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Pairwise comparison of mt DNA sequences in two Croatian sheep populations

The sequencing analysis of the proximal part of the D loop region at mtDNA was performed to assess the genetic divergence and population structure of two sheep breeds in Croatia (Krk island sheep and Dubrovnik sheep). The mtDNA sequences of approximately 482 base pairs were obtained. Sequencing of this part of the region from 20 unrelated animals revealed 23 polymorphic sites characterizing 17 haplotypes. Of the 17 haplotypes , 14 (88.88 %) were not shared. The average haplotype diversity was Hd: 0, 984 and the average nucleotide diversity was Pi: 0, 01444, and it indicates higher level of genetic diversity in Krk sheep. The topology according to the neighbor-joining and maximum parsimony methods showed mosaic composition of the 17 haplotypes, suggesting that the populations were not completely divergent (the samples comprised one significant cluster). One type of sequences was similar to European Merinolandschaf type of sheep mtDNA and the other 3 out of 20 sequences were different. Our data support the hypothesis that the first haplotype represents a trace of Merinisation of these populations. Another 3 sequences (from Krk island sheep) belongs to the original primitive sheep, which have inhabited the island of Krk for thousands of years. These findings suggest that modern Krk island sheep were derived from at least two maternal lineages, the autochthonous and imported one.

mtDNA; Krk sheep; Dubrovnik sheep

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