Testing character-evolution models in phylogenetic paleobiology: a case study with Cambrian echinoderms
April Wright, Peter J. Wagner, David F. Wright
Abstract
Macroevolutionary inference has historically been treated as a two-step process, involving the inference of a phylogenetic tree, and then inference of a macroevolutionary model using that tree. Newer models, such as the fossilized birth-death model, blend the two steps. These methods make more complete use of fossils than the previous generation of Bayesian phylogenetic models. They also involve many more parameters than prior models, including parameters about which empiricists may have little intuition. In this paper, we set forth a framework for fitting complex, hierarchical models. We ultimately fit and use a joint tree and diversification model to estimate a dated phylogeny of the Cincta (Echinodermata), a morphologically distinct group of Cambrian echinoderms that lack the five-fold radial symmetry characteristic of extant members of the phylum. Although the phylogeny of cinctans remains poorly supported in places, we show how models of character change and diversification contribute to understanding patterns of phylogenetic relatedness and testing macroevolutionary hypotheses. Finally our new analysis raises interesting questions about how incorporating age information is expected to affect a phylogeny, and provides a framework for future systematic and macroevolutionary studies of cinctan echinoderms.