Population Expansion but Limited Gene Flow in Kuhl's Blue-Spotted Maskray Along the Tanzanian Coast

Abstract

The blue-spotted maskray Neotrygon kuhlii (Müller & Henle, 1841) is a member of the Dasyatidae family of stingrays which grows slowly. Members of this group mature late and have a low fecundity rate. The ICUN Red List of Threatened Species lists N. kuhlii species as data deficient (DD) because information on its ecology and life history is not readily available. The purpose of this study was to determine the genetic diversity, demographic history and population structure of N. kuhlii, all of which are critical information for efforts aimed at conserving the species. The investigation was carried out along Tanzania's coastline using 595 base pairs of partial mitochondrial cytochrome oxidase subunit I (COI) sequence. The haplotype diversity ranged between 0.37 and 0.70 and nucleotide diversity between 0.11% and 0.50%. The findings show that samples from Unguja had higher mean molecular diversity indices than those from other sampling sites. Nonetheless, samples from Mafia and Unguja were found to have the largest effective population size. Genetic variations were found between the subpopulations under study, suggesting limited genetic connectivity among the studied subpopulations. The COI sequences of N. kuhlii from most subpopulations studied showed signs of past population expansion, which are typical for most Western Indian Ocean (WIO) fauna. The findings highlight the need for enhanced management and conservation strategies for N. kuhlii and other coastal stingray species in Tanzania, particularly in areas where sampling sites showed low levels of genetic diversity and effective population size.