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Abstract We investigate the species-level taxonomy and evolutionary history of Nearctic ants in the Crematogaster scutellaris group (Hymenoptera: Formicidae), drawing on evidence from morphology and UCE (ultraconserved element) phylogenomics. The New World species in this group form a well-supported clade that originated in the Late Miocene (~7.3 Mya) and subsequently diverged into three major lineages: the C. coarctata clade (south-western Nearctic), the C. opaca clade (south-western Nearctic and northern Neotropics) and the C. lineolata clade (eastern Nearctic and Caribbean, with four isolated south-west endemics). We hypothesize trans-Beringian dispersal into the New World, west-to-east movement within North America and restriction of mesophilic species to the east with increasing aridification of the west. The ancestral nesting behaviour of these ants is inferred to be ground-dwelling, and this is still the predominant condition in the arid west, whereas most species in the eastern United States are arboreal. We resurrect from synonymy nine species and describe three new species: C. detecta sp. nov. (from Nevada), C. parapilosa sp. nov. (Florida) and C. vetusta sp. nov. (Arizona). We provide a worker-based key to the 34 species of Crematogaster occurring in America north of Mexico, but emphasize that there are still ongoing taxonomic issues that need to be resolved. 

Abstract Using genetic, morphological, and geographical evidence, we investigate the species-level taxonomy and evolutionary history of the Pseudomyrmex elongatulus group, a clade of ants distributed from southwestern United States to Costa Rica. Through targeted enrichment of 2,524 UCE (ultraconserved element) loci we generate a phylogenomic data set and clarify the phylogenetic relationships and biogeographic history of these ants. The crown group is estimated to have originated ~8 Ma, in Mexico and/or northern Central America, and subsequently expanded into southern Central America and the southwestern Nearctic. The P. elongatulus group contains a mix of low- and high-elevation species, and there were apparently multiple transitions between these habitat types. We uncover three examples of one species—of restricted or marginal geographical distribution—being embedded phylogenetically in another species, rendering the latter paraphyletic. One of these cases involves an apparent workerless social parasite that occurs sympatrically with its parent species, with the latter serving as host. This suggests a sympatric origin of the parasite species within the distribution range of its host. Species boundaries are tested using three molecular delimitation approaches (SODA, bPTP, BPP) but these methods generate inflated species estimates (26–46 species), evidently because of a failure to distinguish population structure from species differences. In a formal taxonomic revision of the P. elongatulus group, based on almost 3,000 specimens from ~625 localities, we allow for geographic variation within species and we employ distinctness-in-sympatry criteria for testing hypotheses about species limits. Under these guidelines we recognize 13 species, of which nine are new: P. arcanus, sp. nov. (western Mexico); P. capillatus, sp. nov. (western Mexico); P. cognatus, sp. nov. (Chiapas, Mexico to Nicaragua); P. comitator, sp. nov. (Chiapas, Mexico); P. ereptor, sp. nov. (Veracruz, Mexico); P. exoratus, sp. nov. (southeastern Mexico, Honduras); P. fasciatus, sp. nov. (Chiapas, Mexico to Costa Rica); P. nimbus, sp. nov. (Costa Rica); and P. veracruzensis, sp. nov. (Veracruz, Mexico). Our study highlights the value of combining phylogenomic, phenotypic, and geographical data to resolve taxonomic and evolutionary questions. 

The genus-level taxonomy of the ant subfamily Leptanillinae (Hymenoptera: Formicidae) is here revised, with the aim of delimiting genus-level taxa that are reciprocally monophyletic and readily diagnosable based upon all adult forms. This new classification reflects molecular phylogenetics and is informed by joint consideration of both male and worker morphology. Three valid genera are recognized in the Leptanillinae:Opamyrma,Leptanilla(=Scyphodonsyn. nov.,Phaulomyrma,Leptomesites,Noonillasyn. nov.,Yavnellasyn. nov.), andProtanilla(=Anomalomyrmasyn. nov.,Furcotanilla).LeptanillaandProtanillaare further divided into informal, monophyletic species groups. Synoptic diagnoses are provided for all genera and informal supraspecific groupings. In addition, worker-based keys to all described species within the Leptanillinae for which the worker caste is known are provided; and male-based keys to all species for which males are known, plus undescribed male morphospecies for which molecular data are published. The following species are described as new:Protanilla wallaceisp. nov.,Leptanilla acherontiasp. nov.,Leptanilla belantansp. nov.,Leptanilla bethyloidessp. nov., andLeptanilla najaphallasp. nov. 

A high-resolution map of ant diversity allows an assessment of how well biodiversity centers overlap across taxa. 

