| Intraspecies variations within species is common and widespread in plant,and the main causes of controversies in identification and delimitation of species.However,few literatures have focused on this subject.Using 14 species from Saussurea as a model,this study explores this variation and try to answer three problems related to it,that is: 1)the comparison of intraspecific variations within species;2)the correlation among intraspecific morphological diversities,genetic diversities or distribution ranges;3)the difficulty in species identification and delimitation caused by intraspecific variation.The study collected a total of 169 populations and 385 individual of 14 species,which are classified into three groups according to the degrees of intraspecific variation according to our morphological comparison.The first one are those showed little variation for three species,that is,S.katochaete,S.kingii and S.stella;the second one are those exhibit a serious of variations in a number of traits for five species,that is,S.elegans,S.parviflora,S.nivea,S.mongolica and S.cordifolia;the third are those variated evidently,close to or reaching the degree of varieties or subspecies,for six species,that is,S.japonica,S.brunneopilosa,S.przewalskii,S.ussuriensis,S.Pectinata and S.semilyrata.We sequenced the nuclear ITS and chloroplast mat K,psb A-trn H,trn K-rps16,and analyzed the correlation among the level of genetic diversity,the extent of morphological differentiation or the range of geographical distribution.The results showed that there is no significant correlation among them and 14 species can be classified into the following five groups based on the genetic and morphological diversity.(1)The species with little morphological and genetic variation.There is only one S.kingii.This species is widely distributed throughout the Qinghai-Tibet Plateau.We conducted extensive investigations on the distribution area of this species and collected samples of 24 individuals from 14 populations.Morphological analysis revealed that this species showed slight variation in plant height,achenes wrinkles,etc.,but all individuals had outer involucre with apical enlargement.Therefore it is easy to identify.Genetically,the maximum distance within the nuclear ITS species of this species is 0.8%,and the maximum distance of the chloroplast sequence is 0.1%,which is a lower intraspecies variability level.Systematic analysis shows that all individuals are clustered into a monophyletic on the results of the two sets of data.Therefore,we consider this species to be a "good species" of the genus.(2)The species with little morphological variations but high genetic variation.Only one species,i.e.,S.stella,belong to this group.This species distributed mainly in the southeastern part of the Qinghai-Tibet Plateau and occurred usually in swamps or beside rivers.Possibly due to the special habitat and the unique leaf which is red,asteriated arranged,and functioned as a warning to herbivory,this species is free from any controversies in delimitation and are among the few species without any synonym in the genus.Our morphological analysis found only slight differences in the length of the crown and the number of heads among different individuals,which exist mainly within population,irrelevant with the distribution.However,the genetic diversity within the species was found to be unexpectedly high.The nuclear ITS are recovered in three clades on the phylogenetic tree,with a genetic distance reaching 2.5%.The chloroplast sequences are also high,up to 0.9%,which is higher than the distance between many closely related species.Moreover,the genetic diversity are clearly correlated to geographical distribution.Thus,we speculated that this species is a typical "morphologically cryptic species".We further inferred that geographic segregation might derived from genetically isolation and resulting genetic differentiation of this species,but the selection from the herbivory eliminated any variation in morphology.(3)The species with high level of morphological variation but low level of genetic variation.Only one species,i.e.,S.japonica.This species is widely distributed in the Loess Plateau and neighboring regions.The morphological variated evidently.According to whether the stem has wings is divided into two varieties,namely var.japonica and var.pteroclada.Because the heads are small and some of the groups have been independently species(S.microcephala).According to the shape of the basal leaves,The species can be divided into four categories namely undivided,lyrate-pinnately parted,deeply lobed,bipinnatae,In this study,we collected 48 individuals.The analysis found that the genetic diversity within the species was low,the nuclear ITS was within 0.6%,the chloroplast sequence was within 0.3%,and the phylogenetic tree of the two groups of data.Therefore,the significant morphological variation of this species may be unrelated to genetic diversity,only to phenotypic plasticity.(4)The species with varied morphological variations,low level of ITS variations and high level of chloroplast variations.There are four species,one of which is S.katochaete,which has unique morphology in the leaf margin and crown hair,and the difference between the populations is extremely small.S.brunneopilosa has a large difference in morphology.It is treated as two species or two varieties.S.elegans and S.semilyrata often have complex intraspecific morphological variations in leaf shape and total stalk morphology.However,the nuclear ITS differences of the four species are relatively small,and the sampled individuals are monophyly on the phylogenetic tree.Therefore,the analysis results of the nuclear ITS support the definition of four species.However,there are high intraspecific differences in the chloroplast sequences of these four species,each of which appears 2-3 branches in phylogenetic tree.We speculate that the maternal parents of the four species are from a variety of plants,but hybridization and backcrossing leads to gradual agreement between the father.(5)The species with varied level of morphological variations while high genetic variations.There are seven species.the variation of S.pectinata is large,the other six species are S.przewalskii,S.ussuriensis,S.parviflora,S.mongolica,S.cordifolia.There are relatively complex but continuous intraspecific variations in Saussurea.However,these species do not form monophyly in the phylogenetic tree of ITS and chloroplast,but individuals of one species may be clustered with other species with distinct morphology.These species are distributed in the Loess Plateau,Mongolian Plateau and other places,the leaf base is mostly heart-shaped,some species exist hybridization and intermidate,we speculate that these species may be the result of recent radiation differentiation and hybridization.In summary,the main results and novel discovers of this study are: 1)There are significantly different intraspecific variations within the genus in both morphological and genetic diversity,which are not significantly correlated;2)different mechanism,such as radiation,hybridization,adaptation,isolation and differentiation,caused the difficulties in the debilitation of most species within the genus,and resultant,few species could be recognized as “good species” while most are the species of “on the road”;3)some species being little differentiated in morphology,such as S.katochaete and S.stella,may originated from hybridization,or consisted of genetically distinct lineages due to geographical isolation and genetic differentiation. |
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