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Open Access Research article

Genetic isolation and morphological divergence mediated by high-energy rapids in two cichlid genera from the lower Congo rapids

Jeffrey A Markert*, Robert C Schelly and Melanie LJ Stiassny

Author Affiliations

Department of Ichthyology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024-5192, USA

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BMC Evolutionary Biology 2010, 10:149  doi:10.1186/1471-2148-10-149

Published: 19 May 2010

Abstract

Background

It is hypothesized that one of the mechanisms promoting diversification in cichlid fishes in the African Great Lakes has been the well-documented pattern of philopatry along shoreline habitats leading to high levels of genetic isolation among populations. However lake habitats are not the only centers of cichlid biodiversity - certain African rivers also contain large numbers of narrowly endemic species. Patterns of isolation and divergence in these systems have tended to be overlooked and are not well understood.

Results

We examined genetic and morphological divergence among populations of two narrowly endemic cichlid species, Teleogramma depressum and Lamprologus tigripictilis, from a 100 km stretch of the lower Congo River using both nDNA microsatellites and mtDNA markers along with coordinate-based morphological techniques. In L. tigripictilis, the strongest genetic break was concordant with measurable phenotypic divergence but no morphological disjunction was detected for T. depressum despite significant differentiation at mtDNA and nDNA microsatellite markers.

Conclusions

The genetic markers revealed patterns of philopatry and estimates of genetic isolation that are among the highest reported for any African cichlid species over a comparable geographic scale. We hypothesize that the high levels of philopatry observed are generated and maintained by the extreme hydrology of the lower Congo River.