Calibrating phylogenies assuming bifurcation or budding alters inferred macroevolutionary dynamics in a densely sampled phylogeny of bivalve families
Crouch, Nicholas et al. (2021), Calibrating phylogenies assuming bifurcation or budding alters inferred macroevolutionary dynamics in a densely sampled phylogeny of bivalve families, Dryad, Dataset, https://doi.org/10.5061/dryad.1vhhmgqsd
Analyses of evolutionary dynamics can be profoundly affected by age calibrations of phylogenetic nodes under different models of lineage branching. Most time-calibrated molecular phylogenies of extant taxa assume a purely bifurcating model, where nodes are calibrated using the daughter lineage with the older first occurrence in the fossil record. Lineages can also split via budding, in which a parent lineage persists following the origin of a daughter lineage, and nodes are calibrated using the age of the lineage with the younger first occurrence. Here, we use the extensive fossil record of bivalve molluscs for a large-scale empirical test of how the choice of branching model affects macroevolutionary analyses. We time-calibrated 91% of nodes in a phylogeny of 97 extant bivalve families using 86 calibration points ranging in age from 2.59 to 485 Ma. Allowing budding-based calibrations minimizes conflict between the tree topology and timing of evolutionary events in the fossil record, reducing the summed duration of inferred “ghost lineages,” from 6.76 billion yrs (Gyr; bifurcating model) to 1.00 Gyr (budding model). Adding 31 extinct paraphyletic families – many major groups contain such extinct taxa – shifts deep splits further back in time and raises ghost-lineage totals to 7.86 Gyr (bifurcating) and 1.92 Gyr (budding), but more accurately reflects the time since separation of lineages. Lineage-through-time plots from phylogenetic data scaled under a bifurcating model of evolution push more inferred bivalve diversification into the Paleozoic, conflicting with other palaeontological evidence on the magnitude of the end-Paleozoic extinction and subsequent recovery, and strongly reduce the magnitude of the Cenozoic diversification of the group. Consideration of the hypothesized branching model within a given clade is essential when node-calibrating phylogenies, and for a major clade with a robust fossil record, an evolutionary model that allows budding and does not force bifurcations is the most appropriate one, and likely common for many other clades as well.
National Science Foundation, Award: EAR-0922156
National Science Foundation, Award: DEB-0732854
National Aeronautics and Space Administration, Award: EXOB08-0089