Abstract Coraciiformes contains more than 200 species with great differences on external morphology and life-style. The evolutionary relationships within Coraciiformes and the phylogenetic placement of Coraciiformes in Aves are still questioned. Mitochondrial genome (mitogenome) sequences are popular markers in molecular phylogenetic studies of birds. This study presented the genome characteristics of three new mitogenomes in Coraciiformes and explored the phylogenetic relationships among Coraciiformes and other five related orders with mitogenome data of 30 species. The sizes of three mitogenomes were 17,383 bp (Alcedo atthis), 17,892 bp (Halcyon smyrnensis) and 17,223 bp (Megaceryle lugubris). Each mitogenome contained one control region and 37 genes that were common in vertebrate mitogenomes. The organization of three mitogenomes was identical to the putative ancestral gene order in Aves. Among 13 available Coraciiform mitogenomes, 12 protein coding genes showed indications of negative selection, while the MT-ND6 presented sign of positive selection or relaxed purifying selection. The phylogenetic results supported that Upupidae and Bucerotidae should be separated from Coraciiformes, and that Coraciiformes is more closely related to Piciformes than to Strigiformes, Trogoniformes and Cuculiformes. Our study provide valuable data for further phylogenetic investigation of Coraciiformes.

中文翻译：

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喙形目（Megaceryle lugubris、Alcedo atthis、Halcyon smyrnensis）的三个新线粒体基因组的表征及其系统发育的见解

摘要 喙形目有200多种，外部形态和生活方式差异很大。喙形目内的进化关系和喙形目在鸟类中的系统发育位置仍然受到质疑。线粒体基因组（有丝分裂基因组）序列是鸟类分子系统发育研究中的常用标记。本研究展示了喙形目中三个新的有丝分裂基因组的基因组特征，并利用30个物种的有丝分裂基因组数据探讨了喙形目与其他五个相关目之间的系统发育关系。三个有丝分裂基因组的大小分别为 17,383 bp (Alcedo atthis)、17,892 bp (Halcyon smyrnensis) 和 17,223 bp (Megaceryle lugubris)。每个有丝分裂基因组包含一个控制区域和 37 个在脊椎动物有丝分裂基因组中常见的基因。三个有丝分裂基因组的组织与 Aves 中假定的祖先基因顺序相同。在 13 个可用的 Coraciiform 丝裂基因组中，12 个蛋白质编码基因显示出负选择的迹象，而 MT-ND6 则呈现出正选择或宽松纯化选择的迹象。系统发育结果支持Upupidae和Bucerotidae应该与Coraciiformes分开，并且Coraciiformes与Piciformes的关系比与Strigiformes，Trogoniformes和Cuculiformes的关系更密切。我们的研究为喙形目的进一步系统发育研究提供了有价值的数据。系统发育结果支持Upupidae和Bucerotidae应该与Coraciiformes分开，并且Coraciiformes与Piciformes的关系比与Strigiformes，Trogoniformes和Cuculiformes的关系更密切。我们的研究为喙形目的进一步系统发育研究提供了有价值的数据。系统发育结果支持Upupidae和Bucerotidae应该与Coraciiformes分开，并且Coraciiformes与Piciformes的关系比与Strigiformes，Trogoniformes和Cuculiformes的关系更密切。我们的研究为喙形目的进一步系统发育研究提供了有价值的数据。