Thesis supervisor: Senior Research Fellow Tiit Teder (University of Tartu) and professor Nikita Kluge, (University of St. Petersburg)
Opponent: Tommi Nyman (East-Finland University)
Insects probably constitute the largest share of unknown biota. Ichneumonidae, a family of hymenopteran parasitoids is one of the largest insect families of all. Because of their lifestyle, ichneumonid wasps play an important role in terrestrial ecosystems, particularly in suppressing and regulating their host populations. They are also one of the most frequently used groups of parasitoids in biological control of insect pests. The world fauna of Ichneumonidae is estimated to comprise between 60,000 and 100,000 species, while just slightly over 24,000 species have been described by now.
The taxonomy of the focal genus of this thesis – Lathrolestes – is similarly poorly known. The primary component of this thesis was therefore to describe the species composition of the genus. For this purpose, a high number of specimens was examined in major world ichneumonid collections, additional material was collected in extensive field works. As a result, 40 species were described as new to science. The up-to-date list of Lathrolestes totals now 103 species in the World fauna. The research conducted in this thesis thus increased the known fauna of the genus by as much as almost 40%. The very high share of previously undescribed species confirms the view that the fraction of insect species described is just the “tip of the iceberg”. Apart from describing new species and mapping their distribution records, previously described species were revised to clarify the taxonomy of the genus. Also, identification keys for different regions were produced.
The existing and new knowledge of the biogeography of the genus suggests that the most species-rich region is the north temperate zone. The latitudinal diversity trends of the genus are thus consistent with the classical understanding of general diversity patterns in Ichneumonidae, according to which their diversity tends to decrease from temperate latitudes towards the tropics. Also, as reviewed in the thesis, different Lathrolestes species have a remarkably diverse host use, attacking hosts ranging from free-living larvae to those concealed in the substrate. Accordingly, the highly diverse ovipositor morphology within the genus is likely to reflect specialization for using different types of hosts on or within different substrates.