Phylogenetic positions of Thai members of Gymnema, Gymnemopsis and Sarcolobus (Apocynaceae, Asclepiadoideae, Marsdenieae), and two new Sarcolobus species uncovered by morpho-molecular evidence.

The present study assesses the phylogenetic position of certain Thai members of Gymnema, Gymnemopsis, and Sarcolobus in relation to other known Marsdenieae species. Fifteen accessions newly sequenced from Thailand were added to the dataset of the homologous sequences of 125 accessions of Marsdenieae downloaded from GenBank. In our molecular phylogeny, almost all the delimited major clades and their relationships are largely congruent with those revealed in previous studies. The monophyly of Gymnema (including the former Jasminanthes species) and that of Sarcolobus, as presently circumscribed, are confirmed. The new accessions of these two genera from Thailand are well grouped with the members of their respective genera. Our analyses provide the first molecular evidence for recognition of Gymnemopsis, a small Asian genus that has never been included in the previous phylogenetic studies, as a distinct genus. All elements of Gymnemopsis are retrieved as a well-supported monophyletic group that is strongly supported as sister to Lygisma, another small Asian genus that most closely resembles it in growth habit, color of latex, indumentum on plant parts, corona structure and follicle traits. Combined molecular phylogenetic, morphological and ecological data also support recognition of two new Sarcolobus species from Thailand, Sarcolobus busbanianus sp. nov. and S. flavus sp. nov. Similarities and differences between these new species and their close relative, S. carinatus, are discussed. In addition, this study also reveals the first record for Thailand of Gymnema lacei. Keys to the species of Gymnemopsis (for all members of the genus), Gymnema and Sarcolobus (for Thai members of these genera) are provided.

Molecular phylogeny of Vincetoxicum (Apocynaceae, Asclepiadoideae) from Thailand and integrative taxonomy corroborating a new cryptic species within Vincetoxicum kerrii.

An updated phylogeny of the genus Vincetoxicum s.l. based on DNA sequences of the nuclear internal transcribed spacer (ITS) region and three plastid markers is presented. In total, 21 accessions newly sequenced from Thailand were added to the dataset of the homologous sequences of 75 other Vincetoxicum taxa downloaded from GenBank. In our analysis, the relationships between the well-supported clades largely correspond to those revealed in previous studies. With some exceptions, the phylogenetic positions of the Thai taxa in relation to other conspecifics and congeners generally reflect the geographic distributions of taxa. Moreover, recent extensive sampling throughout Thailand and in-depth investigation have revealed V. kerrii, a slender twiner widespread from South China to Indo-China, to be a species complex. A combination of molecular, morphological, anatomical, ultrastructural and ecological evidence allowed us to reveal a new cryptic species hidden within V. kerrii, described here under the name V. simplex. A comprehensive description, illustrations, photographs, and comparison with the morphologically similar species are provided. Although V. simplex and V. kerrii s.s. resemble one another in various aspects of vegetative and reproductive structures, the latter is phylogenetically closely related to V. irrawadense, which is much less similar morphologically to both V. simplex and V. kerrii s.s. than the latter two are to each other. In addition to the new cryptic species recognized in the present study, a new record for Thailand, V. microstachys, is also reported.

The diversity and evolution of pollination systems in large plant clades: Apocynaceae as a case study.

Background and Aims: Large clades of angiosperms are often characterized by diverse interactions with pollinators, but how these pollination systems are structured phylogenetically and biogeographically is still uncertain for most families. Apocynaceae is a clade of >5300 species with a worldwide distribution. A database representing >10 % of species in the family was used to explore the diversity of pollinators and evolutionary shifts in pollination systems across major clades and regions. Methods: The database was compiled from published and unpublished reports. Plants were categorized into broad pollination systems and then subdivided to include bimodal systems. These were mapped against the five major divisions of the family, and against the smaller clades. Finally, pollination systems were mapped onto a phylogenetic reconstruction that included those species for which sequence data are available, and transition rates between pollination systems were calculated. Key Results: Most Apocynaceae are insect pollinated with few records of bird pollination. Almost three-quarters of species are pollinated by a single higher taxon (e.g. flies or moths); 7 % have bimodal pollination systems, whilst the remaining approx. 20 % are insect generalists. The less phenotypically specialized flowers of the Rauvolfioids are pollinated by a more restricted set of pollinators than are more complex flowers within the Apocynoids + Periplocoideae + Secamonoideae + Asclepiadoideae (APSA) clade. Certain combinations of bimodal pollination systems are more common than others. Some pollination systems are missing from particular regions, whilst others are over-represented. Conclusions: Within Apocynaceae, interactions with pollinators are highly structured both phylogenetically and biogeographically. Variation in transition rates between pollination systems suggest constraints on their evolution, whereas regional differences point to environmental effects such as filtering of certain pollinators from habitats. This is the most extensive analysis of its type so far attempted and gives important insights into the diversity and evolution of pollination systems in large clades.

Pollinator and floral odor specificity among four synchronopatric species of Ceropegia (Apocynaceae) suggests ethological isolation that prevents reproductive interference.

Possession of flowers that trap fly pollinators is a conservative trait within the genus Ceropegia, in which pollination systems can be generalized or highly specialized. However, little is known about the role of plant-pollinator interactions in the maintenance of species boundaries. This study examined the degree of plant-pollinator specialization and identified the parameters responsible for specificity among four co-occurring Ceropegia species with overlapping flowering times. All investigated plant species were functionally specialized on pollination by Chloropidae and/or Milichiidae flies and each Ceropegia species was, in turn, ecologically highly specialized on only two pollinating fly morphospecies, though one plant species appeared more generalist. Species-specific fly attraction was due to the differences between plant species in floral scents, floral morphology, colour patterns, and presence of other functional structures, e.g., vibratile trichomes, which were shown to contribute to pollinator attraction in one study species. The combination of these olfactory and visual cues differentially influenced pollinator preferences and thus hindered heterospecific visitation. Furthermore, a pollinator exchange experiment also highlighted that species integrity is maintained through efficient ethological isolation (pollinator attraction). The mechanical isolation mediated by the fit between floral morphology and size and/or shape of fly pollinators appears less pronounced here, but whether or not the morphological match between male (pollinium) and female (guide rails) reproductive organs can impede hybridization remains to be investigated.