The arboreal ant genus Tetraponera is widely distributed in the Paleotropics. Five species groups were previously recognized in the Afrotropical region (including Madagascar), and two of these were revised. This paper provides a taxonomic treatment of the remaining species. A survey of the T. allaborans group on the African mainland leads to the recognition of fourteen species: T. clypeata (Emery) (= T. braunsi (Forel) syn. nov.); T. continua (Forel) (= T. claveaui (Santschi) syn. nov.); T. cortina sp. nov.; T. dispar sp. nov.; T. emeryi (Forel) (= T. braunsi durbanensis (Forel) syn. nov.); T. exactor sp. nov.; T. furtiva sp. nov.; T. gerdae (Stitz); T. liengmei (Forel); T. mayri (Forel); T. pedana sp. nov.; T. penzigi (Mayr) (= T. scotti Donisthorpe syn. nov. = T. zavattarii (Menozzi) syn. nov. = T. penzigi praestigiatrix Santschi syn. nov.); T. pumila sp. nov.; and T. tessmanni (Stitz). A full revision of the Malagasy species of the T. allaborans group is deferred, but the following new synonymy is established: T. hysterica (Forel) = T. hysterica inflata (Emery) syn. nov.; T. longula (Emery) = T. sahlbergii deplanata (Forel) syn. nov.; T. mandibularis (Emery) = T. flexuosa (Santschi) syn. nov.; T. morondaviensis (Forel) = T. arrogans (Santschi) syn. nov. = T. demens (Santschi) syn. nov. = T. hysterica dimidiata (Forel) syn. nov.; and T. sahlbergii = T. sahlbergii spuria (Forel) syn. nov. = T. plicatidens (Santschi) syn. nov. In the T. ambigua group the following synonymy is reinstated (syn. rev.): T. ambigua (Emery) = T. erythraea (Emery) = T. bifoveolata (Mayr) = T. angolensis Santschi; and T. ophthalmica (Emery) = T. unidens Santschi. A new species is described in the Madagascar-endemic T. grandidieri group: T. elegans sp. nov. Scrutiny of the T. natalensis group indicates the occurrence of ten species: T. andrei (Mayr), T. anthracina (Santschi), T. caffra (Santschi), T. insularis sp. nov., T. kosi sp. nov., T. mocquerysi (André), T. natalensis (F. Smith), T. redacta sp. nov., T. schulthessi (Santschi), and T. setosa sp. nov. T. insularis is known only from Madagascar, while the other nine species are confined to the African mainland. The following new synonymy is proposed for the T. natalensis group (senior synonym cited first): T. anthracina = T. poultoni Donisthorpe syn. nov. = T. triangularis (Stitz) syn. nov.; T. mocquerysi = T. mocquerysi biozellata (Karavaiev) syn. nov. = T. mocquerysi elongata (Stitz) syn. nov. = T. emacerata (Santschi) syn. nov. = T. triangularis illota (Santschi) syn. nov. = T. ledouxi Terron syn. nov. = T. lemoulti (Santschi) syn. nov. = T. mocquerysi lepida Wheeler syn. nov. = T. monardi (Santschi) syn. nov. = T. emacerata oberbecki (Forel) syn. nov. = T. emacerata odiosa (Forel) syn. nov.; and T. natalensis = T. angusta (Arnold) syn. nov. = T. capensis (F. Smith) syn. nov. = T. natalensis cuitensis (Forel) syn. nov. = T. mocquerysi lutea (Stitz) syn. nov. = T. natalensis obscurata (Emery) syn. nov. = T. prelli (Forel) syn. nov. = T. natalensis usambarensis (Forel) syn. nov. The extensive synonymy under T. mocquerysi and T. natalensis reflects the conviction that previous taxonomists underestimated the extent of intraspecific variation in these taxa, but further study and testing of this conclusion is warranted. An illustrated worker- and queen-based key is provided for all species of Tetraponera occurring in Africa and Madagascar, except the Malagasy members of the T. allaborans group. 

The ant subfamily Leptanillinae (Hymenoptera: Formicidae) consists of minute soil-dwelling species, with several genera within this clade being based solely upon males, including Yavnella Kugler. The dissociation of males and workers has resulted in taxonomic confusion for the Leptanillinae. We here describe the worker caste of Yavnella, facilitated by maximum-likelihood and Bayesian inference from 473 partitioned ultra-conserved element loci, this dataset including 49 other leptanilline species, both described and undescribed. Yavnella laventa sp. nov. is described from seven worker specimens collected in south-western Iran from the Milieu Souterrain Superficiel, a subterranean microhabitat consisting of air-filled cavities among rock and soil fragments, which is subject to similar environmental conditions as caves. This species has bizarrely elongated appendages, which suggests that it is confined to cavities, in contrast with the soil-dwelling behaviour observed in other leptanilline ants. Based on its gracile phenotype relative to other Leptanillinae, Y. laventa shows remarkable adaptations for subterranean life, making it one of a very few examples of this syndrome among the ants. Moreover, the discovery of the worker caste of Yavnella expands our morphological knowledge of the leptanilline ants. We provide worker- and male-based diagnoses of Yavnella, along with a key to the genera of the Leptanillinae for which workers are known. The worker caste of Yavnella as known from this species is immediately recognisable, but the possibility must be noted that described workers of Leptanilla may in fact belong to Yavnella. Further molecular sampling is required to test this hypothesis. ZooBank: urn:lsid:zoobank.org:pub:A54A5766-F35A-4074-9353-1C70FE3955D3