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

The energy expenditures of mating signals are often divergent between species and influence heterospecific mating, thus mediating the direction of gene flow across the species boundaries. The relative energetics of the mating signals can be underpinned by mitochondrial haplotype 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. Using multiple case studies, we highlighted the connections between mitochondrial functions, mating signal energetics, and hybridization across visual, acoustic, kinesthetic, and chemosensory signaling modalities. Integrating mitochondrial functions and mating signal energetics at the species boundaries will illuminate the organismal mechanisms underlying the formation and maintenance of species boundaries.