ABSTRACT

Efforts to reconstruct the phylogenetic history of (: Formicidae) have been boosted in the last few years by accumulation of comprehensive molecular data sets exploring multiple loci on a wide range of taxa within the family. In contrast, the wealth of morphological information for the group remains scattered across the literature comprising more than a century’s worth of taxonomic and anatomical research with little standardization. The present study addresses this problem by providing a synthesis of the external skeletal morphology of ants with special emphasis on the poneromorph subfamilies (, , , Paraponerinae, , and Proceratiinae). Particular attention was devoted to documenting and standardizing morphological characters for phylogenetic inference. The morphological analysis was undertaken by constructing a digital atlas of 28 standard views containing 5250 scanning electron micrographs documenting worker morphology from which detailed anatomical comparison could be accurately performed. The final matrix describes 139 characters (60% of which are completely new or coded cladistically here for the first time) for 105 terminals representing ,90% of extant poneromorph genera plus all other extant formicid subfamilies, with the exception of the rare Martilinae, and nonformicid outgroups. This matrix was analyzed with parsimony under both equal weights and implied weights (i.e., where characters are downweighted as a function of their homoplasy). The poneromorph subfamilies form a paraphyletic assemblage with the dorylomorphs, leptanillo- morphs, and myrmicomorphs nested inside. All the above subfamilies are in turn reconstructed as nested within a paraphyletic group comprising the formicomophs + myrmeciomorphs. These results are in concordance with traditional precladistic views of the subfamily relationships but are markedly different from current estimates based on molecular data.

INTRODUCTION formally within Ponerinae s.l. are more closely related to other subfamilies than Poneromorph ants comprise an informal among themselves (Keller, 2000; Ward and group of six subfamilies that were until recently Brady, 2003; Saux et al., 2004; Brady et al., classified as the single subfamily Ponerinae 2006; Moreau et al., 2006; Ouellette et al., (herein sensu lato), but that currently includes 2006). Such accumulation of evidence led the subfamilies Amblyoponinae, Ectatommi- Bolton (2003) to propose the elevation of nae, Heteroponerinae, Paraponerinae, Poner- the major tribes within the old assembly to inae sensu stricto, and Proceratiinae (Bolton, subfamily status, hence splitting the group 2003). Taken together, poneromorphs total into six subfamilies and restricting the 1631 recognized species of worldwide distribu- name Ponerinae to the subgroup of genera tion arranged in 54 genera (seven of them mostly corresponding to the previously extinct) and 10 tribes (Agosti and Johnson, recognized tribe Ponerini. In his 2003 2007). Synopsis and Classification of Formicidae Since first erected by Lepeletier de Saint- Bolton arranged the ant subfamilies into Fargeau (1835) as the family-group taxon informal groups convenient for the ‘‘estab- Pone´rites, the group has undergone many lishment of identity rather than the postula- taxonomic changes in both its generic com- tion of phylogenetic hypotheses’’ (Bolton, position and its internal arrangement. Cir- 2003: 3), and thus the name poneromorphs cumscription of Ponerinae s.l. became prob- was introduced as a replacement term to lematic as the number of included species refer to this traditional, long-standing, but expanded greatly from its original concep- now considered unnatural, taxon. Table 1 tion: it is now recognized that this assemblage shows the classification of poneromorph was defined by symplesiomorphic characters genera followed in this study. while serving as an all-purpose taxon to host a For most of the 20th century the subfamily, diverse array of species that did not fit any of while considered a valid taxonomic entity, was the other well established subfamilies (Keller, explicitly treated as a paraphyletic group in 2000). In addition, phylogenetic analyses discussions of ant phylogeny. W.M. Wheeler have shown that different groups of genera (1928) considered Ponerinae s.l. as the ‘‘prim-

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