# Gene Flow Across Large Distances in the Cavity‐Nesting Wasp Deuteragenia subintermedia in a Central European Forest

## TL;DR

This study finds that the solitary wasp Deuteragenia subintermedia maintains genetic connectivity across a large forest area despite uneven deadwood availability.

## Contribution

The study provides novel evidence of long-distance gene flow in a deadwood-dependent insect species in a fragmented forest landscape.

## Key findings

- No genetic population structure was detected in Deuteragenia subintermedia across a 90 km forest region.
- Environmental variables did not impact genetic connectivity in the studied wasp species.
- Forest retention elements like deadwood appear sufficient for maintaining connectivity for this species.

## Abstract

Habitat connectivity and maintaining gene flow between populations is central for long‐term population persistence and is an essential element in conservation planning. However, data on dispersal ability and genetic population structure is lacking for almost all insect species. We here investigate if forest localities in the temperate, central European Black Forest are connected by gene flow. For this, we used partial genome sequencing on specimens of the solitary cavity‐nesting wasp Deuteragenia subintermedia (Hymenoptera, Pompilidae), a forest specialist that primarily nests in deadwood. We assumed that spatially uneven availability of standing deadwood has led to genetic substructuring. Contrary to our expectations, we did not find signs of population structure either on a regional or an individual level. Hence, for this solitary wasp species, dispersal seems not to be restricted across the Black Forest study sites (approximately 90 km distance) and none of the investigated environmental variables impacted genetic connectivity.

Retention forestry is widely considered a promising approach to conserve forest biodiversity, and beneficial effects of more heterogeneous forest structure have been shown for several taxa. However, it is often unclear if the approaches taken locally can provide connectivity for specimens over the landscape or if they lead to “biodiversity islands” with little to no connection among each other. In this study, we tested if forest structural retention elements, especially standing deadwood, are distributed closely enough in the landscape of the Black Forest to allow connectivity of deadwood‐dependent species by investigating if a common spider‐hunting forest wasp, D. subintermedia, shows signs of isolation and structured populations across approximately 90 km of forest areas separated by open landscapes.