An interactive key to Central European species of the Pteromalus albipennis species group and other species of the genus (Hymenoptera: Chalcidoidea: Pteromalidae), with the description of a new species

Abstract

BackgroundParasitoid wasps of the genus Pteromalus play an important role in biological pest control, however, the genus includes a large number of cryptic species, which makes reliable identification difficult. The latest identification key dates back to Graham (1969) and since then many new species have been described and nomenclatural changes proposed.New informationHere we present an interactive and fully illustrated identification key in Xper3 for 27 species of the Pteromalus albipennis species group as well as for 18 similar species. In addition to qualitative traits, a large set of body measurements is incorporated in the key. We also explored a new set of qualitative features on the propodeum and metasternum. During field work, a new species of the P. albipennis species group, P. capito Baur sp. n., could be reared from flower heads of Asteraceae, which is described here. It looks very similar to P. albipennis and P. cingulipes, however, several qualitative characters and body ratios distinguish it clearly from the most similar species.

Phylogeny, taxonomics, and ovipositor length variation of thePteromalus albipennisspecies group (Hymenoptera: Chalcidoidea: Pteromalidae: Pteromalinae)

“…Regarding the species united in node 3, that is, P. albipennis , P. caudiger , and P. cingulipes , P. caudiger appears to be polyphyletic with respect to samples of P. albipennis , in part well supported, and may thus be considered as a synonym of P. albipennis , although there are some morphological characters to separate these taxa (Klimmek & Baur, 2018). Another taxonomic issue involves P. cingulipes and P. albipennis (node 4).…”

“…We analyzed 30 wasp samples (each comprising 2–16 wasps from the same species and locality), representing 18 different currently recognized Pteromalus species, identified using the key by Klimmek and Baur (2018). The ingroup comprised 15 species of the P. albipennis species group, the outgroup consisted of three Pteromalus species that do not belong to this group (Table 1).…”

“…ImageJ 1.49v (Schneider et al., 2012) was then used to measure the length of the gaster. Gaster length positively correlates with the ovipositor length (Klimmek & Baur, 2018), that is, the absolute gaster length can serve as proxy of the absolute ovipositor length. We chose absolute gaster/ovipositor length over relative length because the absolute length determines whether or not the parasitoid female can reach and use hosts within the flower heads.…”

“…We investigate whether or not the species delimitations proposed by Baur (2002), Lutz (2014), Klimmek and Baur (2018), and S. Maletti, F. Traunmüller, S. Schmidt, R. S. Peters, H. Baur (unpublished) are congruent with taxonomic inferences that can be drawn from a phylogenomic analysis. Furthermore, we assess whether or not absolute ovipositor length is a good predictor of phylogenetic relatedness or if it can be identified as a variable and rapidly evolving trait, which could suggest that it is under continuous divergent selective pressure.…”

“…Recent attempts to taxonomically revise at least parts of the group using morphology, morphometrics, and single‐ or two‐gene datasets allowed for some first progress within this previously widely neglected genus, but also pointed to taxonomic ambiguities and the limited power of single‐ or two‐gene datasets (Baur, 2002; Lutz, 2014; Klimmek & Baur, 2018; S. Maletti, F. Traunmüller, S. Schmidt, R. S. Peters, H. Baur, unpublished). The most obvious differences between the currently hypothesized species lie in the length of the gaster, which positively correlates with the ovipositor length (Klimmek & Baur, 2018). Since the ovipositor establishes in many instances the only direct contact between the adult parasitoid and its host, absolute ovipositor length is directly linked to the host range of the parasitoid species.…”