Genetic Diversity of Feral Populations of Nile Tilapia (Oreochromis niloticus) in Thailand and Evidence of Genetic Introgression

Abstract

The study aimed to understand the genetic diversity of Thai feral populations of Nile tilapia, Oreochromis niloticus, which make a substantial contribution to freshwater fi sh production in the country. The possible introgression from other tilapia populations/species was also investigated. Fourteen microsatellite primers were used to study three feral O. niloticus populations collected from reservoirs representing three types of habitats: 1) a wet-land (Sam Roi Yot, ON-SY); 2) a small reservoir (Bang Phra reservoir, ON-BP); and 3) a large reservoir (Bueng Boraphet, ON-BB). The results showed genetic variation that was high in ON-BP (Ar = 7.99, He = 0.75) and relatively low in ON-BB (Ar = 5.71, He = 0.62) and ON-SY (Ar = 5.78, He = 0.71). Genetic data were imported from two reference populations of O. niloticus [one population each from the Chitralada Villa Royal Residence, Thailand (ON-CD) and the genetically improved GIFT strain (ON-GIFT)] and one O. mossambicus population from South Africa for the model-based clustering analyses. ON-CD contributed to substantial portions of the gene pool of the feral populations. Genetic differentiation among the feral populations was signifi cant (P < 0.017, Bonferroni corrected). Introgression at the intraspecifi c level (from ON-GIFT to ON-BP and ON-BB) was observed while interspecifi c introgression between O. niloticus and O. mossambicus was apparent in ON-SY.