Ant evolution: Amber revelations of extinction, survival and recovery.

Ant fossils from the Cretaceous are rare but critical for understanding the early evolution of this incredibly successful group of animals. New amber fossils fill important gaps, revealing patterns of death, survival, and radiation around the end Cretaceous extinction.

Formalizing Invertebrate Morphological Data: A Descriptive Model for Cuticle-Based Skeleto-Muscular Systems, an Ontology for Insect Anatomy, and their Potential Applications in Biodiversity Research and Informatics.

The spectacular radiation of insects has produced a stunning diversity of phenotypes. During the past 250 years, research on insect systematics has generated hundreds of terms for naming and comparing them. In its current form, this terminological diversity is presented in natural language and lacks formalization, which prohibits computer-assisted comparison using semantic web technologies. Here we propose a Model for Describing Cuticular Anatomical Structures (MoDCAS) which incorporates structural properties and positional relationships for standardized, consistent, and reproducible descriptions of arthropod phenotypes. We applied the MoDCAS framework in creating the ontology for the Anatomy of the Insect Skeleto-Muscular system (AISM). The AISM is the first general insect ontology that aims to cover all taxa by providing generalized, fully logical, and queryable, definitions for each term. It was built using the Ontology Development Kit (ODK), which maximizes interoperability with Uberon (Uberon multispecies anatomy ontology) and other basic ontologies, enhancing the integration of insect anatomy into the broader biological sciences. A template system for adding new terms, extending, and linking the AISM to additional anatomical, phenotypic, genetic, and chemical ontologies is also introduced. The AISM is proposed as the backbone for taxon-specific insect ontologies and has potential applications spanning systematic biology and biodiversity informatics, allowing users to: 1) use controlled vocabularies and create semiautomated computer-parsable insect morphological descriptions; 2) integrate insect morphology into broader fields of research, including ontology-informed phylogenetic methods, logical homology hypothesis testing, evo-devo studies, and genotype to phenotype mapping; and 3) automate the extraction of morphological data from the literature, enabling the generation of large-scale phenomic data, by facilitating the production and testing of informatic tools able to extract, link, annotate, and process morphological data. This descriptive model and its ontological applications will allow for clear and semantically interoperable integration of arthropod phenotypes in biodiversity studies.

Genomic-Phenomic Reciprocal Illumination: Desyopone hereon gen. et sp. nov., an Exceptional Aneuretine-like Fossil Ant from Ethiopian Amber (Hymenoptera: Formicidae: Ponerinae).

Fossils are critical for understanding the evolutionary diversification, turnover, and morphological disparification of extant lineages. While fossils cannot be sequenced, phenome-scale data may be generated using micro-computed tomography (µ-CT), thus revealing hidden structures and internal anatomy, when preserved. Here, we adduce the male caste of a new fossil ant species from Miocene Ethiopian amber that resembles members of the Aneuretinae, matching the operational definition of the subfamily. Through the use of synchrotron radiation for µ-CT, we critically test the aneuretine-identity hypothesis. Our results indicate that the new fossils do not belong to the Aneuretinae, but rather the Ponerini (Ponerinae). Informed by recent phylogenomic studies, we were able to place the fossils close to the extant genus Cryptopone based on logical character analysis, with the two uniquely sharing absence of the subpetiolar process among all ponerine genera. Consequently, we: (1) revise the male-based key to the global ant subfamilies; (2) revise the definitions of Aneuretinae, Ponerinae, Platythyreini, and Ponerini; (3) discuss the evolution of ant mandibles; and (4) describe the fossils as †Desyopone hereon gen. et sp. nov. Our study highlights the value of males for ant systematics and the tremendous potential of phenomic imaging technologies for the study of ant evolution.

The ant abdomen: The skeletomuscular and soft tissue anatomy of Amblyopone australis workers (Hymenoptera: Formicidae).

