*Department of Ornithology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024
In Body Size Effects and Rates of Cytochrome-b Evolution in Tube-nosed Seabirds [Volume 15(10):13601371] we presented the results of a likelihood ratio test for rate heterogeneity in our sequence data. In our test, we relied on 1 degree of freedom. However, the appropriate number was 88. This follows from the fact that two likelihood scores can be compared, one with a clock constraint and one without, if they are calculated using the same topology. In this test, there are N-2 degrees of freedom, where N is equal to the number of terminal taxa in the analysis. In our case, this is 90-2, or 88. Fortunately, this error does not change our results since we can still reject a clock, even with 88 degrees of freedom.
We thank Cliff Cunningham for contacting us and kindly explaining our error.
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2 Current address and address for correspondence: Scott E. Stanley, Genaissance Pharmaceuticals, Five Science Park, New Haven, CT 06511. E-mail: s.stanley{at}genaissance.com
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