The remote isolate of the Croatian littoral – 50 years of research on the island of Susak with new insights into its genetic diversity

This paper presents a review of the 50-year long anthropological and epidemiological research of the Susak population. Island of Susak is an example of extreme genetic isolate, with a very low level of heterozygosity and a significantly high level of inbreeding, due to the practice of endogamy. Its specific features have put the island in the focus of diverse research during the last five decades and in this study we additionally present new insights into the island’s maternal genetic heritage. For this purpose, mitochondrial DNA (mtDNA) haplogroup diversity was defined based on SNPs of the control and coding region on the sample of 64 autochthonous individuals from the island. Only three main haplogroups were detected – H, T and one W sample, with a limited number of haplotypes, and certain typical European haplogroups (U, K, J, V, X,) were completely absent. Haplotype analysis revealed five possible founder lineages of altogether 16 different haplotypes. Island of Susak also has the second lowest reported GDV (gene diversity index) among Croatian isolates, which is in line with its reduced mtDNA diversity. Since such island communities are most likely to disappear in the near future, we see these results as a valuable contribution for further population genetics and epidemiological studies.