Abstract
The kind and duration of phylogenetic topological “signatures” left in the wake of macroevolutionary events remain poorly understood. To this end, we examined a broad range of simulated phylogenies generated using trait-biased, heritable speciation probabilities and mass extinction that could be either random or selective on trait value, but also using background extinction and diversity-dependence to constrain clade sizes. In keeping with prior results, random mass extinction increased imbalance of clades that recovered to pre-extinction size, but was a relatively weak effect. Mass extinction that was selective on trait values tended to produce clades of similar or greater balance compared to random extinction or controls. Allowing evolution to continue past the point of clade-size recovery resulted in erosion and eventual erasure of this signal, with all treatments converging on similar values of imbalance, except for very intense extinction regimes targeted at taxa with high speciation rates. Return to a more balanced state with extended post-extinction evolution was also associated with loss of the previous phylogenetic root in most treatments. These results further demonstrate that while a mass extinction event can produce a recognizable phylogenetic signal, its effects become increasingly obscured the further an evolving clade gets from that event, with any sharp imbalance due to unrelated evolutionary factors.
Highlights
How the interplay of speciation and extinction has shaped the Tree of Life remains one of the chief unsolved mysteries of evolutionary biology
Mass extinctions can contribute to, but not maintain, increased imbalance. Our results extend those of Heard and Mooers [45], examining the long-term consequences of recovery from random vs. selective mass extinctions when speciation probability is determined by a heritable trait
Our results again demonstrate that mass extinction that acts randomly on clades with traitbiased speciation probability produces greater imbalance than that acting in a directionallyselective manner
Summary
How the interplay of speciation and extinction has shaped the Tree of Life remains one of the chief unsolved mysteries of evolutionary biology. Processes of origination of new taxa are countered by a steady, low rate of species deaths (background extinction), as well as infrequent but highly destructive episodes of mass extinction. Tree shape should encode the evolutionary history of the described clade. Metrics of phylogenetic tree shape such as tree. Erasure of tree balance signature by continued evolution
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