2005 The Society for the Study of Evolution. All rights reserved.
Evolution, 59(9), 2005, pp. 20592061
THE ULTIMATE CAUSES OF PHENOTYPIC INTEGRATION: LOST IN TRANSLATION1
STEVAN J. ARNOLD
Department of Zoology, Oregon State University, Corvallis, Oregon 97331-2914
Received July 20, 2005.
Hence if a man goes on selecting, and thus augmenting,
any peculiarity, he will almost certainly modify unin-
tentionally other parts of the structure, owing to the mys-
terious laws of correlation. (Darwin 1859)
Since Darwin's time we have come to recognize two major
proximate causes of genetic correlation within populations
(pleiotropy and linkage disequilibrium). Today's challenge,
taken up by Phenotypic Integration, is to understand the ul-
timate causes of phenotypic and genetic correlation. A major
advance on this front was made by Olson and Miller (1958)
who proposed that phenotypic correlations between morpho-
logical structures may often reflect functional interactions.