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Öğe Foraging efficiency and outcomes of interactions of two pupal parasitoids attacking the invasive spotted wing drosophila(Academic Press Inc Elsevier Science, 2016) Wang, Xin-Geng; Kaçar, Gülay; Biondi, Antonio; Daane, Kent M.Two generalist pupal drosophilid parasitoids, Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) and Trichopria drosophilae Perkins (Hymenoptera: Diapriidae), are sympatric and among only a few parasitoid species attacking the invasive Drosophila suzukii Matsumura (Diptera: Drosophilidae) in many regions of the world. In this study, we evaluated their foraging efficiency when attacking D. suzukii infesting cherry fruit in a laboratory cage experiment; and we examined their potential interspecific interactions, including outcomes of intrinsic competition, host discrimination, and the impact of their interaction on pest control. We show that both parasitoids readily parasitized D. suzukii pupae located inside fruit or buried in soil. However, T. drosophilae was more efficient than P. vindemiae and that parasitism by either parasitoid species was higher in the fruit than in the soil. Generally, the parasitoid species that oviposited first in the host out-competed the later parasitoid in multiparasitized hosts, we assume, through physiological suppression. Both parasitoids discriminated against hosts parasitized previously by the other species. In an additive-series design experiment with single (D. suzukii) or two (D. suzukii and Drosophila melanogaster Meigen) host species, T. drosophilae performed similarly regardless of the presence of a competitor, while P. vindemiae achieved a higher parasitism when alone. The observed parasitism when the two parasitoid species were present together was always lower than the expected one, assuming each species acted independently. This indicates a negative effect by P. vindemiae on interspecific competition on host suppression. (C) 2016 Elsevier Inc. All rights reserved.Öğe Life-history and host preference of Trichopria drosophilae, a pupal parasitoid of spotted wing drosophila(Springer, 2016) Wang, Xin-Geng; Kaçar, Gülay; Biondi, Antonio; Daane, Kent M.Trichopria drosophilae is a cosmopolitan pupal parasitoid that attacks many species of Drosophilidae, including the invasive Drosophila suzukii. This study reports on the life-history traits and host preferences of a Californian population of T. drosophilae and compares its life-time fecundity with a South Korean population of T. drosophilae. Female parasitoids emerge with a high mature egg-load (47.6 +/- 2.3 eggs per female). The number of mature eggs of female T. drosophilae was affected by the female age and body size but not by the interaction between these two factors. The parasitoid did not show preference among differently aged (1-4 days old) D. suzukii pupae and host age did not affect the parasitoid's fitness, except that offspring developmental time slightly increased with host age. In a choice test, more offspring successfully developed from the larger D. suzukii than the smaller D. melanogaster, and adult females reared from D. suzukii were larger than those that were reared from D. melanogaster, apparently at no cost in parasitoid fitness. T. drosophilae females from the Californian and the South Korean populations survived 27.5 and 20.2 days, produced a total of 63.8 and 52.0 offspring, and had an intrinsic rate of increase of 0.124 and 0.113, respectively, when provided with adult food and D. suzukii pupae as host material.Öğe Linear functional response by two pupal Drosophila parasitoids foraging within single or multiple patch environments(Public Library Science, 2017) Kaçar, Gülay; Wang, Xin-Geng; Biondi, Antonio; Daane, Kent M.Functional response describes the number of prey or hosts attacked by a predator or parasitoid as a function of prey or host density. Using three different experimental designs, we found a linear functional response by two insect parasitoids (the pteromalid Pachycrepoideus vindemiae and the diapriid Trichopria drosophilae) to their hosts (the drosophilids Drosophila suzukii and D. melanogaster). A linear function response is considered unusual for insect parasitoids. The first design was a 'fixed time within patch experiment' where individual parasitoids were exposed to a range of host densities for 24 h; the second two designs were a 'variable time functional response' and a 'selective functional response' experiments where individual parasitoids were presented with a range of host patches and allowed to freely select and explore only one patch (variable time) or forage for 24 h (selective). In all experimental designs, the number of hosts parasitized increased linearly until reaching an upper limit. Under the laboratory conditions used, the functional response of P. vindemiae was limited by its egg supply and time (host handling time) whereas T. drosophilae was limited by time only. The linear functional response by both parasitoids likely resulted from a constant attack rate and an incremental foraging strategy where the parasitoids left a poor (low density) host patch or remained in a higher quality host patch when there was successful oviposition and adequate host density.
