Скачать или смотреть The evolution of reproductive accessory glands across fishes | Lucas Eckert

Reproductive accessory glands are organs involved in reproduction but not directly in the production or release of gametes. In fish, the function of these glands has only been described in a handful of species, where they appear to play diverse and crucial roles in reproduction. To date, the selective factors leading to the evolution of accessory glands in fishes remain a mystery with two leading alternative hypotheses — they evolved in response to pressures from sperm competition and/or from parental care. In this study, we tested these hypotheses and explored the evolutionary past of accessory glands. To do so, we conducted a systematic literature survey on ray-finned fishes, documenting the presence or absence of male reproductive accessory glands, as well as information regarding parental care, spawning behaviour, and mating system, for 618 species, representing 267 families. We found accessory glands in 26 different families and 116 species, with the majority of species found in three clades: the blennies, the gobies, and the catfish. We then reconstructed the evolutionary history of reproductive accessory glands using stochastic character mapping and found that accessory glands were gained 14-18 times and lost 7-11 times in ray-finned fishes. By using a Bayesian analysis of correlation between discrete binary traits and comparing transition rate estimates, we show that reproductive accessory glands are strongly correlated with, and are more likely to appear in, lineages with male parental care, pair spawning, and females mating with only one male. The strong association between accessory glands and male parental care supports the hypothesis that these glands arose as a means to enhance parental care activities. The associations with pair spawning and female monogamy provide no evidence for the sperm competition hypothesis. This study represents the first large-scale phylogenetic comparative analysis of accessory glands across fishes and provides novel insights into the evolution of an important and complex aspect of reproduction.