Controlling for body size leads to inferential biases in the biological sciences

Rogell, BjörnSveriges lantbruksuniversitet,Stockholms universitet,Zoologiska institutionen,Swedish University of Agricultural Sciences, Sweden,Institutionen för akvatiska resurser,Department of Aquatic Resources,Stockholm University,Stockholm Univ, Dept Zool, Svante Arrhenius vag 18, Stockholm, Sweden.;Swedish Univ Agr Sci, Inst Freshwater Res, Dept Aquat Resources, S-17893 Drottningholm, Sweden. (författare)

Many traits correlate with body size. Studies that seek to uncover the ecological factors that drive evolutionary responses in traits typically examine these responses relative to associated changes in body size using multiple regression analysis. However, it is not well appreciated that in the presence of strongly correlated variables, the partial (i.e., relative) regression coefficients often change sign compared to the original coefficients. Such sign reversals are difficult to interpret in a biologically meaningful way, and could lead to erroneous evolutionary inferences if the true mechanism underlying the sign reversal differed from the proposed mechanism. Here, we use simulations to demonstrate that sign reversal occurs over a wide range of parameter values common in the biological sciences. Further, as a case-in-point, we review the literature on brain size evolution; a field that explores how ecological traits relate to the evolution of relative brain size (brain size relative to body size). We find that most studies show sign reversals and thus that the inferences of many studies in this field may be inconclusive. Finally, we propose some approaches to mitigating this issue.

Dowling, Damian K.Monash Univ, Sch Biol Sci, Clayton, Vic 3800, Australia. (författare)
Husby, Arild,Associate Senior LecturerUppsala universitet,Evolutionsbiologi,Norwegian Univ Sci & Technol, Ctr Biodivers Dynam, N-7491 Trondheim, Norway.(Swepub:uu)arihu528 (författare)
Stockholms universitetZoologiska institutionen (creator_code:org_t)
Sveriges lantbruksuniversitet

Av författaren/redakt...: Rogell, Björn; Dowling, Damian ...; Husby, Arild, As ...

Om ämnet

Av lärosätet: Stockholms universitet; Sveriges Lantbruksuniversitet; Uppsala universitet

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