Systematic Taxonomyand Resource Conservation On The Primulina Hance(Gesneriaceae)

The genus PrimulinaHance?Gesneriaceae,Didymocarpoideae?was established in 1883 composedof the single species P.tabacumHance.Based on molecular phylogenetic study,Wang et al.?2011?and Weber et al.?2011?performed phylogenetic reconstruction of Chirita Clarke and the related genera,and Primulina was thereby concomitantly revised.The newly defined Primulina is one of the largest genera of the Old World Gesneriaceae,comprising currently around 190 species mainly distributed in Karst and Danxia landform areas in S and SW China and N Vietnam with more than 50 taxa described in the last few years in S China and surrounding areas,and new taxa are being foundcontinually.The habitat of Primulinaplants is very special,and the distribution range is extremely narrow,so that most species are in the endangered or vulnerable state.Besides,Primulina plants have high ornamental values and landscape development prospects.In this study,we observed the morphological characteristics of leaf epidermis and pollens of 45species,and discussed their taxonomic significances.In addition,based on the sequences of three chloroplast DNA and one nuclear gene?ITS?,we reconstructed the phylogenetic tree of91 taxaand 87 species in Primulina,and discussed the systematic position of new taxon as well as the genetic relationship among species.We conducted a comprehensive plant resource survey of Primulina in Karst and Danxia landforms in southern China and surrounding areas,based on which,we analyzed the biodiversity and geographical distribution patterns,and evaluated the ex situ conservation of them.The main conclusions as follows:1.Leaf Epidermis MorphologyThe leaf epidermis structures of 45 species were observed under SEM.The upper epidermal cells of leaf blade are polygonal or irregular in shape,and the anticlinal walls of them are straight and arched,or shallow corrugated and corrugated respectively.The lower epidermal cells of leaf blade were mostly irregular,and the anticlinal walls are corrugated or shallow corrugated.In a few species,the lower epidermiscells are polygonal with straight or straight and arched anticlinal walls.The stomatal apparatuses are usually scattered in the lower leaf epidermis,and are all anisocytic type.The stomatal shape and the characteristics of the inner edges of outer dome covers have little difference among species,so the taxonomic significance ofthemis very small.The size of stomata is between 21.91³0.45×19.94²6.31?m,the stomatal density is 33²30/mm²,and the stomatal size and density are useful for species identification in Primulina.The indumentum types of leaf show a high diversity,including cement apparatus,short glandular hair,long glandular hair,short pubescence,long pubescence,hook shaped hair and some other types,all of which belong to multi-cell and single row type,with evident knots between cells.The hairs vary in type,number,and length among species,thus have important taxonomic significance.It is the first time that found that there is a special short pubescence on the upper and lower surfaces of the leaves blade of P.Shaoguanensis ined with densely granular appendages after the third cell upwards the base.2.Pollen MorphologyThe pollens of 45 species on Primulinaare studiedunder scanning electronic microscope?SEM?.The polar axis length of pollen is 17.01³5.14?m,and the equatorial axis length is12.05²2.4?m,P/E=0.94¹.87.Pollen grainsare prolate,subprolate or sub-spherical.The polar view is 3-cracked rounded,round or round triangular,with 3 colporate,which are slender and slightly wider near two ends or wider in the middle while attenuates in the two ends.The colpus membranesare decorated with granular or tumor-like protuberances.The exine ornamentations are usually reticular,while a few of them are rugulate,echinate,granular,verrucate-cerebroid-like.The muris are wide,narrow or nonuniform.The ridgesare flat or slightly concave and the intersections of ridges have small granular protrusions.The luminas are rounded,nearly rounded,oblong,irregular shapes,shallow poroid or some other types with different sizes.The pollen morphology in the genus Primulina are similar,but with different exine sculpturepatterns,which has some significance for specific classification in Primulina.3.Molecular SystemsBased on the sequences of three chloroplast DNA and one nuclear gene?ITS?,the phylogenetic tree comprising 91 taxa and 87 species in Primulinawas reconstructed,forming five major branches.Except Clade B branch?PP=77?,the support of each branch is quite high?PP=100?.In the subfield branches,the relationshipsamong species are very clear?PP=100?,with the exception ofP.huaijiensis.The results of this study support the incorporation of Chiritopsis W.T.Wang,Chirita Clarkeand Wentsaiboea D.Fang&W.T.Wang into Primulina Hance,forming Primulina sensu lato.Except forP.huaijiensis,the relationshipsamong the five new species found in this research was basically clear in the phylogenetic tree,and the results were consistent with the morphological studies to support the establishment of new species.Meanwhile,base on morphological and molecular data,P.hochiensisvar.RosulataF.Wen&Y.G.Wei is raised to the rank of species,as P.Rosulata?F.Wen&Y.G.Wei?Z.L.Ning&X.Y.Zhuang.4.Ex Situ ConservationIn this research,101 species were introduced and cultivated in SCBG,the survival species was 90with a survival rate of 89.1%after four years,and60%of them could flower normally.Under the shed cultivation conditions inGuangzhou,36 species of 60 normal flowering species flower earlier than the original habitat.The flowering periods of most cultivated plants are earlier and about 1-2 months longer than those in original habitats.The 16 species growth in the limestone cliff and 8 species growth in the cave cultivated experiment under the same garden.The result showed that the 16 species growing on the limestone cliff were survival,and the 8 species of themwere excellent.However,the 8species grown in the cave plants were died.Although cultivated in the same garden,the species grown in caves were smaller in size,and weaker in ecological competitiveness and adaptability than those on the shekpiks of the limestone or on the rocks under sparse forests.12 hybrid combinations of 17 species showed that hybridization among species is easy in genus Primulina,and the hybrid progeny usually have higher ornamental values than their parents in several aspects including flower color and plant architecture.Besides,yellow corolla was showed as a dominant trait in F₁.