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 the 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.

在气候变化背景下，学界通常假设物种会通过改变地理分布（即地理范围）来追踪其适应的环境条件——生态位（niche）。然而近期研究表明，气候变化过程中生态位并非始终保持保守，反而会发生位移，使种群得以原地存续或拓展至新区域。本研究以栖息于北美西部沙漠的沙漠角蜥（*Phrynosoma platyrhinos*）为研究对象，评估其在末次冰盛期（Last Glacial Maximum, LGM）后气候变暖背景下的分布范围与生态位位移程度。研究采用基于线粒体DNA序列的系统地理学方法，通过区分表现出种群稳定遗传信号与近期（推测为末次冰盛期后）地理扩张遗传信号的种群，来重建该物种在LGM时期的分布范围。随后利用两套末次冰盛期气候模拟模型，对比该物种现今占据的气候生态位与LGM时期的气候生态位。遗传分析结果显示，沙漠角蜥在整个末次冰期期间均存续于莫哈韦沙漠南部与索诺兰沙漠，并在LGM后从上述沙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，LGM后沙漠角蜥的气候生态位向更温暖、更干燥的新型气候拓展，使其得以在南部沙漠持续存续；与此同时，该物种的气候生态位在LGM后向温度与降水波动幅度更大的方向发生了位移。本研究得出结论：LGM末期的气候变化同时推动了该蜥蜴的分布范围与生态位位移。目前促成该物种生态位位移的具体机制尚不明确，但表型可塑性可能是其适应气候变化的重要助力。