Dear Blake, In short, isometry, positive allometry and negative allometry cannot be studied using multivariate regressions of multivariate data (such as geometric morphometric coordinate data). These are concepts that only exist in bivariate plots of size and a single variable.
Suggested reading on Multivariate Allometry, see Klingenberg 1996 in Advances in Morphometrics (available here: http://www.flywings.org.uk/papers_page.htm) and Monteiro 1999 Systematic Biology, and and then also read this important review Sheets & Zelditch 2013 Hystrix (in the "Yellow Book"). You should perhaps be more be thinking about comparing trajectories in shape space (e.g. Adams & Collyer 2009 Evolution). See for example comparing different ontogenetic trajectories in Adams & Nistri 2010 BMC Evo Bio, Klingenberg & Spence's study of heterochrony in waterstriders (1993, Evolution). Best, Emma ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Emma Sherratt, PhD. Lecturer in Zoology, Zoology Division, School of Environmental and Rural Science, Room L120 Bldg C02, University of New England, Armidale, NSW, Australia, 2351 Tel: +61 2 6773 5041 email: emma.sherr...@une.edu.au Twitter: @DrEmSherratt Caecilians are legless amphibians... * __ (\ .-. .-. /_") \\_//^\\_//^\\_// `"` `"` `"`* learn more about them here: www.emmasherratt.com/caecilians On 1 June 2015 at 08:51, Blake Dickson <bdick...@g.harvard.edu> wrote: > Hey all, > > So I have a question regarding using centroid size in analyses of scaling. > > I want to test how something scales with increasing body size in a 3D GM > context. If I use centroid size, gained from 3D landmarks, as a measure of > the size of my object and skull length as a measure of body size, what > scaling would I assume to be isometric? Do I treat centroid size as a > single dimension unit (length) and assume isometry is 1:1; or rather > centroid size as a multidimensional unit? > > Thanks, > Blake > > -- > MORPHMET may be accessed via its webpage at http://www.morphometrics.org > > To unsubscribe from this group and stop receiving emails from it, send an > email to morphmet+unsubscr...@morphometrics.org. > -- MORPHMET may be accessed via its webpage at http://www.morphometrics.org To unsubscribe from this group and stop receiving emails from it, send an email to morphmet+unsubscr...@morphometrics.org.
