Busschau Theo, Conradie Werner, Jordaan Adriaan, Daniels Savel R
Department of Botany & Zoology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa.
South African Institute for Aquatic Biodiversity, Private Bag 1015, Grahamstown 6140, South Africa; Port Elizabeth Museum, P.O. Box 13147, Humewood 6013, South Africa.
Zoology (Jena). 2017 Apr;121:72-82. doi: 10.1016/j.zool.2016.11.005. Epub 2016 Dec 10.
We examined species boundaries among two phylogenetically closely related and morphologically similar South African fossorial legless skink species, Acontias breviceps and Acontias gracilicauda. Samples of these two species were collected throughout their distribution ranges and sequenced for three DNA loci (two mitochondrial loci, 16S rRNA and cytochrome b (Cyt b), plus the nuclear locus prolactin). Phylogenetic relationships were determined using maximum parsimony, Bayesian inference and maximum likelihood analyses of the combined DNA sequence data set. The total evidence topology retrieved two paraphyletic clades in both Acontias species with strong statistical support. The phylogenetic results revealed that A. breviceps specimens from the Eastern Cape Province were basal (Clade 1), while the Highveld specimens of A. breviceps from the Mpumalanga Province (Clade 2) were retrieved as sister to A. gracilicauda (Clade 1). In addition, the A. gracilicauda specimens from the interior of the Northern Cape Province (Clade 2) were found embedded within the A. occidentalis species complex. These clades were characterised by marked sequence divergence for the Cyt b locus. Furthermore, no maternal or nuclear haplotypes were shared between clades within both A. breviceps and A. gracilicauda, alluding to genetic and reproductive isolation. The results provide overwhelming evidence to assign A. breviceps from the Mpumalanga Highveld to a novel species. Further sampling is required to accurately delineate species boundaries within A. gracilicauda. The conservation implications of our results are briefly discussed.
我们研究了两种系统发育关系密切且形态相似的南非穴居无腿石龙子物种——短头无腿石龙子（Acontias breviceps）和细尾无腿石龙子（Acontias gracilicauda）之间的物种界限。在这两个物种的整个分布范围内采集了样本，并对三个DNA位点（两个线粒体位点，16S rRNA和细胞色素b（Cyt b），以及核位点催乳素）进行了测序。使用最大简约法、贝叶斯推断和对合并的DNA序列数据集进行最大似然分析来确定系统发育关系。总证据拓扑结构在两个无腿石龙子物种中均检索到两个并系分支，且有强有力的统计支持。系统发育结果显示，东开普省的短头无腿石龙子标本处于基部（分支1），而姆普马兰加省高草原地区的短头无腿石龙子标本（分支2）被检索为细尾无腿石龙子（分支1）的姐妹种。此外，北开普省内陆地区的细尾无腿石龙子标本（分支2）被发现嵌入西方无腿石龙子物种复合体中。这些分支的特征是Cyt b位点存在明显的序列分歧。此外，短头无腿石龙子和细尾无腿石龙子的各分支之间没有共享母系或核单倍型，这暗示了遗传和生殖隔离。这些结果提供了压倒性的证据，将姆普马兰加高草原地区的短头无腿石龙子归为一个新物种。需要进一步采样以准确划定细尾无腿石龙子的物种界限。我们简要讨论了研究结果对保护的影响。
