Ultra-Conserved Elements and morphology reciprocally illuminate conflicting phylogenetic hypotheses in Chalcididae (Hymenoptera, Chalcidoidea)

Recent technical advances combined with novel computational approaches have promised the acceleration of our understanding of the tree of life. However, when it comes to hyperdiverse and poorly known groups of invertebrates, studies are still scarce. As published phylogenies will be rarely challenged by future taxonomists, careful attention must be paid to potential analytical bias. We present the first molecular phylogenetic hypothesis for the family Chalcididae, a group of parasitoid wasps, with a representative sampling (144 ingroups and seven outgroups) that covers all described subfamilies and tribes, and 82% of the known genera. Analyses of 538 Ultra-Conserved Elements (UCEs) with supermatrix (RAxML and IQTREE) and gene tree reconciliation approaches (ASTRAL, ASTRID) resulted in highly supported topologies in overall agreement with morphology but reveal conflicting topologies for some of the deepest nodes. To resolve these conflicts, we explored the phylogenetic tree space with clustering and gene genealogy interrogation methods, analyzed marker and taxon properties that could bias inferences and performed a thorough morphological analysis (130 characters encoded for 40 taxa representative of the diversity). This joint analysis reveals that UCEs enable attainment of resolution between ancestry and convergent/divergent evolution when morphology is not informative enough, but also shows that a systematic exploration of bias with different analytical methods and a careful analysis of morphological features is required to prevent publication of artifactual results. We highlight a GC content bias for maximum-likelihood approaches, an artifactual mid-point rooting of the ASTRAL tree and a deleterious effect of high percentage of missing data (>85% missing UCEs) on gene tree reconciliation methods. Based on the results we propose a new classification of the family into eight subfamilies and ten tribes that lay the foundation for future studies on the evolutionary history of Chalcididae.

From Arge to Zenarge: adult morphology and phylogenetics of argid sawflies (Hymenoptera: Argidae)

The Argidae is the second most diverse family of the ‘Symphyta’ with more than 900 described species. Here we present the first comprehensive phylogenetic study for the family. We compare the adult skeleton anatomy of representatives of 57 described argid genera from different biogeographic regions. We score 223 characters for 117 terminal taxa, and apply maximum parsimony inference to reconstruct the phylogeny, using equal weights and implied weights analyses. The Argidae sensu stricto, i.e. all Argidae except Zenarge, are consistently retrieved as monophyletic. The position of Zenarge changes according to the implied weighting parameters: ((Zenarge+Pergidae)+Argidae) at low (1–3) k-values, (Zenarge+(Pergidae+Argidae)) at high (4–30) k-values. We describe in detail the skeletal anatomy of Zenarge turneri and propose to raise it to family status: Zenargidae stat. revis. We consider the ridge on the teloparameres (=harpes) of the male genitalia to be the main autapomorphy of adults of the Argidae sensu stricto. We recover two main clades within the family and suggest recognizing these as the subfamilies Arginae and Sterictiphorinae. We trace the evolution of characters on the preferred implied weights tree. The genera Arge, Didymia, Pampsilota, Ptenos and Sphacophilus were paraphyletic.

Subforaminal bridges in Hymenoptera (Insecta), with a focus on Chalcidoidea

Variation in structures of the posterior surface of the head in Hymenoptera is compared and interpreted according to theories of head capsule evolution, with focus on understanding previously baffling conditions in the superfamily Chalcidoidea. Features are investigated separately without first classifying subforaminal bridges into subcategories. In Proctotrupomorpha (including Chalcidoidea), Ceraphronoidea and some Ichneumonoidea, there are multiple posterior pits associated with the tentorium. In most examined Hymenoptera with a subforaminal bridge, there was a differentiated median area, typically with highly variable microtrichia. This area is elevated in Cephoidea and Pamphilioidea, but is not elevated in other Hymenoptera. Subforaminal bridges in Apocrita previously classified as hypostomal bridges are discussed in the context of A.P. Rasnitsyn's hypothesis that relative importance of adult feeding drives subforaminal bridge evolution.

Morphological phylogenetics of the Tenthredinidae (Insecta : Hymenoptera)

The Tenthredinoidea is the most diverse superfamily of non-apocritan Hymenoptera. It is also one of the largest herbivorous groups within the order, some species having substantial economic impact. Until very recently, no comprehensive phylogenetic analyses of the superfamily had been undertaken. This paper presents the largest morphological dataset assembled so far for elucidating the phylogeny of the Tenthredinoidea. In total, 129 taxa were scored for 146 characters from the adult head, thorax, wings and ovipositor apparatus. The emphasis of the taxon sample is on Tenthredinidae (104 terminals), which is by far the largest family in the Tenthredinoidea. The results of the cladistic analyses confirm the monophyly of the Tenthredinoidea, the first split being between the Blasticotomidae and the remaining families (Tenthredinoidea s. str., also monophyletic), and the monophyly of all families except Tenthredinidae. The analyses fail to consistently retrieve any of the six currently recognised subfamilies within Tenthredinidae, although core clades of Heterarthrinae, Nematinae, Selandriinae and Tenthredininae are often supported. Diprionidae are placed inside the Nematinae under some weighting conditions. The failure to corroborate the tenthredinid subfamilies might be ascribed to an insufficient character/terminal ratio, but also to problems with the existing classification. Inclusion of characters from the male genitalia and the larval stages as well as molecular data currently being assembled will hopefully lead to a more robust classification of the Tenthredinidae in the future.

