Genetic diversity and structure in the Sado captive population of the Japanese crested ibis.

The Japanese crested ibis Nipponia nippon is a critically threatened bird. We assessed genetic diversity and structure in the Sado captive population of the Japanese crested ibis based on 24 and 50 microsatellite markers developed respectively for the same and related species. Of a total of 74 loci, 19 showed polymorphisms in the five founder birds of the population, and therefore were useful for the analysis of genetic diversity and structure. Genetic diversity measures, A, ne, He, Hoand PIC, obtained by genotyping of the 138 descendants were similar to those of other species with population bottlenecks, and thus considerably low. The low level of genetic diversity resulting from such bottlenecks was consistent with the results of lower genetic diversity measures for the Sado captive relative to the Chinese population that is the source population for the Sado group as determined using previously reported data and heterozygosity excess by Hardy-Weinberg equilibrium tests. Further, individual clustering based on the allele-sharing distance and Bayesian model-based clustering revealed that the founder genomes were equally at population in total, and with various admixture patterns at individual levels inherited by the descendants. The clustering results, together with the result of inheritance of all alleles of the microsatellites from the founders to descendants, suggest that planned mating in captive-breeding programs for the population has succeeded in maintaining genetic diversity and minimizing kinship. In addition, the Bayesian model-based clustering assumed two different components of genomes in the Sado captive Japanese crested ibis, supporting a considerably low level of genetic diversity.

Non-invasive sampling technique for DNA extraction from captive Japanese Crested Ibis on Sado Island.

The Japanese Crested Ibis Nipponia nippon is a critically threatened bird. The post-hatch eggs of the current captive population of this species on Sado Island have been stored at room temperature for the long-term. In this study, we investigated the suitability of the vascularized chorioallantois membrane from the eggs as a non-invasive DNA source. Using microsatellite loci developed for the Japanese Crested Ibis, we performed three experiments for comparison of genotypes obtained among DNA. First, DNA from five different sites of the identical membrane showed the same genotypes at either of two loci examined. Second, DNA from the membrane of each full-sibling birds and blood of their parents showed the genotypes that were consistent with Mendelian parent-offspring relationships at any of eight loci examined. Third, DNA from the membrane and blood of the same bird showed the matched genotypes at any of eight loci examined. These results indicate that the vascularized chorioallantois membrane from post-hatch eggs stored at room temperature for the long- term can be used as a reliable DNA source of offspring that had hatched from the egg. This study will promote a molecular genetics study on genetic diversity of the current captive Japanese Crested Ibis population on Sado Island.