| As a perennial herb, Ophiopogon japonicus belongs to Ophiopogon in liliaceae family. It is a model and most widely distributed species of Ophiopogon. Previous researches indicated that O. japonicus from Mt. Jinfoshan in Chongqin had profuse variation in chromosome number. Hence, we exhaustively sampled in Mt. Jinfoshan, the projection area of which is 0.5 square meter and altitude is 700-900 meter. Through investigating the habitat niche in Mt. Jinfoshan, studying O.japonicus both in the choromosome level and genomic level, this research showed that:1, Abundant variation of somatic chromosome number existed in O. japonicus. Chromosome counting exposes two basic chromosome numbers(x=17&18 respectively) and ploidy variation like diploid, tetraploid, pentaploid, hexaploid frequently happended in this population2, The result of FISH(Fluorescent in situ hybridization) showed that tetraploid has 2 pairs of signals.3, The genomic data from amplification by primers based on convallariae that is a closely related genera of O. japonicus and self-designed primers according to EST-SSR revealed the distinct divergence between these individuals with different chromosome basic number.Variation in chromosome basic number resulted in the reproductive isolation and contributes the species of x=17 and x=18 divergent into two species. Here we provide a new support of sympatric speciation in a case study of instantaneous speciation model in sibling species of O. japonicus. At last, protections for plant germplasm resources and genetic diversities are proposed basing on our research.
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