A mandible arresting system in neotropical social wasps (Vespidae; Polistinae): structural diversity within homogeneous functionality

Microtrichia are epidermal protuberances that may serve as temporary adhesive devices. Several insects possess these structures; however, they have not previously been reported in social wasps. With scanning electron microscopy, we characterize the shape and abundance of microtrichia in ten species of social wasps (Vespidae: Polistinae) and three species of related taxa (Vespidae: Eumeninae, Pompilidae, and Scoliidae). Semi-thin sections of the head of Leipomeles spilogastra and Apoica albimacula were also studied. We found microtrichia on a thin, flexible membrane connected to the mandible in all the Vespidae specimens. The flexible membrane can be divided into three regions: the basal region that covers the mandibular mesial emargination, the medial region located around the height of the mandibular condyles, and the distal region that appears anterior to the apodeme folding. Basal and distal regions of the membrane are extensively covered by microtrichia while the medial region has either less microtrichia or is entirely devoid of them. The shape and density of the microtrichia differed between species, and these traits are unrelated with nest material construction or phylogenetic closeness. We propose that the microtrichial membrane described is a passive mechanism to keep the wasps' mandibles retracted through a mechanical interlocking system. It is possible that this energy-saving mechanism is present in other mandibulate insects.

Skeletal morphology of Opius dissitus and Biosteres carbonarius (Hymenoptera: Braconidae), with a discussion of terminology

The Braconidae, a family of parasitic wasps, constitute a major taxonomic challenge with an estimated diversity of 40,000 to 120,000 species worldwide, only 18,000 of which have been described to date. The skeletal morphology of braconids is still not adequately understood and the terminology is partly idiosyncratic, despite the fact that anatomical features form the basis for most taxonomic work on the group. To help address this problem, we describe the external skeletal morphology of Opius dissitus Muesebeck 1963 and Biosteres carbonarius Nees 1834, two diverse representatives of one of the least known and most diverse braconid subfamilies, the Opiinae. We review the terminology used to describe skeletal features in the Ichneumonoidea in general and the Opiinae in particular, and identify a list of recommend terms, which are linked to the online Hymenoptera Anatomy Ontology. The morphology of the studied species is illustrated with SEM-micrographs, photos and line drawings. Based on the examined species, we discuss intraspecific and interspecific morphological variation in the Opiinae and point out character complexes that merit further study.

Head capsule characters in the Hymenoptera and their phylogenetic implications

The head capsule of a taxon sample of three outgroup and 86 ingroup taxa is examined for characters of possible phylogenetic significance within Hymenoptera. 21 morphological characters are illustrated and scored, and their character evolution explored by mapping them onto a phylogeny recently produced from a large morphological data set. Many of the characters are informative and display unambiguous changes. Most of the character support demonstrated is supportive at the superfamily or family level. In contrast, only few characters corroborate deeper nodes in the phylogeny of Hymenoptera.

Morphological aspects of testes and sperm ultrastructure in the "symphyta" Digelasinus diversipes kirby 1882 (hymenoptera: Argidae: Dielocerinae)

In Digelasinus diversipes, spermatozoa are maintained in bundles, with 74 spermatozoa on average, in the seminal vesicle. These spermatozoa are very short (20 μm) and consist of a head and flagellum. The head includes an acrosome (perforatorium covered by the acrosomal vesicle) and a nucleus. A regular electron-lucent region separates the acrosomal vesicle from the perforatorium, which is inserted parallel to the anterior ending of the nucleus. The small flagellum is composed of two symmetrical mitochondrial derivatives, a centriolar adjunct, an axoneme (9 + 9 + 2), and two accessory bodies. The centriolar adjunct begins above the posterior end of the nucleus and ends covering the anterior tip of two mitochondrial derivatives. In the terminal region of the axoneme, the central microtubules terminate first. The presence of a subacrosomal space, a short mitochondrial derivative diameter, and a short spermatodesm is the ultrastructure characteristics of spermatozoa shared by all "symphyta" species. Differences in the insertion of the perforatorium into the nucleus and the position of the centriolar adjunct distinguish Dielocerinae and the Arginae studied previously. The number of spermatozoa per cyst is variable. Furthermore, additional characteristics that had not been described for "symphyta" were also found, such as the number of follicles per testis.

Structural and ultrastructural characteristics of male reproductive tract and spermatozoa in two Cryptinae species (Hymenoptera: Ichneumonidae)

This study represents the first characterization of male reproductive tracts and ultrastructural description of sperm of Cryptinae species. In Lymeon dieloceri and Pachysomoides sp., the male reproductive tract is formed by a pair of testis, two deferent ducts, two accessory glands and one ejaculatory duct. The spermatozoa are similar to those described for other Hymenoptera, with: (1) the acrosome formed by the acrosomal vesicle covering the perforatorium, which has its base inserted in a cavity located in the nucleus point; (2) a thin nucleus with electron-dense chromatin; (3) an electron-dense centriolar adjunct located between the nucleus and one of the two mitochondrial derivatives; (4) an axoneme with a 9 + 9 + 2 microtubule arrangement; (5) two long mitochondrial derivatives with peripheral cristae and; (6) two accessory bodies located between the two mitochondrial derivatives and the axoneme. These ichneumonids present structural characteristics similar to other parasitic wasps, such as presence of a single follicle per testis, layer of extracellular material enveloping the acrosome and accessory microtubules ending before others in final portion of the flagellum. However, male reproductive system and the spermatozoa presented morphological characteristics that allowed their differentiation, such as oval shapes accessory glands and the symmetric mitochondrial derivatives in L. dieloceri compared to the spherical accessory glands and asymmetrical derivatives observed in Pachysomoides sp. Taken together, data presented here demonstrates that diversity of morphological characteristic from the male reproductive tract and spermatozoa in Hymenoptera might provide a character system that can be used, in association with other systems, to resolve various uncertainties about the evolutionary relationships of this insect group.