Meeting Abstract

12.1  Friday, Jan. 4  Origin and loss of cichlid craniofacial diversity MCGEE, MD*; BORSTEIN, SR; WAINWRIGHT, PC; University of California Davis; California State University Sacramento; University of California Davis mcgee@ucdavis.edu

Cichlid fishes are famous for their exceptional diversity, particularly in craniofacial morphology. Despite remarkable phenotypic diversity in locations like the East African Rift Valley, it is not currently known which lineages produced the extremes of cichlid phenotypic diversity, or how extinction events have altered patterns of morphospace occupation in cichlids. We generated a dataset of lateral head images of one species from each of the two hundred and twenty three genera of cichlids. We then digitized a set of ten craniofacial landmarks to generate a cichlid morphospace using geometric morphometrics. We reveal a major axis of craniofacial diversity associated with dorsoventral compression or expansion. Surprisingly, cichlid phenotypes associated with the extremes of the diversity axes were not from the well-known recent lake radiations, but were from older lineages found in fast-flowing river and flooded forest habitats in Africa, Asia, and South America. This suggests that the processes generating extreme phenotypes may not be the same as the processes generating phenotypic diversity over extremely short time scales. We also examined the largest vertebrate extinction event in modern history, which occurred when introduced Nile perch extirpated hundreds of endemic cichlids in Lake Victoria. We generated a craniofacial morphospace of over one hundred Victorian cichlids and recorded whether each species crashed after the Nile perch introduction or was relatively unaffected. Craniofacial morphology was a strong predictor of a species’ likelihood of crashing, suggesting that the dynamics of extinction in Victorian cichlids were not simply a result of increased predation in the lake, but were biased towards particular phenotypes.