Recent studies of insect anatomy evince a trend towards a comprehensive and integrative investigation of individual traits and their evolutionary relationships. The abdomen of ants, however, remains critically understudied. To address this shortcoming, we describe the abdominal anatomy of Amblyopone australis Erichson, using a multimodal approach combining manual dissection, histology, and microcomputed tomography. We focus on skeletomusculature, but additionally describe the metapleural and metasomal exocrine glands, and the morphology of the circulatory, digestive, reproductive, and nervous systems. We describe the muscles of the dorsal vessel and the ducts of the venom and Dufour's gland, and characterize the visceral anal musculature. Through comparison with other major ant lineages, apoid wasps, and other hymenopteran outgroups, we provide a first approximation of the complete abdominal skeletomuscular groundplan in Formicidae, with a nomenclatural schema generally applicable to the hexapod abdomen. All skeletal muscles were identifiable with their homologs, while we observe potential apomorphies in the pregenital skeleton and the sting musculature. Specifically, we propose the eighth coxocoxal muscle as an ant synapomorphy; we consider possible transformation series contributing to the distribution of states of the sternal apodemes in ants, Hymenoptera, and Hexapoda; and we address the possibly synapomorphic loss of the seventh sternal-eighth gonapophyseal muscles in the vespiform Aculeata. We homologize the ovipositor muscles across Hymenoptera, and summarize demonstrated and hypothetical muscle functions across the abdomen. We also give a new interpretation of the proximal processes of gonapophyses VIII and the ventromedial processes of gonocoxites IX, and make nomenclatural suggestions in the context of evolutionary anatomy and ontology. Finally, we discuss the utility of techniques applied and emphasize the value of primary anatomical research.

Review of the Leptogenys unistimulosa species group (Hymenoptera: Formicidae) with the description of a new Amazonian species

ABSTRACT Leptogenys elzasoares new species, is described from workers and a male collected near Manaus in the Brazilian Amazon. The worker is recognizable by the presence of 12 chaetae (stout setae) on the clypeal median lobe, the straight mandible, and its bicolored body; the head and mesosoma are black while the gaster is brightly ferruginous. For the first time, the males of L. bohlsi Emery, 1896, L. unistimulosa Roger, 1863, and L. parensis Lattke, 2011 are described. A new key to the males of the unistimulosa species group is provided, and the key to workers of Lattke (2011) is updated to include the new species. Finally, we also report new records of L. parensis from French Guiana, expanding the known distribution by over 780 km northwest.

A tardigrade in Dominican amber.

Tardigrades are a diverse group of charismatic microscopic invertebrates that are best known for their ability to survive extreme conditions. Despite their long evolutionary history and global distribution in both aquatic and terrestrial environments, the tardigrade fossil record is exceedingly sparse. Molecular clocks estimate that tardigrades diverged from other panarthropod lineages before the Cambrian, but only two definitive crown-group representatives have been described to date, both from Cretaceous fossil deposits in North America. Here, we report a third fossil tardigrade from Miocene age Dominican amber. Paradoryphoribius chronocaribbeus gen. et sp. nov. is the first unambiguous fossil representative of the diverse superfamily Isohypsibioidea, as well as the first tardigrade fossil described from the Cenozoic. We propose that the patchy tardigrade fossil record can be explained by the preferential preservation of these microinvertebrates as amber inclusions, coupled with the scarcity of fossiliferous amber deposits before the Cretaceous.

Monomorium (Hymenoptera: Formicidae) of the Arabian Peninsula with description of two new species, M. heggyi sp. n. and M. khalidi sp. n.

We present a revised and updated synoptic list of 44 Arabian Monomorium species, including two new species of the M. salomonis species-group: M. heggyi sp. n., and M. khalidi sp. n. We propose the following new synonyms: M. abeillei André (= M. wahibiense Collingwood & Agosti syn. n.); M. areniphilum Santschi (= M. fezzanense Collingwood & Agosti syn. n., = M. hemame Collingwood & Agosti syn. n. = M. marmule Collingwood & Agosti syn. n.); M. bicolor Emery (= M. phoenicum Santschi syn. n.); M. harithe Collingwood & Agosti (= M. najrane Collingwood & Agosti syn. n.); M. niloticum Emery (= M. matame Collingwood & Agosti syn. n.); and M. nitidiventre Emery (= M. yemene Collingwood & Agosti syn. n.). An illustrated key and distribution maps are presented for the treated species. Ecological and biological notes are given when available. The majority of Arabian Monomorium species (24) are endemic to the peninsula. All except one of the remaining species are more broadly ranging Afrotropical and Palearctic species, supporting the view of Arabia as a biogeographical crossroads between these two regions. Monomorium floricola (Jerdon), the sole species of Indomalayan origin, is recorded for the first time from the Arabian Peninsula.

