Genetic diversity is important for long‐term viability of a population. Low genetic diversity reduces persistence and survival of populations and increases susceptibility to diseases. Comparisons of the neutral markers with functional loci such as immune genes [Toll‐like receptors; TLR] can provide useful insights into evolutionary potential of a species and how the diversity of pathogens and selection pressures on their hosts are directly linked to their environment. In this study, we compare genetic diversity in neutral (eleven microsatellite loci) and adaptive (seven TLR loci) loci to determine genetic variation in a nonmigratory western Himalayan passerine, the black‐throated tit (Aegithalos concinnus), distributed across an elevation gradient with varying degree of pathogen‐mediated selection pressure. We further compare the diversity in TLR loci with a high‐elevation sister species, the white‐throated tit (Aegithalos niveogularis). Our results indicate a lack of population genetic structure in the black‐throated tit and signatures of a past bottleneck. In contrast, we found high diversity in TLR loci and locus‐specific (TLR7) signatures of pathogen‐mediated selection, which was comparable to diversity in the white‐throated tit. Levels of diversity at TLR5 locus corresponded very closely with neutral microsatellite variation. We found evidence of positive selection in TLR1LA, TLR5, and TLR7 loci highlighting the importance in pathogen recognition. Our finding demonstrates that reduction in neutral variation does not necessarily lead to reduction in functional genetic diversity and probably helps in revival of population in a widespread species.

中文翻译：

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遗传漂移和瓶颈不会在喜马拉雅雀形目中的小空间尺度上影响Toll样受体基因的多样性

遗传多样性对于人口的长期生存能力至关重要。遗传多样性低会降低种群的持久性和生存率，并增加对疾病的易感性。中性标记与功能基因座（例如免疫基因）的比较[Toll样受体；[TLR]可以提供有用的见识，以了解物种的进化潜力以及病原体的多样性和寄主选择压力如何直接与其环境相关联。在这项研究中，我们比较了中性（11个微卫星基因座）和适应性（7个TLR基因座）基因座的遗传多样性，以确定非迁移性西喜马拉雅pass鱼碱（黑喉山雀（Aegithalos concinnus））分布在海拔高度梯度上，且病原体介导的选择压力程度不同。我们进一步比较了TLR基因座与高海拔姐妹物种白喉山雀（Aegithalos niveogularis）。我们的研究结果表明，黑喉山雀缺乏种群遗传结构，且过去的瓶颈特征不明显。相比之下，我们发现病原体介导的选择的TLR基因座和基因座特异性（TLR7）标记具有高度多样性，这与白喉山雀的多样性相当。TLR5基因座的多样性水平与中性微卫星变异非常接近。我们在TLR1LA，TLR5和TLR7基因座中发现了阳性选择的证据，突显了病原体识别的重要性。我们的发现表明，中性变异的减少不一定会导致功能遗传多样性的减少，并且可能有助于恢复广泛物种的种群数量。