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Two new species of genus Helicteres (Malvaceae, Helicteroideae), Helicteres Taynguyenenis and Helicteres dakmilensis from the Central Highlands of Vietnam are described and illustrated. H. taynguyenensis is morphologically similar to Helicteres angustifolia widely distributed in mainland SE Asia to China, Japan and Australia, but differs from the latter by having shorter petioles, larger calyx and petals, and longer androgynophores. Helicteres dakmilensis is closely related to Helicteres poilanei endemic to Vietnam, but distinguished by shorter petioles, fewer secondary veins, persistent stipules and bracts, larger calyx and fruits. The IUCN conservation status, vernacular name, illustrations, photographs, and comparison with the closest allies are provided for each of the new species.

The premise of the study Though phenological studies in montane forests are important, particularly in tropical Asia where primitive angiosperms are found, the phenology in these forests is still poorly understood. To characterize the phenological patterns and reveal the relationships between meteorological factors and phenology, we observed the leafing, flowering, and fruiting phenology in the tropical montane forests of Vietnam. Methods We observed the leafing, flowering, and fruiting phenology of 91 species every three months in five plots (elev. 1460–1920 m) in Bidoup-Nui Ba National Park, Vietnam, and analyzed how the number of species that were leafing, flowering, or fruiting varied in relation to precipitation, temperature, or daylength. Key results The leafing phenology showed a peak at the beginning of the wet season (April) and was significantly influenced by all of day length, precipitation, and temperature. The flowering phenology did not show any distinct peaks and was influenced by day length and precipitation. The fruiting phenology showed a low peak from the wet season (July) to the beginning of the dry season (December) and was not significantly influenced by any of the meteorological factors. Main conclusion The community-wide phenological patterns of leafing, flowering, and fruiting in the tropical montane forest of Bidoup-Nui Ba are unique among the tropical forests of East and Southeast Asia. In particular, our observation suggests that masting in tropical montane forests may be an ancestral state of both general flowering in tropical rainforests and masting found in temperate forests in East and Southeast Asia.

A revision of the genus Lasianthus Jack (Rubiaceae) from Vietnam is here presented. 73 species and four subspecies are recognized, of which three species are described as new to science (L. bachmaensis, L. chii and L. yersinii) and two species are the new record to the flora of the country (L. latifolius and L. viridiramulis). The Vietnamese species are arranged into two sections: sect. Lasianthus and sect. Nudiflorae Hook.f. Eighteen taxa names are reduced to synonymy according to recent studies. Lists of examined specimens, information on the distribution, habitat and ecology, phenology, vernacular names, taxonomic notes and color plates are provided for 77 taxa. Preliminary conservation status assessments are also given for the three species. A key for identifying all Vietnamese Lasianthus species is provided as well.

We document the taxonomic history of Dischidia ruscifolia Decne ex Becc. After a critical study of the available original material and additional specimens an epitype is designated. We confirm that D. myrtillus is a synonym of Dischidia ruscifolia and the name is typified. Clarification of the identity of D. ruscifolia allowed the identification of a new species that is here published and illustrated as Dischidia argentii Arshed, J.R. Callado & Tandang. The new species differs largely in its floral morphology and particularly in its glabrous corolla throat, absent corolline corona, gynostegium outline, and pollinium shape.

Reproductive interference (RI), an interspecific mating interaction that reduces the fitness of at least one of the species involved, can lead to exclusive distributions in closely related species. A hypothesis previously proposed is that RI in plants may occur by ovule usurpation, in which pistils lack interspecific incompatibility and mistakenly accept heterospecific pollen, thereby losing an opportunity for conspecific pollen fertilization. However, few comparative studies have evaluated the consistency of the inferred mechanism within and among individuals and populations. We conducted hand-pollination experiments in six populations of three native Taraxacum species that suffered from different levels of RI from an alien congener, T. officinale, and compared pollen–pistil interactions among populations. We also investigated the interactions for eight individual T. japonicum plants whose response to heterospecific pollen deposition had been previously measured. Our results revealed that pollen tubes often penetrated native ovaries following heterospecific pollination in populations suffering from strong RI, whereas they seldom did in populations suffering from marginal RI. However, the relative frequency of the pollen tube penetration was not significantly related to the strength of alien RI. Not all pistils on an individual plant showed the same pollen receptivity following heterospecific pollination; rather, some accepted and some refused the pollen tubes. The relationship between pollen tube penetration following heterospecific pollination and the strength of the alien RI was also not significant among individuals. Our present results generally support the ovule usurpation hypothesis, but suggest that other factors, such as competition for pollinator services, variation in the effects of heterospecific pollen donors, and condition of the native inflorescences, might also affect the observed RI strength.

This paper presents a re-evaluation of the taxonomic identity of Sciaphila major described from Sarawak, Borneo, Malaysia which has been considered conspecific with S. secundiflora. We revealed that S. major is clearly distinguishable from S. secundiflora s.s. by the arrangement of flowers on rachis (spirally and subdensely arranged vs. secundly and laxly arranged), rachis length in a fully developed inflorescence [(2–)3–6(–7) cm vs. 6–19 cm], tepal length of male flowers (2–2.3 mm vs. 3–4 mm) and the number of perianth segments (more than 6 vs. 6). By spirally-arranged and white flowers, S. major is most similar to S. alba, but is distinguishable by plant height (15–25 cm vs. 25–35 cm in S. alba), rachis length in a fully developed inflorescence [(2–)3–6(–7) cm vs. 8–14 cm)], the number of flowers (usually less than 20 vs. usually more than 20), the arrangement of flowers on rachis (subdensely arranged vs. laxly arranged), the number of male perianth segments (usually more than 6 vs. usually 6) and the condition of floral disc (flat vs. bowl-shaped). We also provide an updated key to the species of Sciaphila distributed in Borneo.

