The genetic structure of the ash obligate moth prays fraxinella suggests that it is not affected by current habitat fragmentation

Tree diseases may cause the extirpation or functional extinction of a common tree species on large spatial scales. For example, ash dieback (Hymenoscyphus fraxineus) is expected to cause widespread loss of European ash (Fraxinus excelsior). This type of widespread loss of a tree species may have consequences for the ability of some insects to move between woodlands, particularly obligate species (species reliant on one tree species for food). Our aim was to use ddRAD-seq genetic data to determine the population structure of Prays fraxinella (ash bud moth), an ash-obligate micro-moth, and to assess its ability to maintain connectivity across fragmented patches of native broadleaf woodlands. We found no evidence of genetic structuring at local (up to 44 km) spatial scales, and no evidence of inbreeding. At regional scales (up to 426 km), we found evidence of mixed ancestry and long-distance dispersal. Our research highlights that given its ability to maintain gene flow in areas where woodlands have historically been very fragmented, P. fraxinella may continue to maintain connectivity under moderate future tree losses under ongoing ash dieback outbreaks. Implications for insect conservation: Our research highlights the potential indirect impacts of ash-dieback through losses in connectivity. This approach should be extended to other ash-obligate species, under various levels of existing fragmentation, to inform conservation strategies more fully for managing ash dieback.