The mymarid wasp Platystethynium triclavatum (Hymenoptera: Mymaridae) has been recently recorded as an egg parasitoid of the bush-cricket Barbitistes vicetinus (Orthoptera: Tettigoniidae). This species is endemic to northeastern Italy and has become an economically significant agricultural and forest pest. Biological attributes of P. triclavatum in relation to its host were still to be defined. Field parasitization rates and the number of individuals emerging from a single host egg were assessed by extracting eggs from soil at five outbreak sites in the Euganean Hills, while a laboratory choice experiment was conducted to evaluate the parasitoid’s preference for eggs of different ages. The natural emergence period was determined by periodically inspecting parasitized eggs buried in the ground. Additionally, genetic characterization of subpopulations from the Euganean Hills was conducted by analyzing both nuclear and mitochondrial DNA fragments. We found low parasitization rates across all sites. However, parasitoids successfully oviposited in B. vicetinus eggs of different ages, exhibiting a higher parasitism rate in one-year-old eggs compared to newly laid eggs. The average number of individuals that can hatch from a single B. vicetinus egg (95) can better reflect the potential impact of this parasitoid on regulating host populations. The hatching period was observed from the end of July to August. Subpopulations showed low values of haplotype diversity, with two main haplotypes diffused across almost all the sites. The absence of a geographical structure and a wide distribution within the landscape suggest a natural dispersal ability of P. triclavatum in the local area.
Biological insights and genetic characterization of a ground-searching mymarid wasp parasitizing eggs of a tettigoniid forest pest
Martinez-Sanudo I.;Maretto L.;Mazzon L.
2024
Abstract
The mymarid wasp Platystethynium triclavatum (Hymenoptera: Mymaridae) has been recently recorded as an egg parasitoid of the bush-cricket Barbitistes vicetinus (Orthoptera: Tettigoniidae). This species is endemic to northeastern Italy and has become an economically significant agricultural and forest pest. Biological attributes of P. triclavatum in relation to its host were still to be defined. Field parasitization rates and the number of individuals emerging from a single host egg were assessed by extracting eggs from soil at five outbreak sites in the Euganean Hills, while a laboratory choice experiment was conducted to evaluate the parasitoid’s preference for eggs of different ages. The natural emergence period was determined by periodically inspecting parasitized eggs buried in the ground. Additionally, genetic characterization of subpopulations from the Euganean Hills was conducted by analyzing both nuclear and mitochondrial DNA fragments. We found low parasitization rates across all sites. However, parasitoids successfully oviposited in B. vicetinus eggs of different ages, exhibiting a higher parasitism rate in one-year-old eggs compared to newly laid eggs. The average number of individuals that can hatch from a single B. vicetinus egg (95) can better reflect the potential impact of this parasitoid on regulating host populations. The hatching period was observed from the end of July to August. Subpopulations showed low values of haplotype diversity, with two main haplotypes diffused across almost all the sites. The absence of a geographical structure and a wide distribution within the landscape suggest a natural dispersal ability of P. triclavatum in the local area.Pubblicazioni consigliate
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