Distinct population structure in a phenotypically homogeneous rock‐dwelling cichlid fish from Lake Tanganyika

Abstract

Several lineages of cichlid fishes in the East African Great Lakes display stunning levels of morphological diversification. The rapid evolution of rock-dwelling polygynous mouthbrooders in Lake Malawi, for example, was in part ascribed to their allopatric distribution on disjunct stretches of rocky coast, where even short habitat discontinuities reduce gene flow effectively. However, as seen in other cichlids, ecological barriers do not always prevent gene flow, whereas genetic structure can develop along continuous habitat, and morphological diversification does not necessarily accompany genetic differentiation. The present study investigates the population structure of Variabilichromis moorii, a monogamous substrate-brooding lamprologine of rocky coasts in Lake Tanganyika, which occurs over about 1000 km of shoreline almost without phenotypic variation. Phylogeographic analyses of mitochondrial DNA sequences indicated that dispersal is infrequent and generally occurs between adjacent locations only. Exceptions to this pattern are closely related haplotypes from certain locations on opposite lakeshores, a phenomenon which has been observed in other species and is thought to reflect lake crossing along an underwater ridge in times of low water level. Genetic population differentiation, estimated from mitochondrial DNA and microsatellite data in six adjacent populations, was equally high across localities separated by sandy shores and along uninterrupted stretches of rocky shore. Our results suggest that ecological barriers are not required to induce philopatric behavior in Variabilichromis, and that morphological stasis persists in the face of high levels of neutral genetic differentiation.

Competition-driven speciation in cichlid fish

“…The population genetic data are consistent with a pattern of genetic isolation by distance, which is not unusual for hard substrate-associated cichlids of the region, and has been shown in other lamprologines (Variabilichromis moorii 27 and Neolamprologus caudopunctatus 28 ). The population genetic data suggest that the selective processes that have led to diversification have taken place over local spatial scales.…”

Species-Specific Population Structure in Rock-Specialized Sympatric Cichlid Species in Lake Tanganyika, East Africa

“…In particular, a strong phylogeographic pattern disrupted by the occasional presence of closely related and even identical haplotypes on opposite sides of the lake found in Tropheus, Eretmodus, and another highly structured rock-dweller, Variabilichromis moorii, suggests incidental gene flow in association with periods of low lake level (Sturmbauer et al 1997Duftner et al 2006). Furthermore, this and other recent population genetic analyses of sympatric species indicate that speciesspecific differences in traits related to dispersal superimpose on extrinsic forces and create variable patterns of population structure and diversity (this study; Duftner et al 2006;Koblmu¨ller et al 2006).…”

“…We do not know of studies on the population structure of Lake Victoria cichlids, but a representative of the ''Lake Victoria superflock'' from an unstructured satellite lake displayed little if any genetic structure (Abila et al 2004). In contrast, studies of rock specialists from Lake Tanganyika demonstrated high population differentiation along continuous stretches of shoreline as well as across habitat barriers Duftner et al 2006). The present study compares genetic differentiation and diversity in nuclear and mitochondrial markers in representatives of three endemic tribes of Lake Tanganyika, Eretmodus cyanostictus (Eretmodini), Ophthalmotilapia ventralis (Ectodini), and Tropheus moorii (Tropheini; Poll 1986).…”

Phylogeny and phylogeography of Altolamprologus: ancient introgression and recent divergence in a rock-dwelling Lake Tanganyika cichlid genus

“…In the two East African lakes Malawi and Tanganyika, stenotopic cichlid species inhabiting the discontinuous rocky littoral consistently show remarkable genetic population differentiation, even across very short geographic distances (e.g. van Oppen et al, 1997;Markert et al, 1999;Rico & Turner, 2002;Pereyra et al, 2004;Duftner et al, 2006;Koblmüller et al, 2011;Sefc et al, 2007;Wagner & McCune, 2009;Nevado et al, 2013;Van Steenberge et al, 2015;Sefc et al, 2016). Differentiation is lower and only occurs on a larger geographic scale in less specialized species and species that inhabit the intermediate habitat, i.e.…”