Head capsule characters in the Hymenoptera and their phylogenetic implications

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.