Data from: Climate, not Aboriginal landscape burning, controlled the historical demography and distribution of fire-sensitive conifer populations across Australia

Climate and fire are the key environmental factors that shape the distribution and demography of plant populations in Australia. Because of limited palaeoecological records in this arid continent, however, it is unclear as to which factor impacted vegetation more strongly, and what were the roles of fire regime changes owing to human activity and megafaunal extinction (since ca 50 kya). To address these questions, we analysed historical genetic, demographic and distributional changes in a widespread conifer species complex that paradoxically grows in fire-prone regions, yet is very sensitive to fire. Genetic demographic analysis showed that the arid populations experienced strong bottlenecks, consistent with range contractions during the Last Glacial Maximum (ca 20 kya) predicted by species distribution models. In southern temperate regions, the population sizes were estimated to have been mostly stable, followed by some expansion coinciding with climate amelioration at the end of the last glacial period. By contrast, in the flammable tropical savannahs, where fire risk is the highest, demographic analysis failed to detect significant population bottlenecks. Collectively, these results suggest that the impact of climate change overwhelmed any modifications to fire regimes by Aboriginal landscape burning and megafaunal extinction, a finding that probably also applies to other fire-prone vegetation across Australia.

气候与火灾是塑造澳大利亚植物种群分布与种群动态的核心环境因子。然而，受限于这片干旱大陆的古生态记录匮乏，学界仍难以明确二者对植被的影响强度差异，亦无法厘清约5万年前以来，人类活动与巨型动物灭绝所引发的火制度（fire regime）变化所扮演的角色。为解答上述疑问，我们对一类广泛分布的针叶树物种复合体展开了分析——该类群虽生长于火频发区域，却对火灾极为敏感，由此得以探究其历史时期的遗传、种群动态与分布变化。遗传种群动态分析结果显示，干旱区域的种群经历了强烈的种群瓶颈效应，这与物种分布模型所预测的末次冰盛期（约2万年前）期间的分布范围收缩现象相符。在南部温带区域，种群规模整体保持稳定，随后在末次冰期结束之际，随气候转暖出现了一定程度的种群扩张。与之形成对比的是，在火灾风险最高的易燃热带稀树草原区域，种群动态分析未能检测到显著的种群瓶颈效应。综合来看，上述结果表明，气候变化对植被的影响远超原住民景观用火管理与巨型动物灭绝所带来的火制度改变；这一结论或同样适用于澳大利亚境内其他火频发植被群落。