The Effects Of Altitude On Population Genetic Characters Of Elymus Species

Altitude is a key factor of affecting biological evolution and genetic relationship in plant species.In order to clarify the micro-evolution mechanism of Elymus species to adapt to the change of altitude,we should reveal the relationship with Elymus population genetic characteristics and interspecific hybridization-differentiation.First,in order to study the effect of altitude on the morphological traits of Elymus species,thirteen morphological traits of 810 individuals from 27 populations of hexaploid E.nutans,tetraploid E.burchan-buddae and E.sibiricus were investigated.These materials were collected at the altitude ranges from 3,098 m to 4,203 m.The results showed that the variation coefficients of E.nutans,E.burchan-buddae and E.Sibiricus ranged from 8.8% to 59.1%,8.2% to 53.7% and 7.6% to 56.7%,respectively.The length of lemma had the smallest variation coefficient,compared to other traits.The Elymus populations with similar attitude were clustered together.Significant relationship were observed between altitude and morphological traits(P<0.01).And principal component analysis showed that the single plant height,single ear weight,length and width of palea,lemma,glume and boot leaf,and floret number were the principal factors of inducing the variation of morphological characteristics in Elymus species.Thus,the above results indicated that altitude shaped the morphological traits of Elymus species.Different species and morphological traits had different responses to altitude.Tetraploid Elymus species had higher sensitivity to altitude than hexaploid species.Therefore,some morphological traits can be used for analyzing the evolution of Elymus species along altitude.Second,We wanted to know that the level of genetic diversity of the species can reflect the adaptability of the species or population to the environment and the evolutionary potential of the species and the stability of the population.So,nucleotide sequences from ITS and Waxy nuclear genes were applied to investigate nucleotide diversity in 18 natural populations of the hexaploid Elymus nutans and the tetraploid E.burchan-buddae(Poaceae)from Qinghai-Tibetan Plateau at different altitudes.Analysis the nucleotide diversity results show that:(1)the hexaploid Elymus nutans were much larger than the tetraploid E.burchan-buddae in many diversity index of nucleic acid within each altitude group,So,the result indicates that the evolution rate of nuclear genes of the hexaploid species is faster than that of the tetraploid plant.(2)The nucleotide diversity in the high-altitude populations were lower than that in the middle and lower altitude groups,As Elymus plants are closer to the critical limit of its habitat range,the nucleic acid polymorphism will be gradually reduced.