DNA barcoding and delimitation of critically endangered indigenous and introduced tilapias (pisces cichlidae) of Pangani catchment, Northern Tanzania.

Abstract

The Pangani catchment of Northern Tanzania harbours the critically endangered endemic tilapias of the genus Oreochromis. The introduction of non-native congenerics and consequent hybridization complicates taxa identification and phylogeny based on morphological systematics. We therefore morphologically and molecularly identified these tilapias and delimited their Molecular Operational Taxonomic Units (MOTUs) based on Cytochrome Oxidase Subunit I (CO1) gene for future management and conservation. A total of 132 indigenous and introduced tilapia specimens were morphologically identified, barcoded using the CO1 gene and delimited by Kimura 2 Parameter distance approaches, Automatic Barcode Gap Discovery (ABGD), Neighbour Joining (NJ) tree and haplotype analysis. Theoverall mean conspecific, congeneric and confamillial genetic distances based on the K2P model were 0.54%, 5.32% and 13.29% respectively. All taxa had a mean K2P distance < 2% and 90% (n = 10), were clearly delimited by the ABGD method. The NJ tree delimited tilapia taxa commensurate to the genetic distances depicted by DNA barcoding. However, DNA barcoding and NJ tree coherently failed to discriminate the morphologically distinct allopatric Oreochromis jipe and Oreochromis hunteri taxa. Moreover, the two methods depicted lack of monophyly in Oreochromis korogwe MOTUs implying that the taxon could consist of at least one MOTU. We conclude that the integration of morphological-based taxonomy and DNA barcoding among ichthyofaunal taxa herein will be invaluable in conservation and management of native tilapias in Pangani basin.