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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-07182013-103724 |
| Date | 18 July 2013 |
| Creators | Sidney, Nwigwe Chimdi |
| Contributors | Ms L Joubert, Dr AM Venter |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-07182013-103724/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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