Identification of source populations for reintroduction in extinct populations based on genome-wide SNPs and mtDNA sequence: a case study of the endangered subalpine grassland butterfly Aporia hippia (Lepidoptera; Pieridae) in Japan

The use of genetically closely related populations as reintroduction sources is crucial in restoration programmes for endangered species because genetically distant populations may cause genetic disturbances. Aporia hippia (Lepidoptera; Pieridae) is an endangered subalpine grassland butterfly in Japan and its distribution area is restricted to the Asama, Yatsugatake and Akaishi Mountains in central Honshu Island. In the Yatsugatake Mountains, its population is probably already extinct, and reintroduction from the other sites is now under consideration. Here, we estimated the genetic diversity and spatial genetic structure of A. hippia in Japan to identify candidate source populations for reintroduction in extinct populations via multiplexed inter-simple sequence repeat genotyping by sequencing (MIG-seq) and mitochondrial DNA sequencing methods. The MIG-seq method indicated the presence of very few genetic differences among the populations. The mitochondrial DNA sequencing method identified two haplotypes: haplotype A in the Asama, Yatsugatake and northern Akaishi Mountains, and haplotype B in the central and southern Akaishi Mountains. The two haplotypes exhibited only a one base pair substitution between them. Implications for insect conservation: Based on these results, we suggest the existence of two conservation units: the first group consisting of populations in the Asama, Yatsugatake, and northern Akaishi Mountains, and the second group consisting of those in the central and southern Akaishi Mountains. According to this genetic proximity, however, all populations of A. hippia in Japan can also be defined as one conservation unit group, given the risk of inbreeding depression or difficulty of adaptation in different environments.