Publication details

Population genomics of introduced Nile tilapia Oreochromis niloticus (Linnaeus, 1758) in the Democratic Republic of the Congo: Repeated introductions since colonial times with multiple sources

Authors	GERAERTS Mare VANGESTEL Carl ARTOIS Tom FERNANDES Jorge Manuel de Oliveira JORISSEN Michiel W P MANDA Auguste Chocha MIZANI Celestin Danadu SMEETS Karen SNOEKS Jos SONET Gontran TINGBAO Yang VAN STEENBERGE Maarten Wouter VREVEN Emmanuel WAMUINI Soleil Lunkayilakio VANHOVE Maarten Pieterjan HUYSE Tine
Year of publication	2022
Type	Article in Periodical
Magazine / Source	Molecular Ecology
MU Faculty or unit	Faculty of Science
Citation
Web	https://doi.org/10.1111/mec.16479
Doi	http://dx.doi.org/10.1111/mec.16479
Keywords	cichlid; genetic integrity; genetic structure; independent introductions; invasive species; RAD sequencing
Description	During colonial times, Nile tilapia Oreochromis niloticus (Linnaeus, 1758) was introduced into non-native parts of the Congo Basin (Democratic Republic of the Congo, DRC) for the first time. Currently, it is the most farmed cichlid in the DRC, and is present throughout the Congo Basin. Although Nile tilapia has been reported as an invasive species, documentation of historical introductions into this basin and its consequences are scant. Here, we study the genetic consequences of these introductions by genotyping 213 Nile tilapia from native and introduced regions, focusing on the Congo Basin. Additionally, 48 specimens from 16 other tilapia species were included to test for hybridization. Using RAD sequencing (27,611 single nucleotide polymorphisms), we discovered genetic admixture with other tilapia species in several morphologically identified Nile tilapia from the Congo Basin, reflecting their ability to interbreed and the potential threat they pose to the genetic integrity of native tilapias. Nile tilapia populations from the Upper Congo and those from the Middle-Lower Congo are strongly differentiated. The former show genetic similarity to Nile tilapia from the White Nile, while specimens from the Benue Basin and Lake Kariba are similar to Nile tilapia from the Middle-Lower Congo, suggesting independent introductions using different sources. We conclude that the presence of Nile tilapia in the Congo Basin results from independent introductions, reflecting the dynamic aquaculture history, and that their introduction probably leads to genetic interactions with native tilapias, which could lower their fitness. We therefore urge avoiding further introductions of Nile tilapia in non-native regions and to use native tilapias in future aquaculture efforts.