Specialized ovipositor sensilla of Cretaceous wasps (Insecta: Hymenoptera) possibly reveal a unique way of host detection

Insects have evolved complex sensory systems that are important for feeding, defence and reproduction. Parasitoid wasps often spend much time and effort in searching for concealed hosts with the help of specialized sensilla. However, the early evolution of such behaviour and sensilla is poorly known. We describe two fossil female wasps, †Tichostephanus kachinensis sp. nov. and †Tichostephanus longus sp. nov., from mid-Cretaceous Kachin amber. Phylogenetic analyses based on morphological data retrieved †Tichostephanus as deeply nested within Evanioidea and closely related to extant Gasteruptiidae and Evaniidae. Both of these Cretaceous wasps possess features, e.g. coronal tubercles and flexible ovipositor sheaths, that indicate that they might have laid eggs in wood where their larvae possibly parasitized insect larvae. They have a peculiar and unique 'bottle brush' of sensilla close to the apex of their ovipositor sheaths, which has not been observed in any extant parasitoid wasps. These sensilla comprise many regularly arranged plate-shaped setae, attached in relatively large sockets and with rows of longitudinal ridges. Such specialized sensilla perhaps served to enhance the ability to detect hosts inside wood.

Eocene amber provides the first fossil record and bridges distributional gap in the rare genus Robsonomyia (Diptera: Keroplatidae)

Until now, the genus Robsonomyia was represented by two extant species: R. reducta Matile & Vockeroth, 1980 from North America and R. sciaraeformis (Okada, 1939) from Asia. This paper presents the first fossil members of the genus Robsonomyia, which is also the first record from Europe. Two new fossil species from Baltic amber are described: R. baltica Pełczyńska, Krzemiński & Blagoderov, sp. nov. and R. henningseni Pełczyńska, Krzemiński & Blagoderov, sp. nov.. The presence of fossil Robsonomyia spp. on the European continent suggests Holarctic distribution of the genus in the past. We also discuss possible pathways of its intercontinental dispersion.

A revised terminology for male genitalia in Hymenoptera (Insecta), with a special emphasis on Ichneumonoidea

Applying consistent terminology for morphological traits across different taxa is a highly pertinent task in the study of morphology and evolution. Different terminologies for the same traits can generate bias in phylogeny and prevent correct homology assessments. This situation is exacerbated in the male genitalia of Hymenoptera, and specifically in Ichneumonoidea, in which the terminology is not standardized and has not been fully aligned with the rest of Hymenoptera. In the current contribution, we review the terms used to describe the skeletal features of the male genitalia in Hymenoptera, and provide a list of authors associated with previously used terminology. We propose a unified terminology for the male genitalia that can be utilized across the order and a list of recommended terms. Further, we review and discuss the genital musculature for the superfamily Ichneumonoidea based on previous literature and novel observations and align the terms used for muscles across the literature.

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.

Morphology of sting apparatus of Chrysidoidea (Hymenoptera, Aculeata)

The main synapomorphy for Aculeata is the sting apparatus, which allows the female to envenom potential prey or hosts. The sting is the modified ovipositor which is not used for laying eggs anymore. Here, we explore the morphology of the sting apparatus within the families of Chrysidoidea. 27 skeletal structures were recognized, including three (dp1vf, dorsal projection of first valvifer; ppa, projection of posterior area of the second valvifer; vl9, ventral lap of tergite 9) that have not been observed previously, and 13 pairs of muscles, including four (superior dorsal T9-2vf (M5); inferior dorsal T9-2vf (M6); postero-lateral T9-2vf/mbr (M9); anterolateral 2vf/bl-2vv/fu (M11)) that have not been observed previously. Very conserved morphological patterns were observed; character support in the sting apparatus was found at the subfamily level, and within three families at the genus level. In addition, we describe the variation within the sting apparatus structures and musculature, propose evolutionary hypotheses about the function and evolution of the structures, and summarize phylogenetic conclusions for Chrysidoidea.

