Data from: Range and niche shifts in response to past climate change in the desert horned lizard (Phrynosoma platyrhinos)

During climate change, species are often assumed to shift their geographic distributions (geographic ranges) in order to track environmental conditions – niches – to which they are adapted. Recent work, however, suggests that niches do not always remain conserved during climate change but shift instead, allowing populations to persist in place or expand into new areas. We assessed the extent of range and niche shifts in response to the warming climate after the Last Glacial Maximum (LGM) in the desert horned lizard (Phrynosoma platyrhinos), a species occupying the western deserts of North America. We used a phylogeographic approach with mitochondrial DNA sequences to approximate the species range during the LGM by identifying populations that exhibit a genetic signal of population stability versus those that exhibit a signal of a recent (likely post-LGM) geographic expansion. We then compared the climatic niche that the species occupies today with the niche it occupied during the LGM using two models of simulated LGM climate. The genetic analyses indicated that P. platyrhinos persisted within the southern Mojave and Sonoran deserts throughout the latest glacial period and expanded from these deserts northwards, into the western and eastern Great Basin, after the LGM. The climatic niche comparisons revealed that P. platyrhinos expanded its climatic niche after the LGM towards novel, warmer and drier climates that allowed it to persist within the southern deserts. Simultaneously, the species shifted its climatic niche towards greater temperature and precipitation fluctuations after the LGM. We concluded that climatic changes at the end of the LGM promoted both range and niche shifts in this lizard. The mechanism that allowed the species to shift its niche remains unknown, but phenotypic plasticity likely contributes to the species ability to adjust to climate change.

在气候变化过程中，物种通常被认为会调整其地理分布（即地理范围），以追踪其所适应的环境条件——生态位（niche）。然而，近期研究表明，气候变化期间生态位并非始终保持保守，反而可能发生偏移，使得种群能够在原栖息地存续，或拓展至新的分布区域。本研究以栖息于北美西部荒漠的沙漠角蜥（*Phrynosoma platyrhinos*）为研究对象，评估了末次冰盛期（Last Glacial Maximum, LGM）后气候变暖背景下该物种的地理范围与生态位偏移程度。我们采用基于线粒体DNA序列（mitochondrial DNA sequences）的系统地理学研究方法，通过识别呈现种群稳定性遗传信号的种群，以及呈现近期（大概率为冰盛期后）地理扩张遗传信号的种群，来估算该物种在末次冰盛期的地理范围。随后，我们利用两套末次冰盛期气候模拟模型，将该物种当前占据的气候生态位与其在末次冰盛期的气候生态位进行对比。遗传分析结果显示，沙漠角蜥在末次冰期晚期存续于莫哈韦沙漠南部与索诺兰沙漠，并在末次冰盛期后从这两处荒漠向北扩张至大盆地的西部与东部区域。气候生态位对比结果表明，该物种在冰盛期后将其气候生态位拓展至更温暖、更干燥的新型气候环境中，使其得以在南部荒漠存续。与此同时，该物种的气候生态位在冰盛期后朝着温度与降水波动幅度更大的方向偏移。我们得出结论：末次冰盛期末的气候变化同时推动了该蜥蜴的地理范围与生态位偏移。目前该物种实现生态位偏移的机制尚不明确，但表型可塑性（phenotypic plasticity）可能有助于其适应气候变化。