Perspective: A Fitness Landscape Perspective on Species Boundary and Gene Flow for Taxonomic Practitioners in the Genomic Era.

Speciation can be conceptualized as evolution across dynamic fitness landscapes, where groups of individuals occupy peaks or plateaus that change across space and time. Within such landscapes, gene flows between species can be expected outcomes, which result in the episodic and temporal permeability of species boundaries. Because species recognition and gene flow both arise from the same underlying fitness landscape dynamics, they are emergent, instead of causally linked, properties. Therefore, despite their frequent correlation, studies in systematics should decouple species recognition from the presence or absence of gene flow.