A Nonstationary Markov Model Detects Directional Evolution in Hymenopteran Morphology

Directional evolution has played an important role in shaping the morphological, ecological, and molecular diversity of life. However, standard substitution models assume stationarity of the evolutionary process over the time scale examined, thus impeding the study of directionality. Here we explore a simple, nonstationary model of evolution for discrete data, which assumes that the state frequencies at the root differ from the equilibrium frequencies of the homogeneous evolutionary process along the rest of the tree (i.e., the process is nonstationary, nonreversible, but homogeneous). Within this framework, we develop a Bayesian approach for testing directional versus stationary evolution using a reversible-jump algorithm. Simulations show that when only data from extant taxa are available, the success in inferring directionality is strongly dependent on the evolutionary rate, the shape of the tree, the relative branch lengths, and the number of taxa. Given suitable evolutionary rates (0.1-0.5 expected substitutions between root and tips), accounting for directionality improves tree inference and often allows correct rooting of the tree without the use of an outgroup. As an empirical test, we apply our method to study directional evolution in hymenopteran morphology. We focus on three character systems: wing veins, muscles, and sclerites. We find strong support for a trend toward loss of wing veins and muscles, while stationarity cannot be ruled out for sclerites. Adding fossil and time information in a total-evidence dating approach, we show that accounting for directionality results in more precise estimates not only of the ancestral state at the root of the tree, but also of the divergence times. Our model relaxes the assumption of stationarity and reversibility by adding a minimum of additional parameters, and is thus well suited to studying the nature of the evolutionary process in data sets of limited size, such as morphology and ecology.

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 new Orussus species from South Korea, and a key to the East Asian Orussidae (Hymenoptera)

Orussus melanosoma Lee & Wei, sp. nov. from South Korea is described and illustrated. Phylogenetic analyses place the new species basally in Orussus, together with other species from the Far East. A key to species of Orussidae from the eastern Palaearctic is provided. 

Baltorussus total makeover: rejuvenation and sex change in an ancient parasitoid wasp lineage

The Orussidae is a small and rare but phylogenetically important family of parasitoid wasps. The fossil record of the family is also very poor. Baltorussus velteni was described from Baltic amber from an allegedly female specimen. This and another recently discovered specimen are examined with microCT scanning and standard microscopy. We reveal that both the holotype and the new specimen are actually males. Furthermore, the results of the microCT scanning allow us to integrate the fossils in a morphological data set assembled for extant Orussidae. Phylogenetic analyses consistently retrieve Baltorussus as a separate basal lineage within the crown group, whereas two Cretaceous fossils are placed as stem group orussids and a Dominican amber fossil in an extant genus. Based on the positions of the fossils, we estimate that the extant Orussidae radiated in the mid-Cretaceous (approx. 100 Ma ago). This is considerably younger than a previously suggested Early Jurassic date (180 Ma ago), which was primarily based on biogeographic evidence.

The hymenopteran tree of life: evidence from protein-coding genes and objectively aligned ribosomal data

Previous molecular analyses of higher hymenopteran relationships have largely been based on subjectively aligned ribosomal sequences (18S and 28S). Here, we reanalyze the 18S and 28S data (unaligned about 4.4 kb) using an objective and a semi-objective alignment approach, based on MAFFT and BAli-Phy, respectively. Furthermore, we present the first analyses of a substantial protein-coding data set (4.6 kb from one mitochondrial and four nuclear genes). Our results indicate that previous studies may have suffered from inflated support values due to subjective alignment of the ribosomal sequences, but apparently not from significant biases. The protein data provide independent confirmation of several earlier results, including the monophyly of non-xyelid hymenopterans, Pamphilioidea + Unicalcarida, Unicalcarida, Vespina, Apocrita, Proctotrupomorpha and core Proctotrupomorpha. The protein data confirm that Aculeata are nested within a paraphyletic Evaniomorpha, but cast doubt on the monophyly of Evanioidea. Combining the available morphological, ribosomal and protein-coding data, we examine the total-evidence signal as well as congruence and conflict among the three data sources. Despite an emerging consensus on many higher-level hymenopteran relationships, several problems remain unresolved or contentious, including rooting of the hymenopteran tree, relationships of the woodwasps, placement of Stephanoidea and Ceraphronoidea, and the sister group of Aculeata.

