MEPS 594:193-201 (2018)  -  DOI: https://doi.org/10.3354/meps12540

ABSTRACT: Lunar or semi-lunar cycles of reproduction are a widespread phenomenon in marine organisms. It is common practice to infer the adaptive value of these reproductive cycles based on the population-level pattern. This practice may be flawed if there are multiple types of individuals within the population employing different reproductive cycles. Such phenotypic diversity can be thought of in terms of alternative, mixed or conditional strategies. Here, we capitalized on a long-term field study and a carefully controlled laboratory experiment of individually identifiable clown anemonefish Amphiprion percula to investigate the individual-level strategies underlying population-level patterns of reproduction. The field study revealed that A. percula exhibit a lunar cycle of reproduction at the population level, and that there is naturally occurring variation among and within individuals in the number of times they reproduce per month. The laboratory experiment revealed that the number of times individuals reproduce per month is dependent on their food availability. Individuals employed a conditional strategy with 3 tactics: reproduce 1, 2 or 3 times mo^-1, depending on food availability. Breaking down the population-level pattern by reproductive tactic, we showed that each reproductive tactic has its own non-random lunar, semi-lunar (½ lunar) or trient-lunar (⅓ lunar) cycle of reproduction. We conclude that the adaptive value of A. percula reproductive cycles, and likely the reproductive cycles of many other marine organisms, should not be inferred from the population-level pattern. Instead, the adaptive value of lunar, semi-lunar and trient-lunar cycles should be investigated for the individuals that express them.

KEY WORDS: Reproductive cycles · Spawning patterns · Phenotypic plasticity · Animal behavior · Adaptive value · Clownfish · Coral reef fish · Marine ecology