演化速率与选择强度，以与已发表的化石及现生分类群的相关数值进行对比。本次计算仅针对前进演化序列中具有统计学显著性的单向演化段开展，以最大限度降低不同演化模式、方向与速率的演化变化之间的混杂效应。演化速率与选择强度的取值区间为10^−7~10^−6达尔文（darwins）及10^−6~10^−5霍尔丹（haldanes）。就所有研究性状而言，加权平均演化速率为5.86×10^−7达尔文，平均选择强度为6.44×10^−7。当世代时长分别为0.5年、1年与2年时，计算得到的平均演化速率依次为2.15×10^−6、4.31×10^−6及8.61×10^−6霍尔丹，对应的平均选择强度依次为2.39×10^−6、4.78×10^−6及9.56×10^−6。正向与负向演化速率及选择强度的量级不存在统计学差异，单个性状未呈现统一的正向或负向取值趋势，且未检测到性状复合体。演化序列中的不同性状呈现出镶嵌式的变化模式。本次分析的演化序列中，80%为多物种支系。单个性状与平均数值均可直接估算这些支系在物种形成瞬间的演化速率。柱苔藓虫属的前进演化（anagenesis）速率较低，与已发表的多种化石原生生物、无脊椎动物及脊椎动物的演化速率相近。但此前的演化速率计算并未将单向前进演化的效应与停滞、随机游走、趋势反转或速率波动的效应区分开来。柱苔藓虫属中8%的性状所对应的前进演化序列具有统计学显著性，这一比例与一项针对53个化石支系的251个演化性状序列的研究（Hunt, 2007）中得到的5%相近。停滞与突变-漂变是化石记录中最易检测到的演化模式，尽管前进演化仍是塑造微观演化与宏观演化进程的潜在重要动力。