Phylogeny of the ophrynopine clade revisited: review of the parasitoid sawfly genera Ophrella Middlekauff, Ophrynopus Konow and Stirocorsia Konow (Hymenoptera : Orussidae)

The rare family Orussidae comprises the only parasitoid sawflies and are sister to the Apocrita, the latter comprising most of Hymenoptera. Because of this, their morphology and relationships have been particularly important for interpreting the morphology of and biological transitions within the order as a whole. Within the Orussidae the ophrynopines are a comparatively diverse clade with a predominantly southern hemisphere distribution. Here, a revised and expanded morphological dataset incorporating several new taxa is used to test ophrynopine relationships and provide further insights into their evolutionary history. The analyses largely corroborate previous results. The distribution pattern and the fossil record indicate that the ophrynopines radiated in the early Cenozoic in the Australasian-Oceanian and the Neotropic regions and later dispersed into the Nearctic, Eastern Palaearctic and Indomalayan regions. The South American genus Ophrella Middlekauff, 1985 is well supported as a monophyletic genus, whereas Ophrynopus Konow, 1897 is paraphyletic with respect to Stirocorsia Konow, 1897. Three new species, Ophrella eldorado Vilhelmsen, sp. nov., Ophrynopus guarani Blank, D.R. Smith & Vilhelmsen, sp. nov., and Ophrynopus rupestris Vilhelmsen, Costa & Alvarenga, sp. nov. are described. Ophrella lingulata Middlekauff, 1985 is treated as a junior synonym of Ophrella amazonica (Westwood, 1874). Stirocorsia is treated as a junior synonym of Ophrynopus. The species Ophrynopus apicalis (Togashi, 2000), Ophrynopus kohli (Konow, 1897), Ophrynopus maculipennis (F. Smith, 1859) and Ophrynopus tosensis (Tosawa & Sugihara, 1934), formerly in Stirocorsia, are transferred to Ophrynopus. Revised keys to the species of Ophrella, Ophrynopus and the genera in the ophrynopine clade are provided. In addition, Orussidae are recorded from Bolivia and French Guiana for the first time.

A total-evidence approach to dating with fossils, applied to the early radiation of the hymenoptera

Phylogenies are usually dated by calibrating interior nodes against the fossil record. This relies on indirect methods that, in the worst case, misrepresent the fossil information. Here, we contrast such node dating with an approach that includes fossils along with the extant taxa in a Bayesian total-evidence analysis. As a test case, we focus on the early radiation of the Hymenoptera, mostly documented by poorly preserved impression fossils that are difficult to place phylogenetically. Specifically, we compare node dating using nine calibration points derived from the fossil record with total-evidence dating based on 343 morphological characters scored for 45 fossil (4--20 complete) and 68 extant taxa. In both cases we use molecular data from seven markers (∼5 kb) for the extant taxa. Because it is difficult to model speciation, extinction, sampling, and fossil preservation realistically, we develop a simple uniform prior for clock trees with fossils, and we use relaxed clock models to accommodate rate variation across the tree. Despite considerable uncertainty in the placement of most fossils, we find that they contribute significantly to the estimation of divergence times in the total-evidence analysis. In particular, the posterior distributions on divergence times are less sensitive to prior assumptions and tend to be more precise than in node dating. The total-evidence analysis also shows that four of the seven Hymenoptera calibration points used in node dating are likely to be based on erroneous or doubtful assumptions about the fossil placement. With respect to the early radiation of Hymenoptera, our results suggest that the crown group dates back to the Carboniferous, ∼309 Ma (95% interval: 291--347 Ma), and diversified into major extant lineages much earlier than previously thought, well before the Triassic. [Bayesian inference; fossil dating; morphological evolution; relaxed clock; statistical phylogenetics.].

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.

Per arborem ad astra: morphological adaptations to exploiting the woody habitat in the early evolution of Hymenoptera

We survey morphological features of larval and adult wasps that undergo their entire larval development inside wood and interpret them in view of the lifestyle. The evolution of some of the characters is explored by mapping them on a recently published phylogeny of Hymenoptera. Based on this phylogeny, it is reasonable to assume that wood-living wasps evolved from a xylophagous/mycetophagous stage as displayed by woodwasps to a carnivorous/parasitoid lifestyle, preying on woodboring insect larvae. The latter mode of life is probably ancestral to the Apocrita which comprise the majority of the order; they share this lifestyle with their sister group, the Orussidae. However, most apocritan wasps have radiated into other habitats, the Orussidae and Stephanidae apparently being the only taxa that have retained the ancestral lifestyle of carnivorous wasps. Other apocritan lineages associated with wood (e.g., Aulacidae, Megalyridae, basal Cynipoidea and some Ichneumonoidea and Chalcidoidea) possibly entered this habitat secondarily and independently acquired morphological traits associated with it. The woody habitat was occupied by Hymenoptera during a crucial stage in their evolution where the transition from the phytophagous to carnivorous lifestyle took place. The anatomy of both larva and adults was extensively transformed in the process.

