EXPERIMENTAL CLADISTIC-ANALYSIS OF ANATOMICALLY PRESERVED ARBORESCENT LYCOPSIDS FROM THE CARBONIFEROUS OF EURAMERICA - AN ESSAY ON PALEOBOTANICAL PHYLOGENETICS
EXPERIMENTAL CLADISTIC-ANALYSIS OF ANATOMICALLY PRESERVED ARBORESCENT LYCOPSIDS FROM THE CARBONIFEROUS OF EURAMERICA - AN ESSAY ON PALEOBOTANICAL PHYLOGENETICS
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DOI：
10.2307/2399752
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发表时间：
1992-01-01
影响因子：
1.9
通讯作者：
WILLARD, DA
中科院分区：
文献类型：
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作者：
BATEMAN, RM;DIMICHELE, WA;WILLARD, DA
这种对木本石松类（产木材）的进化支序分析，是唯一的维管植物化石群，仅限于最有力的可用数据：解剖学上保存的化石，已被精心重建为概念上的完整植物。石炭纪的10个属有16个种：4个假草本/“灌木”和12个乔木（树大小）种，它们是欧亚大陆宾夕法尼亚煤沼泽的缩影。详细描述了69个营养性状和46个生殖性状;重新定义了几个关键术语，并重新评估了同源性。在整个数据矩阵中采用二进制编码，尽管X编码有限，但仅包含5%的缺失值。缺乏一个可接受的外群需要建设一个假设的祖先的字符极化和树rooting.Our实验方法分析了完整的数据矩阵加上四个子矩阵（生长习性字符排除，Chaloneria排除，营养特性，生殖特性只）和筛选拓扑结构的次最小以及最小的长度。解释集中在10个单系属，并稍微倾向于拓扑结构（（Paurodendron，Oxroadia）（Anabathra（Chaloheria（Sigillaria（（Diaphorodendron，Synchysidendron）（Hizemodendron（Lepidodendron，Lepiophloios）。其他简约的拓扑结构允许分离的Paulodendron Oxroadia分支（可能是合理的），换位或统一的Anabathra和Chaloneria，并增加Sigillaria的Diaphorodendron Synchysidendron分支。仅限于营养性状的分析易位Hizemodendron接近基地的分支，从而团结非树木作为一个表面上的并系群。仅限于生殖性状的分析更接近所有性状的分析，但未能解决四个基础，bisporangiate锥形属之间的关系，Hizemodendron和Lepidodendron之间。这些观察结果对部分植物和孤立器官的无性生殖的价值提出了质疑。吝啬地使用日益复杂和K选择的生殖策略作为整体无性生殖的基础，不可避免地使部分不协调的营养结构（包括树的习惯）同质化。因此，四个原始的、双孢子囊锥状的属（Paulodendron，Oxroadia，Anabathra，Chaloneria）的一个分辨不好的并系丛对着三个支持良好的单系科的一个单系单孢子囊锥状分支：Sigillariaceae（Sigillaria）相对于Diaphorodendronaceae（Diaphorodendrons. str.，Synchysidendron）和鳞木科（Hizemodendron，Lepidodendron sens. str.，它们的共同特征是每个大孢子囊只有一个功能性大孢子。这种明显的种子状繁殖的进化趋势增加了生态专化性，并与适应性情景相一致。与生殖特征相比，营养特征，如有限生长，集中的根状根茎，以及构成包平面的少量构件类型，（根形和茎必不可少，侧枝和冠枝可选）显然倾向于非适应性的跳跃进化。控制早期发育的基因突变允许生长结构发生根本性变化，随之而来的表观遗传调整和适应性磨练影响了许多其他营养性状。原生的假草本植物Hizemodendron的（异时）起源假设也适用于Chaloneria和其他假草本植物（Paurodendron，Oxroadia），可以说包括他们的价值在评分的习惯性状的假设的祖先。其他限制目前的数据矩阵是大量的属级自形（至少部分反映了前宾夕法尼亚州的树木物种的情况下），包括只有一个双孢子囊锥树（Anabathra）和只有一个假定的isoetalean（Chaloneria）。需要更原始的OTU来研究本研究中所有OTU共享的深刻性格状态的起源（例如，次生加厚，有限生长，集中的根茎，异孢子生殖），并证实了单孢子囊锥和单一功能大孢子的单系假说。重复简化的生长结构的原生和功能冗余的大孢子的发育表明，进化并没有一贯增加形态的复杂性之间的arboasthenglycopsids。负担最高的突触型（因此同源性最低）倾向于代表中等规模的特征。我们还没有发现任何显着的缺点，分支分析一组完全灭绝的OTU。相反，我们建议进一步研究的一些不足的方面的系统发育重建一般：（1）缺失值的影响，树长计算和字符状态优化;（2）最低可接受的水平的经验支持（apomorphic状态每个OTU）;（3）手段识别heterochromy在分支图;（4）较少的方法学约束的表型分支，严格的分支分析。
This evolutionary cladistic analysis of the arborescent (wood-producing) lycopsids, an exclusively fossil group of vascular plants, is confined to the strongest available data: anatomically preserved fossils that have been painstakingly reconstructed into conceptual whole plants. Ten Carboniferous genera are represented by 16 species: four pseudoherbs/"shrubs" and 12 of the arboreous (tree-sized) species that epitomize the Pennsylvanian coal swamps of Euramerica. The 69 vegetative and 46 reproductive characters are described in detail; several key terms are redefined and homologies reassessed. Binary coding was imposed throughout the data matrix, which contained only 5% missing values despite limited X-coding. Lack of an acceptable outgroup necessitated construction of a hypothetical ancestor for character polarization and tree rooting.Our experimental approach analyzed the full data matrix plus four submatrices (growth habit characters excluded, Chaloneria excluded, vegetative characters only, reproductive characters only) and screened topologies of subminimal as well as minimal length. Interpretation focuses on the ten monophyletic genera and marginally favors the topology ((Paurodendron, Oxroadia) (Anabathra (Chaloheria (Sigillaria ((Diaphorodendron, Synchysidendron) (Hizemodendron (Lepidodendron, Lepidophloios))))))). Other parsimonious topologies allow dissociation of the Paurodendron-Oxroadia clade (probably justified), transposition