Hemotological and morphometric measurements from geladas

Primates have adapted to numerous environments and lifestyles but very few species are native to high elevations. Here, we investigated high-altitude adaptations in the gelada (Theropithecus gelada), a monkey endemic to the Ethiopian Plateau. We examined genome-wide variation in conjunction with measurements of haematological and morphological traits. Our new gelada reference genome is highly intact and assembled at chromosome-length levels. Unexpectedly, we identified a chromosomal polymorphism in geladas that could potentially contribute to reproductive barriers between populations. Compared to baboons at low altitude, we found that high-altitude geladas exhibit significantly expanded chest circumferences, potentially allowing for greater lung surface area for increased oxygen diffusion. We identified gelada-specific amino acid substitutions in the alpha-chain subunit of adult haemoglobin but found that gelada haemoglobin does not exhibit markedly altered oxygenation properties compared to lowland primates. We also found that geladas at high altitude do not exhibit elevated blood haemoglobin concentrations, in contrast to the normal acclimatization response to hypoxia in lowland primates. The absence of altitude-related polycythaemia suggests that geladas are able to sustain adequate tissue-oxygen delivery despite environmental hypoxia. Finally, we identified numerous genes and genomic regions exhibiting accelerated rates of evolution, as well as gene families exhibiting expansions in the gelada lineage, potentially reflecting altitude-related selection. Our findings lend insight into putative mechanisms of high-altitude adaptation while suggesting promising avenues for functional hypoxia research.灵长类动物已适应多样的环境与生活方式，但仅有极少物种自然栖息于高海拔区域。本研究聚焦于埃塞俄比亚高原特有物种狮尾狒（Theropithecus gelada）的高海拔适应机制并展开调查。我们结合全基因组变异分析与血液学、形态学性状检测开展相关研究。我们构建的全新狮尾狒参考基因组完整性极高，达到染色体级别的组装水平。令人意外的是，我们在狮尾狒群体中发现了一种染色体多态性，该变异或可导致种群间产生生殖隔离。与低海拔狒狒相比，高海拔狮尾狒的胸围显著更大，这或许能提升肺部表面积，从而增强氧气扩散效率。我们在成年血红蛋白的α链亚基中发现了狮尾狒特有的氨基酸替换，但相较于低地灵长类，狮尾狒的血红蛋白并未表现出显著改变的氧合特性。同时我们发现，高海拔狮尾狒并未出现血液血红蛋白浓度升高的现象——这与低地灵长类应对低氧环境的典型习服反应截然不同。未出现海拔相关的红细胞增多症，表明即便身处低氧环境，狮尾狒仍能够维持充足的组织氧供。最后，我们鉴定出多个进化速率加快的基因与基因组区域，以及狮尾狒谱系中发生扩张的基因家族，这些变化或反映了高海拔相关的选择压力。本研究的发现不仅为高海拔适应的潜在机制提供了新见解，同时也为低氧相关功能研究指明了极具前景的方向。