Data from: Genetic parentage analysis confirms a polygynandrous breeding system in the European grayling (Thymallus thymallus)

Knowing the breeding system of a species is important in order to understand individual variation in reproductive success. Large variation in reproductive success and thus reproductive skew strongly impacts on the effective number of breeders and thus the long-term effective population size (Ne). Fishes, in particular species belonging to the salmonid family, exhibit a wide diversity of breeding systems. In general, however, breeding systems are rarely studied in detail in the wild. Here we examine the breeding system of the spring-spawning European grayling Thymallus thymallus from a small Norwegian stream using parentage assignment based on the genotyping of 19 polymorphic microsatellite loci. In total 895 individual grayling fry and 154 mature grayling (57 females and 97 males) were genotyped. A total of 466 offspring were assigned a father, a mother, or a parent pair with a confidence of 90% or higher. Successfully reproducing males had on average 11.9 ± 13.3 (SD) offspring with on average 2.1 ± 1.2 partners, whereas successful females had on average 9.5 ± 12.8 offspring and 2.3 ± 1.5 partners. Parents with more partners also produced more offspring. Thus the grayling breeding system within this small stream revealed a polygynandrous breeding system, similar to what has been observed for many other salmonid fish species. The present study thus unambiguously corroborates a polygynadrous breeding system in the European grayling. This knowledge is critical for managing populations of this species, which has suffered significant local population declines throughout its range over the last several decades.

了解物种的繁殖系统，是理解繁殖成功率个体差异的核心前提。繁殖成功率的显著差异及其引发的繁殖偏斜（reproductive skew），会对有效繁殖者数量乃至长期有效种群规模（Ne）产生极强的影响。鱼类，尤其是鲑科（salmonid）鱼类，展现出极为丰富的繁殖系统多样性。但总体而言，野外自然种群的繁殖系统鲜少被深入研究。本研究以挪威一处小型溪流中的春季产卵欧洲茴鱼（Thymallus thymallus）为研究对象，基于19个多态性微卫星位点的基因分型结果开展亲权鉴定（parentage assignment），以此解析其繁殖系统。本研究共对895尾茴鱼幼体及154尾成熟个体（57尾雌性、97尾雄性）进行了基因分型。总计466尾幼体获得了置信度不低于90%的父本、母本或完整亲本对鉴定结果。成功繁殖的雄性个体平均可产生11.9±13.3（标准差，SD）尾后代，平均拥有2.1±1.2个配偶；而成功繁殖的雌性个体平均可产生9.5±12.8尾后代，平均拥有2.3±1.5个配偶。配偶数量更多的亲本，其后代数量也更多。由此可见，该小型溪流中的欧洲茴鱼繁殖系统属于多元交配制（polygynandrous），与诸多其他鲑科鱼类的繁殖特征一致。本研究因此明确证实了欧洲茴鱼存在多元交配的繁殖系统。这一研究结果对于该物种的种群管理具有至关重要的指导意义：近数十年来，欧洲茴鱼在其整个分布范围内均出现了显著的局地种群衰退。