These complicated issues aside, there is a simpler reason not to use a residual from a regression as the basis for further analyses. If two characters are under natural selection based on some combination -- such as selection on a ratio between them -- then the current value of character Y is a response, not to the current value of character X, but to its value in the past. Response to selection is not instant, so we'd really want to regress Y on past values of X. How far in the past depends on information on the strength of selection. We don't yet know that, and we don't have values of X in the past.
Far better to make a joint analysis of selection on both of them. Once one takes the residual one has built in the assumption that the response of one character to another is instantaneous, in effect that the selection involved is infinitely strong and the heritabilities complete. I believe that Hansen and Bartoszek have warned about this in a paper in Systematic Biology in 2012. Joe ---- Joe Felsenstein [email protected] Department of Genome Sciences and Department of Biology, University of Washington, Box 355065, Seattle, WA 98195-5065 USA -- MORPHMET may be accessed via its webpage at http://www.morphometrics.org --- You received this message because you are subscribed to the Google Groups "MORPHMET" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
