A Total-Group Phylogenetic Metatree for Cetacea and the Importance of Fossil Data in Diversification Analyses

Phylogenetic trees provide a powerful framework for testing
macroevolutionary hypotheses, but it is becoming increasingly apparent
that inferences derived from extant species alone can be highly
misleading. Trees incorporating living and extinct taxa are are needed to
address fundamental questions about the origins of diversity and disparity
but it has proved challenging to generate robust, species--rich
phylogenies that include large numbers of fossil taxa. As a result, most
studies of diversification dynamics continue to rely on molecular
phylogenies. Here, we extend and apply a recently developed meta-analytic
approach for synthesizing previously published phylogenetic studies to
infer a well-resolved set of species level, time-scaled phylogenetic
hypotheses for extinct and extant cetaceans (whales, dolphins and allies).
Our trees extend sampling from the $\sim 90$ extant species to over 500
living and extinct species, and therefore allow for more robust inference
of macroevolutionary dynamics. While the diversification scenarios we
recover are broadly concordant with those inferred from molecular
phylogenies they differ in critical ways, notably in the relative
contributions of extinction and speciation rate shifts in driving rapid
radiations. The metatree approach provides the most immediate route for
generating higher level phylogenies of extinct taxa, and opens the door to
re-evaluation of macroevolutionary hypotheses derived only from extant
taxa.