Shared biochemical pathways for ornamentation and immune function: Rethinking the mechanisms underlying honest signaling of parasite resistance

Abstract Biologists have long considered the potential for individuals to assess mating displays of prospective mates as a source of information about parasite load and the potential to resist future infection. For decades, resource trade-offs were proposed to be the mechanism that would create an uncheatable connection between immune defenses and the production of the display. However, new theory emphasizes signaling based on shared biochemical pathways that are required for both immune defense and display production. Because shared pathways at the subcellular level may underlie variation in both immune performance and behavior, biologists are increasingly looking to mitochondrial function for explanations as to why links between parasite resistance and mating displays might be fundamental.