| Abstract: | 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. |
