基于种子发芽率评估长芒苋在我国不同纬度地区的入侵风险

外来入侵植物长芒苋Amaranthus palmeri已经传入我国多个地区,定量评估其入侵风险对制定高效防控措施具有重要意义。外来植物入侵风险应该是由传入后能发芽并完成生活史的繁殖体如种子的量决定的,但已开展的适生区预测等风险评估通常忽略了该因素。基于此,本研究先通过同质园试验, 比较了采自我国不同纬度的11个长芒苋种群与来自原产地美国种群的种子发芽率,分析了种群间发芽率的差异及其与纬度的相关性;然后,通过一年内连续多次在不同纬度地区的交互种植试验,分析了不同纬度种群间种子的发芽率和完成生活史的入侵窗口期差异,并判断是否发生了本地适应;最后,根据发芽率和入侵窗口期评估了长芒苋在我国不同纬度地区的入侵风险。同质园试验表明,种子发芽率与种群所处纬度显著正相关(P<0.05),发芽率随纬度升高而增高。交互种植试验表明,不同种群发芽率的差异是由于本地适应导致的,长芒苋在我国的入侵窗口期随纬度升高而缩短。基于不同种群种子发芽率和入侵窗口期的纬度差异,我们判断长芒苋在我国中低纬度至中高纬度区域内入侵风险较高,应该重点防控。长芒苋在高纬度和低纬度地区的入侵风险相对较低。但长芒苋种子萌发的本地适应可能会增加其在高、低纬度地区的入侵风险。因此,亟须加强对已传入种群的监测预警与早期防控力度,抑制其繁殖增长和进一步的扩散蔓延。

Invasion risk assessment of Amaranthus palmeri at different latitudinal regions in China based on seed germination rate

Amaranthus palmeri S. Watson, an invasive alien plant, has been introduced to many parts of China. Quantitative assessment of invasion risks is of great significance to formulate effective prevention and control measures. The invasion risks of alien plants should be determined by the amount of propagule such as seeds that can germinate and complete their life cycle after introdutction. However, previous risk assessments, such as the prediction of suitable areas, usually ignore the population demographic character. In this study, the germination rates of seeds collected from, 11 populations of A. palmeri at different latitudes in China were compared with those from the native populations by common garden experiments. The relationships between latitude, thousand-seed weight and collection year and germination rate of seeds were also analyzed. Secondly, the differences in the seed germination rate and invasion window period for complete life cycle among populations at different latitudes were analyzed by reciprocal transplant experiments for several consecutive times within a year. Meanwhile, whether local adaptation occurred in the germination rate of different populations was analyzed. Finally, the invasion risks at different latitudes were assessed based on the seed germination rate and invasion window period. Common garden experiments showed that the germination rate was positively correlated with the latitudes of populations (P<0.05). The germination rate of seeds increased with latitudes. Reciprocal transplant experiments showed that the differences of germination rate of collected populations were caused by local adaptation. The invasion window period of A. palmeri in China was shortened with increasing latitudes. Based on the differences in the seed germination rate and the invasion window period along latitudes, we concluded that the regions from low-mid to mid-high latitudes have higher invasion risks and should be focused for prevention and control. Invasion risks of A. palmeri were relatively lower at high latitudes and low latitudes. However, local adaptation of A. palmeri is conducive to increasing invasion risks at high and low latitudes. Therefore, it is urgent to strengthen the monitoring and early warning of introduced A. palmeri populations to inhibit their reproductive growth and prevent their further expansion.