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.针对一组野生褐鳟（*Salmo trutta* L.）的主要组织相容性复合体（Major histocompatibility complex, MHC）I类连锁微卫星数据与亲权鉴定数据的分析显示，在自然环境中，共享更多MHC I类等位基因的幼鱼会呈现出更紧密的空间聚集特征。该结果验证了实验室实验的预测结论：实验室研究曾证实，幼鱼对与自身共享MHC等位基因的个体存在层级化的结群偏好。全同胞幼鱼均产自同一产卵床（redd），若仅因幼鱼从产卵床扩散范围有限而形成被动的亲属聚集模式（即“产卵床效应”），则所有全同胞幼鱼对的空间分布应无显著差异。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空间距离显著更小，体现出更紧密的聚集趋势：无共享等位基因组：311.5±21.03米（标准误s.e.）；共享1个等位基因组：222.2±14.49米；共享2个等位基因组：124.9±23.88米；P<0.0001。在已知母本不同、无额外亲缘关系（最大似然亲缘系数maximum likelihood relatedness, ML-r=0）的幼鱼对中，同样观测到共享更多MHC I类等位基因的幼鱼聚集更紧密的显著趋势：无共享等位基因组：457.6±3.58米；共享1个等位基因组：422.4±3.86米；共享2个等位基因组：381.7±10.72米；P<0.0001。这类幼鱼对理应源自不同产卵床，因此被动聚集的可能性极低。上述数据表明，共享MHC I类等位基因在全同胞幼鱼离开产卵床后的亲属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MHC介导的亲属聚集相关模式。