Black-veined White museomics

Current rates of climate change and habitat degradation are causing biodiversity declines globally, with global extinction rates far beyond estimated background extinction rates. Studies on vertebrates highlight how conservation genomics can be an effective tool to identify and manage threatened populations. However, it is unclear how metrics of genomic erosion, commonly applied in conservation genomics, translate to invertebrate species which can have markedly different population sizes and life history strategies. The Black-veined White butterfly (Aporia crataegi) disappeared from Britain in the 1920s, but the exact reasons for its extirpation are unknown. Here, we sequenced historical DNA from 17 museum specimens collected between 1854 and 1924 to determine levels of genomic erosion in the species as it approached extirpation. We provide evidence for a bottleneck of British populations around the period of the colonisation of the British Isles following the last glacial maximum. Moreover, we find increased inbreeding as shown by larger runs of homozygosity within the genome and evidence of both purging and accumulation of different classes of predicted deleterious variants, indicating that this species likely suffered from additional bottlenecks after colonisation potentially resulting in a slow decline within the British Isles. In contrast to levels of inbreeding and mutational load, reductions in genome-wide heterozygosity were comparable to a butterfly species with stable demographic trends. Our results indicate that levels of inbreeding and mutational load may be more informative metrics for identifying threatened invertebrate populations. Additionally, these results highlight the utility using museum insect specimens for conservation, as well as shedding light on the tempo of the extirpation of A. crataegi in Britain. This data was used in https://doi.org/10.1101/2023.12.19.572305