Genetic structure of Lake Magadi tilapia populations

Abstract

The control region of the mitochondrial DNA haplotype frequencies were significantly different among the two separate lagoon populations of Oreochromis alcalicus grahami in Lake Magadi and of O. a. alcalicus from lake Natron, and DNA fingerprint similarity indices were significantly higher for intra-population comparisons of the two Magadi lagoon populations and the Lake Natron population than the inter-population similarity indices among these populations. A modified F st measure indicated population sub-division and the phylogeographic partitioning of the VNTR fragments observed were unique to specific populations further indicating substantial genetic differentiation. The lagoon populations within Lake Magadi demonstrated the same degree of genetic differentiation as either of these populations did to the outgroup (the Lake Natron population). There appears to be limited gene flow between Lake Magadi tilapia populations and this population structure has important implications for protecting locally adapted populations within this unique ecosystem. 2000 The Fisheries Society of the British Isles

Eco‐morphological differentiation in Lake Magadi tilapia, an extremophile cichlid fish living in hot, alkaline and hypersaline lakes in East Africa

“…Unfortunately, no census estimate is available for LM. However, using mtDNA sequence data, Wilson et al (2000) estimated an (long-term) effective population size of only a few hundreds and found evidence for recent population expansion for the population, which is congruent with the expansion inferred in our study. Whether the dramatic population expansion in LM is related to its adaptation to a new niche (floating surface biota) is an interesting hypothesis that needs further investigation.…”

“…1), three scenarios seem plausible: (i) all three populations could have split simultaneously, (ii) the LM population could have been isolated from the FSL and ROM populations (inhabiting the main Lake Magadi) before they were themselves separated by trona deposits, and (iii) the barrier imposed by trona between FSL and ROM, may have preceded the geological separation of LM and the Lake Magadi populations, leading to the split of ROM from a combined population of LM and FSL before they in turn got separated. Earlier studies in the Magadi system have suggested that migration between the lagoons of Lake Magadi is rare leading to genetic differentiation among the populations (Wilson et al 2000(Wilson et al , 2004Kavembe et al 2014). However, a recent study found significant genetic exchange between populations of congeneric species inhabiting various lagoons of Lake Natron (Zaccara et al 2014;Ford et al 2015).…”

Air breathing in Magadi tilapia Alcolapia grahami, under normoxic and hyperoxic conditions, and the association with sunlight and reactive oxygen species

“…The presence of a diel cycle in ROS concentration at Lake Magadi is supported by the following: the rapid decline of ROS in water held in the dark at ambient temperature as would occur at night, the low ROS levels observed in morning water collected from Fish Springs Lagoon (bucket and field observations) and high ROS levels observed in the presence of mid-afternoon sunlight (bucket and field observations). Diel patterns in ROS concentrations with a peak in mid-afternoon are common in freshwater and coastal systems (Cooper & Lean, 1989;Wilson et al, 2000;Häkkinen et al, 2004). At Lake Magadi, samples for ROS were collected 3-5 cm below the water surface, yet the fish live at all depths.…”

Pronounced genetic differentiation of small, isolated and fragmented tilapia populations inhabiting the Magadi Soda Lake in Kenya

“…However, an earlier study by Wilson et al (2000) based on minisatellites using samples from only two lagoons of the main Lake Magadi and a subset of samples from a single location in Lake Natron reported substantial genetic differentiation between the three populations studied. The difference in the studies by Wilson et al (2000Wilson et al ( , 2004 could be attributed to the low resolution power of the markers and the limited number of samples used (Wan et al, 2004).…”