Hi Thomas As put by Kim, the usual way to deal with allometry is multivariate regression. You can then work on the residuals, which stand for the part of shape variation independent from size variation.
To me the main problem is when you have several samples : regressing the whole dataset onto centroid size will mix two things : the within and among samples allometries (i.e. static and evolutionary allometry), which are not necessarily the same (see Klingenberg 96 in the NATO ASI book). Theoretically you should first test whether the allometric directions are similar in your different groups then (and only if the answer is yes) apply the regression to the whole dataset (the 'pooled within group' allometry). Unfortunatelly, in my experience, allometric directions are often different among groups, which makes it very difficult to get rid of the among groups allometry... I am not aware of any way of dealing with allometry in this case. There is a discussion on this in Klingenberg's 96 paper and a very recent paper re advocate the CPC-Burnaby method Mccoy MW, Bolker BM, Osenberg CW, et al. Size correction: comparing morphological traits among populations and environments OECOLOGIA 148 (4): 547-554 JUL 2006 Hope this helps. Any suggestions about the multigroup allometry problem would be warmly welcome!! Vincent Debat -- Replies will be sent to the list. For more information visit http://www.morphometrics.org
