The Phylogenetic Relationships Between Ulmus Gaussenii Cheng And Its Close Relatives In Genus Ulmus Based On The ITS, AtpB-rbcL And Pollen Morphology

Endemic and endangered plant of Ulmus gaussenii Cheng is spermatophyte unique to China. It is identified and named by famous plant taxonomist of Professor Zheng wanjun in 1955. Also, It had been listed in "The red book of plants in China". The study is to explore the systematic position of U. gaussenii Cheng in genus Ulmus by pollen morphology characteristics and the phylogenetic tree constructed by DNA sequence data.Firstly, Pollen morphology of two endangered elms peculiar to Mt.Lanya were examined and described comprehensively under light Microscope (LM). They are U. gaussenii Cheng, U. chenmoui Cheng. The result show that the pollen grains are mainly subpheroidal in shape, and polygonal to rounded or irregular-shaped in polar view. The ornamentation of exine is verrucate, the apertures are of 4-6 pores located in equator and subequato. U. gaussenii of pollen morphology showed typical endangered characteristics when compared with U. pumlia. The results indicate that U. gaussenii has a near relationship with U. chenmoui by similar ornamentation.Secondly, in this paper, Phylogenetic relationships of U. gaussenii was examined based on DNA sequences of the chloroplase atpB-rbcL gene and the ITS region of nuclear ribosomal DNA. Our data support its placement in genus Ulmus, but the pollen morphology characteristics. The sequence of atpB-rbcL in 24 species ranged from 735 to 834. The total G+C content varied from 29.3% to 31.6%. With PAUP4.0, Mega4.0, MrBayes 3.0 analysis, the phylogenetic trees were constructed. The main implication of the phylogenetic analysis show U. gaussenii has near relationship with U. glaucescens var. lasiocarpa, U. japonica var.suberosa, U. macrocarpa, U. erythrocarpa based on Bayesian-tree and NJ-tree.The sequence of ITS in 20 species ranged from 549bp to 646bp, with the content of conserved sites, varied site and parsim-info site are 566bp,83bp and 26bp respectively. The total G+C content varied from 61.5% to 68%. With PAUP4.0, Mega4.0, MrBayes 3.0 analysis, the phylogenetic tree were constructed. The main implication of the phylogenetic analyzed show U.gaussenii has near relationship with U. glaucescens var. lasiocarpa, U. japonica var.suberosa, U. macrocarpa, U. lamellose based on Bayesian-tree and NJ-tree. In addition, our result suggest that the position of U. glaucescens var. lasiocarpa and U. japonica var.suberosa which were variety in Ser.Glabrae Moss need to be discussed further.Four major methods such as Maximum Parsimony, Neighbor Joining, Maximum Likelihood and Bayesian inference are widely used for phylogenrtic reconstruction. During the analyzing process, we applied distance method and bayesian method, as they give more resolution and higer support value. Also, the species of interrelationshiops in genus are also discussed.Thirdly, although we get different result from pollen morphology characteristics and the phylogenetic tree constructed by DNA sequence data, but the data based on molecular data support its placement in genus Ulmus that was defined traditionally. We could get ideal result if we combined more molecular datas and other analytical methods in the future.