Study On Local Adaptation Of Three Common Herbage Species From Tibetan Plateau

Study of local adaptation is of fundamental importance to understanding adaptation evolution,shift,and extinction risks of plant population especially under rapid climate change background.Also,understanding plant local adaptation plays a key role in selecting seed sources for restoration project.The evaluation of plant local adaptation is often affected by many external factors,including the maternal environment experienced by seed development,the time of sowing and seed state before sowing.However,due to the difference in research period,research conditions and emphasis,previous studies on local adaptation of plant are mostly limited to a single life cycle stage or a few phenotypic traits,lacking systematic research on the entire life cycle of plants.In addition,the intrinsic link between phenotypic traits at various stages and plant fitness is unclear.Therefore,seeds of three herbage species from Tibetan Plateau,Comastoma pulmonarium,Elymus nutans and Halenia elliptica,were used in this study,combined with common garden and reciprocal sowing experiments.This study main focus on:1)the effect of storage on the local adaptation of the tested species;2)the effect of maternal environment on the local adaptation of E.nutans and H.elliptica;3)the contribution of different phenotypic traits in the whole life cycle stage of C.pulmonarium and H.elliptica to their fitness.The main results are as follows:1.The effect of seed storage on plant germination phenotype,emergence phenotype,seedling phenotype and the characteristics of adult growth and reproduction were studied based on the fresh and stored(6 months at room condition)seeds.The results showed that storage not only affected the temperature threshold for germination and its relationship with altitude of E.nutans population,but also significantly increased seedling emergence of this species under field conditions(P<0.05).For example,the base temperature for germination of freshly seeds was negatively correlated with altitude(R~2=0.637,P=0.003),but this relationship became irrelevant after seeds were stored(R~2=0.012,P=0.749).In addition,although storage did not affect the fitness of C.pulmonarium and H.elliptica,it significantly affected the phenotypic traits of both species at the seedling stage(P<0.05).For instance,storage increased leaf crown length,leaf crown width,plant height and number of leaves for all populations of C.pulmonarium to varying degrees,while the effects on seedling phenotypic traits of H.elliptica were different among populations.These results suggest that it should be possible to use fresh seeds in studies of plant local adaptation at the seedling stage.2.The effects of maternal environment on the evaluation of local adaptation of E.nutans and H.elliptica were conducted by combing common garden and reciprocal sowing experiments.The results showed that common garden experiment weakened the differences in germination phenotypes among populations,and eliminated the effects of the population’s maternal environment on species adaptability.In addition,the maternal environment mediated by different common gardens will affect the formation of native adaptive advantage of E.nutans.For example,in the reciprocal sowing site of Maqu,the cumulative fitness for seeds harvested from Maqu common garden from 2019 to 2021 did not differ significantly among populations(P>0.05),while for seeds harvested from Xiahe common garden,the native population has as adaptive advantage in its own habitat.Furthermore,the maternal environment in which the common garden was located has an impact on the seedling emergence,seedling survival,leaf crown length,leaf crown width,seedling plant height,number of leaves,adult plant height,aboveground biomass,stem diameter and fitness of H.elliptica,but the degree of influence varied among populations.3.The contribution of phenotypic traits at different life cycle stage of C.pulmonarium and H.elliptica to their fitness were investigated based on dominance analysis.The results showed that the seedling survival and aboveground biomass at the adult stage of the plant have the highest cumulative contribution to the fitness of C.pulmonarium and H.elliptica.Seedling survival was a key phenotypic trait which determining the fitness of two species,and the contribution to their fitness were 54.5%and 67.6%,respectively.These results indicate that population performance and differences at the adult stage should be the focus of attention,especially in the study of local adaptation for biennials.This study is the first to systematically consider the effects of seed storage on germination phenotype,emergence phenotype,emergence phenotype,seedling phenotype and adult plant growth and reproduction.Furthermore,the contribution of phenotypic traits at different life cycle stages of plants to their fitness was quantified.Based on this,we aimed to provide scientific evidence for building an explicit evaluation system for local adaptation,but also provide scientific data supporting for grassland management and restoration in Tibetan Plateau ecosystem.