Morphological phylogeny of army ants and other dorylomorphs (Hymenoptera: Formicidae)

Abstract. The dorylomorph group of ants comprises the three subfamilies of army ants (Aenictinae, Dorylinae, Ecitoninae) together with the subfamilies Aenictogitoninae, Cerapachyinae, and Leptanilloidinae. We describe new morphological characters and synthesize data from the literature in order to present the first hypothesis of phylogenetic relationships among all dorylomorph genera. These data include the first available character information from the newly discovered male caste of Leptanilloidinae. We used ant taxa from Leptanillinae, Myrmeciinae, and the poneromorph (Ponerinae sensu lato) subfamilies Amblyoponinae, Ectatomminae, and Paraponerinae as outgroups. We scored a total of 126 characters from twenty-two terminal taxa and used these data to conduct maximum parsimony and bootstrap analyses. The single most-parsimonious tree and bootstrap results support a single origin of army ants. The Old World army ant genus Dorylus forms a monophyletic group with the enigmatic genus Aenictogiton, which is currently known only from males; the second Old World army ant genus Aenictus is sister to this clade. This result generates the prediction that females of Aenictogiton, when discovered, will be observed to possess the army ant syndrome of behavioural and reproductive traits. The monophyly of the New World army ants (Ecitoninae) is supported very strongly, and within this group the genera Eciton, Nomamyrmex, and Labidus form a robust clade. The monophyly of Leptanilloidinae is also upheld. The subfamily Cerapachyinae appears paraphyletic, although this conclusion is not supported by strong bootstrap results. Relationships among genera of Cerapachyinae similarly are not resolved robustly, although parsimony results suggest clades consisting of (Acanthostichus + Cylindromyrmex) and (Cerapachys + Sphinctomyrmex). We tested for the effect of incompletely known taxa by conducting a secondary analysis in which the two genera containing ∼50% missing character data (Aenictogiton and Asphinctanilloides) were removed. The strict consensus of the seventeen most-parsimonious trees from this secondary analysis is poorly resolved outside the army ants and contains no clades conflicting with the primary analysis. The position of Leptanilla shifts from forming the sister group to Leptanilloidinae (without high bootstrap support) in the primary analysis, to falling within a polytomy at the base of the root of the dorylomorphs when incompletely known taxa are removed. This instability suggests that the placement of Leptanilla within the dorylomorphs in our primary analysis may be spurious.     

Structure and chemistry of the Dufour gland in Pristomyrmex ants (Hymenoptera, Formicidae)

Billen, J., Ito, F., Tsuji, K., Schoeters, E., Maile, R. and Morgan, E. D. 2000. Structure and chemistry of the Dufour gland in Pristomyrmex ants (Hymenoptera, Formicidae). —Acta Zoologica (Stockholm) 81 : 159–166 All individuals of the three species of Pristomyrmex studied have a Dufour gland with a conspicuous hammer‐shaped distal part, that is connected to a thin‐walled proximal reservoir through a very narrow stalk. The secretory distal part is formed by high columnar cells that are characterized by a highly folded apical wall. The lateral cell junctions apically correspond with the crenel tops, which gives individual cells a peculiar shape with a deep apical depression. The cytoplasm of the secretory cells contains a very well developed smooth endoplasmic reticulum and Golgi apparatus, numerous mitochondria and lysosomes. Histochemical analysis indicates a positive reaction for the presence of a lipid secretion in the hammer‐like part. Gas chromatographic analysis of glands of P. pungens workers reveals the secretion to be formed of a mixture of simple volatile monoterpene hydrocarbons; α–pinene, β–pinene, limonene and camphene. Similar, but species characteristic mixtures of four monoterpenes were found in Pristomyrmex brevispinosus and Pristomyrmex sp.1. Behavioural experiments did not allow a conclusive determination of the function of the gland.     

