Range expansion of Galinsoga quadriradiata into the mountains of China

Can shifts in trait values among populations of an invasive plant help assess invasion risks and predict future spread?

Invasive plants are increasingly moving into high-altitude areas of mountain ranges due to climate change, changing land use and anthropogenic disturbances. However, there has been relatively little attention paid to how mountains affect the upward expansion of invasive plants. It is often suggested that high mountain ranges are less likely to be invaded due to stressful abiotic environments, with plants exposed to lower temperatures, shorter growing seasons and less fertile soils than their lower altitude counterparts. The importance of these factors is compounded by the fact that conditions are highly variable over a relatively small range of altitude. Invasive plants must therefore be able to acclimate to very different environments over small distances to move upslope.

In their new study published in AoBP, Liu et al. tested the differentiation of dispersal-related traits in the invasive Galinsoga quadriradiata across populations at different elevations in the Qinling and Bashan Mountains in China. G. quadriradiata, often called Peruvian Daisy or Shaggy Soldier, is an annual herbaceous plant originating in Central and South America. It is a harmful agricultural invasive weed, mainly established in moist, warm temperate and subtropical zones around the world on abandoned land or farmland. Since its first report on Lushan Mountain in Jiangxi Province in 1979, it has been found across all suitable climatic areas in China.

The invasive plant Galinsoga quadriradiata in the mountains of central China. Image credit: G. Liu.

Liu et al. collected data on the seed mass–area ratio, an important seed dispersal-related trait, of 45 populations from along an elevational gradient and quantified genetic variation of 23 populations using inter-simple sequence repeat markers. Their results suggest that the dispersal ability of G. quadriradiata decreases along elevational dispersal routes as a result of genetically based rapid evolution and phenotypic plasticity, challenging the common argument that dispersal ability of invasive plants increases along dispersal routes.

These findings provide new insight into how the dispersal ability of invasive plants may change along elevational gradients. This is important for assessing the upward expansion dynamics of invasive plants in high mountains and to predict future spread in these ecosystems. The authors suggest that further research is needed to link the traits from this study directly to dispersal ability as well as to investigate these patterns across broader geographic gradients.

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