Insect morphometry is reproducible under average investigation standards.

Morphometric research is being applied to a growing number and variety of organisms. Discoveries achieved via morphometric approaches are often considered highly transferable, in contrast to the tacit and idiosyncratic interpretation of discrete character states. The reliability of morphometric workflows in insect systematics has never been a subject of focused research, but such studies are sorely needed. In this paper, we assess the reproducibility of morphometric studies of ants where the mode of data collection is a shared routine.We compared datasets generated by eleven independent gaugers, that is, collaborators, who measured 21 continuous morphometric traits on the same pool of individuals according to the same protocol. The gaugers possessed a wide range of morphometric skills, had varying expertise among insect groups, and differed in their facility with measuring equipment. We used intraclass correlation coefficients (ICC) to calculate repeatability and reproducibility values (i.e., intra- and intergauger agreements), and we performed a multivariate permutational multivariate analysis of variance (PERMANOVA) using the Morosita index of dissimilarity with 9,999 iterations.The calculated average measure of intraclass correlation coefficients of different gaugers ranged from R = 0.784 to R = 0.9897 and a significant correlation was found between the repeatability and the morphometric skills of gaugers (p = 0.016). There was no significant association with the magnification of the equipment in the case of these rather small ants. The intergauger agreement, that is the reproducibility, varied between R = 0.872 and R = 0.471 (mean R = 0.690), but all gaugers arrived at the same two-species conclusion. A PERMANOVA test revealed no significant gauger effect on species identity (R 2 = 0.69, p = 0.58).Our findings show that morphometric studies are reproducible when observers follow the standard protocol; hence, morphometric findings are widely transferable and will remain a valuable data source for alpha taxonomy.

† Camelosphecia gen. nov., lost ant-wasp intermediates from the mid-Cretaceous (Hymenoptera, Formicoidea).

Fossils provide primary material evidence for the pattern and timing of evolution. The newly discovered "beast ants" from mid-Cretaceous Burmite, †Camelosphecia gen. nov., display an exceptional combination of plesiomorphies, including absence of the metapleural gland, and a series of unique apomorphies. Females and males, represented by †C. fossor sp. nov. and †C. venator sp. nov., differ in a number of features which suggest distinct sexual biologies. Combined-evidence phylogenetic analysis recovers †Camelosphecia and †Camelomecia as a clade which forms the extinct sister group of the Formicidae. Notably, these genera are only known from alate males and females; workers, if present, have yet to be recovered. Based on ongoing study of the total Aculeata informed by the beast ant genera, we provide a brief diagnosis of the Formicoidea. We also provide the first comprehensive key to the major groupings of Mesozoic Formicoidea, alongside a synoptic classification in which †Zigrasimeciinaestat. nov. and †Myanmyrma maraudera comb. nov. are recognized. Finally, a brief diagnosis of the Formicoidea is outlined.

A general theory of genital homologies for the Hexapoda (Pancrustacea) derived from skeletomuscular correspondences, with emphasis on the Endopterygota.

