Investigating the genetic diversity of the genus Gammarus in the springs and rivers of Golestan National Park using the COI mitochondrial gene sequence

Gammarus is the largest genus of aquatic crustaceans in the family Gammaridea, with more than 200 species worldwide. These crustaceans are very important components of the food chain in running waters. Therefore, their population changes can affect all communities, especially the health of fish stocks, and disturb the balance of the ecosystem. Due to their small size, high abundance and sensitivity to environmental conditions, they are suitable as indicator species for evaluation. This study investigated the genetic diversity of the genus Gammarus between different populations in Golestan National Park. After sampling, the common identification keys were used to identify the basic morphology and the COI mitochondrial gene sequence was used to conduct molecular studies. Genealogical relationships were determined by maximum likelihood (ML) method. The genetic distance in the populations and some indices of genetic diversity (number of haplotypes (h), haplotype diversity (Hd) and nucleotide diversity (Pi)) were calculated. Based on the results of the genealogical trees, the samples were placed in two separate clades (western and central) and separated from the gene bank samples with high bootstrap. The results of molecular variance analysis showed that the diversity between populations (72.49) is more than the diversity within populations (27.51) and the value of Fst index (0.68) shows the significant genetic difference between populations and the limitation of gene flow. Haplotype diversity is equal to 0.94, the highest and lowest of which is related to Khandushan River (1.00) and Golestan Spring (.40). Also, among the identified haplotypes, 17 haplotypes had only one individual, which indicates the high diversity of Gammarus populations in Golestan National Park. Also, G. komareki was identified as a dominant species complex with many hidden species in the region that have not yet been accurately identified.