or unification of Anabathra and Chaloneria, and addition of Sigillaria to the Diaphorodendron-Synchysidendron clade. The analysis confined to vegetative characters translocates Hizemodendron close to the base of the clade, thus uniting the non-trees as an ostensibly paraphyletic basal group. The analysis confined to reproductive characters more closely resembles the analysis of all characters, but fails to resolve relationships among the four basal, bisporangiate-coned genera, and between Hizemodendron and Lepidodendron. These observations cast doubt on the value of partial-plant and isolated-organ phylogenies.Parsimonious use of the increasingly sophisticated and K-selected reproductive strategies as the basis of the overall phylogeny inevitably renders homoplastic the partly discordant vegetative architectures (including the tree habit). Consequently, a poorly resolved paraphyletic plexus of four primitive, bisporangiate-coned genera (Paurodendron, Oxroadia, Anabathra, Chaloneria) subtends a monophyletic monosporangiate-coned clade of three well-supported, monophyletic families: the Sigillariaceae (Sigillaria) are primitive relative to the Diaphorodendraceae (Diaphorodendron sens. str., Synchysidendron) and the Lepidodendraceae (Hizemodendron, Lepidodendron sens. str., Lepidophloios), which together are characterized by a single functional megaspore per megasporangium. This apparently progressive evolutionary trend toward seedlike reproduction increased ecological specialization and is consistent with adaptive scenarios.In contrast with reproductive features, vegetative features such as the determinate growth, centralized rhizomorphic rootstock, and small number of module types that constitute the bauplan (rhizomorph and stem essential, lateral and crown branches optional) apparently predisposed the arborescent lycopsids to nonadaptive saltational evolution. Mutation of genes controlling early development allowed radical changes in growth architecture, and consequent epigenetic readjustment and adaptive honing affected many other vegetative characters. The progenetic (heterochronic) origin postulated for the pseudoherb Hizemodendron may also apply to Chaloneria and the other pseudoherbs (Paurodendron, Oxroadia), arguably comprising their value in scoring habit characters for the hypothetical ancestor.Other limitations of the present data matrix are the large number of genus-level autapomorphies (at least partly reflecting the absence of pre-Pennsylvanian arboreous species), the inclusion of only one bisporangiate-coned tree (Anabathra) and of only one putative isoetalean (Chaloneria). More primitive OTUs are needed to investigate the origins of profound character states shared by all OTUs in the present study (e.g., secondary thickening, determinate growth, centralized rhizomorph, heterospory), and to confirm the crucial hypotheses of monophyly for the monosporangiate cone and the single functional megaspore. Repeated simplification of growth architecture by progenesis and of megaspore ornamentation by functional redundancy show that evolution did not consistently increase morphological complexity among the arborescent lycopsids. Synapomorphies of highest burden (and therefore lowest homoplasy) tend to represent features of intermediate scale.We have not identified any significant drawbacks of cladistically analyzing an exclusively extinct set of OTUs. Rather, we recommend further study of some under-researched aspects of phylogeny reconstruction in general: (1) the effect of missing values on tree length calculations and on character state optimization; (2) the minimum acceptable level of empirical support (apomorphic states per OTU); (3) means of recognizing heterochrony in cladograms; and (4) less methodologically constrained phenetic adjuncts to strict cladistic analyses.