The internal phylogeny of ants (Hymenoptera: Formicidae)

Abstract. The higher phylogeny of the Formicidae was analysed using 68 characters and 19 taxa: the 14 currently recognized ant subfamilies plus 5 potentially critical infrasubfamilial taxa. The results justified the recognition of 3 additional subfamilies: Aenictogitoninae Ashmead (new status), Apomyrminae Dlussky & Fedoseeva (new status), and Leptanilloidinae Bolton (new subfamily). A second analysis on these better delimited 17 subfamilies resulted in 24 equally most parsimonious trees. All trees showed a basal division of extant Formicidae into two groups, the first containing (Myrmicinae, Pseudomyrmecinae, Nothomyrmeciinae, Myrmeciinae, Formicinae, Dolichoderinae, Aneuretinae) and the second the remaining subfamilies. Clades appearing within these groups included the Cerapachyinae plus 'army ants', the Nothomyrmeciinae plus Myrmeciinae, the 'formicoid' subfamilies (Aneuretinae + Dolichoderinae + Formicinae), and the Old World army ants (Aenictinae + Aenictogitoninae + Doryline), but relationships within the last two groups were not resolved, and the relative positions of the Apomyrminae, Leptanillinae and Ponerinae remained ambiguous. Moreover, a bootstrap analysis produced a consensus tree in which all branches were represented in proportions much lower than 95%. A reconstruction of the ground plan of the Formicidae indicated that the most specialized of all recent ants are the members of the subfamily Dorylinae and the least specialized ones are the monotypic Apomyrminae.     

Molecular phylogeny and biogeography of the spider ants, genus Leptomyrmex Mayr (Hymenoptera: Formicidae)

This study provides the first phylogenetic reconstruction of the ant genus Leptomyrmex Mayr, a prominent endemic component of rain forest and wet sclerophyll forest in Australia, New Guinea and New Caledonia. Five genes are used to reconstruct phylogeny and estimate of ages of diversification in order to test congruence of the history of nuclear and mitochondrial genes: three protein-coding nuclear genes: arginine kinase (argK, 897 bp), long wavelength rhodopsin (LW Rh, 546 bp) and wingless (Wg, 409 bp), as well as the large subunit ribosomal gene 28S (482 bp) and the mitochondrial gene cytochrome oxidase I (COI, 658 bp). Four different partitioning schemes were tested for optimal resolving power; results show that partitioning by gene, translational pattern and codon position were uniformly favoured over less complex partitions. Nuclear markers showed relatively minor sequence divergence and provided strongly supported topology; phylogeny based solely on mtDNA produced somewhat conflicting topology but offered little power to resolve species complexes. Monophyly of the genus Leptomyrmex was recovered, as was the sister-group relationship of 'micro-' and 'macro-'Leptomyrmex species. Divergence dating analyses estimate that Leptomyrmex arose in the Eocene (stem age ～ 44 million years ago (ma)), and that the 'macro-' species diverged from the 'micro-' species in the early Oligocene (～ 31 ma). Diversification of the crown group 'macro-' and 'micro-'Leptomyrmex occurred in the Miocene (～ 15 ma and 7.9 ma, respectively). New Guinean and New Caledonian lineages appear to have diverged from Australian lineages only recently (～ 4.7 ma and 10.3 ma, respectively), and the latter clade is inferred to have reached New Caledonia from Australia via long distance dispersal. These results challenge previous hypotheses of Leptomyrmex classification and assumptions about their historical dispersal, but are in agreement with the current knowledge of the geological history of Melanesia.     

The ant genus Aenictus from Laos,with description of a new species (Hymenoptera: Formicidae: Aenictinae)

Ants of the genus Aenictus are recorded from Laos for the first time. Here, we report six species including a new species and a new status: Aenictus binghami Forel, A. cf. dentatus Forel, A. doydeei Jaitrong et Yamane, sp. nov., A. cf. fuchuanensis Zhou, A. hodgsoni Forel, stat. nov., and A. nishimurai Terayama et Kubota. A. doydeei sp. nov. is very probably a nocturnal species.     

