On the Origin of Coexisting Species

Speciation is frequently initiated but rarely completed, a phenomenon hypoth-esized to arise due to the failure of nascent lineages to persist. Although a fail-ure to persist often has ecological causes, key gaps exist between ecological and evolutionary theories that, if filled, would clarify when and why speciation succeeds or fails. Here, we apply ecological coexistence theory to show how the alignment between different forms of niche opportunity and niche use shape the initiation, progression, and completion of speciation. Niche evolu-tion may drive coexistence or competitive exclusion, and an ability to coexist ecologically may help or hinder speciation. Our perspective allows progress towards unifying the origin and maintenance of species diversity across the tree of life.

Automated summary

Speciation often begins but rarely completes, possibly due to the failure of nascent lineages to persist. Key gaps between ecological and evolutionary theories exist, and bridging these gaps can help clarify the success or failure of speciation. The application of ecological coexistence theory can aid in understanding the initiation, progression, and completion of speciation, and contribute to unifying the origin and maintenance of species diversity across the tree of life.