Host Specificity of the Parasitic Wasp Anaphes flavipes (Hymenoptera: Mymaridae) and a New Defence in Its Hosts (Coleoptera: Chrysomelidae: Oulema spp.)

Abstract

The parasitic wasp Anaphes flavipes (Förster, 1841) (Hymenoptera: Mymaridae) is an important egg parasitoid of cereal leaf beetles. Some species of cereal leaf beetle co-occur in the same localities, but the host specificity of the wasp to these crop pests has not yet been examined in detail. A lack of knowledge of host specificity can have a negative effect on the use of this wasps in biological control programs addressed to specific pest species or genus. In this study, laboratory experiments were conducted to assess the host specificity of A. flavipes for three species of cereal leaf beetles (Oulema duftschmidi Redtenbacher, 1874, Oulema gallaeciana Heyden, 1879 and Oulema melanopus Linnaeus, 1758) in central Europe. For the first time, a new host defence against egg parasitoids occurring in O. gallaeciana from localities in the Czech Republic, a strong dark sticky layer on the egg surface, was found and described. The host specificity of A. flavipes was studied in the locality with the presence of this defence on O. gallaeciana eggs (the dark sticky layer) (Czech Republic) and in a control locality (Germany), where no such host defence was observed. Contrary to the idea that a host defence mechanism can change the host specificity of parasitoids, the wasps from these two localities did not display any differences in that. Respectively, even though it has been observed that eggs with sticky dark layer can prevent parasitization, the overall rate of parasitization of the three species of cereal beetles has not been affected. However, in our view, new host defence can influence the effects of biological control, as eggs of all Oulema spp. in the locality are protected against parasitization from the wasps stuck on the sticky layer of the host eggs of O. gallaeciana.

Female manipulation of offspring sex ratio in the gregarious parasitoidAnaphes flavipesfrom a new two-generation approach

“…However, due to the high fertility, we may assume that there will be a high population density of wasps and a higher probability that females will mate randomly with an unrelated male. We have such results for A. flavipes in our previous study Samková et al (2020a, submitted), similar to those in the study of van Alphen & Visser (1990), and King (1993), where the proportion of females offspring increased with superparasitism. Superparasitism simulates a higher population density of wasps (van Alphen & Visser 1990), resulting in a higher probability that unmated females mate randomly.…”

“…Anaphes flavipes were reared from host eggs ( Oulema spp.) collected in cereal fields (barley and wheat) in two localities in Prague-Suchdol, Czech Republic (GPS: 50.1385N, 14.3695E; 50.1367N, 14.3638E) from the end of April until the end of June in the years 2012, 2015, 2016 identically as in our previous studies (Samková et al 2019a, b, c, 2020, recorded in Suppl. materials).…”

“…Mated females (not older than 24 hours post emergence) were placed in Petri dishes with host eggs. Before the start of the experiment and during the experiment, the females were not fed, and they had free access to water (modified from Samková et al 2019a, b, c, 2020).…”

“…The Oulema species complex, including two ecologically very close species of O. duftschmidi Redtenbacher, 1874 and O. melanopus Linnaeus, 1758, was used identically as in our previous studies (Samková et al 2019a b c, 2020) and in other studies (Anderson & Paschke 1968, 1969), because these species occur together in the same localities at the same time (Van de Vijver et al 2019, Samková et al 2020) and are distinguished only on the basis of genital preparation (Bezděk & Baselga 2015). We consider these species particularly safe and convenient for our experiments because 1) their host eggs do not differ in length and weight (Samková et al 2019a), 2) the wasps A. flavipes are not host-specific (Samková et al 2020) and 3) the offspring of these two host species do not differ in size (Samková et al 2019a) and 4) show no morphological abnormalities (unpublish.). In the present study, the host culture was established from adults collected at the same time as host eggs in two localities in the Czech Republic (in Prague-Suchdol [identical to those of the parasitic wasps] and Police nad Metují [GPS: 50.5277N, 16.2456E]), using a net or individual sampling.…”

“…Host eggs were removed along with a 1 cm long piece of leaf and then used in the experiments. Since A. flavipes females refuse host eggs older than 72 hours (Anderson & Paschke 1968), we used eggs not older than 24 hours (modified from Samková et al 2019a, b, c, 2020).…”