The basicoxal gland, a new exocrine structure in poneromorph ants (Hymenoptera, Formicidae)

The tegumental epithelium of the outer dorsolateral region in the proximal part of the coxae in the mid‐ and hindlegs of both workers and queens of the ants Odontomachus rixosus and O. simillimus is differentiated into a conspicuous and hitherto unknown exocrine gland. The glandular cells display a clear microvillar differentiation of their apical cell membrane, and are lined with the tegumental cuticle, which in this part contains crack‐like channels perpendicular to its surface, that carry the glandular secretions to the outside. Apical microvilli support the transport of substances, and contain an extension of tubular smooth endoplasmic reticulum in their centre. The function of the gland may be that of providing lubricant substances to the articulation region of the generally heavily sclerotized ponerine ant species. The gland is also found in several other ponerine and amblyoponine species, but not in the ectatommine species studied. The foreleg coxae lack a basicoxal gland in all species examined, which may be explained by the more limited articulation between the thorax and the coxae in the forelegs compared to the mid‐ and hindlegs.     

A new data of worker polymorphism in the ant genus Dorylus (Hymenoptera: Formicidae: Dorylinae)

Recently, in southern and central Vietnam, foraging columns of D. orientalis which contained not only “typical” workers but also a few “atypical” workers were collected. The atypical worker mentioned above is characterized by a set of the following features: (1) head narrowed anteriorly, (2) median portion of clypeus strongly projecting anteriad, and (3) antenna 8-segmented. Sequences of the 658-base standard mitochondrial DNA barcoding region were completely identical between typical and atypical workers. Therefore, the condition observed was a case of worker polymorphism within a colony. The mode of polymorphism observed has the following interesting aspects: (1) workers are clearly subdivided into two series by a set of qualitative characters; (2) the “typical series” is numerically much more dominant than the “atypical series” (the latter occupied less than 1% of the whole of the workers collected); (3) a wider size variation was observed in the former (HW, 0.48–1.41 mm; ML, 0.42–1.12 mm) than in the latter (HW, 0.44–1.13 mm; ML, 0.35–0.79 mm); and (4) within the atypical series, smaller workers are numerically much dominant. Rareness of the workers belonging to the atypical series in foraging column as well as morphological differences between the two series suggests a certain possibility that the atypical series does not adapt to foraging but to other tasks in the colony's life history.     

The Dufour gland closing apparatus in Formica sanguinea Latreille (Hymenoptera,Formicidae)

Summary A closing apparatus of the Dufour gland is described in the formicine ant Formica sanguinea Latreille 1798. Four sets of muscles are involved, two of which directly attach to the slit-like duct. The latter shows a considerable cuticular thickening of its intima at this level. Ultrastructural observations reveal that the muscles are attached to a cuticula by means of intracellular microtubules in the duct cells. These microtubules run parallel to the myofilaments. Together with the increased contact area for muscular attachments they are believed to ensure the accurate muscular mechanism assuring a well-controlled spraying activity of this gland. Opening of the duct is probably achieved by active muscular contractions, while its closure may be achieved by a passive return to the rest position of the thickened cuticular intima.Research assistant of the Belgian National Fund for Scientific Research     

Studies on California ants: a review of the genus Temnothorax (Hymenoptera,Formicidae)

The following ten new species of the ant genus Temnothorax are described and illustrated: T. anaphalantus (California, Baja California), T. arboreus (California), T. caguatan (Oregon, California, Baja California), T. morongo (California, Baja California), T. myrmiciformis (California, Baja California), T. nuwuvi (Nevada), T. paiute (California, Nevada), T. pseudandrei (Arizona, California), T. quasimodo (California) and T. wardi (California). A key to workers of the twenty-two Temnothorax species known or expected to occur in California is provided.     

The phylogeny of the ant tribe Formicini (Hymenoptera: Formicidae) with the description of a new genus

Abstract. The holarctic ant tribe Formicini is revised, the new genus Bajcaridris described, and possible phylogenetic relationships are discussed. The subgenus Iberoformica is synonymized with Formica. A synopsis, diagnosis and keys to the genera are provided.     

