Rapid phenotypic divergence in the small African cyprinid Rastrineobola argentea (Pellegrin 1904) (Teleostei: Cyprinidae) in Lake Victoria, Uganda

Publication Type:Journal Article
Year of Publication:2015
Authors:H. Ahnelt, Keckeis, H. , Mwebaza-Ndawula, L.
Journal:African Journal of Ecology
Pagination:n/a - n/a
Date Published:Jan-08-2015

During the 1980s, the ecosystem of Lake Victoria underwent major changes in its physical and biological characteristics (Chapman et al., 2008; Hecky et al., 2010). After decline of most native fish species (Van Rijssel & Witte, 2013), the abundance of the pelagic cyprinid Rastrineobola argentea (Pellegrin 1904) gradually increased in inshore areas of Lake Victoria, where it started to exploit new food sources (Mwebaza-Ndawula, 1998; Wanink, 1999; Campbell, Hecky & Wandera, 2003). The pelagic offshore populations of R. argentea nearly exclusively feed on zooplankton (Njiru et al., 2004; Witte et al., 2007; Ojwang et al., 2014), whereas the inshore populations shifted to ‘mixed’ feeding, preying on macrobenthic invertebrates and on zooplankton (Mwebaza-Ndawula, Kiggundu & Ochieng, 1999; Campbell, Hecky & Wandera, 2003; Semyalo, Nattabi & Larsson, 2009). A dietary shift can influence fish head shape to optimize prey ingestion, thus affecting gape width, eye size and gill raker number for selecting food particles (Svanbäck & Eklöv, 2003; Leaver & Reimchen, 2012). This study was therefore designed to determine the extent to which the shift of R. argentea from a pelagic zooplanktivorous lifestyle to a lifestyle involving ingestion of macrobenthic prey is reflected in related morphological traits. Our results highlight that at the first stages of differentiation, characters do not respond equally. Head length, predicted to increase after the shift to a benthic habitat, did not change, and eye size changed in the opposite direction as proposed by Wund et al. (2008) and Kaeuffer.

Short Title:Afr. J. Ecol.
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