During the Miocene, Hyaenidae was a highly diverse family of Carnivora that has since been severely reduced to four extant genera, each of which contains only a single species. These species include the bone-cracking spotted, striped, and brown hyenas, and the specialised insectivorous aardwolf. Previous genome studies have analysed the evolutionary histories of the spotted and brown hyenas, but little is known about the remaining two species. Moreover, the genomic underpinnings of scavenging and insectivory, defining traits of the extant species, remain elusive. To tackle these questions, we generated an aardwolf genome and analysed it together with those from the other three species. We provide new insights into the evolutionary relationships between the species, the genomic underpinnings of their scavenging and insectivorous lifestyles, and their respective genetic diversities and demographic histories. High levels of phylogenetic discordance within the family suggest gene flow between the aardwolf lineage and the ancestral brown/striped hyena lineage. Genes related to immunity and digestion in the bone-cracking hyenas and craniofacial development in the aardwolf showed the strongest signals of selection in their respective lineages, suggesting putative key adaptations to carrion or termite feeding. We also found a family-wide expansion in olfactory receptor genes suggesting that an acute sense of smell was a key early adaptation for the Hyaenidae family. Finally, we report very low levels of genetic diversity within the brown and striped hyenas despite no signs of inbreeding, which we putatively link to their similarly slow decline in Ne over the last ~2 million years. We found much higher levels of genetic diversity in both the spotted hyena and aardwolf and more stable population sizes through time. Taken together, these findings highlight how ecological specialisation can impact the evolutionary history, demographics, and adaptive genetic changes of a lineage.

中文翻译：

---

现存的ya科的生态专业化和进化网状

在中新世时期，鬣狗科是食肉动物的一个高度多样化的家族，此后被严重地简化为四个现存属，每个属仅包含一个物种。这些物种包括开裂的斑点，条纹和褐色的鬣狗，以及专门的食虫性土狼。先前的基因组研究已经分析了斑点鬣狗和棕色鬣狗的进化历史，但对其余两个物种知之甚少。此外，清除和昆虫食性的基因组基础（定义了现存物种的性状）仍然难以捉摸。为了解决这些问题，我们生成了一个土狼基因组，并将其与其他三个物种的基因组一起进行了分析。我们提供了有关物种之间进化关系，其清除和食虫生活方式的基因组基础的新见解，以及它们各自的遗传多样性和人口历史。该家族中高水平的系统发育失调表明基因在土狼和后裔棕色/条纹鬣狗血统之间流动。与开裂的鬣狗中的免疫力和消化力有关的基因以及在土狼中颅面发育的基因在其各自的血统中显示出最强的选择信号，表明推测的关键适应性是腐肉或白蚁摄食。我们还发现嗅觉受体基因在整个家族中都有扩展，这表明嗅觉的敏锐感是H虫科的关键早期适应方法。最后，尽管没有近亲繁殖的迹象，我们报道了棕色和条纹鬣狗内部的遗传多样性水平很低，我们推测这与近200万年来它们类似缓慢的Ne下降有关。我们发现斑鬣狗和土狼的遗传多样性水平更高，并且随着时间的推移种群数量更加稳定。综上所述，这些发现凸显了生态专业化如何影响进化史，人口统计学和世系的适应性遗传变化。