The hidden figures at species boundaries: the mitochondrial energetics behind mating signal divergence

The energy expenditure of mating signals is often divergent between species and mediates heterospecific mating, thus influencing the direction of gene flow across the species boundaries. The relative energetics of the mating signals can be underpinned by mitochondrial haplotypic divergence between species, which contributes to hybrid mitonuclear incompatibility and speciation. Here, we discuss the connection between mitochondrial variation, mating signal energetics, and their impact on gene flow across the species boundaries. With multiple case studies, we highlighted the connections between mating signal energetics and gene flow across visual, acoustic, kinesthetic, and chemosensory signaling modalities. Integrating mitochondrial functions and mating signal energetics at the species boundaries will illuminate the organismal mechanism underlying the formation and maintenance of species boundaries.