Depth-dependent abundance of Midas Cichlid fish (Amphilophus spp.) in two Nicaraguan crater lakes
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The Midas Cichlid species complex (Amphilophus spp.) in Central America serves as a prominent model system to study sympatric speciation and parallel adaptive radiation, since small arrays of equivalent ecotype morphs have evolved independently in different crater lakes. While the taxonomy and evolutionary history of the different species are well resolved, little is known about basic ecological parameters of Midas Cichlid assemblages. Here, we use a line transect survey to investigate the depth-dependent abundance of Amphilophus spp. along the shores of two Nicaraguan crater lakes, Apoyo and Xiloá. We find a considerable higher density of Midas cichlids in Lake Xiloá as compared to Lake Apoyo, especially at the shallowest depth level. This might be due to the higher eutrophication level of Lake Xiloá and associated differences in food availability, and/or the presence of a greater diversity of niches in that lake. In any case, convergent forms evolved despite noticeable differences in size, age, eutrophication level, and carrying capacity. Further, our data provide abundance and density estimates for Midas Cichlid fish, which serve as baseline for future surveys of these ecosystems and are also relevant to past and future modeling of ecological speciation.
KeywordsSympatric speciation Parallel adaptive radiation Fish density estimates Crater Lake Apoyo Crater Lake Xiloá Ecology
We are grateful to C. Heule, N. Hue and A. Theis for assisting us with diving; B. Christ and T. Suter for their helping hand at dive sites; the Ministerio del Ambiente y los Recursos Naturales Nicaragua (MARENA) for research permits; E. P. van den Berghe for logistical help and scientific expertise; and two anonymous referees, Associated Editor C. Sturmbauer and the Editor K. Martens for valuable comments on the manuscript; T. Roth for statistical support, and the “Fuerzas Armadas de Nicaragua” for boat cruises and air supply. This project was funded by grants from the European Research Council (ERC) and the Swiss NSF.
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