Our understanding of mechanisms operating over deep timescales to shape phenotypic diversity often hinges on linking variation in one or few trait(s) to specific evolutionary processes. When distinct processes are capable of similar phenotypic signatures, however, identifying these drivers is difficult. We explored ecomorphological evolution across a radiation of ground-dwelling squirrels whose history includes convergence and constraint, two processes that can yield similar signatures of standing phenotypic diversity. Using 4 ecologically-relevant trait datasets (body size, cranial, mandibular, and molariform tooth shape), we compared and contrasted variation, covariation, and disparity patterns in a new phylogenetic framework. Strong correlations existed between body size and 2 skull traits (allometry) and among skull traits themselves (integration). Inferred evolutionary modes were also concordant across traits (Ornstein-Uhlenbeck with 2 adaptive regimes). However, despite these broad similarities, we found divergent dynamics on the macroevolutionary landscape, with phenotypic disparity being differentially shaped by convergence and conservatism. Such among-trait heterogeneity in process (but not always pattern) reiterates the mosaic nature of morphological evolution, and suggests ground squirrel evolution is poorly captured by single process descriptors. Our results also highlight how use of single traits can bias macroevolutionary inference, affirming the importance of broader trait-bases in understanding phenotypic evolutionary dynamics.

Supp_Data_1_mtDNASpreadsheet list of mitochondrial DNA sequences used in phylogenetic inference, with publication names and web location accessed.Supp_Data_2_UCE_backbonesList of UCE-derived backbone topologies used in this study, in Newick format.Supp_Data_3_bootstrapped_treesList of species-level phylogenetic hypotheses used in this study, in Newick format, with branch lengths.Supp_Data_4_cranial_shapeSpreadsheet containing new cranial morphometric data published in this study. Tabs contain 1) list of museum specimens used along with housing institutions and provenance; 2) list of codes describing those housing institutions, and; 3) centroid sizes and Procrustes-aligned landmark data for all specimens.Supp_Data_5_evol_model_parametersList of macroevolutionary process model parameters inferred in this study for all morphological structures. These parameters were also used as the input for trait simulation.