中国梭梭属植物历史分布格局及其驱动机制

Historical distribution pattern and driving mechanism of Haloxylon in China

梭梭属(Haloxylon)植物是藜科的古老孑遗物种,探究末次间冰期(lastinterglacial period,LIG)和末次盛冰期(lastglacial maximum period,LGM)以来中国梭梭属植物的历史地理分布格局及其驱动机制,对了解气候变化背景下旱生植物区系的发展与演化具有重要意义。本研究利用梭梭属85个自然分布点数据(60条梭梭(Haloxylon ammodendron)分布记录、25条白梭梭(H.persicum)分布记录)和2套环境因子数据,整合GIS空间分析和9种物种分布模型,分析了梭梭属末次间冰期以来的地理分布格局变化及其驱动机制。基于62个梭梭属种群的叶绿体基因测序数据,利用最小成本路径方法,模拟了末次间冰期以来梭梭属可能的扩散路径。利用R软件prcomp函数对影响梭梭属分布的环境变量进行主成分分析(principal component analysis,PCA),评价了环境变量对梭梭属适宜分布的贡献,并分析了关键变量与分布适宜性的相关性。结果表明:(1)集成模型的模拟精度较单一模型显著提升,且对白梭梭的模拟精度高于梭梭;(2)末次间冰期以来,梭梭属植物的分布均经历了显著收缩和冰后期扩张,末次间冰期至末次盛冰期时期,在准噶尔盆地、塔里木盆地西部广泛分布的梭梭大面积向西退缩至避难所(准噶尔盆地西北缘和塔里木盆地西北缘);白梭梭从准噶尔盆地、塔里木盆地西端向南退缩至避难所(准噶尔盆地南缘);末次盛冰期至今,梭梭向东沿甘肃北部扩张直至内蒙古西部阿拉善荒漠,白梭梭向东北方向小范围扩张,占据了准噶尔盆地西部和南缘;(3)末次间冰期以来的气候波动对梭梭属植物的分布存在较大限制,降水因子主导了梭梭属适宜分布面积的变化,温度因子影响了梭梭属分布适宜性的高低。

Aims: Under the influence of Quaternary climate fluctuation, xerophytes may have experienced large-scale migration and expansion. It is highly important to study the historical and geographical distribution pattern of xerophytes to understand the evolution of xerophyte flora under the background of climate fluctuation. The purpose of this study is to reveal the distribution pattern and driving mechanisms of Haloxylon in China since the last interglacial period(LIG)and the last glacial maximum period(LGM).Methods: Based on 85 natural distribution sites and 2 sets of environmental factors, the geographic distribution pattern change, and driving mechanisms of Haloxylon since the LIG were analyzed by integrating GIS spatial analysis and 9 species distribution models. Based on the chloroplast gene data of 62 Haloxylon populations, we used the least cost path method to simulate the possible diffusion paths of Haloxylon since the LIG. Principal component analysis(PCA) of environmental variables affecting the distribution of Haloxylon was carried out by using the prcomp function in R 4.1.1. The contribution of environmental variables to the suitable distribution of Haloxylon was evaluated, and the correlation between key variables and the degree of suitability was analyzed. Results: We found that the precision of the integrated model was significantly improved compared with that of the single model. Since the LIG, the distribution of Haloxylon has undergone a significant decrease and post-glacial expansion. From the LIG to the LGM, Haloxylon ammodendron retreated westward from Junggar Basin and western Tarim Basin to the northwest and eastern margin of Junggar Basin and northwest margin of Tarim Basin. Haloxylon persicum retreated from the western end of Junggar Basin and Tarim Basin to the south of Junggar Basin. Since the LGM, H. ammodendron has expanded eastward, through northern Gansu and eastern region of the Qaidam basin to Alxa Desert in western Inner Mongolia. Haloxylon persicum has expanded northeast on a small scale, occupying the central and western part of Junggar Basin. The change of key climatic factors in the suitable distribution area of Haloxylon is relatively low. PCA results showed that the score coefficient of the precipitation factor in the first principal component is higher. The analysis of the relationship between the environmental factors affecting the distribution of Haloxylon and the suitability of the distribution area demonstrated that there is a significant correlation between temperature factors and the suitability of the distribution of Haloxylon. Conclusion: The climate change in Quaternary caused the geographical distribution of Haloxylon to narrow and then subsequently expand. The main migration paths of Haloxylon are through the Junggar Basin and Hexi Corridor. Precipitation factors mainly affect the change of suitable distribution area of Haloxylon, while temperature factors mainly affect the degree of distribution suitability of Haloxylon.