Phylogeny and generic concepts of the parasitoid wasp family Aulacidae (Hymenoptera: Evanioidea)

The results of the first phylogenetic investigation of members of the Aulacidae of the world are presented. The main objective was to test the monophyly of the currently recognised genera. In total, 79 morphological characters were scored for a substantial sample of the extant aulacid fauna, including 72 species, as well as 12 outgroup taxa belonging to Evaniidae, Gasteruptiidae, Megalyridae, Trigonalidae, Braconidae and Stephanidae. All zoogeographic regions were represented. The dataset was analysed under different conditions (ordered, unordered, equal and implied weighting). The results under different weighting conditions are not fully congruent and many relationships remain unresolved. However, the analyses demonstrate that the current generic classification of the Aulacidae is not a natural one. There is support for a very large, monophyletic clade which includes all Pristaulacus Kieffer spp. + Panaulix Benoit spp. This suggests a wider generic concept for Pristaulacus, which is redefined and rediagnosed here. As a consequence, Panaulix becomes a junior synonym of Pristaulacus (syn. nov.), and the two described species of Panaulix are transferred to Pristaulacus: Pristaulacus rex (Benoit, 1984), comb. nov., and Pristaulacus irenae (Madl, 1990), comb. nov. The genus Aulacus Jurine was consistently paraphyletic and is not valid as currently defined. Furthermore, we failed to retrieve a consistent topology among the different clades of Aulacus. A satisfactory reclassification of Aulacus, however, requires a much more comprehensive taxon sample and/or additional character data.

Phylogenetic implications of the mesosomal skeleton in Chalcidoidea (Hymenoptera, Apocrita) – tree searches in a jungle of homoplasy

Results from a comparative anatomical study of the mesosomal skeleton of Chalcidoidea are presented. External and internal features are described and illustrated for 39 chalcidoid taxa, representing 16 families and 29 subfamilies. This is the most comprehensive morphological study ever conducted for the superfamily. The mesosoma was dissected, macerated and investigated using scanning electron microscopy. The mesothorax and metathorax contributed most of the phylogenetically relevant information. The metafurca is highly variable within Chalcidoidea but seems to be relatively constant at the subfamily level. One hundred and fifty-four morphological characters were scored and analysed cladistically. Outgroup species were chosen from six apocritan superfamilies: Stephanoidea, Ceraphronoidea, Cynipoidea, Platygastroidea, Proctotrupoidea and Mymarommatoidea. Some previously suggested chalcidoid relationships were retrieved: (1) Pteromalidae: Pteromalinae + Miscogasterinae + Panstenoninae; (2) Perilampidae + Eucharitidae; (3) Chalcididae + Leucospidae + Eurytomidae; (4) Eulophidae: Eulophinae + Tetrastichinae + Entedoninae; and (5) Eupelmidae + Encyrtidae. Mymarommatoidea renders Chalcidoidea paraphyletic in our analyses; however, the taxon sample is too restricted to provide a robust hypothesis. Three previously unreported putative autapomorphies of Chalcidoidea were revealed: (1) presence of an exposed, triangular or diamond-shaped prosternum; (2) presence of a percurrent mesopleural sulcus anteriorly terminating in the acropleuron; and (3) presence of paired metapectal plates lateral to the metafurca.

Flexible ovipositor sheaths in parasitoid Hymenoptera (Insecta)

The structure of the ovipositor sheaths is examined in a number of parasitic wasps as well as a few non-parasitic taxa. Parasitic wasps in the families Aulacidae, Braconidae, Ichneumonidae, Megalyridae, and Stephanidae with a very elongate, external ovipositor have the lateral wall of the sheath finely transversely subdivided by narrow furrows. This makes the sheath highly flexible, allowing it to support the ovipositor proper during ovipositing. The taxa having such a flexible sheath all drill into wood to lay their eggs. Support at the tip of the ovipositor is crucial in the initial stages of oviposition. The flexible ovipositor sheath is possibly a very ancient trait, arising prior to the radiation of extant Apocrita. This is corroborated by their presence in fossil Hymenoptera from the Upper Jurassic. The occurrence of short and/or concealed ovipositors with rigid sheaths in many extant apocritan taxa must therefore be assumed to be the result of multiple reversals.