Contrasting Evolutionary Flexibility in Sister Groups: Disparity and Diversity in Mesozoic Heart Urchins
Contrasting Evolutionary Flexibility in Sister Groups: Disparity and Diversity in Mesozoic Heart Urchins
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对比姐妹群体的进化灵活性：中生代心海胆的差异和多样性
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发表时间：
1999
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通讯作者：
G. Eble
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作者：
G. Eble
关于分枝历史中时间不对称性的一般主题的研究通常特别关注下古生代的辐射。然而，后古生代的模式却鲜为人知。本文从系统发育的角度分析了中生代心脏海胆的差异性和多样性变化，特别是姐妹群Holasteroida和Spatangoida，它们的副系统干群Disasteroida，以及更具包容性的分支--无口超目之间的对比。基于地标的38维形态空间代表测试体系结构被用来从总方差和总范围两个方面描述形态演化。总方差也被划分为口头和流产贡献，反映了不同程度的发育根基和功能。差异和多样性之间的不协调是明显的，表现为所有类群的形态多样化减速，以及在无口纲、全口纲和斯帕坦戈达的历史早期不成比例的高差异。早期Atelostomatan的差异高峰与Holasteroida和Spatangoida目的起源相吻合的发现支持了高等类群在生物学等级中是半独立实体的看法，并作为形态差异的有意义的替代。在白垩纪末期大灭绝的全行星和扇形小行星响应的比较中，形态选择性是明显的。与坎帕尼亚-马斯特里赫特样本相比，古新世Satangoid幸存者的差异没有变化，这表明没有选择性，而全息小行星的差异损失更明显(尽管晚白垩世差异水平相当高)，表明形态选择性。口腔和流产模式表明，差异变化背后有特定的因果关系。全息小行星和Satangoid的起源更符合对堕胎结构个体发育所固有的发育灵活性的探索，而不是与对生态空间占领的统一功能驱动相一致。在组内，几种模式也与内在对照最一致。从非小行星到全息小行星和Spatangoid，口腔标志物的发育模块化增加和发育抑制减少是明显的。对于流产的地标，没有观察到从非小行星到全息小行星和Spatangoid的差异的实质性变化，这表明尽管时间推移和生态分化，发展仍然受到限制。更广泛地说，这项研究表明，高等类群下古生代辐射的潜在特征差异和进化机制的特定拓扑结构(例如，发育灵活性)不必局限于任何特定的时间段或等级水平。发表为《姐妹群的对比进化灵活性：中生代无口棘皮动物的差异和多样性》，《古生物学》26(1)2000：56-79。
The general theme of temporal asymmetries in clade histories has often been studied with particular attention to the lower Paleozoic radiations. Post-Paleozoic patterns, however, are less well understood. In this paper, disparity and diversity changes in Mesozoic heart urchins were analyzed in light of an ordinal-level phylogeny, with particular reference to contrasts among the sister groups Holasteroida and Spatangoida, their paraphyletic stem group Disasteroida, and the more inclusive clade, the superorder Atelostomata. A 38-dimensional landmark-based morphospace representing test architecture was used to describe morphological evolution in terms of total variance and total range. Total variance was also partitioned into oral and aboral contributions reflecting different degrees of developmental entrenchment and functionality. Discordances between disparity and diversity were evident, and were expressed as deceleration in morphological diversification in all groups, as well as disproportionately higher disparity early in the histories of the Atelostomata, Holasteroida and Spatangoida. The finding that the early Atelostomatan disparity peak coincides with the origin of the orders Holasteroida and Spatangoida lends support to the perception of higher taxa as semi-independent entities in the biological hierarchy and as meaningful proxies for morphological distinctness. Morphological selectivity was apparent in a comparison of holasteroid and spatangoid responses to the end-Cretaceous mass extinction. Paleocene spatangoid survivors showed no change in disparity relative to the Campanian-Maastrichtian sample, suggesting nonselectivity, while holasteroids suffered more pronounced loss in disparity (despite a rather high Late Cretaceous level of disparity), indicating morphological selectivity. Oral and aboral patterns suggested particular lines of causation behind changes in disparity. The origin of holasteroids and spatangoids is more consistent with an exploration of the developmental flexibility inbuilt in the ontogeny of aboral constructions than with a uniform functional drive towards ecospace occupation. Within groups, several patterns were also most consistent with intrinsic controls. An increase in the developmental modularity of and decrease in developmental constraint on oral landmarks were evident from disasteroids to holasteroids and spatangoids. For aboral landmarks, no substantial change in disparity was observed from disasteroids to holasteroids and spatangoids, suggesting the maintenance of a developmental constraint despite the passage of time and ecological differentiation. More generally, this study suggests that particular topologies of disparity and evolutionary mechanisms potentially characteristic of the lower Paleozoic radiations of higher taxa (e.g., developmental flexibility) need not be confined to any particular time period or hierarchical level. Published as Contrasting Evolutionary Flexibility in Sister Groups: Disparity and Diversity in Mesozoic Atelostomate Echinoids in Paleobiology 26(1) 2000: 56-79.