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Browsing by Author "Österblad, Ika"

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  • Österblad, Ika (2016)
    Parasitoid host interactions are intimately associated with food web dynamics as well as with evolutionary change. The parasitoid s possibility to expand its host range or switch to different hosts is affected by parasitic strategy. Strong specialization to a narrow host repertoire can arise e.g. if the larva spends considerable time in close contact with an active, developing host (koinobiosis). In contrast, an ectoparasitic larva, growing rapidly on a sessile host, does not have to be equally tightly adapted to host physiology. This may permit a wider host range. However, there are other restricting factors, such as egg production capacity. Extant parasitoids show a staggering species diversity, most notably among the Hymenoptera. Theories concerning speciation in association with host range have been developed, but draw from knowledge of merely a small part of this diversity. This study adds information by showing a number of radical host shifts in the evolutionary history of the ichneumonid wasp genus Gelis. Species of this genus exploit either insect prepupae or spider eggs. These are similar in being rather defenceless, aside from a protective silk covering. Nonetheless, differences are large enough to restrict Gelis species to each utilise only one of the two groups. In order to trace ancient host group shifts, host data was mapped onto a phylogeny constructed through bayesian analysis of sequence data. Sequences from the COI (mitochondrial) and ITS2 (nuclear, noncoding) regions were used. The results suggested at least four host group shifts within the genus. In addition, wing reduction was found to have occurred in two different lineages. Through COI barcode sequence clustering supported by morphological traits, a previously undescribed species from the G. bicolor-species complex was detected. The phylogenetic analyses also indicated the existence of further cryptic species, and the genus Thaumatogelis Schwarz was found to be nested within Gelis.