Despite the expansive old-growth forests of California's Sierra Nevada, its greatest diversity of butterflies is found in non-forested habitats, such as alpine meadows and fell-fields. These unique “sky island” habitats support a number of endemic butterflies, such as the Ivallda Arctic (Oeneis chryxus ivallda). Unlike other, more colorful butterflies in the region, the dark, cryptic coloration of O c ivallda is hypothesized to aid in both thermoregulation and camouflage in the relatively cool, rocky environments they inhabit. Faced with warming temperatures, some alpine butterfly populations may track their climatic niche and stay ahead of advancing treelines by moving up mountain slopes. However, many O c ivallda populations already occur at or near mountain summits, limiting their potential for elevational shifts. On 2 July 2022, we observed a previously unrecorded O c ivallda population at the summit of Mount Whitney (4421 m). Popular data repositories (eg GBIF and iNaturalist) confirmed that no other butterflies have been observed here. Mount Whitney is the highest mountain in the conterminous US, and all higher summits in Canada and Alaska are—at least for the moment—permanently snow- or glacier-covered, unsuitable for butterfly occupancy. This observation therefore marks what we believe is the highest extant butterfly population in North America. Of the 12 O c ivallda individuals observed during a one-hour survey, three were collected for whole-genome resequencing as part of the California Conservation Genomics Project (CCGP; https://www.ccgproject.org/). Two individuals are pictured, one from the summit of Mount Whitney (above) and the other from the summit of Mount Dana (3981 m; below), approximately 170 km to the northwest of Whitney. In light of this observation, alpine butterflies in the Sierra Nevada are clearly exhausting their potential for elevational shifts in the face of warming temperatures. Preventing extinction may require proactive conservation practices, such as translocation and even assisted migration. Detailed population genomic data, such as those produced by the CCGP, will help inform these efforts.

尽管加利福尼亚州内华达山脉拥有广阔的原始森林，但其蝴蝶多样性最丰富的地方却是在非森林栖息地，例如高山草甸和荒野。这些独特的“天空岛”栖息地栖息着许多特有蝴蝶，例如北极伊瓦尔达蝴蝶 ( Oeneis chryxus ivallda )。与该地区其他颜色更丰富的蝴蝶不同，奥西瓦尔达的深色、神秘色彩被认为有助于它们栖息的相对凉爽的岩石环境中的体温调节和伪装。面对气温升高，一些高山蝴蝶种群可能会追踪其气候生态位，并通过爬上山坡来保持领先于林线的发展。然而，许多奥西瓦尔达种群已经出现在山顶或附近，限制了它们海拔变化的潜力。 2022 年 7 月 2 日，我们在惠特尼山 (4421 m) 山顶观察到了此前未记录的奥西瓦尔达种群数量。流行的数据存储库（例如 GBIF 和 iNaturalist）证实这里没有观察到其他蝴蝶。惠特尼山是美国本土最高的山峰，而加拿大和阿拉斯加的所有更高的山峰（至少目前是这样）永久被雪或冰川覆盖，不适合蝴蝶栖息。因此，这一观察结果标志着我们认为北美现存蝴蝶数量最多。在一项为期一小时的调查中观察到的12 名O civallda个体中，有 3 名被收集用于全基因组重测序，作为加州保护基因组计划 (CCGP；https://www.ccgproject.org/) 的一部分。照片中有两个人，一个来自惠特尼山 (Mount Whitney) 山顶（上图），另一个来自达纳山 (Mount Dana)（海拔 3981 米；下图），距离惠特尼西北约 170 公里。根据这一观察结果，面对气温变暖，内华达山脉的高山蝴蝶显然正在耗尽其海拔变化的潜力。防止灭绝可能需要采取积极的保护措施，例如易地甚至协助迁徙。详细的群体基因组数据（例如 CCGP 生成的数据）将有助于为这些工作提供信息。