Figure 1.

Compelling examples of developmental bias and its evolutionary effect in animals. (A) By combining experiments in vivo and in vitro, comparative analyses, and mathematical modeling, researchers have shown that the evolutionary diversity in tooth morphology among mammals is shaped by the mechanism by which teeth develop. Pictured is the skull of a crabeater seal, Lobodon carcinophaga. (B) The oral and pharyngeal jaws of cichlid fishes are putative examples of how a bias caused by plasticity, itself possibly favored by selection, can feed back to facilitate adaptive divergence and convergence in independently evolving lineages. (C) In Drosophila, the phenotypic divergence between species in wing shape is aligned with the phenotypic bias associated with random mutation, one explanation for which is that developmental bias coevolves with phenotypic divergence. (D) Artificial selection on the size and color of Mycalesine butterfly eye spots demonstrates the effects of bias misaligned or aligned with the direction of selection. Photo credits: (A) Panther Media GmbH, Alamy Stock Photo; (B) Kevin Parsons; (C) Martin Hauser Phycus, CC-BY-3.0-DE; (D) Saenko et al., BMC Biology 2010 8:111, CC-BY-2.0.