This study used codon analysis (dN/dS and Tv/Ti) to investigate selection pressure and genetic structure in the highly polymorphic Psammobates tentorius species complex, and amino acid sequences to construct a phylogeny tree for it. Our results revealed a strong selection signal at node ‘C2 + C3’, possibly driven by aridity intensification resulting from the development of the Benguela Current. A similar signal was noticed at C3, possibly due to the same driving force. These findings suggest that environmental selection pressure favoured those groups and that further cladogenic events were possible. Selection pressure was also found to be high at C1, C4 and C7, which may indicate that they are also favoured by the current selection pressure. The codon-based phylogeny did not retrieve any potentially undescribed species, but nonetheless provided support for the validity of the seven distinct clades retrieved with the DNA sequence data. The amino acid sequence-based phylogeny generally supported the seven lineages as valid putative species. Investigation at the genomic scale could, however, help to solve the issue. In general, we found the codon, dN, dS, Tv, Ti and amino acid sequence-based phylogenetic inferences useful in species delimitation and recommend their use in species delimitation studies.

中文翻译：

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基于密码子的Psammobates tentorius（Bell，1828）物种复合体中选择压力和遗传结构的分析，以及从密码子和氨基酸序列推断出的系统发育

这项研究使用密码子分析（dN / dS和Tv / Ti）来研究高多态沙门氏菌（Tsammobates tentorius）的选择压力和遗传结构物种复合体和氨基酸序列为其构建系统发育树。我们的结果表明，在节点“ C2 + C3”处有很强的选择信号，这可能是由Benguela Current的发展导致的干旱加剧所驱动的。在C3处发现了类似的信号，可能是由于相同的驱动力所致。这些发现表明，环境选择压力有利于这些人群，并且可能发生进一步的成盖事件。还发现选择压力在C1，C4和C7处较高，这可能表明它们也受到当前选择压力的青睐。基于密码子的系统发育没有检索到任何可能未描述的物种，但是仍然为使用DNA序列数据检索到的七个不同进化枝的有效性提供了支持。基于氨基酸序列的系统发育通常支持这七个谱系作为有效推定物种。但是，基因组规模的研究可以帮助解决该问题。通常，我们发现基于密码子，dN，dS，Tv，Ti和基于氨基酸序列的系统发育推论对物种划界很有用，并建议将其用于物种划界研究。