Determining the amount and distribution of genetic variation represents a fundamental step for the inference of evolutionary processes acting on populations of endangered species. For these species, adaptive evolutionary potential is highly reduced by the loss of genetic variation due to drift. Here, we examined genetic diversity at the mitochondrial control region (CR), 17 microsatellites, and six Toll-like receptor (TLR) genes, known to play a key role on the innate immune response of vertebrates in the Antioquia wren (AW) Thryophilus sernai, an endangered passerine bird inhabiting the remnant fragments of tropical dry forest in the northernmost part of the Cauca river canyon, Colombia. We found very low variation for the three types of markers. The CR showed scarce variability, while only six of the 17 microsatellites analyzed and two of the six TLRs sequenced were polymorphic. Population structure analyses suggest the occurrence of one single population in the area. Selection tests could not detect signatures of positive selection for the variable sites in the species, and assessment of amino acid changes found within the lineage do not suggest any functional effects that could be associated to selection in either polymorphic TLR loci. Comparisons with species showing widespread and restricted distribution supports a low TLR variability typical of small populations. These results suggest current low evolutionary potential for the species, as its reduced genetic diversity is expected to increase extinction risk by limiting the ability to cope with environmental changes. Our study supports current evidence suggesting drift as the main driver shaping TLR variation.

确定遗传变异的数量和分布是推断作用于濒危物种种群的进化过程的基本步骤。对于这些物种，由于漂移导致遗传变异的丧失，适应性进化潜力大大降低。在这里，我们检查了线粒体控制区（CR），17个微卫星和6个Toll样受体（TLR）基因的遗传多样性，已知这些基因在脊椎动物Antioquia wren（AW）Thryophilus的先天免疫应答中起关键作用塞内是一种濒临灭绝的雀形目鸟，栖息在哥伦比亚考卡河峡谷最北端的热带干燥森林的残留碎片中。我们发现这三种标记物的变异非常低。CR显示出很少的变异性，而分析的17个微卫星中只有6个和6个TLR序列中的2个是多态的。人口结构分析表明，该地区只有一个人口。选择测试无法检测到物种中可变位点的阳性选择特征，并且对谱系内发现的氨基酸变化的评估未表明任何与多态性TLR基因座中的选择有关的功能作用。与显示分布广泛且受限制的物种进行的比较支持了小种群典型的低TLR变异性。这些结果表明该物种当前的低进化潜力，因为其遗传多样性的降低有望通过限制应对环境变化的能力而增加灭绝风险。我们的研究支持目前的证据，表明漂移是影响TLR变化的主要因素。