Reticulated flatwoods salamander (Ambystoma bishopi) populations began decreasing dramatically in the 1900s. Contemporary populations are small, isolated, and may be susceptible to inbreeding and reduced adaptive potential because of low genetic variation. Genetic variation at immune genes is especially important as it influences disease susceptibility and adaptation to emerging infectious pathogens, a central conservation concern for declining amphibians. We collected samples from across the extant range of this salamander to examine genetic variation at major histocompatibility complex (MHC) class Iα and IIβ exons as well as the mitochondrial control region. We screened tail or toe tissue for ranavirus, a pathogen associated with amphibian declines worldwide. Overall, we found low MHC variation when compared to other amphibian species and did not detect ranavirus at any site. MHC class Iα sequencing revealed only three alleles with a nucleotide diversity of 0.001, while MHC class IIβ had five alleles with a with nucleotide diversity of 0.004. However, unique variation still exists across this species' range with private alleles at three sites. Unlike MHC diversity, mitochondrial variation was comparable to levels estimated for other amphibians with nine haplotypes observed, including one haplotype shared across all sites. We hypothesize that a combination of a historic disease outbreak and a population bottleneck may have contributed to low MHC diversity while maintaining higher levels of mitochondrial DNA variation. Ultimately, MHC data indicated that the reticulated flatwoods salamander may be at an elevated risk from infectious diseases due to low levels of immunogenetic variation necessary to combat novel pathogens.

中文翻译：

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濒临灭绝的网状扁平木sal（Ambystoma bishopi）的退化主要组织相容性复杂变异。

在1900年代，网状sal木（Ambystoma bishopi）种群开始急剧减少。当代的种群很小，孤立，由于遗传变异低，可能易于近交繁殖并降低适应潜力。免疫基因的遗传变异特别重要，因为它影响疾病的易感性以及对新兴传染病原体的适应性，这是两栖动物数量下降的主要保护重点。我们从该sal的广泛范围收集了样本，以检查主要组织相容性复合体（MHC）Iα和IIβ类外显子以及线粒体控制区的遗传变异。我们在鼻或脚趾组织中筛选了鼻病毒，这种病毒与全球两栖动物数量减少有关。总体，与其他两栖动物相比，我们发现MHC变异较低，并且在任何位置均未检测到鼻病毒。MHCIα类测序仅发现3个等位基因，核苷酸多样性为0.001，而MHCIIβ类具有5个等位基因，核苷酸多样性为0.004。但是，该物种的范围内仍然存在独特的变异，在三个位点有私人等位基因。与MHC多样性不同，线粒体变异与其他两栖动物的估计水平相当，观察到九种单倍型，包括在所有位点共有的一种单倍型。我们假设历史性疾病暴发和人口瓶颈相结合可能导致低MHC多样性，同时保持较高水平的线粒体DNA变异。最终，