Living in sympatry via differentiation in time, space and display characters of courtship behaviors of bioluminescent marine ostracods

Distinguishing among courtship signals can be extremely important for individuals in regions where related species co-occur, including among sympatric species pairs and along hybrid zones. Reef habitats off the coast of Belize are shared by bioluminescent ostracods that perform nightly bioluminescent displays used in courtship. These displays vary in light pulse durations, interpulse distances and intervals, and direction. Here, we test how six sympatric species of marine ostracods (three described and three undescribed species) partition the display arena in time and space. Males from all six species can be differentiated based on morphology and species-specific luminescent display traits. Timing of nightly courtship display initiation and peak display timing differed among species by 5–25 min, and the order of appearance for each species was consistent across nights. In addition to varying temporally, species used different microhabitats (grassbed, sand channels, reef slopes and reef crest) for their courtship displays. Our findings support the hypothesis that species with more similar display traits (pulse duration, interpulse distance, number of pulses) differ most in the time and space used for courtship. The large number of axes for displacement of both luminescent display traits and spatio-temporal habitat use for courtship suggests that ostracods have the genetic toolkit for rapid diversification. This species complex living in sympatry yields a rich system for testing how genetic determination of behavioral traits relates to sexual selection and speciation.