A revision of the ant genus Mystrium in the Malagasy region with description of six new species and remarks on Amblyopone and Stigmatomma (Hymenoptera, Formicidae, Amblyoponinae)

Masashi Yoshimura,Brian Fisher

doi:10.3897/zookeys.394.6446

Abstract

The genus Mystrium is revised for the Malagasy region. Six species, Mystrium barrybressleri sp. n., Mystrium labyrinth sp. n., Mystrium eques sp. n., Mystrium mirror sp. n., Mystrium shadow sp. n., and Mystrium janovitzi sp. n. are described as new. Two existing names, Mystrium fallax Forel and Mystrium stadelmanni Forel, are synonymized with Mystrium voeltzkowi Forel and Mystrium mysticum Roger, respectively. All recognized species, including species outside of the Malagasy region, are assigned to one of the three newly proposed species groups. The associations between existing names and males are reexamined, and males of eight of the ten Malagasy species are described or redescribed. The taxonomic history of Mystrium highlights the importance of using unique identifiers when designating type specimens and the use of deposited vouchers in phylogenetic and ecological studies. Keys to species for workers, queens, and males are provided. Furthermore, a neotype for Mystrium mysticum is designated, as well as lectotypes for Mystrium camillae Emery, Mystrium rogeri Forel, Mystrium fallax Forel, Mystrium oberthueri Forel, Mystrium stadelmanni Forel, and Mystrium voeltzkowi Forel. Stigmatomma gingivale (Brown) is reassigned to Amblyopone as comb. rev. and Amblyopone awa Xu & Chu, Amblyopone kangba Xu & Chu, Amblyopone meiliana Xu & Chu, and Amblyopone zomae Xu & Chu are transferred to the genus Stigmatomma as comb. n.

Highlights

The genus Mystrium Roger, 1862 was originally described from Madagascar, and ten species names were regarded as valid prior to this revision (Fig. 1)
In our previous work (Yoshimura and Fisher 2012), we proposed that the elongated mandible in the genus Amblyopone Erichson, 1842 evolved separately from that in the XMAS (Xymmer Santschi, 1914 + Mystrium + Adetomyrma Ward, 1994 + Stigmatomma Roger, 1859) clade; we did not propose any diagnostic characters to distinguish between Amblyopone and XMAS clade genera
The characters uniquely observed in Mystrium within the subfamily Amblyoponinae are given in italics

Summary

Introduction

The genus Mystrium Roger, 1862 was originally described from Madagascar, and ten species names were regarded as valid prior to this revision (Fig. 1). Later Menozzi (1929) revised the genus Mystrium, including all six Malagasy species, M. camillae, and M. silvestrii, and provided a key for workers to all of these species. This revision (Menozzi 1929) was the last taxonomic work on the Malagasy Mystrium. Recent research in Madagascar demonstrated that the previous taxonomic works were insufficient to diagnose the species boundaries of Mystrium in the Malagasy region. Comprehensive morphological and distributional examinations using recently accumulated material enabled us to recognize ten species in this region; six species are new, and two existing names, Mystrium fallax and M. stadelmanni, are synonymized with M. voeltzkowi and M. mysticum, respectively. In this study, based on the comparison between Mystrium, the other genera in the XMAS clade (Yoshimura and Fisher 2012), and Amblyopone, we consider the presence of the dentiform setae on the labrum as a diagnostic character in workers to distinguish the genus Amblyopone from genera in the XMAS clade

Materials and methods

Methods

Results