Conservation Genetics and Genomics of the Narrowly Endemic Island Marble Butterfly

The purpose of this study was to collect and analyze non-invasive DNA specimens from the endangered island marble butterfly (Euchloe ausonides insulanus) to assess population structure, identify adaptive potential, facilitate captive propagation, and support translocation planning. We used DNA extracted from meconium, exuviae, and natural mortalities to generate and test thirteen new microsatellite markers for use in population structure and kinship analyses. We also used DNA from natural mortalities to generate ~10,000 SNPs, which were used to assess genomic diversity. Whole mitochondrial genomes were assembled, annotated, and used to infer a phylogeny with museum specimens of insulanus collected ~100 years ago from Vancouver Island and other members of the E. ausonides species complex. The results indicated that insulanus suffers from low heterozygosity, a small effective population size (Ne), and low allelic diversity. There was evidence of high levels of inbreeding in some individuals, but inbreeding was uneven across the population. There was no population structure or partitioning by host plant detected. The mitogenomes of extant insulanus were all identical and there was a loss of allelic diversity in modern samples compared to insulanus from museums. Extant insulanus formed a clade with museum specimens and we identified multiple putatively diagnostic alleles to differentiate insulanus from other subspecies. Based on these results, we outline considerations for species management decisions and genetic monitoring.