Polyrhachis

Rudy Kohout has spent more than 2 decades revising members of this diverse genus. His ongoing publications focus on sets of species placed in species groups. These groups are organized by subgenera. Dorrow (1995) presented the first contemporary reorganization of what had previously slowly developed into a messy tangle of poorly organized groups and forms. Kohout's revisions have altered some of Dorrow's groupings. This has come about as particular species and groups have been more carefully assessed. There no longer exists any published overview detailing how all the species groups are organized under their respective subgenera. Antwiki does present some of these updated group revisions and species keys (species groups are presented on their respective subgenera for many groups; see the subgenera listed in the taxobox on the right side of this page). Phylogenetic analyses, using molecular sampling, has yet to be applied to examine how the currently organized groups are related. Most modern revisions have been clear in stating that the current groupings are logical constructs largely based on similarities in morphology and are not phylogenetic hypotheses. Both the species groups and subgenera are important considering the current taxonomic state of the genus as a whole.

Identification
See the nomenclature section below for links to more Polyhrachis keys.

Species richness
Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data



Biology
Most species of Polyrhachis nest arboreally and forage on low vegetation while a few are ground-foraging and nesting. Morphologically, this is a very diverse group of ants.

Spider Mimics


A Polyrhachis-mimicking spider from Trivandrum, India. Photo by Kalesh Sadasivan.

Phylogeny
(Mezger & Moreau 2015) Spiny ants (Polyrhachis Smith) are a hyper-diverse genus of ants distributed throughout the Palaeotropics and the temperate zones of Australia. To investigate the evolution and biogeographic history of the group, we reconstructed their phylogeny and biogeography using molecular data from 209 taxa and seven genes. Our molecular data support the monophyly of Polyrhachis at the generic level and several of the 13 recognized subgenera, but not all are recovered as monophyletic. We found that Campomyrma Wheeler consists of two distinct clades that follow biogeographic affinities, that the boundaries of Hagiomyrma Wheeler are unclear depending on the analysis, that Myrma Billberg might be treated as one or two clades, and that Myrmhopla Forel is not monophyletic, as previously proposed. Our biogeographic ancestral range analyses suggest that the evolution of Polyrhachis originated in South-East Asia, with an age of the modern crown-group Polyrhachis of 58 Ma. Spiny ants dispersed out of South-East Asia to Australia several times, but only once to mainland Africa around 26 Ma.

Nomenclature

 *  POLYRHACHIS [Formicinae: Camponotini]
 * Polyrhachis Smith, F. 1857a: 58. Type-species: Formica bihamata, by original designation.
 * [Polyrhachis Shuckard, in Swainson & Shuckard, 1840: 172. Nomen nudum.]
 * Polyrhachis subgenus of Myrma: Wheeler, W.M. 1911c: 860; Wheeler, W.M. 1911f: 170.
 * [Myrma subgenus of Polyrhachis: Forel, 1915b: 106; Forel, 1917: 251; Wheeler, W.M. 1922a: 702, 993; Emery, 1925b: 198 (see note under Myrma).]
 * Subgenera of Polyrhachis (alphabetical order with synonyms indicated): nominal plus Aulacomyrma (= Johnia), Campomyrma, Chariomyrma, Cyrtomyrma, Hagiomyrma, Hedomyrma (= Dolichorhachis, = Morleyidris), Hemioptica, Hirtomyrma, Myrma (= Anoplomyrma, = Hoplomyrmus, = Pseudocyrtomyrma), Myrmatopa (= Irenea), Myrmhopla (= Cephalomyrma, = Florencea), Myrmothrinax (= Evelyna).
 * [All subgenera were given as provisional junior synonyms of Polyrhachis by Brown, 1973b: 178-184. The list was repeated in Hölldobler & Wilson, 1990: 19 with all subgenera listed as junior synonyms. They reverted to subgeneric status in Bolton, 1994: 50; see under individual entries. The entry of Chariomyrma, Hagiomyrma and Hedomyrma under the synonymy of Polyrhachis by Taylor & Brown, D.R. 1985: 131, is not considered as confirmation as the three subgenera all range outside the Austral Region.]
 *  Polyrachis Arnold, 1924: 741, incorrect subsequent spelling.

Dorow (1995) provides the latest revision of the species into subgenera and species-groups. These hierarchical arranged names are not supported by any strong evidence that these groups between the genus and species level represent monophyletic units. Regardless, much of the framework for these names has been in place for some time and they do serve as a welcome convenience for organizing the complex diversity of species. Rudy Kohout has been revising species by geographic areas and within specific subgenera and species-groups for more than two decades. Kohout's ongoing taxonomic work has largely followed the arrangement of Dorow (1995) with some modifications becoming necessary as more species have been described.

Aulacomyrma - key to Polyrhachis (Aulacomyrma) species
 * Polyrhachis porcata species-group
 * Polyrhachis dohrni species-group

Campomyrma
 * The gravis species-group and a key to species.
 * The micans species-group and a key to species.
 * The xiphias species-group and a key to species.

Chariomyrma

Cyrtomyrma  - key to Australian Cyrtomyrma species

Hagiomyrma - key to Polyrhachis Hagiomyrma group species

Hedomyrma 

Hemioptica  - species key

Hirtomyrma

Myrma 
 * aculeata species group

Myrmatopa 

Myrmhopla  - key to Australian Myrmhopla species


 * arachne species group


 * armata species group


 * bicolor species group


 * cephalotes species group


 * cleophanes species group


 * cryptoceroides species group


 * daphne species group


 * dives species group


 * flavoflagellata species group - key to flavoflagellata species


 * furcata species group


 * hector species group


 * mucronata species group


 * nigriceps species group


 * ochracea species group


 * sexspinosa species group


 * viehmeyeri species group

Myrmothrinax

Polyrhachis
 * Key to the subgenus Polyrhachis workers (includes lamellidens and bihamata species-groups)