Milder winters would alter patterns of freezing damage for epiphytic lichens from the trans-Himalayas

This is the supporting dataset to the paper Worthy et al. 2024 published in Scientific Reports. All methods used to produce the data are described in the methods section of the associated manuscript. A key is provided within each dataset to explain the headings and nature of each column of the data. ABSTRACT Trans-Himalayan winters are projected to become milder, with shifting precipitation patterns and freeze-thaw cycles; changing stressors for their lichen communities. Lichens from Antarctica and high latitudes are cryoresistant when dry, but susceptible to cell damage if frozen when wet, or subjected to repeated freeze-thaw events. Little is known regarding cryoresistance in high-elevation, mid-latitude lichens. We collected thalli of nine species of epiphytic lichenized fungi, from three regions of the trans-Himalayas; at ≈ 4000 m, 3400 m and 2400 m elevation. We subjected thalli to differing freezing (continuous -18°C and -36°C or freeze-thaw cycles in natural daylight) and moisture conditions. Even dry thalli suffered some damage. Frozen wet thalli had greater chlorophyll degradation and reduced chlorophyll content. There were no clear elevational trends in freeze-thaw susceptibility: it caused more damage than continuous freezing. The most freeze-thaw resilient lichens were Dolichousnea longissima (from 4000 m) and Usnea florida (from 2400 m). However, species from coldest sites were most resilient to extreme freezing. Under predicted climate change conditions these sites would experience fewer annual freeze-thaw cycles, annual sub-zero days and frost days. Reduced freezing constraints might allow range expansion of mid-elevation lichens, but increase competitive pressures and temperature stressors impacting high-elevation lichens. HYPOTHESES We aimed to test the following series of non-mutually exclusive hypotheses: 1. Dry thalli are less susceptible to freezing damage than are wet thalli. 2. Freeze-thaw cycles cause greater damage than continuous freezing. 3. Freeze-thaw cycles cause most damage to lichen from higher elevations. 4. Severe freezing temperatures have least impact on lichen from higher elevations. 5. Lichen from sites which rarely have sub-zero temperatures will be least able to recover after freezing damage.本数据集为发表于《Scientific Reports》的Worthy等人2024年研究论文的配套数据集。所有用于生成该数据集的实验方法均已在相关手稿的方法章节中详述。每个数据集内均附有数据表头说明文件，用以解释各数据列的表头含义与数据性质。 摘要 跨喜马拉雅地区的冬季预计将愈发温和，降水格局与冻融循环（freeze-thaw cycles）模式发生改变，进而对当地地衣群落造成变化的环境胁迫。来自南极洲与高纬度地区的地衣在干燥状态下具备抗冻性（cryoresistant），但当处于湿润状态下结冰，或经历反复冻融循环事件时，极易出现细胞损伤。目前学界对中纬度高海拔地衣的抗冻性（cryoresistance）了解甚少。本研究从跨喜马拉雅地区的三个海拔区域（分别约4000米、3400米与2400米）采集了9种附生地衣型真菌（lichenized fungi）的地衣体（thalli）。我们将地衣体置于不同的冷冻条件（持续-18℃、-36℃，或在自然光下进行冻融循环）与湿度环境中开展实验。即便干燥的地衣体也出现了一定程度的损伤。湿润结冰的地衣体叶绿素降解程度更高，叶绿素含量也更低。冻融敏感性未呈现明确的海拔梯度趋势，且其造成的损伤程度高于持续冷冻。抗冻融能力最强的地衣分别是采自4000米海拔的长枝松萝（*Dolichousnea longissima*）与采自2400米海拔的佛罗里达松萝（*Usnea florida*）。然而，来自最冷生境的地衣物种对极端低温的耐受性最强。在预测的气候变化情景下，这些生境的年冻融循环次数、年零下日数与霜日都将减少。冷冻胁迫的缓解可能会促进中海拔地衣的分布扩张，但同时也会加剧竞争压力与温度胁迫，对高海拔地衣造成负面影响。 研究假说 本研究旨在检验以下一系列非互斥假说： 1. 干燥状态的地衣体相较于湿润状态的地衣体，更不易受到冷冻损伤。 2. 冻融循环相较于持续冷冻，会对地衣造成更严重的损伤。 3. 冻融循环对高海拔来源的地衣造成的损伤最为显著。 4. 极端低温对高海拔来源的地衣的影响最小。 5. 来自极少出现零下温度生境的地衣，在遭受冷冻损伤后的恢复能力最差。