Morphometric differentiation among haplochromine cichlid fish species of a satellite lake of Lake Victoria

Abstract

Lake Victoria holds a young but species‐rich assemblage of cichlid fishes, which form a monophyletic assemblage with additional species from surrounding water bodies, termed the Lake Victoria superflock. Lake Victoria is surrounded by smaller lakes that are somewhat disconnected from the main lake. Lake Kanyaboli is such a small lake, having markedly reduced species diversity, in part comprised of Lake Victoria species and endemics. Here, we studied the modern haplochromine component of the cichlid fauna, represented by Lipochromis maxillaris, Astatotilapia nubila, Xystichromis phytophagus and Astatotilapia sp. ‘Bigeye’, as well as a number of unidentified modern haplochromine specimens. We used landmark‐based geometric morphometrics to study the degree of morphological divergence among those young entities. Twenty landmarks and 14 interlandmark distances were used for shape analysis. Multivariate analysis revealed significant differences between all four species, but principal component analysis and canonical variate analysis did not clearly discriminate between A. nubila and X. phytophagus, demonstrating great overall morphological similarity despite clear dietary differences. Besides coloration there was sexual dimorphism in body proportions, so that only male individuals were analysed further. In all four species, the observed similarities and differences in body shape conform to the type of ecological specialization of the fish. Most unidentified specimens overlapped the range of A. nubila and X. phytophagus, while the assignment test based on the canonical variate analysis suggested 70% of the three overlapping entities as separate units. To test their reproductive distinctness and to demonstrate potential hybridization, nuclear genetic data are needed.

Genetic distinction of four haplochromine cichlid fish species in a satellite lake of Lake Victoria, East Africa

“…The results of our comparative morphological analysis (Odhiambo et al. 2011) corroborated the original strategy to collect and analyse all unidentifiable specimens, in that almost all collected adult specimens that did not fall within any of the already recognized species clustered in one homogenous cloud separated somewhat from A. nubila and X. phytophagus (figure 6b in Odhiambo et al. 2011).…”

“…The recently published geometric morphometric analysis of the same individuals showed clear morphological differences between L. maxillaris and A. sp . ‘ Bigeye ’ but could not clearly separate X. phytophagus , A. nubila and the unidentified specimens in morphospace, despite their clear differentiation in terms of colour and feeding ecology (Odhiambo et al. 2011).…”

“…2008) in Lake Kanyaboli, a small satellite lake of Lake Victoria covering an area of approximately 11 km 2 and separated from the Lake Victoria by a dense papyrus swamp (Fig. 1 in Odhiambo et al. 2011).…”

“…‘ Bigeye ’ but could not clearly separate X. phytophagus from A. nubila in morphospace, despite their clear differentiation in terms of colour and trophic ecology. Furthermore, the unidentified specimens clustered in close association with X. phytophagus and A. nubila (Odhiambo et al. 2011).…”

Fast adaptive responses in the oral jaw of Lake Victoria cichlids

“…Phenotypic plasticity is described as the environmentally sensitive production of alternative phenotypes by given genotypes (DeWitt and Scheiner ). Plasticity is a common phenomenon in cichlids and laboratory experiments have confirmed the ability of many cichlid species to change the jaw apparatus in response to different diets (Witte ; Hoogerhoud ; Meyer ; Wimberger ; Huysseune ; Smits et al ; Bouton et al ; Stauffer and Van Snik Gray ; Kerschbaumer et al ; Muschick et al ; Gunter et al ), although different diets in the wild do not always lead to divergence in morphology in cichlids (see Odhiambo et al ). Some of these studies tested plasticity of the premaxilla and showed a shorter ascending arm and a larger angle β of the premaxilla as a phenotypic response to a feeding style involving manipulation of prey (especially biting, Witte ; Wimberger ; Bouton et al ).…”