The identity of Ceropegia hirsuta in Thailand has been questioned. Although this plant is quite similar to the original C. hirsuta from India, being entirely hirsute, with yellowishshaded flowers, a curved, funnel-shaped corolla tube, and broad corolla lobes shorter than the corolla tube, there are several clear differences in morphological traits between the materials collected in Thailand and the type and further specimens collected in India. Moreover, C. hirsuta s.s. is restricted to Peninsular India. In this study, using molecular phylogenetic analysis based on DNA sequence data for ITS (nuclear) and trnT-L, trnL, and trnL-F (all cpDNA) markers, and classical morphology-based delineation, we demonstrate that the plant from Thailand represents a species on its own clearly separated from C. hirsuta s.s. as well as from all other known congeners. Therefore, we here describe it as a new species, C. citrina.A detailed description, illustrations, and photographs are provided, together with a comparison of morphological traits of C. citrina, C. hirsuta and another Thai species, C. foetidiflora. We also provide characterization of floral volatile compounds and pollinators.Our study emphasizes that morphological convergence may lead to errors in taxonomic treatment within the genus Ceropegia, and that phylogenetic relationships are largely congruent with geographic distribution.

A time-consuming yet mandatory step during in vitro sexual propagation of orchids is the treatment of seeds with a disinfecting solution that also serves to scarify the seeds. If the seeds are not properly disinfected, microorganisms grow within the culture vessel, thus reducing the efficacy of the process and burdening the operation with unnecessary materials and labour. On the other hand, a long period of disinfection may damage the seed. The literature is inconclusive with respect to the proper combination of solution strength and duration of the treatment, especially with respect to Mediterranean orchids. The objective of this research is to determine optimal disinfection/scarification times for two species with thin and thick seed coats, respectively. Seeds of Anacamptis laxiflora (Lam.) and Himantoglossum robertianum (Loisel.) were treated in 1% NaClO solution for 5, 15, 25, 35 and 45 minutes and sown in modified organic Malmgren medium. Logistic regression models were fitted to the results. Due to the small number of observations per treatment, regression models of infection rates on treatment duration had no more predictive ability than the mean infection rate. On the other hand, regression models of germination rates on treatment duration proved statistically significant or nearly so. Treatment of only a few minutes in 1% NaClO seems to be optimal for seeds with relatively permeable seed coats such as those of A. laxiflora (Lam.). Conversely, treatment of 45 minutes in 1% NaClO may be inadequate for seeds with relatively impermeable seed coats such as those of H. robertianum (Loisel.).

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.