The army ant Aenictus silvestrii and its related species in Southeast Asia,with a description of a new species (Hymenoptera: Formicidae: Aenictinae)

Three species of Aenictus with reduced numbers of antennal segments (8–9) occur in Southeast Asia: A. jarujini sp. nov., A. latifemoratus and A. silvestrii. Aenictus latifemoratus is new to Java and Borneo, while A. silvestrii is recorded for the first time from Borneo.     

The sting bulb gland in myrmecia and Nothomyrmecia (Hymenoptera : Formicidae): A new exocrine gland in ants

A new exocrine gland has been discovered within the sting of the endemic Australian ants of the genera Myrmecia and Nothomyrmecia (Hymenoptera : Formicidae). It consists of approximately 20 secretory cells with their accompanying duct cells, located between the ducts of the venom and Dufour glands in the proximal part of ths sting bulb, hence my suggestion to designate it as the sting bulb gland. Ultrastructural examination reveals the development of both granular and smooth endoplasmic reticulum in the glandular cells, which possibly may indicate the elaboration of a rather complex secretion. Although the function of the gland remains unknown, its exclusive presence in these ants provides another argument for a closer phylogenetic relationship between both genera than is reflected by their actual classification.     

Secostruma, a new subterranean tetramoriine ant genus (Hymenoptera: Formicidae)

Abstract. Secostruma , a very specialized new subterranean ant recovered from a soil-core sample taken in Sabah, East Malaysia, is described for the first time. Its most striking adaptations and their possible functions are discussed, and its affinities investigated. Analysis of its main features and comparison with two possible parent-groups leads to the conclusion that Secostruma is a member of the Tetramorium-group of genera.     

A new species of the Aenictus wroughtonii group (Hymenoptera,Formicidae) from South-East China

A new species of army ant from the Aenictus wroughtonii group is described and illustrated based on the worker caste. Aenictus gutianshanensis Staab, sp. n. is known form a single colony collected in the subtropical mixed evergreen broad-leaved forest of the Gutianshan National Nature Reserve, South-East China. The new species is probably most closely related to A. vieti Jaitrong & Yamane, 2010 known from North Vietnam and Taiwan. It is suggested that the abundant records of A. camposi Wheeler & Chapman, 1925 from East and South-East China should be reevaluated, as they are probably A. gutianshanensis or A. vieti and not A. camposi, which is distributed in Sundaland, the Philippines, and the southernmost part of continental South-East Asia.     

The ant subfamily Pseudomyrmecinae (Hymenoptera: Formicidae): phylogeny and evolution of big-eyed arboreal ants

Abstract. The ant subfamily Pseudomyrmecinae comprises three genera of hyperoptic, arboreal ants, widely distributed in tropical and subtropical regions: Pseudomyrmex (∼200 species, New World), Myrcidris (two species, South America) and Tetraponera (∼100 species, Palaeotropics). The phylogenetic relationships among these ants were investigated using DNA sequence data (∼5.2 kb from 18S rDNA, 28S rDNA, wingless, abdominal-A, and long-wavelength rhodopsin genes) and 144 morphological characters, both separately and in combination. Data were gathered from a representative set of forty-nine pseudomyrmecine species, plus eighteen species from various outgroups. There was substantial agreement among the results obtained from different datasets, and from different methods of phylogenetic inference (parsimony, Bayesian inference). The monophyly of the following groups is strongly supported (100% bootstrap support and 1.00 posterior probability in the molecular dataset): Pseudomyrmecinae, Pseudomyrmex, and Pseudomyrmex + Myrcidris. The status of the genus Tetraponera is less clear: the DNA sequence data indicate that the genus is paraphyletic, but morphological features and a unique insertion in the 28S gene support the monophyly of this taxon. Seven of nine Pseudomyrmex species groups, established previously on the basis of morphology alone, are strongly upheld, but monophyly is rejected for the P. pallens group and the P. viduus group. In the latter case, molecular evidence indicates the existence of two independent clades, associated with the ant-plants Triplaris and Tachigali, respectively, whose convergent morphological features had caused them to be placed erroneously in the same species group. The present results confirm an earlier assertion that obligate associations with domatia-bearing plants have arisen at least twelve times in the subfamily. Molecular and morphological data support the hypothesis of a sister-group relationship between Pseudomyrmecinae and Myrmeciinae (84% parsimony bootstrap, combined dataset), which implies a Cretaceous origin of the stem-group pseudomyrmecines in the southern hemisphere. Pseudomyrmecines appear to have arisen in the Palaeotropics and later dispersed from Africa to South America, where they experienced a pronounced burst of diversification.     

