Meeting Abstract
34.1 Monday, Jan. 5 Comparative Evolution of Trophic Morphology Among the East African Cichlids of Lakes Malawi, Victoria, and Tanganyika COOPER, W. J.*; MCINTYRE, A. M.; MCGEE-MOORE, A. C.; KERN, B. S.; ALBERTSON, R. C.; Syracuse University; Syracuse University; Syracuse University; Syracuse University; Syracuse University wjcooper@syr.edu
The explosive trophic divergences among East African Rift Lake cichlids represent some of the best known examples of adaptive radiations. These relatively young lineages have undergone morphological diversification that is equivalent to the combined diversity of multiple fish families. The remarkable nature of these events is heightened by the fact that lakes Malawi, Victoria and Tanganyika represent natural replicates of these phenomena. In addition, the ages of these lakes closely follow a logarithmic distribution (Tanganyika, 8-10 my; Malawi, 1-2 my; Victoria, 100-200 ky). These circumstances offer an ideal situation for examining chronological patterns of cichlid evolution. We performed a comparative morphometric study of cichlid heads using specimens from a large percentage of the genera that are endemic to each lake. These data were used in relative warp analyses, and all heads were represented in a shared "shape space" that permitted us to determine whether trophic convergence was accompanied by morphological convergence. We calculated the morphological diversity of all three lineages, and estimates of cranial shape diversity were plotted on a geological timeline. Non-parametric re-sampling techniques were employed in order to statistically compare the cranial shape diversity of the cichlids from each lake. Although these lineages have served as textbook examples of adaptive radiations, this study represents the first time that their trophic diversity has been quantified. Such quantification is a necessary prerequisite for a rigorous comparative study of the incredible morphological evolution that has repeatedly occurred within the East African Rift Lakes.
