SICB+ Here we glow again: Convergent evolution of substrate storage in fireflies and ostracods Lau, ES*; Oakley, TH; University of California, Santa Barbara; University of California, Santa Barbara email@example.com https://emlau.weebly.com/
How convergent phenotypes evolve and to what degree this convergence extends across biological levels, or multi-level convergence, is fundamental to understanding evolution. Luminous fireflies and cypridinid ostracod crustaceans (“sea fireflies”) provide an excellent comparative system for understanding multi-level convergence because they produce strikingly similar bioluminescent phenotypes for defense and mate-attraction that are evolutionarily convergent. In line with multi-level convergence, the genetic bases of light production in these organisms are also radically different: Fireflies and ostracods produce light using non-homologous enzymes that react with different bioluminescent substrates. These substrates are chemically unstable, so fireflies and ostracods biochemically modify their bioluminescent substrates for storage. However, it is unknown whether fireflies and ostracods use convergent genetic mechanisms to modify their respective substrates for storage. Here we identified the genetic basis of substrate storage in ostracods and show that fireflies and ostracods use homologous enzymes to modify substrates for storage. Our results reveal that, despite having radically distinct substrates for bioluminescence, fireflies and ostracods evolved convergent mechanisms to modify these substrates for storage. This is the first record of convergence, at a genetic level, in the bioluminescence systems of fireflies and ostracods. Moreover, our findings suggest that these mechanisms evolved convergently because they were functionally constrained by the biochemical modifications necessary for substrate storage in fireflies and ostracods. Generally speaking, studying multi-level convergence addresses longstanding questions on predictability in evolution, like why and how convergent phenotypes arise from similar and disparate evolutionary trajectories.