The evolution of myrmicine ants: phylogeny and biogeography of a hyperdiverse ant clade (Hymenoptera: Formicidae)

This study investigates the evolutionary history of a hyperdiverse clade, the ant subfamily Myrmicinae (Hymenoptera: Formicidae), based on analyses of a data matrix comprising 251 species and 11 nuclear gene fragments. Under both maximum likelihood and Bayesian methods of inference, we recover a robust phylogeny that reveals six major clades of Myrmicinae, here treated as newly defined tribes and occurring as a pectinate series: Myrmicini, Pogonomyrmecini trib.n. , Stenammini, Solenopsidini, Attini and Crematogastrini. Because we condense the former 25 myrmicine tribes into a new six‐tribe scheme, membership in some tribes is now notably different, especially regarding Attini. We demonstrate that the monotypic genus Ankylomyrma is neither in the Myrmicinae nor even a member of the more inclusive formicoid clade—rather it is a poneroid ant, sister to the genus Tatuidris (Agroecomyrmecinae). Several species‐rich myrmicine genera are shown to be nonmonophyletic, including Pogonomyrmex, Aphaenogaster, Messor, Monomorium, Pheidole, Temnothorax and Tetramorium. We propose a number of generic synonymies to partially alleviate these problems (senior synonym listed first): Pheidole = Anisopheidole syn.n. = Machomyrma syn.n. ; Temnothorax = Chalepoxenus syn.n. = Myrmoxenus syn.n. = Protomognathus syn.n. ; Tetramorium = Rhoptromyrmex syn.n. = Anergates syn.n. = Teleutomyrmex syn.n. The genus Veromessor stat.r. is resurrected for the New World species previously placed in Messor; Syllophopsis stat.r. is resurrected from synonymy under Monomorium to contain the species in the hildebrandti group; Trichomyrmex stat.r. is resurrected from synonymy under Monomorium to contain the species in the scabriceps‐ and destructor‐groups; and the monotypic genus Epelysidris stat.r. is reinstated for Monomorium brocha. Bayesian divergence dating indicates that the crown group Myrmicinae originated about 98.6 Ma (95% highest probability density 87.9–109.6 Ma) but the six major clades are considerably younger, with age estimates ranging from 52.3 to 71.1 Ma. Although these and other suprageneric taxa arose mostly in the middle Eocene or earlier, a number of prominent, species‐rich genera, such as Pheidole, Cephalotes, Strumigenys, Crematogaster and Tetramorium, have estimated crown group origins in the late Eocene or Oligocene. Most myrmicine species diversity resides in the two sister clades, Attini and Crematogastrini, which are estimated to have originated and diversified extensively in the Neotropics and Paleotropics, respectively. The newly circumscribed Myrmicini is Holarctic in distribution, and ancestral range estimation suggests a Nearctic origin. The Pogonomyrmecini and Solenopsidini are reconstructed as being Neotropical in origin, but they have subsequently colonized the Nearctic region (Pogonomyrmecini) and many parts of the Old World as well as the Nearctic region (Solenopsidini), respectively. The Stenammini have flourished primarily in the northern hemisphere, and are most likely of Nearctic origin, but selected lineages have dispersed to the northern Neotropics and the Paleotropics. Thus the evolutionary history of the Myrmicinae has played out on a global stage over the last 100 Ma, with no single region being the principal generator of species diversity. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub: BB6829C4‐DA79‐45FE‐979E‐9749E237590E .