Data from: An unexpected clade of South American ground beetles (Coleoptera: Carabidae: Bembidion)

Phylogenetic relationships of the Antiperyphanes Complex of the genus Bembidion are inferred using DNA sequences from seven genes (two nuclear ribosomal, four nuclear protein coding, and one mitochondrial protein coding). Redefined subgenera within the complex are each well-supported as monophyletic. Most striking was the discovery that a small set of morphologically and ecologically heterogeneous species formed a clade, here called subgenus Nothonepha. This unexpected result was corroborated by the discovery of deep pits in the lateral body wall (in the mesepisternum) of all Nothonepha, a trait unique within Bembidion. These pits are filled with a waxy substance in ethanol-preserved specimens. In one newly discovered species (Bembidion tetrapholeon sp. n., described here), these pits are so deep that their projections into the body cavity from the two sides touch each other internally. These structures in Bembidion (Nothonepha) are compared to very similar mesepisternal pits which have convergently evolved in two other groups of carabid beetles. The function of these thoracic pits is unknown. Most members of subgenus Nothonepha have in addition similar but smaller pits in the abdomen. A revised classification is proposed for the Antiperyphanes Complex.

本研究基于7个基因的DNA序列（2个核核糖体基因（nuclear ribosomal）、4个核蛋白编码基因（nuclear protein coding）及1个线粒体蛋白编码基因（mitochondrial protein coding）），对步甲属（Bembidion）Antiperyphanes复合群的系统发育关系进行了推断。该复合群内经重新定义的各亚属均得到了强有力的支持，被认定为单系群（monophyletic）。最引人注目的发现为：一组形态与生态特征均呈现异质性的小型物种构成了一个演化支（clade），我们将其命名为Nothonepha亚属。这一意外结果得到了佐证：所有Nothonepha亚属物种的体侧壁（位于中胸侧腹板（mesepisternum））均存在深凹窝，该特征在步甲属中为该亚属所特有。在乙醇保存标本（ethanol-preserved specimens）中，这些凹窝内填充有蜡质物质。在本次新发现并于本文记述的四斑步甲（Bembidion tetrapholeon sp. n.）中，这些凹窝极深，两侧凹窝向体腔延伸的凸起在内部彼此接触。我们将步甲属（Nothonepha）的这类结构，与另外两类步甲科（Carabidae）甲虫中趋同演化（convergently evolved）出的极为相似的中胸侧腹板凹窝进行了对比分析。目前此类胸部凹窝的功能尚不清楚。此外，Nothonepha亚属的多数类群在腹部还拥有类似但尺寸更小的凹窝。本研究同时为Antiperyphanes复合群提出了修订后的分类系统。