INCLUDING FOSSIL TIPS OFTEN, BUT NOT ALWAYS, VASTLY IMPROVES THE RECONSTRUCTION OF TRAIT EVOLUTION USING PHYLOGENETIC COMPARATIVE METHODS

Collecting data for use in constructing phylogenies is a valuable but time- and resource-consuming pursuit. As a result, indicators of the potential value of including certain species in a phylogeny a priori could prove useful when planning this stage of research. Here, we used a simulation approach to investigate whether there are trends in the ability for phylogenetic comparative methods to recover the correct model of trait evolution based on certain characteristics of the phylogeny. First, we used an array of different diversification rates to simulate phylogenies containing varying proportions of fossil and extant tips. We then simulated the evolution of a single trait across each phylogeny using multiple continuous trait evolution models. We then compared the fit of the correct and incorrect models to the simulated traits. Finally, we assessed the importance of the phylogenetic and functional uniqueness of individual tips to recover the correct model of evolution. This quantitative evaluation allows us to discern whether there are certain tip characteristics or phylogeny shapes associated with identifying the correct trait evolution models. Our preliminary results indicate that the inclusion of fossils can be highly beneficial to reconstructing certain trait histories (e.g., Ornstein-Uhlenbeck and ACDC) but not to others (e.g., Brownian motion). In fact, in many cases, increasing the proportion of fossils in a phylogenetic dataset is far more beneficial and perhaps more time- and resource-efficient than increasing the overall number of taxa in the dataset. As a whole, these results provide valuable insights into the planning and construction of phylogenetic datasets that include both modern and fossil taxa.