Lifting the blue-headed veil – integrative taxonomy of the Acanthocercus atricollis species complex (Squamata: Agamidae)

We present the first integrative review of the African agamid lizard Acanthocercus atricollis, a broadly distributed species found from Ethiopia through East Africa to Angola and South Africa. Since the original description of the species approximately 170 years ago six subspecies have been described, mainly on the basis of coloration characters. Our study presents new morphological and genetic data, which together suggest that A. atricollis is a complex of multiple species. External morphological characters and cranial osteology support some of the taxonomic differentiation implied by coloration. We also provide complementary 16S rRNA mitochondrial DNA (mtDNA) sequence data analysed in the context of species delimitation. Our integrated data support several systematic and taxonomic changes, including (1) Acanthocercus branchi is part of the A. atricollis complex, (2) the subspecies A. gregorii, A. minutus, A. ugandaensis, and A. kiwuensis merit species rank, (3) A. atricollis loveridgei is a synonym of A. a. gregorii, (4) Agama cyanocephalus, a former synonym of A. atricollis, is now recognized as full species distributed in Angola, Zambia and extreme northern Namibia. The distribution and diversity of the A. atricollis species complex supports the presence of a biogeographic arid corridor connecting eastern and southern Africa.

本研究首次针对非洲鬣蜥科棘鬣蜥属的黑项棘鬣蜥（Acanthocercus atricollis）开展系统性综合评述。该物种分布范围广泛，从埃塞俄比亚经东非延伸至安哥拉与南非境内。自约170年前该物种被首次正式描述以来，已有6个亚种被确立，其分类依据主要为体色特征。本研究提供了全新的形态学与遗传学数据，综合分析结果表明，黑项棘鬣蜥实为一个由多个独立物种构成的复合群。外部形态特征与颅骨骨骼学证据，佐证了体色特征所暗示的部分分类分化关系。本研究同时补充提供了用于物种界定分析的16S核糖体RNA（16S rRNA）线粒体DNA（mtDNA）序列数据。本研究的整合数据支持多项分类系统学与分类学修订方案，具体包括：1. 布氏棘鬣蜥（Acanthocercus branchi）隶属于黑项棘鬣蜥复合群；2. 原亚种格雷戈里棘鬣蜥（A. gregorii）、小型棘鬣蜥（A. minutus）、乌干达棘鬣蜥（A. ugandaensis）及基伍棘鬣蜥（A. kiwuensis）均应提升为独立物种；3. 黑项棘鬣蜥洛弗里奇亚种（A. atricollis loveridgei）实为A. a. gregorii的同物异名；4. 曾作为黑项棘鬣蜥同物异名的蓝头鬣蜥（Agama cyanocephalus）现已被认定为独立物种，分布于安哥拉、赞比亚及纳米比亚极北部地区。黑项棘鬣蜥复合群的分布格局与物种多样性，佐证了连接东非与南非的生物地理干旱廊道的存在。