bioRxiv preprint doi: https://doi.org/10.1101/2021.05.06.442968; this version posted May 6, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 1 A simple hierarchical model for 2 heterogeneity in the evolutionary 3 correlation on a phylogenetic tree 1,2 3 3 4 Liam J. Revell , Ken S. Toyama , and D. Luke Mahler 1 5 Department of Biology, University of Massachusetts Boston, Boston, Massachusetts 6 02125 2 7 Facultad de Ciencias, Universidad Catolica´ de la Sant´ısimaConcepcion,´ Concepcion,´ 8 Chile 3 9 Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario 10 M5S 3B2, Canada 11 Corresponding author: 1;2 12 Liam J. Revell 13 Email address:
[email protected] 14 ABSTRACT 15 Numerous questions in phylogenetic comparative biology revolve around the correlated evolution of two 16 or more phenotypic traits on a phylogeny. In many cases, it may be sufficient to assume a constant 17 value for the evolutionary correlation between characters across all the clades and branches of the tree. 18 Under other circumstances, however, it’s desirable or necessary to account for the possibility that the 19 evolutionary correlation differs through time or in different sections of the phylogeny. Here, we present 20 a method designed to fit a hierarchical series of models for heterogeneity in the evolutionary rates and 21 correlation of two quantitative traits on a phylogenetic tree.