We examined variation at MHC Class IIB genes in a recently established population of dark-eyed juncos (Junco hyemalis) in a coastal urban environment in southern California, USA relative to an ancestral-range population from a nearby species-typical montane environment. The founding population is estimated to have been quite small, but we predicted that variation at the major histocompatibility complex (MHC) among the founders would nevertheless be preserved owing to the high functional significance of MHC. Previous studies of MHC in songbirds have had varying degrees of success in isolating loci, as passerines show extensive MHC gene duplication. In order to compare diversity in the two populations, we employed two published approaches to sequencing MHC Class II exon 2: direct sequencing with exon-based primers, and traditional cloning and sequencing with intron-based primers. Results from both methods show that the colonist population has maintained high levels of variation. Our results also indicate varying numbers of alleles across individuals, corroborating evidence for gene duplication in songbird MHC. While future studies in songbirds may need to take a genomic approach to fully understand the structure of MHC in this lineage, our results show that it is possible to use traditional methods to reveal functional variation across populations.

中文翻译：

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在最近建立的鸣禽种群中维持 MHC IIB 类多样性

我们检查了最近在美国加利福尼亚州南部沿海城市环境中建立的黑眼 juncos (Junco hyemalis) 种群中 MHC IIB 类基因的变异，相对于来自附近物种典型山地环境的祖先范围种群。创始群体估计相当小，但我们预测，由于 MHC 的高功能意义，创始者之间主要组织相容性复合体 (MHC) 的变异仍将保留。先前对鸣禽的 MHC 研究在分离基因座方面取得了不同程度的成功，因为雀科动物表现出广泛的 MHC 基因重复。为了比较两个群体的多样性，我们采用了两种已发表的方法对 MHC II 类外显子 2 进行测序：使用基于外显子的引物直接测序，以及使用基于内含子的引物进行传统克隆和测序。两种方法的结果表明，殖民人口一直保持着高水平的变异。我们的结果还表明不同个体的等位基因数量不同，证实了鸣禽 MHC 中基因重复的证据。虽然未来对鸣禽的研究可能需要采用基因组方法来充分了解该谱系中 MHC 的结构，但我们的结果表明，可以使用传统方法来揭示不同种群的功能变异。