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Photographs of Vincetoxicum sangyojarniae sp. nov. a–b, V. aff. flexuosum c–d and V. tenue e–f: a, c, e flowers in top view; b, d, f flower buds in side view. Photographs taken by A. Kidyoo
Source publication
An unknown Vincetoxicum species has recently been discovered in eastern Thailand. It is a twiner that resembles in its morphology Vincetoxicum flexuosum s.l., a variable taxon widely occurring from tropical Asia to Australia. Morphological examination showed that despite similarities in growth habit, leaf shape, gross appearance of inflorescence st...
Citations
... Its phylogenetic position revealed in the present study suggests that its recognition as an independent is, in turn, closely related to the highly supported clade consisting of the polyploid New Caledonian V. biglandulosum (for polyploidy information on this species, see Liede-Schumann et al. 2020) and the polyploid African species. These relationships largely correspond to those found in the studies of Liede-Schumann et al. (2012, 2016 and also support the reinstatement of V. tenue as a valid species distinct from V. flexuosum, which has been suggested by Kidyoo and Kidyoo (2023). Moreover, the split of the two accessions of by molecular data are surprising, as there is no marked morphological similarity between the Thai and African members of this clade, nor between the species within each of these distribution areas. ...
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.
Specialized pollination systems frequently match a particular set of floral characteristics. Vincetoxicum spp. (Apocynaceae, Asclepiadoideae) have disk‐shaped flowers with open access to rewards and reproductive organs. Flowers with these traits are usually associated with generalized pollination. However, the highly modified androecium and gynoecium that characterize asclepiads are thought to be associated with specialized pollinators.
In V. sangyojarniae , we investigated floral biology, pollination, and the degree of pollinator specialization in two localities in Thailand. We examined floral traits that target legitimate pollinators.
Flowers of V. sangyojarniae opened only at night, emitted floral scents containing mainly ( E )‐ β ‐ocimene, 1‐octen‐3‐ol, ( E )‐4,8‐dimethyl‐1,3,7‐nonatriene ( E ‐DMNT) and N ‐(3‐methylbutyl)acetamide, and provided sucrose‐dominated nectar openly to insect visitors. Assessment of pollinator effectiveness indicated that V. sangyojarniae is functionally specialized for pollination by cecidomyiid flies. Although various insects, particularly cockroaches, frequently visited flowers, they did not carry pollinaria.
Our results suggest that V. sangyojarniae attracts its fly pollinators by emitting floral volatiles bearing olfactory notes associated with the presence of fungi or, less likely, of prey captured by predatory arthropods (food sources of its pollinators) but offers a nectar reward upon insect arrival. Hence, there is a mismatch between the advertisement and the actual reward. Our results also suggest that the size of floral parts constitutes a mechanical filter where reciprocal fit between flower and insect structures ensures that only suitable pollinators can extract the pollinaria, a prerequisite for successful pollination.
