High nuclear genetic diversity of Birecik semi-wild population of endangered Bald Ibis (Geronticus eremita) from Turkey

The Northern Bald Ibis (Geronticus eremita) is an endangered species. The western population is estimated to be approximately 700 individuals, located in the Souss Massa region of Morocco. In contrast, the eastern population, now semi-wild, is approximately 300 birds, situated in Birecik, Turkey. Recent reintroduction attempts in Europe have relied exclusively on captive populations derived from the western population and have been accompanied by research on their genetic structure and diversity. However, to date there has been no comprehensive study of a similar nature on the eastern population. In this study, we used five polymorphic microsatellite markers that are specific to the Bald Ibis to investigate the genetic diversity in 100 individuals of the Birecik population. We further sequenced the mitochondrial ND5 fragment in 46 adult individuals in order to reveal genetic differences between the eastern and western populations. Despite the limited number of founder individuals, the nuclear diversity of the Birecik population exhibited a high level of diversity, as measured by allelic richness and expected heterozygosity. However, mtDNA ND5 sequencing revealed a single haplotype (eastern haplotype 1) in all individuals of the eastern population, which differs from the haplotype (western haplotype 1) found in the western population by a single nucleotide. A specific mutation in mtDNA haplotypes, different migratory behavior, and highly restricted gene flow resulting from a long period of breeding as a semi-wild population, combined with geographical isolation, suggest that the eastern population (now only represented by the Birecik semi-wild population) is distinct from the western population. This unexpectedly high genetic diversity indicates the Birecik semi-wild population could act as the source population for reintroduction elsewhere.