绢蒿荒漠植物种子大小、形状变异及其生态适应特征

Variations in seed mass,shape and adaptation characteristics in Seriphidium desert

广布于北疆地区的绢蒿荒漠草地作为重要牧场蕴含着丰富的生物多样性。收集了绢蒿荒漠的88种植物种子,对种子大小、形状及物种生活型进行了测定和分析,利用系统比较的方法对不同种子的大小和形状两个主要性状进行了谱系信号分析,并对不同种子对荒漠、半荒漠环境条件的适应类型进行了归纳分类。结果表明,88种种子大小可划分为A型(0.01~0.10mg)、B型(0.10~1.00mg)、C型(1.00~10.00mg)和D型(10.00~50.00mg)4种类型,其中B和C型种子在数量上占优势地位。所涉及物种可分为6种生活型,以一年生、多年生及短命植物为主。种子形状指数为0.00~0.20,细长或扁平种子有42种,球形或接近球形种子有46种。种子大小和形状在不同科间、科内种间以及同种植物异型种子间均具有极显著差异。种子大小无明显的谱系信号,存在一定的可塑性。种子形状具有明显的谱系信号,表现出较强的稳定性。绝大多数植物种子能够通过种子多型性、产生种子粘液、具有助力传播结构、特殊生活型以及动物消化道传播等适应对策对特殊环境产生很强的适应性。

Seriphidium desert grassland is widely distributed across the northern Xinjiang region and is known for its abundant plant diversity.We collected the seeds of 88 plant species from this grassland and measured seed mass,shape index and life form.We also analyzed the phylogenetic signal of seed mass and the shape index using phylogenetic comparative methods,in order to identify seed adaptation types for desert and semi-desert environments.Results showed that the seed mass of plants can be divided into four classes:A(0.01-0.10 mg),B(0.10-1.00 mg),C(1.00-10.00 mg)and D(10.00-50.00 mg),with classes B and C being dominant in quantity.The plant species divided into six life forms,of which the dominant are annual,perennial and ephemeral herbaceous.The shape index of seeds was determined by the variance of three dimensions(length,width and height),with the index scores ranging between 0.00 and 0.20.The shape of 42 species was close to sphericity while the remaining 46 species were flat or enlongated.There were significant differences in seed size and shape between families and between species of the same family,as well as seed heteromorphism within the same species.We found that seed mass had no significant phylogenetic signal and showed stability.However,seed shape had a significant phylogenetic signal and showed instability.Most seeds evidenced very strong adaptability to the extreme environment through seed heteromorphism,mucilaginous diaspore,appendages for seed dispersal,specialized life forms and endozoochorous dispersal by animals.