Data from: MHC-mediated spatial distribution in brown trout (Salmo trutta) fry

Major histocompatibility complex (MHC) class I-linked microsatellite data and parental assignment data for a group of wild brown trout (Salmo trutta L.) provide evidence of closer spatial aggregation among fry sharing greater numbers of MHC class I alleles under natural conditions. This result confirms predictions from laboratory experiments demonstrating a hierarchical preference for association of fry sharing MHC alleles. Full-siblings emerge from the same nest (redd), and a passive kin association pattern arising from limited dispersal from the nest (redd effect) would predict that all such pairs would have a similar distribution. However, this study demonstrates a strong, significant trend for reduced distance between pairs of full-sibling fry sharing more MHC class I alleles reflecting their closer aggregation (no alleles shared, 311.5±(s.e.)21.03m; one allele shared, 222.2±14.49m; two alleles shared, 124.9±23.88m; P<0.0001). A significant trend for closer aggregation among fry sharing more MHC class I alleles was also observed in fry pairs, which were known to have different mothers and were otherwise unrelated (ML-r=0) (no alleles: 457.6±3.58m; one allele (422.4±3.86 m); two alleles (381.7±10.72 m); P<0.0001). These pairs are expected to have emerged from different redds and a passive association would then be unlikely. These data suggest that sharing MHC class I alleles has a role in maintaining kin association among full-siblings after emergence. This study demonstrates a pattern consistent with MHC-mediated kin association in the wild for the first time.针对野生褐鳟（Salmo trutta L.）群体的主要组织相容性复合体（Major histocompatibility complex, MHC）I类连锁微卫星数据和亲本分型数据表明，自然环境中共享更多MHC I类等位基因的幼鱼存在更为紧密的空间聚集现象。该结果验证了实验室实验的相关预测：此前的实验室研究已证实，幼鱼对共享MHC等位基因的同伴存在层级化的社交偏好。 全同胞幼鱼均诞生于同一产卵巢（redd），若仅因从产卵巢扩散受限而形成被动的亲缘聚集模式（即“巢效应”），则所有全同胞对的空间分布应趋于一致。但本研究发现，共享更多MHC I类等位基因的全同胞幼鱼对之间的距离显著更小，体现出更紧密的空间聚集（无共享等位基因：311.5±21.03（标准误）m；共享1个等位基因：222.2±14.49m；共享2个等位基因：124.9±23.88m；P<0.0001）。 此外，在已知母本不同且无其他亲缘关系（最大似然亲缘系数ML-r=0）的幼鱼对中，同样观察到共享更多MHC I类等位基因的幼鱼聚集更紧密的显著趋势（无共享等位基因：457.6±3.58m；共享1个等位基因：422.4±3.86m；共享2个等位基因：381.7±10.72m；P<0.0001）。这类幼鱼对均被认为诞生于不同的产卵巢，因此被动聚集的可能性微乎其微。 上述数据表明，共享MHC I类等位基因在全同胞幼鱼诞生后的亲缘聚集维持过程中发挥了重要作用。本研究首次在野生环境中证实了由MHC介导的亲缘聚集相关分布模式。