No consensus exists for the homology and terminology of the male genitalia of the Hexapoda despite over a century of debate. Based on dissections and the literature, genital skeletomusculature was compared across the Hexapoda and contrasted with the Remipedia, the closest pancrustacean outgroup. The pattern of origin and insertion for extrinsic and intrinsic genitalic musculature was found to be consistent among the Ectognatha, Protura, and the Remipedia, allowing for the inference of homologies given recent phylogenomic studies. The penis of the Hexapoda is inferred to be derived from medially-fused primary gonopods (gonopore-bearing limbs), while the genitalia of the Ectognatha are inferred to include both the tenth-segmental penis and the ninth-segmental secondary gonopods, similar to the genitalia of female insects which comprise gonopods of the eighth and ninth segments. A new nomenclatural system for hexapodan genitalic musculature is presented and applied, and a general list of anatomical concepts is provided. Novel and refined homologies are proposed for all hexapodan orders, and a series of groundplans are postulated. Emphasis is placed on the Endopterygota, for which fine-grained transition series are hypothesized given observed skeletomuscular correspondences.

Central American ants of the genus Megalomyrmex Forel (Hymenoptera: Formicidae): six new species and keys to workers and males.

Megalomyrmex Forel is a distinctive lineage of Neotropical ants, some of which are specialized parasites or predators of the fungus-growing ants Attini. Here we review and key the Central American fauna. Six new species are described from both female castes: M. brandaoi sp. n., M. fungiraptor sp. n., M. longinoi sp. n., M. milenae sp. n., M. megadrifti sp. n. and M. osadrifti sp. n. A worker-based key to all Central American species is presented, and all species are illustrated. Megalomyrmex drifti Kempf is redescribed and the first descriptions of queens for M. miri Brandão and M. foreli Emery are provided. New biological information, several new geographic records, and a discussion of the species-group schema of Brandão (1990) are presented. The male sex of Megalomyrmex is diagnosed at the genus-level and keyed to species for the Central American fauna, where known. The male of each species treated in the key is diagnosed, described, or redescribed. Males are known for fourteen out of twenty total Central American Megalomyrmex species. A distinct but unassociated male is described and keyed (M. male 01). The males of M. miri Brandão and M. wettereri Brandão are described for the first time, and the distinctness of these two species is confirmed. One potential synapomorphy of Megalomyrmex present in males and workers is the presence of a carina which posteriorly delimits the basalmost region of the petiolar dorsum. 

A taxonomic revision of the Meranoplus F. Smith of Madagascar (Hymenoptera: Formicidae: Myrmicinae) with keys to species and diagnosis of the males.

The species-level taxonomy of the ant genus Meranoplus F. Smith from Madagascar is revised. Two new species, M. cryptomys sp. n. and sylvarius sp. n. are described from workers and queens; M. mayri Forel, 1910, and M. radamae Forel, 1891, are redescribed, and queens and males for these two species are described for the first time. The first diagnosis of Meranoplus males for any biogeographic region is provided based on Malagasy species. Illustrated keys to all known Malagasy castes and species are presented. Diagnoses are given for two species groups: the M. mayri group and the M. nanus group. The diagnosis of the M. nanus species group from Bolton (1981) is thereby expanded with six new characters. Two species are known from the M. mayri species group and seven described species are known for the M. nanus species group, including the two new species described herein. The mouthparts, genitalia, and all castes, where known, of Malagasy Meranoplus are illustrated.

New species of Central American Rhopalothrix Mayr, 1870 (Hymenoptera, Formicidae).

The ant genus Rhopalothrix is a rare inhabitant of wet forest leaf litter and soil. We propose a monophyletic R. isthmica clade that is restricted to the Neotropics, contains most of the species in the genus, and has its center of abundance and diversity in Central America. Thirteen species are recognized in the R. isthmica clade, of which eight are described as new and three are redescribed. A key to species in the R. isthmica clade is provided, and the following eight new species are described: R. andersoni Longino & Boudinot, sp. nov., R. apertor Longino & Boudinot, sp. nov., R. atitlanica Longino & Boudinot, sp. nov., R. megisthmica Longino & Boudinot, sp. nov., R. nubilosa Longino & Boudinot, sp. nov., R. subspatulata Longino & Boudinot, sp. nov., R. therion Longino & Boudinot, sp. nov., and R. triumphalis Longino & Boudinot, sp. nov.. Queens are newly associated with workers for three Central American species. New synonymy is proposed for Rhopalothrix plaumanni Brown & Kempf, 1960 = R. acutipilis Kempf, 1962, syn. nov.