Clarifying how microevolutionary processes scale to macroevolutionary patterns is a fundamental goal in evolutionary biology, but these analyses, requiring comparative datasets of population-level variation, are limited. By analyzing a previously published dataset of 2859 ruminant crania, we find that variation within and between ruminant species is biased by a highly conserved mammalian-wide allometric pattern, CREA (CR-aniofacial E-volutionary A-llometry), where larger species have proportionally longer faces. Species with higher morphological integration and species more biased towards CREA have diverged farther from their ancestors, and Ruminantia as a clade diversified farther than expected in the direction of CREA. Our analyses indicate that CREA acts as an evolutionary ‘line of least resistance’ and facilitates morphological diversification due to its alignment with the browser-grazer continuum. Taken together, our results demonstrate that constraints at the population-level can produce highly directional patterns of phenotypic evolution at the macroevolutionary scale. Further research is needed to explore how CREA has been exploited in other mammalian clades.

The raw landmark data was retrieved from a previous publication (Haber 2016, https://doi.org/10.5061/dryad.1vm38) and processed in R ('processing_data.R' script). 

This data package includes the necessary R scripts and data to reproduce results presented in the manuscript. The R script "processing_data.R" contains the code needed to clean and wrangle the raw landmark data and ecological data into formats suitable for analysis, "ruminant_functions_Nov22.R" contains the custom scripts written in order to run the analyses and plot the data. The different "FigureX...R" scripts contain the code needed to replicate the different figures and analyses in the manuscript. The 'data' folder contains the data needed for all figures and analysis. The 'app' folder contains the R scripts supporting the interactive morphospaces as a Shiny dashboard.