Data from: Spatio-temporal variation in parasite communities maintains diversity at the major histocompatibility complex class IIβ in the endangered Rio Grande Silvery Minnow

Climate change will strongly impact aquatic ecosystems particularly in arid and semi-arid regions. Fish-parasite interactions will also be affected by predicted altered flow and temperature regimes, and other environmental stressors. Hence, identifying environmental and genetic factors associated with maintaining diversity at immune genes is critical for understanding species' adaptive capacity. Here we combine genetic (MHC Class IIβ and microsatellites), parasitological and ecological data to explore the relationship between these factors in the remnant wild Rio Grande silvery minnow (Hybognathus amarus) population, an endangered species found in the southwestern United States. Infections with multiple parasites on the gills were observed and there was spatio-temporal variation in parasite communities and patterns of infection among individuals. Despite its highly endangered status and chronically low genetic effective size, Rio Grande silvery minnow had high allelic diversity at MHC Class IIβ with more alleles recognised at the presumptive DAB1 locus compared to the DAB3 locus. We identified significant associations between specific parasites and MHC alleles against a backdrop of generalist parasite prevalence. We also found that individuals with higher individual neutral heterozygosity and higher amino acid divergence between MHC alleles, had lower parasite abundance and diversity. Taken together, these results suggest a role for fluctuating selection imposed by spatio-temporal variation in pathogen communities and divergent allele advantage in maintenance of high MHC polymorphism. Understanding the complex interaction of habitat, pathogens and immunity in protected species will require integrated experimental, genetic and field studies.

气候变化将对水生生态系统造成强烈冲击，在干旱与半干旱区域表现尤为显著。鱼类与寄生虫的相互作用亦将受到预期的径流与温度格局改变，以及其他环境胁迫因子的影响。因此，识别与免疫基因多样性维持相关的环境与遗传因素，对于解析物种的适应性潜能至关重要。本研究整合了遗传（主要组织相容性复合体II类β链（MHC Class IIβ）与微卫星标记（microsatellites））、寄生虫学与生态学数据，旨在探究美国西南部濒危物种——残存野生格兰德河银小鱼（Hybognathus amarus）种群中上述因素间的关联。研究观察到鳃部存在多种寄生虫感染现象，且寄生虫群落结构与个体间感染模式均存在时空变异。尽管格兰德河银小鱼处于高度濒危状态，且长期维持较低的有效种群规模，但其主要组织相容性复合体II类β链位点仍具有较高的等位基因多样性，且推定的DAB1基因座所识别的等位基因数量多于DAB3基因座。我们在广谱性寄生虫普遍流行的背景下，鉴定出特定寄生虫与MHC等位基因间存在显著关联。此外，研究发现，个体中性标记杂合度更高、MHC等位基因间氨基酸分歧度更大的个体，其寄生虫丰度与多样性均更低。综合上述结果，本研究表明，由病原群落时空变异所施加的波动选择，以及等位基因分化优势，在维持高MHC多态性过程中发挥了重要作用。理解受保护物种的生境、病原体与免疫之间的复杂相互作用，需要整合实验、遗传与野外研究工作。