Morphological variations of wild populations of Nile tilapia (Oreochromis niloticus) living in extreme environmental conditions in the Kenyan Rift-Valley

Abstract

In this study, we use geometric morphometric method to establish morphological differences between natural populations of Nile tilapia from two extreme environmental conditions (high temperature and salinity) in Kenya, and compare them to two populations from regions experiencing less extreme conditions. To determine genetic influence on morphology, we correlated genetic data with morphological data. The study observed significant morphological differences between all studied populations, including three closely related hot spring populations (Bogoria, Chelaba and Turtle Springs), and two populations with similar genetic background inhabiting saline environments in Lake Turkana basin (Turkana and Crocodile Lake populations). In addition, allometric growth patterns of the seven populations differed significantly, demonstrating that developmental changes (plastic or adaptive) operated between these populations. Positive correlation between morphometric and genetic data confirmed the influence of genetic factors on morphology. All observed differences were attributed either to genetic and/or environmental factors, which seemed to play a major role in influencing morphology of wild Nile tilapia populations. We recommend further studies to be carried out under controlled conditions to confirm the role of temperature, pH and salinity in morphological diversification of Nile tilapia.

Anthropogenic impacts on the contextual morphological diversification and adaptation of Nile tilapia (Oreochromis niloticus, L. 1758) in East Africa

“…However, it remains unclear how the stockings in the lakes especially Victoria and Kyoga were effected, whether it was the same or varying periods. These results reflect those of Mwanja (2000) who found Kyoga populations less genetically variable and associated it to more recent introductions in terms of history, contrary to Victoria metapopulation. Therefore, our NMDS and CVA results might be revealing the existing genetic intimacy between the introduced populations with their putative ancestral sources.…”

“…It must be noted that, Nile tilapia in EA is reportedly the only Tilapiine species to coexist with Nile perch, from both native and introduced locations (Balirwa 1998). The long history of Nile tilapia to live and share ecosystems with the predator is linked to ecological separation (Balirwa 1998;Mwanja 2000). While Nile perch prefers the open waters, it is believed that Nile tilapia shifted their niche to shore waters to avoid predation pressure (Ogutu-Ohwayo 1990).…”

“…Nile tilapia was introduced into Lakes Victoria and Kyoga from their putative native source, Albert (Mwanja 2000). However, other sources reported that the species might have also been introduced into lakes Victoria and Kyoga from Lakes Edward, Turkana and from pond aquaculture at Kajjansi (Uganda) (Welcomme 1966;Trewavas 1983;Balirwa 1992;Pullin et al 1997).…”

“…However, of a more important note, the shape divergent encountered in George might also be a result of admixture. Mwanja (2000) reported that, in the 1970s, while Nile tilapia fishery was booming on L. George, it prompted a fish processing plant on the lake. Later, overfishing (LoweMcConnell 2010) triggered importation of Nile tilapia from L. Albert to reinforce the dwindled stocks in L. George which culminated into Albert strain planted into L. George.…”

Recurrent changes in cichlid dentition linked to climate‐driven lake‐level fluctuations

“…Morphological variation in dentition among Oreochromis populations has been directly linked to differences in habitat (Ndiwa et al. ), but evidence of morphological shifts within a single population in response to local habitat change is rare, especially over the substantial periods typically required for speciation. Study of fossils has already proven informative in this respect for other teleost fishes (Purnell et al.…”