Department of Genetics, Faculty of Science, Kasetsart University, 50 Paholyothin Road, Bangkok 10900, Thailand.
J Fish Biol. 2012 Jun;80(7):2549-70. doi: 10.1111/j.1095-8649.2012.03303.x. Epub 2012 May 2.
In this study, the phylogenetic relationships among 13 pangasiids and six schilbids of Thailand were reconstructed based on the almost complete mitochondrial cytochrome b (cyt b), 12S rRNA, tRNA-Val and 16S rRNA, as well as the partial nuclear recombination-activating gene 1 (rag1) sequences by using the maximum likelihood and the Bayesian inference methods of phylogenetic reconstruction. The reconstructed phylogeny based on the concatenated sequence data set recovered Pangasiidae and Schilbidae as reciprocally monophyletic groups. Within Pangasiidae, four major clades were recovered, which according to the cyt b genetic distances can be categorized into four genera: Pangasius, Pseudolais, Helicophagus and Pangasianodon. The genus Pangasianodon was strongly supported as the most basal taxon within pangasiids, whereas Pseudolais + Helicophagus were recovered as a sister group of Pangasius. Within the latter, the giant pangasius Pangasius sanitwongsei was recovered as a sister group of the spot pangasius Pangasius larnaudii, Pangasius krempfi as a sister group of Pangasius nasutus + Pangasius conchophilus and Pangasius polyuranodon as a sister species of Pangasius macronema. Other internal phylogenetic relationships, however, were unresolved. Within Schilbidae, Pseudeutropius was supported as the most basal lineage. Eutropiichthys was recovered as a sister group of Clupisoma. The enigmatic Clupisoma sinense was recognized as more closely related to Laides longibarbis than to Clupisoma prateri. Thus, based on the cyt b genetic distances, a recategorization of C. sinense to the genus Laides is suggested. On the basis of a relaxed clock fossil calibration, the divergence of pangasiids and schilbids was estimated to have occurred 14·93 million years before present (b.p.) during the Miocene epoch. The separation between Pangasiidae and Schilbidae took place c. 13·12 Mb.p. during the early middle Miocene. The estimated divergence time of pangasiids is similar to the age of the calibrated fossil, Cetopangasius chaetobranchus, which was discovered in north-central Thailand. This suggests that the oldest pangasiid ancestor diverged into diverse genera in the area.
在这项研究中，基于几乎完整的线粒体细胞色素 b（cyt b）、12S rRNA、tRNA-Val 和 16S rRNA，以及核重组激活基因 1（rag1）序列的部分序列，采用最大似然法和贝叶斯推断法对泰国的 13 种巨鲶科鱼类和 6 种锯鲶科鱼类的系统发育关系进行了重建。基于联合序列数据集重建的系统发育树恢复了巨鲶科和锯鲶科作为相互单系群。在巨鲶科鱼类中，共发现四个主要分支，根据 cyt b 遗传距离可分为四个属：Pangasius、Pseudolais、Helicophagus 和 Pangasianodon。Pangasianodon 属被强烈支持为巨鲶科鱼类中最基础的分类群，而 Pseudolais + Helicophagus 被恢复为 Pangasius 的姐妹群。在后者中，巨型巨鲶 Pangasius sanitwongsei 被恢复为斑点巨鲶 Pangasius larnaudii 的姐妹群，Pangasius krempfi 为 Pangasius nasutus + Pangasius conchophilus 的姐妹群，Pangasius polyuranodon 为 Pangasius macronema 的姐妹种。然而，其他内部系统发育关系仍未解决。在锯鲶科鱼类中，Pseudeutropius 被支持为最基础的谱系。Eutropiichthys 被恢复为 Clupisoma 的姐妹群。神秘的中华锯鲶 Clupisoma sinense 被认为与 Laides longibarbis 的亲缘关系比与 Clupisoma prateri 的更近。因此，根据 cyt b 遗传距离，建议将 C. sinense 重新归类于 Laides 属。基于松弛时钟化石校准，估计巨鲶科鱼类和锯鲶科鱼类的分化发生在 1493 万年前（距今）的中新世。Pangasiidae 和 Schilbidae 的分离发生在中中新世早期，约 1312 万年前。巨鲶科鱼类的估计分化时间与校准化石 Cetopangasius chaetobranchus 的年龄相似，该化石发现于泰国中北部。这表明最古老的巨鲶科鱼类祖先在该地区分化为多个属。
