TAXON INCOMPLETENESS AND DISCRETE TIME BINS AFFECT CHARACTER CHANGE RATES IN SIMULATED DATA

Abstract

Estimating how fast or slow morphology evolves through time (phenotypic change rate; PR) has become common in macroevolutionary studies, and has been important for clarifying key evolutionary events. However, the inclusion of incompletely scored taxa (e.g., fossils) could affect PR estimates and potentially mask real PR patterns. This effect being also affected by the usage of arbitrary discrete time bins. Here, the impact of taxon incompleteness (unscored data) on PR estimates is assessed in simulated data. Three different time bin series were likewise evaluated: bins evenly spanning the tree length (i), a shorter middle bin (ii), and a longer middle bin (iii). The results indicate that PR values decrease as taxon incompleteness increases. Statistical significant PR values, and the dispersion among PR values, depended on the time bins. These outcomes imply that taxon incompleteness can undermine our capacity to infer morphology evolutionary dynamics and that these estimates are also influenced by our choice of discrete time bins. More importantly, the present results stress the need for a better approach to deal with taxon incompleteness and arbitrary discrete time bins.