熊科（食肉目、哺乳动物）基壳的系统发育信号分析,PeerJ

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熊科（食肉目、哺乳动物）基壳的系统发育信号分析
PeerJ ( IF 2.3 ) Pub Date : 2019-03-15 , DOI: 10.7717/peerj.6597
María Eugenia Arnaudo _{1,

2} , Néstor Toledo _{2,

3} , Leopoldo Soibelzon _{2,

4} , Paula Bona _{2,

3}

Affiliation

熊科是一个单系类群，由三个亚科组成：Tremarctinae、Ursinae 和 Ailuropodinae，所有这些亚科都有丰富的地理分布。熊科群体内的系统发育关系尚未得到充分研究，特别是在形态特征（如基本骨）方面。重要的是，基颅骨是一个高度复杂的区域，覆盖了头骨的一小部分，结合了决定其形态的结构和功能方面。熊科（包括Tremarctinae）的系统发育假说是基于考虑头骨、下颌骨和牙齿特征的形态特征，而尚未考虑听觉区和基颅骨的具体特征。为此，我们分析了熊科动物的形状和大小宏观进化，在系统发育背景下测试其形态差异，并通过系统发育信号进行量化。我们使用正交分解分析和 Abouheif C 均值研究了形状（由之前发表的分析中的主成分分析分数描述）和基骨尺寸（由质心尺寸 CS 描述）的系统发育自相关。这些方法的主要优点是它们完全依赖于分支图拓扑并且不需要分支长度估计。此外，还使用 TNT 1.5 软件对祖先节点进行了优化。关于系统发育信号，两种方法都显示出相似的结果：在 PC1 和 PC2 中检测到自相关的存在，而在 PC3、PC4 和 PC5 以及基骨 (CS) 的大小中，没有发生自相关。最重要的节点（存在自相关）是基础节点“Ursidae”和“Ursinae-Tremarctinae”。在最后一组中，观察到独特的基骨形态，在 Tremarctinae 中比在 Ursinae 中更加保守。这些亚科之间的差异可能与涉及不同食物和环境偏好的历史事件有关。Tremarctinae节点中的高系统发育信号可能表明这些熊的基本骨结构是在其进化历史的早期获得的。最后，我们对基骨和头骨长度比率的结果表明，在 Tremarctinae 中，基骨的大小不是由系统发育决定的，而是由其他因素决定的，例如对气候变化的适应性反应和与其他食肉动物的竞争。

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Phylogenetic signal analysis in the basicranium of Ursidae (Carnivora, Mammalia)

Ursidae is a monophyletic group comprised of three subfamilies: Tremarctinae, Ursinae and Ailuropodinae, all of which have a rich geographical distribution. The phylogenetic relationships within the Ursidae group have been underexamined, especially regarding morphological traits such as the basicranium. Importantly, the basicranium is a highly complex region that covers a small portion of the skull, combining both structural and functional aspects that determine its morphology. Phylogenetic hypotheses of the Ursidae (including Tremarctinae) have been made based on morphological characters that considers skull, mandible and teeth features, while specific characters of the auditory region and basicranium have not been taken into account. To do this, we analyse the shape and size macroevolution of the basicranium of Ursidae, testing its morphological disparity in a phylogenetic context, which is quantified by means of the phylogenetic signal. We investigated phylogenetical autocorrelation by shape (depicted by Principal Components Analysis scores from previous published analyses) and basicranium size (depicted by centroid size, CS) using an orthonormal decomposition analysis and Abouheif C mean. The main advantages of these methods are that they rely exclusively on cladogram topology and do not require branch-length estimates. Also, an optimisation of the ancestral nodes was performed using TNT 1.5 software. In relation to the phylogenetic signal, both methods showed similar results: the presence of autocorrelation was detected in PC1 and PC2, while in PC3, PC4 and PC5 and in the size of the basicranium (CS), the absence of autocorrelation occurred. The most significant nodes (where there is autocorrelation) are the basal nodes ‘Ursidae’ and ‘Ursinae-Tremarctinae’. Within this last group, distinctive basicranium morphology is observed, being more conservative in Tremarctinae than in Ursinae. The differences between these subfamilies could be related to historical events involving varying food and environmental preferences. The high phylogenetic signal in the node Tremarctinae probably indicates that the basicranium configuration of these bears was obtained early in their evolutionary history. Finally, our results of the basicranium and skull length ratios indicate that in Tremarctinae, the basicranium size was not determined by phylogeny but instead by other factors, such as adaptive responses to climatic changes and competition with other carnivores.

更新日期：2019-03-15

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