The Origin and Spread of Locally Adaptive Seasonal Camouflage in Snowshoe Hares
The Origin and Spread of Locally Adaptive Seasonal Camouflage in Snowshoe Hares
复制标题
雪鞋兔局部适应性季节性伪装的起源和传播
DOI：
10.1086/710022
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Good, Jeffrey M.
中科院分区：
文献类型：
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作者：
Jones, Matthew R.;Mills, L. Scott;Jensen, Jeffrey D.;Good, Jeffrey M.
面对环境变化，适应是种群持续存在的核心，然而我们很少准确地了解自然种群中适应性变异的起源和传播。太平洋西北海岸的美洲雪鞋兔（Lepus americanus）通过对黑尾长耳兔（Lepus californicus）遗传的褐色色素沉着基因隐性变异的正选择进化出了褐色的冬季伪装。在这里，我们将新的和已发表的agoutiti全基因组和外显子组序列与目标基因分型相结合，研究太平洋西北地区当地季节性伪装适应的进化史。我们发现沿海冬褐兔近亲繁殖和突变负荷显著增加的证据，这与最近向温带沿海环境扩张所产生的间接适应成本相一致。基因渗入通道长度的全基因组分布支持了末次冰期末期的杂交脉冲，这可能通过冬棕色伪装变异的渗入促进了范围的扩大。然而，在agoutii选择性扫掠的特征表明，冬季棕色伪装的传播时间更近。通过模拟，我们发现杂交起源和隐性冬季棕色等位基因随后的选择性扫掠之间的延迟在很大程度上归因于简单等位基因显性所施加的自然选择限制。我们认为，虽然环境变化期间的杂交可能为范围边缘的适应性变异提供了一个关键的储存库，但局部适应的概率和速度将在很大程度上取决于种群人口统计和渐渗变异的遗传结构。
Adaptation is central to population persistence in the face of environmental change, yet we seldom precisely understand the origin and spread of adaptive variation in natural populations. Snowshoe hares (Lepus americanus) along the Pacific Northwest coast have evolved brown winter camouflage through positive selection on recessive variation at theAgoutipigmentation gene introgressed from black-tailed jackrabbits (Lepus californicus). Here, we combine new and published whole-genome and exome sequences with targeted genotyping ofAgoutito investigate the evolutionary history of local seasonal camouflage adaptation in the Pacific Northwest. We find evidence of significantly elevated inbreeding and mutational load in coastal winter-brown hares, consistent with a recent range expansion into temperate coastal environments that incurred indirect fitness costs. The genome-wide distribution of introgression tract lengths supports a pulse of hybridization near the end of the last glacial maximum, which may have facilitated range expansion via introgression of winter-brown camouflage variation. However, signatures of a selective sweep atAgoutiindicate a much more recent spread of winter-brown camouflage. Through simulations, we show that the delay between the hybrid origin and subsequent selective sweep of the recessive winter-brown allele can be largely attributed to the limits of natural selection imposed by simple allelic dominance. We argue that while hybridization during periods of environmental change may provide a critical reservoir of adaptive variation at range edges, the probability and pace of local adaptation will strongly depend on population demography and the genetic architecture of introgressed variation.