Toll-like receptors (TLRs) are one of the first lines of defense against pathogens and are crucial for triggering an appropriate immune response. Among TLRs, TLR2 is functional in all vertebrates and has high ability in detecting bacterial and viral pathogen ligands. The mammals' phylogenetic tree of TLR2 showed longer branches for the Lagomorpha clade, raising the hypothesis that lagomorphs experienced an acceleration of the mutation rate. This hypothesis was confirmed by (i) Tajima's test of neutrality that revealed different evolutionary rates between lagomorphs and the remaining mammals with lagomorphs presenting higher nucleotide diversity; (ii) genetic distances were similar among lagomorphs and between lagomorphs and other mammals; and (iii) branch models reinforced the existence of an acceleration of the mutation rate in lagomorphs. These results suggest that the lagomorph TLR2 has been strongly involved in pathogen recognition, which probably caused a host-pathogen arms race that led to the observed acceleration of the mutation rate.

中文翻译：

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在Lagomorpha中对TLR2编码区的强烈选择表明其进化史不同于其他哺乳动物。

Toll样受体（TLR）是抵御病原体的第一道防线之一，对于触发适当的免疫反应至关重要。在TLR中，TLR2在所有脊椎动物中均具有功能，并具有检测细菌和病毒病原体配体的高能力。哺乳动物的TLR2系统发育树显示出Lagomorpha进化枝更长的分支，提出了Lagomorph经历突变率加速的假说。（i）Tajima的中立性检验证实了这一假设，该检验揭示了lagomorphs与其余具有lagomorphs表现出更高核苷酸多样性的哺乳动物之间的进化速率不同；（ii）象鼻虫之间以及象鼻虫与其他哺乳动物之间的遗传距离相似；（iii）分支模型加强了lagomorphs突变率加速的存在。