Red queen for a day: models of symmetry and selection in paleoecology

The Unified Theory of Biodiversity (UNTB), the Red Queen’s Hypothesis (RQH), and the Cascading Extinctions on Graphs hypothesis (CEG) are explored as members of a spectrum describing the ecological partitioning of species richness. All are models of historical biodiversity, but fare differently in explaining observed features of Phanerozoic biodiversity. The models treat species as symmetric, asymmetric, or partially symmetric respectively. Symmetry in the UNTB is broken by the generation and selection of variation of ecological performance, while the robustness and hence longevity of RQ communities are subject to selection. The CEG model reconciles some of the differences, demonstrating the importance of functional partitioning to both species evolution and selection at the community level. It is concluded that the UNTB explains communities partially on the shortest of evolutionary time scales, while RQ communities would be, at best, geologically ephemeral yet conditionally important.