Museum of Southwestern Biology, University of New Mexico, Albuquerque, New Mexico, USA.
Department of Biology, University of New Mexico, Albuquerque, New Mexico, USA.
Ecol Lett. 2023 Jul;26(7):1223-1236. doi: 10.1111/ele.14235. Epub 2023 May 13.
Predictable trait variation across environments suggests shared adaptive responses via repeated genetic evolution, phenotypic plasticity or both. Matching of trait-environment associations at phylogenetic and individual scales implies consistency between these processes. Alternatively, mismatch implies that evolutionary divergence has changed the rules of trait-environment covariation. Here we tested whether species adaptation alters elevational variation in blood traits. We measured blood for 1217 Andean hummingbirds of 77 species across a 4600-m elevational gradient. Unexpectedly, elevational variation in haemoglobin concentration ([Hb]) was scale independent, suggesting that physics of gas exchange, rather than species differences, determines responses to changing oxygen pressure. However, mechanisms of [Hb] adjustment did show signals of species adaptation: Species at either low or high elevations adjusted cell size, whereas species at mid-elevations adjusted cell number. This elevational variation in red blood cell number versus size suggests that genetic adaptation to high altitude has changed how these traits respond to shifts in oxygen availability.
可预测的特征在不同环境中的变化表明，通过重复的遗传进化、表型可塑性或两者的结合，存在共享的适应性反应。特征-环境关联在系统发育和个体尺度上的匹配意味着这些过程之间的一致性。或者，不匹配意味着进化分歧改变了特征-环境协变的规则。在这里，我们测试了物种适应是否会改变血液特征在海拔上的变化。我们在 4600 米的海拔梯度上测量了 77 个物种的 1217 只安第斯蜂鸟的血液。出乎意料的是，血红蛋白浓度 ([Hb]) 的海拔变化是独立于尺度的，这表明气体交换的物理特性，而不是物种差异，决定了对氧气压力变化的反应。然而，[Hb]调节的机制确实显示出了物种适应的信号：高海拔或低海拔的物种调节了细胞大小，而中海拔的物种调节了细胞数量。这种红细胞数量与大小的海拔变化表明，对高海拔的遗传适应已经改变了这些特征对氧气供应变化的反应方式。
