A Molecular Phylogenetic Study Of Pseudostellaria Pax (Caryophyllaceae)

Pseudostellaria Pax(Alsineae,Caryophyllaceae),a genus comprising about 25 species,distribute in Eastern Asia,North America and Europe.The centre of diversity is in Eastern Asia.Turczaninow formerly named this group Krascheninnikovia which is however a synonym of Eurotia,and could not be regarded as an available generic name.Thus Pseudostellaria is the correct name in 1934.Type species of the genus is P.rupestris.Ohwi in 1937,admitting for the genus 13 species,analyzed and elaborated the classification and distribution of the genus.As some new species of Pseudostellaria have been found in recent years,the species number of the genus increased.There has not been a comprehensive worldwide treatment to Psudostellaria since Ohwi(1937).The systematics work related to Pseudostellaria is rare.So a classification and distribution outline,and a molecular phylogenetic study of Pseudostellaria are necessary to resolve to intergeneric and interspecific systematic relationships.Fristly,on the basis of observation of herbarium specimens and comprehensive analysis of related literature,a classification and distribution outline of Pseudostellaria is presented comprehensively in this paper.The main results are as follows:(1)P.sierrae and P.oxyphylla,the presence of 5 stamens rather than 10 or 10-14 and absence of root tubers,differ from other species of Pseudostellaria.So P.sierrae and P.oxyphylla belonging to Pseudostellaria are not accepted in this study.Based on the results of related numerical taxonomic analysis,characteristics of leaf epidermis and our observation of herbarium specimens,it is not accepted that P.maximowicziana and P.himlaica are the synonym of P.heterantha.(2)There are 22 species in Pseudostellaria to be recognized preliminarily.They are P.rupestris,P.heterophylla,P.sylvatica,P.japonica,P.helanshanensis,P.polymorpha,P.tibetica,P.zhejiangensis,P.davidii,P.himalaica,P.maximowicziana,P.heterantha,P.tianmushansis,P.setulosa,P.longipedicellata,P.palibiniana,P.okamotoi,P.jamesiana,P.europaea,P.ebracteae,P.baekdusanensis,P.rigid.(3)The North temperate disjuncted distribution of Pseudostellaria composed of three isolated geographical regions:North America,the Mediterranean region and Eastern Asia.The centre of diversity is in Eastern Asia.20 species in Eastern Asia,one(P.jamesiana)in North America and one(P.europaea)in Europe.Secondly,22 samples from 16 taxa(P.rupestris,P.heterophylla,P.sylvatica,P.japonica,P.tibetica,P.davidii,P.maximowicziana,P.heterantha,P.tianmushansis,P.tianmushansis,P.palibiniana,P.jamesiana,P.europaea,P.ebracteae,P.rigid,P.sierrae,P.oxyphylla)of Pseudostellaria and 10 samples from 10 taxa(Arenaria densissima,A.przewalskii,A.serpyllifolia,Cerastium davuricum,C.dichotomum subsp.inflatum,Dianthus turkestanicus,Gypsophila perfoliata,Silene aprica,S.vulgaris,Stellaria americana,S.palustris,S.soongorica,Vaccaria hispanica)of related genera(Caryophyllaceae)were obtained by field collecting and herbarium serving.Then PCR amplification of four DNA regions(nrDNA ITS;cpDNA rbcL,matK and rps16)was carried out.In order to further assess the systematic position of Pseudostellaria in Caryophyllaceae,the DNA sequences data of 26 taxa(Bufonia tenuifolia,Drypis spinosa,Honckenya peploides,Minuartia biflora,Sagina pilifera,Schiedea apokremnos,Scleranthus annuus,Spergularia rubra,et.al.)from related genus of Caryophyllaceae were downloaded from Genbank.The final data of ITS+cpDNA combined matrix comprised 63 samples and 3825bp aligned nucleotides.The matrix was analyzed using Maximum Parsimony(MP),Bayesian Inference(BI)and Maximum Likelihood(ML)methods to study phylogenetic relationships between Pseudostellaria and related genera.The assigned six key morphological characters(Habit,Root tubers,Cleistogamous flowers,Petal of the chasmogamous flowers,No.stamen of the chasmogamous flowers,No.style of the chasmogamous flowers)were analyzed on the basis of 4-gene combined phylogenetic tree,and conducted by MacClade.The main results are as follows:(1)According to the combined phylogenetic tree:The core Pseudostellaria clade comprising Eurasian species was monophyletic(BSML=73%,BSMP=82%,PPBI=1.00)and formed two clades.It was related to Solitaria.P.sierra,P.oxyphylla,and P.jamesiana in North America were out of Pseudostellaria.P.sierrae and P.oxyphylla comprised a clade with high support values(BSML=100%,BSMP=100%,PPBI=1.00),which was far away from Pseudostellaria,and allied to that of Stellaria + Cerastium.Whereas P.jamesiana and Stellaria americana from North America with high support values was related Solitaria,but not included to any genera.(2)According to the result of MacClade analysis,within Pseudostellaria,Root tubers are apomorphy.The evolution trend of Clade ? and Clade ? is having cleistogamous flowers and 2 or 3 styles of the chasmogamous flowers.In conclusion,in order to maintain the monophyly of Pseudostellaria,P.sierra,P.oxyphylla,and P.jamesiana in North America should be removed and P.sierra,P.oxyphylla should be set up a new genus Pentandra M.L.Zhang,X.Q.Zeng&S.C.Sanderson.So there are 21 species in Pseudostellaria to be recognized preliminarily now.They are P.rupestris,P.heterophylla,P.sylvatica,P.japonica,P.helanshanensis,P.polymorpha,P.tibetica,P.zhejiangensis,P.davidii,P.himalaica,P.maximowicziana,P.heterantha,P.tianmushansis,P.setulosa,P.longipedicellata,P.palibiniana,P.okamotoi,P.europaea,P.ebracteae,P.baekdusanensis,P.rigid.The phylogenetic results supported to found two clades(Clade ?:P.japonica,P.rigida,P.heterophylla,P.palibinana,P.sylvatica;Clade ?:P.ebracteata,P.europaea,P.tibetica,P.heterantha,P.rupestris,P.tianmushanensis,P.maximowicziana,P.davidii)for the sampled Pseudostellaria,and phylogenetic position of P.europaea and P.ebractea is unfixed in Clade ? or Clade ?.The presence of two recognizable phylogenetic clades within the genus does not support the current classification into two sections.