Let there be nightlights: the ecological role of bioluminescence in a Costa Rican mushroom

Both marine and terrestrial organisms produce light enzymatically in a process called bioluminescence. Though the ecological role of light production is known for some species, such as fireflies and bacteria, the ecological role in mushroom-producing fungi remains relatively unexplored, particularly in Central America. Here, we discovered a bioluminescent mushroom in the high-elevation oak forests of Costa Rica. We developed mushroom models with Light-Emitting Diodes (LEDs) producing various colors: green, blue, red, and yellow. Over three consecutive evenings after sunset, we applied Tanglefoot invertebrate-trapping glue to both mushroom models and actual mushrooms, and collected the traps before sunrise, then identified the trapped invertebrates to Order. We found green LED traps attracted more invertebrates than non-lit control traps, suggesting that light functions to attract invertebrates. The majority of invertebrates attracted to the green lights were Dipteran flies, who would be capable of dispersing fungal spores. The higher-intensity green LEDs attracted more total invertebrates than the dimmer mushrooms, but the results were not significant. Though we predicted that the invertebrate assemblages attracted to green lights would be similar to the invertebrate assemblage attracted to actual mushrooms, the results were not significant. Similarly, the red, blue, and yellow LEDs attracted fewer invertebrates than the green LEDs, but the differences in community composition were not statistically significant. Our findings corroborate other similar studies in tropical regions that found bioluminescent mushrooms may attract invertebrates.