Cranial shape and correlated characters in crocodilian evolution
Cranial shape and correlated characters in crocodilian evolution
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DOI：
10.1111/j.1420-9101.2008.01602.x
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发表时间：
2008-11-01
影响因子：
2.1
通讯作者：
Makovicky, Peter J.
中科院分区：
文献类型：
--
作者：
Sadleir, Rudyard W.;Makovicky, Peter J.
在其8000万年的化石记录中，鳄鱼显示出高度的颅骨变异和趋同，这使它们的系统发育重建变得复杂。来自不同数据分区和特征同源性的相互矛盾的系统发育结果是鳄鱼系统发育的典型特征，分子和形态系统发育假设之间的差异被认为与Gavialis gangeticus和Tomistoma schlegelii的细长鼻颅骨形状有关。细鼻头骨是被认为反映功能或生态专门化的五种已确定的真颌类颅骨生态形态类别（ESCs）之一。本文采用集中变化试验，考察了普通型、钝型和细长型ESCs之间的转换对系统发育时期颅骨特征状态分布的影响。此外，在形态特征矩阵上进行了字符独立性的“无树”字符兼容性分析，以确定是否存在独立于特定树拓扑的字符相关性。结果表明，在系统发育过程中，颅骨ESCs确实影响颅骨特征状态的增益。集中的变化确定了一套广泛的特征状态变化，这些变化与形态学、分子和组合数据树拓扑结构上向细长、一般和钝型ESCs的过渡显著相关，但每个类别的相关特征数量因拓扑结构而异。字符兼容性分析结果不反映集中的更改测试结果，而是反映整个数据的分层分布支持。由于颅骨ESCs影响特征状态转换，非系统发育变量可能通过影响颅骨形态影响鳄鱼系统发育的推断。
Crocodilians show a high degree of cranial variation and convergence throughout their 80 million-year fossil record that complicates their phylogenetic reconstruction. Conflicting phylogenetic results from different data partitions and character homoplasies typify crocodilian phylogeny, and differences between molecular and morphological phylogenetic hypotheses are believed to be associated with the slender-snout skull shape of Gavialis gangeticus and Tomistoma schlegelii. Slender-snout skulls are one of five identified eusuchian cranial ecomorph shape categories (ESCs) thought to reflect functional or ecological specialization. This paper tested the effect of transitions among general, blunt and slender ESCs on cranial character-state distributions in phylogeny using the concentrated changes test. In addition, 'tree-free' character compatibility analysis of character independence was conducted on the morphological character matrix to determine if character correlations are observed independent of specific tree topologies. Results suggest cranial ESCs do affect cranial character-state gains in phylogeny. Concentrated changes identify a broad suite of character-state changes that significantly correlate with transitions to slender, general and blunt ESCs on morphological, molecular and combined-data tree topologies, but numbers of correlated characters for each category differ according to topology. Character compatibility analysis results do not mirror the concentrated changes test results and reflect hierarchically distributed support throughout the data. As cranial ESCs affect character-state transitions, it is possible that nonphylogenetic variables could affect inferences of crocodilian phylogeny by affecting cranial morphology.