基金Acknowlegements We thank Matthew Arnegard, Carlos Botero, Tamra Mendelson, Rafael Rodriqu6z and Sander van Doom for excellent discussions about the need for a new phenotypic distance metric and Maria Servedio for the invitation and encouragement to formalize our ideas. This research was supported as part of the Sexual Selection and Speciation working group by the National Evolutionary Synthesis Center (NESCent), NSF #EF-0905606. RJS and SMF were supported by the University of Colorado and National Science Founda- tion grant IOS-0717421to RJS. MK was supported by a grant from the Vienna Science and Technology Fund (WWTF) to the Mathematics and Biosciences Group at the University of Vienna. EAH thanks Mitch Bern for use of his Master's thesis data and was supported by the National Science Foundation grant lOS - 0643179. DEI and DPLT were supported by the Natural Sciences and Engineering Research Council of Can- ada (Discovery Grants 311931-2005 and 311931-2010 to DEI, CGS-D to DPLT). NS and JAT were supported by the Royal Society, British Ecological Society and John Fell Fund (Ox- ford University). ES supported by NSF-DDIG the American Ornithologists Union, the University of Chicago, and the American Philosophical Society Lewis and Clark award. JACU was funded by National Science Foundation grant lOS 0306175.