Evolutionary responses of dominant and companion species along the precipitation gradient in a typical steppe from 1985 to 2022

Population dynamics may fluctuate dramatically over time in response to changing climate conditions. Thus, assessing how trade-offs in growth and reproduction of plant population respond to climate change may be key for predicting and conserving complex communities, especially in the context of different precipitation. Here, using a long-term experiment along the precipitation gradient, we investigated trade-offs in growth and reproduction of dominant species, Artemisia capillaris and companion species, Aster altaicus , as well as their climate-driven mechanisms. The impact of A. capillaris and A. altaicus on community above-ground biomass (AGB) and species richness (SR) were also evaluated. Our findings indicate that, over the past 37 years, A. capillaris exhibited lateral growth and asexual reproduction across the three sites. In contrast, A. altaicus tended to grow vertically and reproduce sexually, with a significant increase in its AGB. Moreover, the influence of climate fluctuation, characterized by variations in temperature and precipitation over specific time scales, on the two populations diminished from north to south. Long-term average climate, reflecting mean temperature and precipitation, and current climate conditions during the sampling year primarily influenced changes in A. capillaris and A. altaicus in south, respectively. Additionally, from north to south, the contribution of A. altaicus to community AGB and SR increased, while the contribution of A. capillaris to community AGB and SR decreased. Community AGB increased as the coupling index between A. capillaris and A. altaicus intensified. These findings can help us to better understand the coupling of plant traits, populations and communities, aid in the protection of grasslands under future climate change scenarios. • Populations along the precipitation gradient respond to climate change were explored. • Population with high PH/CD, RB/NB and SD/PD was more adaptable to climate change. • Current and past climate both drove populations growth and reproduction trade-offs. • Contribution of populations to community was related to local precipitation.