Genome Size Evolution Of Vitaceae And Phylogenetic Relationships Of Nekemias

Vitaceae is a medium-size family in angiosperm with dominantly tropical distribution,and is well-known for its economic and evolutionary importances.In recent years,molecular phylogenetic relationships within Vitaceae have been well understood,however,studies on genome size within this family have been little reported.Therefore,based on the recent phylogenetic framework within Vitaceae,genome size was measured and the data can provide a chance to study its evolution processes and the effecting factors.Moreover,the phylogenetic relationships within Nekemias,a newly isolated genus and one of the basal clades of Vitaceae,remain unclear,which are very important for a better understanding of the processes of systematics and evolution within this family.The leaf epidermal morphology and the phylogenetic relationships within Nekemias were both performed in this present thesis.By exploring both the genome size evolution at family level and the phylgenetic relationships within Nekemias,the results have contributed much to our well-understanding of the phylogenetic frameworks and evolution patterns of this grape family.1.Genome size evolution of VitaceaeGenome size variation is of fundamental biological importance and has been a longstanding puzzle in evolutionary biology.In the present study,the genome size of 56 accessions corresponding to ten genera and 46 species of Vitaceae and Leeaceae is determined using flow cytometry.Phylogenetically based statistical analyses were used to infer ancestral character reconstructions of nuclear DNA contents.The DNA 1C-values of 38 species are reported for the first time here,with the largest genome(Cyphostemma humile,1C = 3.25 pg)roughly 10.48-fold larger than the smallest(Vitis vulpina,1C = 0.31pg).The large genomes are restricted to the tribe Cayratieae,and most other extant species in the family possess relatively small genomes.Ancestral genome size reconstruction revealed that the most recent common ancestor for the family had a relatively small genome(1C = 0.85 pg).Genome evolution in Vitaceae has been characterized by a trend towards genome size reduction,with just one episode of apparent DNA accumulation in the Cayratieae lineage.Such contrasting patterns of genome size evolution probably resulted from transposable elements and chromosome rearrangements,while neopolyploidization seems to contribute to recent genome increase in some species at the tips in the family tree.2.The morphology of leaf epidermis in NekemiasIn this study,the leaf epidermis of 28 samples representing six species of Nekemias and one species of the related genus of Ampelopsis,was investigated by using light microscopy.The results showed that the shapes of leaf epidermal cells are polygonal or irregular in form.The patterns of the anticlinal walls are straight,arched,sinuous or on the adaxial epidermis.The abaxial epidermis are consistent with that of the adaxial epidermis,except few samples with the strongly sinuous patterns.Anomocytic stomata are found on the abaxial surface.The epidermal hairs styles are multicellular,single-row on both sides and common in N.cantoniensis,N.grossedentata,N.rubifolia,except in N.chaffanjonii,N.hypoglauca.The microstructures of leaf epidermis fully revealed that the genus is located at the base clade of the grape family and with a closely relationships with Ampelopsis.Our results also provide useful reference to the pharmacognostic identification of the interspecific and intraspecific within Nekemias.3.The phylogenetic relationships in NekemiasBased on the combined datasets of five plastid sequences of psbA-trnH,trnL-F,petN-trnC,rps16,and atpB-rbcL,phylogenetic relationships of 40 accessions representing 7 species of Nekemias and its related outgroups(Ampelopsis 10 species and Cissus striata-complex)are reconstructed by using Maximum Parsimony,Maximum Likelihood and Bayesion Inference methods.Phylogenetic results showed that Nekemias is a monophyletic group as one of the basal lineages of Vitaceae.Two major clades within Nekemias are recognizable corresponding to their distribution and related morphology from eastern Asia and North America.Within the Asian lineage,N.megalophylla and N.hypoglauca form a clade and sister to the remainder four species(N.cantoniensis,N.grossedentata,N.rubifolia,N.chaffanjonii),which is also supported by the location of the chalazal knot at the dorsal side of seed.The phylogenetic relationships of the remainder species,especially for N.cantoniensis and N.grossedentata,are poorly supported with many polytomous branchs and probably caused by rapid diversification,which influenced by the changeable environments.