Morphology, Molecules, and Monogenean Parasites: An Example of an Integrative Approach to Cichlid Biodiversity

<div><p>The unparalleled biodiversity of Lake Tanganyika (Africa) has fascinated biologists for over a century; its unique cichlid communities are a preferred model for evolutionary research. Although species delineation is, in most cases, relatively straightforward, higher-order classifications were shown not to agree with monophyletic groups. Here, traditional morphological methods meet their limitations. A typical example are the tropheine cichlids currently belonging to <i>Simochromis</i> and <i>Pseudosimochromis</i>. The affiliations of these widespread and abundant cichlids are poorly understood. Molecular work suggested that genus and species boundaries should be revised. Moreover, previous morphological results indicated that intraspecific variation should be considered to delineate species in Lake Tanganyika cichlids. We review the genera <i>Simochromis</i> and <i>Pseudosimochromis</i> using an integrative approach. Besides a morphometric study and a barcoding approach, monogenean <i>Cichlidogyrus</i> (Platyhelminthes: Ancyrocephalidae) gill parasites, often highly species-specific, are used as complementary markers. Six new species are described. <i>Cichlidogyrus raeymaekersi</i><b>sp. nov.</b>, <i>C</i>. <i>muterezii</i><b>sp. nov.</b> and <i>C</i>. <i>banyankimbonai</i><b>sp. nov.</b> infect <i>S</i>. <i>diagramma</i>. <i>Cichlidogyrus georgesmertensi</i><b>sp. nov.</b> was found on <i>S</i>. <i>babaulti</i> and <i>S</i>. <i>pleurospilus</i>, <i>C</i>. <i>franswittei</i><b>sp. nov.</b> on both <i>S</i>. <i>marginatus</i> and <i>P</i>. <i>curvifrons</i> and <i>C</i>. <i>frankwillemsi</i><b>sp. nov.</b> only on <i>P</i>. <i>curvifrons</i>. As relatedness between <i>Cichlidogyrus</i> species usually reflects relatedness between hosts, we considered <i>Simochromis</i> monotypic because the three <i>Cichlidogyrus</i> species found on <i>S</i>. <i>diagramma</i> belonged to a different morphotype than those found on the other <i>Simochromis</i>. The transfer of <i>S</i>. <i>babaulti</i>, <i>S</i>. <i>marginatus</i>, <i>S</i>. <i>pleurospilus</i> and <i>S</i>. <i>margaretae</i> to <i>Pseudosimochromis</i> was justified by the similarity of their <i>Cichlidogyrus</i> fauna and the intermediate morphology of <i>S</i>. <i>margaretae</i>. Finally parasite data also supported the synonymy between <i>S</i>. <i>pleurospilus</i> and <i>S</i>. <i>babaulti</i>, a species that contains a large amount of geographical morphological variation.</p>