The robustness of geometric morphometrics in testing the morphological equivalence hypothesis among cichlid species from East African Great Lakes

Abstract

As part of an ongoing broader investigation into whether similar morphologies among cichlid species from East African Great Lakes are due to common ancestry or convergent evolution, we used geometric morphometrics to quantitatively test the hyphothesis that Lake Tanganyika's Tropheus spp. is morphologically similar to Lake Malawi's Pseudotropheus spp. and Labeotropheus fuelleborni. Landmark-based techniques were used to investigate body shape variation and the results revealed highly significant differences among these genera with the exception of L. fuelleborni vs. Pseudotropheus (Tropheops) spp. An ordination of all specimens along the first two canonical variate (CV) axes indicated clear interlake separation, especially along the CV I axis, whereby Tropheus moori showed a dorsoventral expansion of the mid body section with a steeper forehead relative to Lake Malawi species. Pseudotropheus (Maylandia) zebra was discriminated from the rest primarily on the basis of its terminally positioned gape, which differed from the inferior subterminal gape that was prevalent in the other species. Thus, the present study reveals a pattern of parallel evolution between L. fuelleborni and Pseudotropheus (Tropheops) spp., but does not support an interlake convergent evolution hypothesis. Contrary to previous researchers' assertions, these results emphasize the robustness of geometric morphometrics when testing morphological equivalence hypothesis among cichlid species. © 2007 The Linnean Society of London.