Systermatic, Classficatic And Phlogenetic Study Of Euphorbieae (Euphorbiaceae) From China

The tribe Euphorbieae is an important group of the subfamily Euphorbioideaein Euphorbiaceae. There are ten genera (more than 2000 species) in this group.There are two genera in China. We study on the pollination biology, leaf epidermis,pollen morphology, cytology, biogeography, molecular systematics and cladistics ofthe tribe Euphorbieae in China. We synthetic discussed the trend of evolution andproblem of the every hierarchical relationship as well as its classification processing,from five biological categories of populations, individual, organ, cell and molecular.At last, we reconstructed the system of the tribe Euphorbieae in China.A combination of dichogamy and herkogamy in hermaphroditic plants is aneffective mechanism to encourage outcrossing and avoid selfing. In this paper, westudied whether such a mechanism completely avoids geitonogamous selfing inEuphorbia lathyris Linn. We studied the florescence syndrome of this species andfound that its florescences are characteristic of dichogamy and herkogamy. Eachindividual plant of this species has an average of three florescences ranging fromone to six, at both staminate and pistillate stages with a ratio of 2:1 in full anthesis.No autonomous selfing was found in the breeding experiments, indicating that thisspecies is pollinator-dependent for seed. But artificial selfing production forgeitonogamy produced high seed set, which implies that selfing can not becompletely avoided if effective pollinators move continuously between flowerswithin an individual plant. A variety of insects were observed to visit E. lathyris, but the most effective and common pollinators were Apis (Megapis) dorsataFabricius (Apidae) and Apis cerana Fabricius (Apidae). A further statisticobservation of these two effective pollinators indicated that they showed nopreference to either staminate or pistillate flowers but always visited them from thelower flowers to upper ones within individuals. We further calculated the frequencyof their visits between and within individual plants. Among the pollinators' bouts,the proportion of geitonogamous visits within an individual plant occupied about37%. Such a case implied that geitonagamous selfing was not avoided in E. lathyrisin spite of floral dichagamy and herkogamy, suggesting that dichogamy andherkogamy in hermaphroditic plants play a more important role in reducinginterference between male and female function than in encouraging outcrossing.The leaf epidermis of 17 species and 4 species of outgroup were investigated.Of which, there are 11 species were reported firstly. The micromorphologiccharacteristics of leaf epidermis of tribe Euphorbieae were divided into 5 types; thetrend of evolution for leaf epidermis micromorphology was discussed. As a result,the micromorphologic characteristics of leaf epidermis have important value of thesubgenus as well as species classification processing.Fifteen populations of fourteen species in this tribe were studied on cytology.Of which 6 species were reported firstly. Combined our works with the former,seven kinds of basic chromosome numbers: x=6, 7, 8,9, 10, 11,17 were recognizedin the world, of which tribe Euphorbieae in China possesses six kinds of basicchromosome numbers: x=6, 7, 8, 10, 11, 17. The tribe in China has the mostprimitive 1A karyotype possessed by the diploid population of E. esula, and themost evolutionary 3B karyotype by E. antiquorum. Combined with syntheticanalysis of the previous works, based on our research, we come to the conclusion asfellow: 1 Pedilanthus which possessed zygomorphic cyathium has the highest basicchromosome number x=17 are evolution, and Euphorbia which possessedactinomorphic cyathium has lower basic chromosome number (x=6, 7, 8, 9, 10. and11) are primitive. 2 This tribe has many ploidy variations. Polyploidy is one of theimportant mechanisms of evolution of tribe Euphorbieae. 3 Different subgenus hasdifferent basic chromosome number. The subgenus Chamaesyce has basic chromosome numbers being x=6, 10 and 11; the subgenus Agaloma has basicchromosome numbers being x=7; the subgenus Euphorbia has basic chromosomenumbers being x=10; the subgenus Poinsettia has basic chromosome numbers beingx=7; the subgenus Esula has basic chromosome numbers being x=7 and 10.The pollen morphology of 11 species and 4 species of outgroup wereinvestigated. Of which, there are 4 species were reported firstly. Themicromorphologic characteristics of pollen of tribe Euphorbieae were divided into3 types; the trend of evolution for pollen micromorphology was discussed. As aresult, the micromorphologic characteristics of pollen have important value of thesubgenus as well as species classification processing.On the basis of classification of morphology and cytotaonomy, 39 species(including 2 out groups) were selected from the tribe in China. The ITS genefragments of nuclaer DNA were amplified from 38 species by PCR method, whichwere approximately 603-658bp in length. And the ndhF gene fragments ofchloroplast DNA were amplified from 38 species by PCR method, which wereapproximately 1411-1496 in length. The two DNA fragments were sequenced. Thephylogeny and evolutionary history of tribe Euphorbieae were explored using thistwo DNA fragments.Considering the present and previous works of Euphorbieae, the data matrixeswere analyzed with PAUP method and resulted in two equally most parsimoniousCladograms. The one of them was selected as the base for discussing cladisticclassification and making cladistic analysis. According to the cladistic analysis,Euphorbieae of China was divided here into 2 genera; Euphorbia of China wasdivided into 7 subgenera and 11 sections. Systematic arrangements are as follows. Euphorbieae Euphorbiinae Euphorbia L. Subgenus 1 Chamaesyce Raf. Section 1 Sclerophyllae (Bioss.) Hurusawa Section 2 Hypericifoliae Pojero Section 3 ChamaesyceSubgenus 2 Agaloma (Raf.) HouseSubgenus 3 EuphorbiaSubgenus 4 Lacanthis Raf.Subgenus 5 Poinsettia (Grah.) HouseSubgenus 6 Tirucalli (Boiss.) S. CarterSubgenus 7 Esula Pers.Section 4 Lathyris Dumort.Section 5 Helioscopiae Dumort.Section 6 Chylogala (Prokh.) Prokh.Section 7 Paralias Dumort.Section 8 Tithymalus DubySection 9 Tulocarpa (Raf.) Prokh.Section 10 Cymatosperm (Prokh.) Prokh.Section 11 EsulaPedilanthus Neck. ex Poit.