Secondary structure alignment and direct optimization of 28S rDNA sequences provide limited phylogenetic resolution in bark and ambrosia beetles (Curculionidae: Scolytinae)

Phylogenetic relationships in Scolytinae were reconstructed from 107 DNA sequences that spanned the D2 and D3 expansion segments, and related core regions of the nuclear large ribosomal subunit (28S). Sequences were analysed by parsimony and Bayesian analyses of aligned sequences aided by a new secondary structure model for the D2–D3 domains. Direct optimization was performed on ambiguous alignment regions in combination with fixed states optimization of unambiguous regions, but performed poorly compared to the Bayesian and parsimony analyses. Generally, the phylogenetic signal mainly resolved relationships within tribes, while deeper divergences were either not resolved or received marginal support. In addition to confirming several previously established clades, we found that Micracini formed the sister group to Cactopinus, a group of mainly cactus feeding scolytine beetles. Furthermore, Ipini was monophyletic with Pseudips and Acanthotomicus subtending to the most basal node of that clade. The monophyly of Corthylini, which consists of the bark and cone feeding Pityophtorina and the ambrosia fungus‐feeding Corthylina, was supported in some of the analyses. A close relationship was found between Phloeotribus and the two Phloeosinini genera Chramesus and Pseudochramesus, suggesting an evolutionary trajectory for the origin of a lamellate antennal club in Phloeotribus.

基于跨越核大亚基核糖体（28S）的D2和D3扩展区段以及相关核心区域的107条DNA序列，重建了小蠹亚科（Scolytinae）的系统发育关系。借助针对D2 - D3结构域的一种新的二级结构模型，通过简约法和贝叶斯分析对比对后的序列进行分析。对模糊比对区域结合明确区域的固定状态优化进行了直接优化，但与贝叶斯分析和简约法分析相比效果不佳。一般来说，系统发育信号主要解决了族内的关系，而更深层次的分歧要么未得到解决，要么仅得到微弱支持。除了确认几个先前已确定的分支外，我们发现微小蠹族（Micracini）是仙人掌小蠹属（Cactopinus）的姊妹群，仙人掌小蠹属是一类主要以仙人掌为食的小蠹甲虫。此外，齿小蠹族（Ipini）是单系的，伪齿小蠹属（Pseudips）和棘小蠹属（Acanthotomicus）位于该分支的最基部节点。由树皮和球果取食的梢小蠹亚族（Pityophtorina）和以虫道真菌为食的小蠹亚族（Corthylina）组成的小蠹族（Corthylini）的单系性在一些分析中得到了支持。发现条小蠹属（Phloeotribus）与两个条小蠹族属（Phloeosinini），即窄条小蠹属（Chramesus）和伪窄条小蠹属（Pseudochramesus）之间存在密切关系，这表明了条小蠹属中片状触角棒起源的进化轨迹。