Figure 4.

Midas cichlid body shape differentiation along the benthic-limnetic axis. The divergence in body shape between benthic and limnetic species from crater lakes Apoyo (six species) and Xiloá (four species) is demonstrated and contrasted to the focal species from Asososca Managua. Depicted are 90% confidence ellipses along PCs 1 and 3 from a joint principal component analysis of body shape. Shape changes along PCs 1 and 3 (scale factor = 0.1) are indicated by thin plate splines. The line terminus refers to the shape change along a particular principal component, compared with the average shape (black dot). The shape change of these axes corresponds to typical body shape differences along the benthic-limnetic axis (relative body height and elongation as well as snout bluntness). Positive values on PC1 and negative values on PC3 indicate rather benthic individuals. Amphilophus tolteca (90% confidence ellipse indicated by broken line) overlaps with benthic and limnetic species from Lakes Apoyo and Xiloá, and in contrast to Lakes Apoyo and Xiloá, no intralacustrine divergence is observed.