Inordinate spinescence: taxonomic revision and microtomography of the Pheidole cervicornis species group (Hymenoptera, Formicidae)

The ant genus Pheidole—for all of its hyperdiversity and global ubiquity—is remarkably conservative with regard to morphological disparity. A striking exception to this constrained morphology is the spinescent morphotype, which has evolved multiple times across distantly related lineages of Indoaustralian Pheidole. The Pheidole cervicornis group contains perhaps the most extraordinary spinescent forms of all Pheidole. Here we present a taxonomic revision of the P. cervicornis group, and use microtomographic scanning technology to investigate the internal anatomy of the thoracic spines. Our findings suggest the pronotal spines of Pheidole majors, are possibly skeletomuscular adaptations for supporting their disproportionately large heads. The ‘head support hypothesis’ is an alternative to the mechanical defense hypothesis most often used to explain spinescence in ants. The P. cervicornis group is known only from New Guinea and is represented by the following four species, including two d...

大头蚁属（Pheidole）尽管兼具极高的物种多样性与全球广布性，但其形态差异度却惊人地保守。这种形态约束的显著例外是具棘形态型（spinescent morphotype），该类群已在印澳区亲缘关系较远的大头蚁属支系中多次独立演化。弯角大头蚁类群（Pheidole cervicornis group）或许拥有大头蚁属中最为出众的具棘类群。本文对弯角大头蚁类群开展了分类学修订，并利用显微计算机断层扫描技术探究了其胸部棘突的内部解剖结构。研究结果显示，大头蚁大型工蚁的前胸棘刺，可能是用于支撑其比例失调的大型头部的骨骼肌肉适应性演化特征。“头部支撑假说”是对当前最常用于解释蚂蚁具棘现象的机械防御假说的替代方案。弯角大头蚁类群仅分布于新几内亚地区，目前已知包含以下4个物种，其中2个……