Utility of DNA barcoding in native Oreochromis species

Area of Science:

• Aquaculture and Fisheries Science
• Molecular Ecology
• Conservation Genetics

Background:

• Oreochromis species are vital for global aquaculture and regional fisheries.
• Understanding genetic diversity within native ranges is crucial for effective resource management.
• Current DNA barcoding data for Oreochromis is insufficient, particularly from wild populations.

Purpose of the Study:

• To assess the availability and geographic origin of mitochondrial cytochrome c oxidase subunit I (COI) gene sequences for Oreochromis species.
• To evaluate the genetic diversity of Oreochromis within their native ranges using available DNA barcode data.
• To identify potential cryptic lineages, hybridization events, and misidentifications within the genus.

Main Methods:

• Retrieved all available mitochondrial COI gene sequences for Oreochromis from the Barcode of Life Data system.
• Filtered sequences to include only those from wild individuals collected within native ranges.
• Analyzed sequence data to identify cryptic lineages, hybridization, and potential ancestral polymorphism.

Main Results:

• 70% of known Oreochromis species lack a COI barcode.
• Only 15% of available COI sequences originate from native wild populations; many come from aquaculture or introduced populations.
• Identified cryptic lineages in Nile tilapia (Oreochromis niloticus) and O. schwebischi, potential hybridization between O. niloticus and O. aureus, and ancestral polymorphism between O. karongae and O. placidus.
• Reported a misidentification of O. mweruensis as O. macrochir.

Conclusions:

• There is a significant lack of genetic data for Oreochromis species from their native ranges.
• Existing data is heavily biased towards non-native or aquaculture sources, complicating assessments of natural genetic variation.
• Improved sampling and genetic analysis within native ranges are essential for the conservation and sustainable management of Oreochromis resources.