Data from: Phylogenetic sampling affects evolutionary patterns of morphological disparity

Cladistic character matrices are routinely repurposed in analyses of
morphological disparity. Unfortunately, the sampling of taxa and
characters within such datasets reflects their intended application - to
resolve phylogeny, rather than distinguish between phenotypes - resulting
in tree shapes that often misrepresent broader taxonomic and morphological
diversity. Here we use tree shape as a proxy to explore how sampling can
affect perceptions of evolving morphological disparity. Through analyses
of simulated and empirical data, we demonstrate that sampling can
introduce biases in trait space occupation between clades that are
predicted by differences in tree symmetry and branch length distribution.
Symmetrical trees with relatively long internal branches predict more
expansive patterns of trait space occupation. Conversely, asymmetrical
trees with relatively short internal branches predict more compact
distributions. Additionally, we find that long external branches predict
greater phenotypic divergence by peripheral morphotypes. Taken together,
our results caution against the uncritical repurposing of cladistic
datasets in disparity analyses. However, they also demonstrate that when
morphological diversity is proportionately sampled, differences in tree
shape between clades can speak to genuine differences in morphospace
occupation. While cladistic datasets may serve as a useful starting point,
disparity datasets must attempt to achieve uniformity of lineage sampling
across time and topology. Only when all potential sources of bias are
accounted for can genuine evolutionary phenomena be distinguished from
artefactual signals. It must be accepted that the non-uniformity of the
fossil record may preclude representative sampling and, therefore, a
faithful characterization of the evolution of morphological disparity.