A of finlaysonia and streptocaulon (periplocoideae; apocynaceae)taxonomic revision

[摘要] English: A taxonomic revision of Finlaysonia Wall. and Streptocaulon Wight and Arn. (Apocynaceae; Periplocoideaea) in Asia is presented. This revision comprises an investigation of the nomenclature of the two genera and their species, macromorphology of all plant parts; micromorphology of leaf epidermal surfaces, seed coat surfaces and translators, pollen wall architecture, geographical distribution, habitat preferences and phylogenetic relationships. The investigation resulted in the identification of characteristics for effective delimitation of the two genera and their respective species, identification keys for both genera and the species within each genus, correction of nomenclature, determination of inter-and intra-phylogenetic relationships and determination of their distribution patterns. Available type material was investigated, type literature was confirmed for all species and synonyms were declared where applicable. Lectotypes, selected from isotypes or syntypes, were declared where holotypes were not cited by authors or were not found in their collections or were destroyed or could not be located at all. Finlaysonia and Streptocaulon are closely related genera and have many characters in common. This includes the presence of colleters on the interpetiolar ridges, in leaf axils, on the leaf petiole and main vein, in the axils of inflorescences and at the inner bases of sepals. The flowers in both genera are rather similar with bowl-shaped, inverted corolla tubes and reflexed lobes, presence of only the primary corona which is divided into a foot and lobe, presence of interstaminal nectaries, translators and pollinia, two semi-inferior, apocarpous many ovuled-ovaries, a compound style, a gynostegium that is the result of fusion between stylar head and anthers, paired follicles and seeds with comas at the micropylar end except in F. obovata where the coma is replaced by a winged, fimbriate margin. Finlaysonia is characterized by trichomes on the outer or inner surfaces of the corolla, presence of anther callosities except in F. pierrei. Streptocaulon, in contrast, is characterized by a glabrous corolla, absence of anther callosities. A number of characters, unique to a specific species and thus diagnostic were used in identifying of the species. Vegetative features provide the most effective means to distinguish and identify the species and combinations of leaf shape, leaf length:width ratios, texture, leaf indumentum and petiole length proved to be taxonomically the most valuable characters. Corolla lobe apex shape, corona lobe shape, anther connective indumentum, style indumentum, follicle and seed shape and size, seed margin appearance and coma length and presence/absence of coma are diagnostically useful. Micromorphological features of the leaf epidermis, such as primary sculpture, as well as stomata characteristics and distribution can also be useful. However, a single character is often insufficient to distinguish between the genera and a combination of characters should to be applied. Finlaysonia and Streptocaulon are widely distributed in Asia with the largest concentration of species in Thailand. Species like F. khasiana, F. obovata, F. pierrei, S. juventas and S. wallichii are common, while F. decidua, F. puberulum, F. venosa, F. insularum, S. cumingii, S, curtisii, S. lanuginosa and S. sylvestre have restricted distributions, at present only known from one or two localities. Most of the species are found on limestone and form part of scrub forest and mixed deciduous forest. Finlaysonia obovata typically are found in mangrove forests along coastal lagunes and tidal rivers, while S. sylvestre and S. juventas are found in riverine forest along fresh water rivers. The phylogenetic treatment was based on morphological characters of vegetative parts, flowers and fruits. The analyses yielded polytomies as strict concensus trees unless the Bootstrap support values were ignored. However, an exciting result from the strict concensus trees was the pairing of S. lanuginosa and S. curtisii in a clade, confirming the finding of Ionta and Judd (2007) and justifying the transfer of these two species from Finlaysonia to Streptocaulon.

[发布机构] University of the Free State