Despite widespread variability and redundancy abounding animal immunity, little is currently known about the rate of evolutionary convergence (functionally analogous traits not inherited from a common ancestor) in host molecular adaptations to parasite selective pressures. Toll‐like receptors (TLRs) provide the molecular interface allowing hosts to recognize pathogenic structures and trigger early danger signals initiating an immune response. Using a novel combination of bioinformatic approaches, here we explore genetic variation in ligand‐binding regions of bacteria‐sensing TLR4 and TLR5 in 29 species belonging to the tit family of passerine birds (Aves: Paridae). Three out of the four consensual positively selected sites in TLR4 and six out of 14 positively selected positions in TLR5 were located on the receptor surface near the functionally important sites, and based on the phylogenetic pattern evolved in a convergent (parallel) manner. This type of evolution was also seen at one N‐glycosylation site and two positively selected phosphorylation sites, providing the first evidence of convergence in post‐translational modifications in evolutionary immunology. Finally, the overall mismatch between phylogeny and the clustering of surface charge distribution demonstrates that convergence is common in overall TLR4 and TLR5 molecular phenotypes involved in ligand binding. Our analysis did not reveal any broad ecological traits explaining the convergence observed in electrostatic potentials, suggesting that information on microbial symbionts may be needed to explain TLR evolution. Adopting state‐of‐the‐art predictive structural bionformatics, we have outlined a new broadly applicable methodological approach to estimate the functional significance of positively selected variation and test for the adaptive molecular convergence in protein‐coding polymorphisms.

中文翻译：

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正选择和收敛进化塑造了山雀（Paridae）中先天免疫受体的分子表型特征。

尽管广泛的变异性和冗余性充斥着动物免疫力，但目前对宿主分子适应寄生虫选择压力的进化收敛速度（功能相似性状并非从祖先继承）知之甚少。Toll样受体（TLR）提供了分子界面，使宿主能够识别病原体结构并触发早期危险信号以启动免疫反应。使用一种新颖的生物信息学方法组合，在这里我们探索了在29种雀形目鸟类（Aves：Paridae）中细菌感测的TLR4和TLR5配体结合区域的遗传变异。TLR4的四个经自愿选择的阳性位点中的三个，以及TLR5的14个在阳性选择位点中的六个，位于功能重要位点附近的受体表面，并基于会聚（平行）方式进化的系统发育模式。在一个N-糖基化位点和两个阳性选择的磷酸化位点上也观察到这种类型的进化，这为进化免疫学中翻译后修饰的融合提供了第一个证据。最后，系统发育和表面电荷分布聚类之间的总体失配表明，在涉及配体结合的整体TLR4和TLR5分子表型中，收敛是普遍的。我们的分析未发现任何广泛的生态特征，无法解释静电势中观察到的趋同，提示可能需要有关微生物共生体的信息来解释TLR的进化。通过采用最先进的预测结构仿生学，我们概述了一种新的，广泛适用的方法学方法，用于估计正选择变异的功能重要性，并测试蛋白质编码多态性中的自适应分子融合。