Phylogenetic Studies In The Cosmopolitan Family Smilacaceae

The phylogenetic relationships of Smilacaceae were comprehensively investigated by means of comparative seed coat, palynology, morphological cladistic and molecular systematics which was based on three DNA regions, including nrDNA ITS and cpDNA rpL16 and matK. The results were summarized as follows:Pollen from 125 species of Smilax, Heterosmilax and Ripogonum was examined using light and scanning electron microscopy. Ten of these were examined further by transmission electron microscopy. Four distinct pollen types grouped into two major pollen classes were distinguished: Class 1, represented by the pollen of all Smilax and Heterosmilax species, is mostly spheroidal, inaperturate, and spinulate or microspinulate, with a thin, fragile exine of varied sculpturing; three pollen types are represented within this class. Class 2 is found only in Ripogonum and contains a single pollen type with prolate, monosulcate, reticulately-sculptured pollen. The unique pollen morphology of Ripogonum supports its removal from Smilacaceae. In contrast, the characteristics of Heterosmilax pollen intergraded with those seen in Smilax, suggesting that the former might be better reduced to synonymy with the latter. A key to the identification of these pollen types is presented along with a discussion of geographic and possible evolutionary trends among them.Seed macromorphology and seed-coat micromorphology of 50 species and 4 varieties belonging to three genera of Smilacaceae were observed under light microscope (LM) and scanning electron microscope (SEM). The seeds are spheroidal, ellipsoid, trigonal-oblate in shape. Under SEM the surface pattern of the seeds shows some variations among the species and eight types have been observed, i.e. Roughly-rugulate, Rugulate, Reticulate, Micro-reticulate, Foveolate, Densely-foveolate, Strialate, Wavelate. The seed of Ripogonum is big and the seed surface is roughly-rugulate, which is distinct from others. Heterosmilax and Smilax make generic separation less strong based on the seed-coat micromorphology. Evidence from seed-coat micromorphological features supports the treatment of reducing Heterosmilax to Smilax. The features of seed surface seem to be quite variational within Smilax andthus are of significant value in the delimitation of some species. The reticulate type is the commonest in Smilax, which includes most of species of Sect. China and Sect. Macranthea, and presumes they are closely related to each other. As well as, Sect. Nemexia and Sect. Coilanthus and Heterosmilax are relative to each other by having similar rugulate seed surface ornamentation.The cladistic analysis included 47 characters with 79 species representing all genera and sections of the Smilacaceae from all over the world, with two genera of the Philasiaceae as outgroups. A matrix of 36 binary and 11 multistate morphological characters was made. The first analysis yielded numerous most parsimonious trees of 275 steps, and then 82 most parsimonious trees with 40.729 steps length were produced by reweighting characters using maximum values of RC, which remained stable after the second reweighting. We found moderate resolution but generally poor bootstrap support for the phylogenetic relationships in the family. From the strict consensus tree and the NJ tree, Ripogonum is a sister to Smilax, but may be better treated as a separate family. Heterosmilax is considered to be derived from ancestral Smilax and occurs as the most derived clade of the Smilacaceae, and thus it is reasonable to retain it as a section in Smilax. Within Smilax most currently recognized sections are polyphyletic, but some major lineages are distinct. The herbaceous Smilax species form a monophyletic clade, and it is also the case for the South American species. Their positions in the cladogram are intriguing and may help to shed light on evolutionary and biogeographic history of the family.Phylogenetic relationships among the species of Smilacaceae were investigated by separate and combined cladistic analyses of nuclear rDNA ITS, and plastid cpDNA rpL16, matK. sequences. Results strongly support a clade of two genera Smilax and Heterosmilax. Ripogonum and Lapaeria are closely related to each other than to Smilax + Heterosmilax, may be better classified in separate families. Within Smilax few of the sections are monophyletic, but some major lineages are evident. The base clade only contains S. aspera, which is the sole member of Smilax section Smilax and is sister to the entire genus. The remainder of the genus is divided into an Old World clade and a New World clade.Based on the different molecular data analyses, the relationships within Smilax failed to get robust clade due to the ambiguous position of species, but some potential close interspecies relationships were inferred, such as S. china, S. trinervula, S. diavidiana form a clade with 99% bts, and S. chigii, S. ferox, S. polycolea form a clade with 95% bts. It was deduced that Smilax had undertaken a rapid, radical diversification during its evolutionary history, and this evolutionary radiation may be an important cause for the poorly resolved phylogenetic reconstruction.