Long-maintained social–ecological systems and genetic diversity in coexisting insects: A case of the straw-thatched roof nesting solitary wasp Symmorphus apiciornatus (Hymenoptera: Vespidae: Eumeninae)

Thatched roofs are artificial environments that serve as nesting sites for a variety of insects, including tube-nesting wasps, but they have been declining drastically in recent years. In this study, we investigated the nesting habits of a eumenine wasp, Symmorphus apiciornatus, nesting in a group at thatched roofs in a northern part of Ibaraki Prefecture, central Japan. Genetic diversity and genetic structure in the area were also investigated. Sex ratios at most study sites were not biased. Males emerged first and waited for females to mate around the natal nests, suggesting a high possibility of breeding between the wasps having emerged at a given thatched roof under the recent situation where there has been a drastic reduction in the number of houses with a thatched roof. Nevertheless, the genetic diversity in a given local population or a thatched roof was relatively high and significant genetic differentiation among thatched roofs was not detected.