Parental care drives the evolution of male reproductive accessory glands across ray-finned fishes

Reproductive accessory glands are organs involved in reproduction that do not directly produce or release gametes but can play crucial roles in securing reproductive success. In fishes, the 2 leading hypotheses about why accessory glands evolved are (1) in response to sperm competition, or (2) to facilitate parental care activities. Here, we investigate the evolutionary history of accessory glands and test these hypotheses by estimating …