Meeting Abstract

P3.185  Tuesday, Jan. 6  The Evolution of Skull Form and Trophic Ecology Among the Cichlid Fishes of Lake Malawi MCINTYRE, Alyssa*; MCGEE-MOORE, Alana; COOPER, W. James; ALBERTSON, R. Craig; Syracuse University; Syracuse University; Syracuse University; Syracuse University ammcinty@syr.edu

An organism’s unique skeletal and muscular structures form a biological machine capable of interacting with its environment. When an animal’s anatomical form changes, the resulting modification in biomechanical function can allow it to occupy a new ecological niche. The cichlid fishes of Lake Malawi are an extraordinary example of rapid evolutionary divergence. In a very short span of evolutionary time (1-2 million years), one species has diversified into several hundred species that inhabit an extremely wide variety of feeding niches. This ecological divergence was produced by a massive radiation in skull form and function. We studied the anatomical diversity of this incredible lineage by dissecting and photographing the skulls and jaws of 102 fishes from 47 of the 53 cichlid genera found in Lake Malawi. The genera examined contain 93% of the cichlid species that are native to the lake. We examined anatomical landmarks that are of biomechanical importance for fish feeding using geometric morphometric analyses, which are coordinate based mathematical analyses of anatomical form. Our results provide a nearly comprehensive measurement of the anatomical diversity of Lake Malawi cichlid skulls, and provide a quantitative description of a classic example of an adaptive radiation. The results confirmed a significant degree of variation among cichlid genera, and indicate that the two major lineages of Lake Malawi cichlids, the "rock dwellers" (mbuna) and the "sand dwellers", have each evolved skull shapes that are not possessed by the other, and these morphologies have allowed each of them to exploit unique ecological opportunities.