Divergent adaptive strategies of paired Meconopsis species and their impact factors along the elevational gradients in the south-eastern margin of Qinghai-Tibet Plateau

Plant functional trait reflects plant growth and resource utilization strategy. Quantitative analysis of variation in plant traits will help us to better understand their environmental adaptation strategies, which is helpful to guide the sustainable utilization with proper theoretical framework and practical implications. Leaf-height-seed (LHS) scheme is to quantify the strategy of plants by the location of three easily measurable functional traits which are specific leaf area (SLA), plant height, and seed mass in three-dimensional space. We applied this scheme to paired Meconopsis species to assess the variation of life-history traits over elevational gradients in the southeastern margin of Qinghai-Tibet Plateau, identify the environmental factors that shape these traits and compare the intraspecific correlations of LHS traits with elevation to the interspecific patterns that have been previously documented. We measured LHS traits of 3 ∼ 6 M. punicea and M. integrifolia populations. Furthermore, we analyzed the impact of environmental factors on LHS traits by regression models. The results showed that both species displayed a significant decrease with increasing elevation for plant height and only the SLA of M. punicea decreased significantly with increasing elevation, while the elevation had no significant effect on seed mass. Moreover, only SLA and plant height for M. punicea in Kaka Mountain, SLA of cauline leaf and plant height for M. integrifolia in Gonggangling Mountain were significantly correlated. Along the elevational gradient, these two species adopted the LHS strategies varied to some extent. M. punicea tended to adopt strategies of slow growth, strong survivability and competitiveness (S-L-L), while M. integrifolia tended to have strategies of rapid growth, strong dispersal and weak competitiveness (L-S-S) within our study elevational range. The most important environmental factor for their trait variation is the growing season mean temperature. Variations in LHS traits of a single species suggested that plant strategy determined by the position within this three-factor triangle is not constant along the elevational gradient. Additionally, our within-species analysis generally failed to support the correlations between LHS traits and elevation that had been previously observed across species.