Introgressive hybridization levels of Tilapiines species in Lake Victoria basin, Kenya inferred from microsatellite and mitochondrial DNA genotyping based on next- generation sequencing

Abstract

Despite their high abundance and species richness, tilapiines have been compromised by various factors especially overfishing, climate change, and un-controlled fish translocations. Fish translocations have negatively impacted native tilapiine populations through competition, predation, hybridization, and introgression compromising their genetic integrity. The hybridization levels of different tilapiines in the Lake Victoria basin remains an understudied aspect relatively. The study utilized nuclear microsatellite and mitochondrial DNA (mtDNA) genetic markers to investigate hybridization signals and compare the genetic diversity of different tilapiines in Lake Victoria, Kenya, using next-generation sequencing. Low levels of hybridization from Oreochromis niloticus into other Oreochromis species were detected by Bayesian clustering analysis and principal coordinate analysis (PCoA). The results contribute to the need for conservation measures of these fish species.

Lack of mitochondrial introgression and limited genetic connectivity among Manyara tilapia (Oreochromis amphimelas) populations in Tanzanian Saline Rift Valley Lakes

“…The measured levels of haplotype and nucleotide diversities among Manyara tilapia ( O. amphimelas ) populations were low compared to levels reported in Nile tilapia from other inland ecosystems in East Africa (Angienda et al., 2011; Kwikiriza et al., 2024; Mbilinyi et al., 2023). The low haplotype and nucleotide diversities observed among Manyara tilapia populations in SRVLs could be attributed to the semi‐arid nature of the regions where these lakes are located.…”

“…Similarly, Kwikiriza et al. (2024) observed limited genetic connectivity between populations of blue spotted tilapia ( O. leucostictus ) in Lake Victoria and Lake Sare, which they attributed to physical isolation caused by a main road and Yala swamp separating the two water bodies. The limited genetic connectivity between Manyara tilapia in Lake Manyara and other SRVLs is likely due to physical isolation between the lake and other SRVLs.…”

Threats to aquatic biodiversity and possible management strategies in Lake Victoria

“…Between 1961 and 1964, unusually high lake levels brought on by a lot of rain made it easier for tilapias to establish themselves (Nassali et al., 2020). The introduction of O. niloticus endangered the native tilapiine species through interspecific competition, hybridization and genetic swamping (Kwikiriza et al., 2023). Currently, O. niloticus predominates the majority of fish landings, whereas other tilapiine species are rarely fished (Wasonga et al., 2017).…”