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Genetic divergence, speciation and morphological stasis in a lineage of African cichlid fishes

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Abstract

Since their discovery at the turn of the century, the species assemblages of cichlid fishes in the East African Lakes Victoria, Malawi and Tanganyika have fascinated evolutionary biologists. Many models have attempted to account for the 'explosive' evolution of several hundred species within these lakes. Here we report a case of surprisingly large genetic divergence among populations of the endemic Tropheus lineage of Lake Tanganyika. This lineage of six species contains twice as much genetic variation as the entire morphologically highly diverse cichlid assemblage of Lake Malawi and six times more variation than the Lake Victoria species flock. Although it is highly variable in coloration, this group of species and its closest relatives have not undergone appreciable morphological change. The observed geographic pattern of genetic variation suggests that major lake level fluctuations affected the distribution and speciation of this lineage of cichlid fishes.
First publ. in: Nature 358 (1992), pp. 578-581
Konstanzer Online-Publikations-System (KOPS)
URL: http://www.ub.uni-konstanz.de/kops/volltexte/2007/3665/
URN: http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-36655
... This hypothesis purports that the ancestor of the Tropheini entered the lake environment in intense competition established species from six non-haplochromine lineages that are endemic to LT. The diversification of the Tropheini has been attributed to extrinsic factors such as the abovementioned deepening lacustrine conditions as well as lake-level fluctuations (Sefc, Mattersdorfer, Hermann, et al., 2017;Sturmbauer, 1998;Sturmbauer et al., 2001;Sturmbauer & Meyer, 1992. Currently, 22 described species (Fricke et al., 2022) and several undescribed species (Konings, 2019;Ronco et al., 2020) comprise the Tropheini and they hold a key ecological position in the rock and cobble shore habitats of LT (Koblmüller et al., 2010;Sturmbauer et al., 2003;Takahashi & Koblmüller, 2014). ...
... The Tropheini are considered a model for synchronized speciation with vicariant events likely produced by extreme water level changes (Sturmbauer et al., 2003;Sturmbauer & Meyer, 1992). success to the expanding littoral habitats and shorelines (Cohen et al., 1997;McGlue et al., 2008), which allowed them to radiate while competing with other ongoing radiations. ...
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... Some examples of fish taxa demonstrating high genetic divergence yet showed conserved morphologies included Foetorepus calauropomus (Myun Park et al., 2020), Mugil curema (Neves et al., 2020), Poecilia sphenops (Bagley et al., 2015), Plectropomus leopardus (Cai et al., 2013), and Tropheus sp. (Sturmbauer and Meyer, 1992) among others. ...
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... As a genetic marker, Cytb has several valuable properties that can be used for inferring different evolutionary and population processes. Cytb gene sequence is characterized by both slowly and rapidly evolving codon positions as well as conserved and variable regions, which makes it ideal for deciphering diversity and systematics questions starting from detailed phylogeny [45][46][47][48][49][50] to the population and recent divergence levels [51][52][53][54]. Cytb gene variability can be used to identify the signs of adaptive evolution [55] as well as local declines in diversity, which is indicative of selective sweeps [56,57]. ...
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Thesis
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