Dataset to study the 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

During colonial times, Nile tilapia Oreochromis niloticus (Linnaeus, 1758)
was introduced in 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, focussing
on the Congo Basin. Additionally, 48 specimens from 16 other tilapia
species were included to test for hybridisation. Using RAD sequencing (27
611 SNPs), we discovered genetic admixture with other tilapia species in
several morphologically identified Nile tilapia from the Congo Basin,
stressing their ability to interbreed and the potential threat they cause
to the genetic integrity of native tilapias. Populations from the Upper
Congo and those from the Middle-Lower Congo are strongly differentiated.
The former show genetic similarity with 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 to avoid introductions of Nile tilapia in
non-native regions and to use native tilapias in future aquaculture
efforts.