Variation Of Floral Traits And Reproductive Adaptation Along Elevational Gradient Of Clematis Tangutica

The flower morphological composition of the angiosperm is considered to be influenced by a variety of factors.The traits of the flower affect the reproductive success rate of the plant,and the variation of characteristics often lead the variation between the biological and non-biological factors to the natural selection in strength and direction.the selection pressure of the environment forces the plant to adjust the characteristics of the flower,but when different plant meet the same pressure,adjustment strategies of them may become different,these characteristics may change with the altitude gradient,some of which will be expressed in the floral organ phenotype,while others are reflected in the allocation of resources(biomass),and some of the seeds obtain a stronger germination ability and seedling opportunities in coercive environment,and the adapting to alpine environment of the special seed germination Strategy have evolved.there are a lot of unique plants in Alpine Meadow of Eastern Qinghai-Tibetan Plateau of China.How to adapt to the stressful environment of Alpine and what reproductive strategies suit these species? which provides a special chance for ecologists and evolutionists ? There is also widely distribution of Clematis tangutica at high altitude areas in east Qinghai-Tibet Plateau.In this study,using Clematis tangutica from different altitudes as experimental materials.By studying the floral traits,the resource allocation of the flower amd and seed germination characteristics of altitude variation is related to the reproductive adaptation,we can reveal how the variation of floral traits can be adjusted with high altitude in poor conditions to achieve the reproductive success.In order to provide evidence for reproductive adaptation and natural selection.The results are as follow:(1)There was a strong positive correlation between calyx length,calyx width and altitude(p < 0.01),flower size is gradually increasing with the increasing of altitude.there was a positive correlation between calyx thickness,calyx weight and altitude(p< 0.05).(2)There was a positive correlation between pistil length,stamen length and altitude(p < 0.05),and a negative correlation between the distance of anther and stigma and altitude(p < 0.05).there was a strong positive correlation between the population of curved stigma to the total number of flowers and altitude(p < 0.01).(3)Elevation had a significant impact on the pollinator-visitation rates of Clematis tangutica;there was a negative correlation between pollinator-visitation rates and altitude,bumble bees were the main pollinators at both alpine and lowland sites in the study area,the number of bumble bees increased In high altitude plots.(4)There was a strong negative correlation between pollen number and altitude(p <0.01),and a negative correlation among pistil,stamen number and altitude(p < 0.05).No significant correlation was seen between pollen-ovule ratio and altitude(p> 0.05).(5)Elevation had a significant impact on the sex allocation of Clematis tangutica;male allocation were strong positively correlated with elevation(p < 0.01),but female allocation were negatively correlated with elevation(p < 0.05),there was a trade-off of male allocation and female allocation.(6)The germination rate of Clematis tangutica seeds increased with increasing altitude under five constant temperature conditions.In particular,the germination index and germination energy of seeds from high altitude is greater than the low altitude at low temperature.Higher elevations tend to have longer germination delay(P<0.05).The seeds weight of high altitude was heavier than the low and medium altitude.Meanwhile the heavier seeds from high to medium altitude have longer radicle length and germ length than the low altitude.The characteristics indicated that the altitude had significant effects on the seed germination ability of the Clematis tangutica.Because of the differing altitudes,the seeds of Clematis tangutica improved the fitness with pass through germination behavior and germination Strategy.