Between 160 and 240 million years of cumulative divergence between two tiny worms resulted in the genomic divergence by sequence comparison you’d expect over that time yet virtually no phenotype divergence. Once you’re a nemotode you’re always a nematode? Who would have predicted that…
Caenorhabditis comparative genomics [18 November 2003]
Analysis of the sequence revealed that major evolutionary changes in genomes do not necessarily lead to gross physical changes in the adapted organism. Ã¢â‚¬Å“C. elegans and C. briggsae diverged 80 to 120 million years ago, somewhat longer ago than human and mouse,Ã¢â‚¬Â Stein wrote in an E-mail to us. Ã¢â‚¬Å“By several measures, the two nematode genomes are very much scrambled relative to each other – far more than human and mouse are. Yet while human and mouse are extremely different in ecological niche, behavior, and anatomy, the two nematode species occupy identical niches, have similar behavior, and are indistinguishable except to experts.
Google ultraconserved phenotype for more information.