A new species, Lasianthus konchurangensis V.S.Dang, T.B.Tran & T.D.Ha (sect. Lasianthus), is described and illustrated from Kon Chu Rang Nature Reserve, Gia Lai Province, the Central Highlands of Vietnam. Lasianthus konchurangensis resembles L. foetidissimus but differs in having larger leaves, more secondary veins, larger calyx and purple corolla. Photographs, vernacular name, preliminary conservation assessment, and a table comparing L. konchurangensis with L. foetidissimus are provided.

In the course of taxonomic studies on Zingiberaceae in Myanmar, a new species of Curcuma assignable to subgenus Ecomatae was discovered in Htamanthi Wildlife Sanctuary, Sagaing Region, northwestern Myanmar. It is described and illustrated here as Curcuma stolonifera. This new species differs from other species in subgenus Ecomatae Skornick. & Sida f. in having a combination of the following characters; long creeping rhizomes, an oblong-lanceolate lamina with reddish midrib, a small number of green bracts, a central inflorescence, pale whitish yellow flowers, and a short slightly L-shaped anther with a curved spur.

Mallotus tokiae (Euphorbiaceae), a poorly known species, was described based upon a single fruiting specimen from Surat Thani Province, peninsular Thailand. We found this species with staminate and slightly mature pistillate flowers in Lampi Island, Myanmar. A new locality record, description of flowers, preliminary conservation assessment and DNA barcoding of this species are provided.

Lasianthus kbangensis V.S.Dang, Vuong & Naiki, a new species belonging to Lasianthus sect. Nudiflorae of Rubiaceae from the Central Highlands of Vietnam, is described and illustrated. This new species is similar to L. oblongilobus H. Zhu, but differs in having larger leaves, longer petioles, smaller calyx (calyx lobes) and corolla, and the color of ripen fruits. A table comparing the new species to closely related species is provided.

The genus, Ochrosia, is widely distributed from the West Indian Ocean throughout tropical Asia to the Middle Southern Pacific region. Ochrosia comprises many island-endemic species, suggesting that long-distance dispersal and isolation after migration are key factors for clarifying the diversification process. However, the phylogeny and biogeography of endemic Ochrosia species have not been evaluated well due to the difficulty of adequate sampling from the entire distribution range of the genus. In this study, we focused on two Ochrosia species endemic to the Bonin (Ogasawara) Islands in the northwest Pacific. The Bonin Islands are of volcanic origins and consist of two islands groups, the Ogasawara and Volcano Islands groups, approximately 300 km apart. Ochrosia nakaiana is endemic to the Ogasawara Islands group, whereas O. hexandra is endemic to the Volcano Islands group. To elucidate the phylogenetic positions of these two endemic Ochrosia species, we conducted molecular phylogenetic studies with dating and biogeographic analyses including other Ochrosia species. The phylogenetic trees showed that the two endemic species had distinct origins; O. nakaiana was closely related to O. oppositifolia and O. iwasakiana, whereas O. hexandra was related to O. mariannensis. Based on the chloroplast DNA phylogeny, the genus, Ochrosia, divided into two major lineages 36.6 million years ago. Further, the two endemic species of the Bonin Islands were independently derived approximately 1-2 million years ago. Ochrosia nakaiana originated from the Southeast Asia, New Caledonia, or other Pacific Islands, while O. hexandra derived from O. mariannensis in Micronesia. We demonstrated different origins of the two endemic Ochrosia species on the Bonin Islands. This study provided an excellent example of the complex origins and speciation of flora in the oceanic islands.

Species radiations have long fascinated biologists, but the contribution of adaptation to observed diversity and speciation is still an open question. Here, we explore this question using the clove genus, Syzygium, the world’s largest genus of tree species comprising approximately 1200 species. We dissect Syzygium diversity through shotgun sequencing of 182 distinct species and 58 additional as-yet unidentified taxa, and assess their genetic diversity against a chromosome-level reference genome of the sea apple, Syzygium grande. We show that Syzygium grande shares a whole genome duplication (WGD) event with other Myrtales. Genomic analyses confirm that Syzygium originated in Sahul (Australia-New Guinea), and later diversified eastward to the Hawaiian Islands and westward in multiple independent migration events. The migrations were associated with bursts of speciation events, visible by poorly resolved branches on phylogenies and networks, some of which were likely confounded by incomplete lineage sorting. Clinal genomic variation in some sublineages follows phylogenetic progression, which coupled with sympatric occurrences of distantly related species suggests that both geographic and ecological speciation have been important in the diversification of Syzygium. Together, these results point to a mixture of both neutral and adaptive drivers having contributed to the radiation of the genus.

Two new species, Lasianthus fansipanensis V.S. Dang & Naiki and Lasianthus sapaensis V.S. Dang & Naiki (sect. Nudiflorae), were discovered in the Hoang Lien National Park of northern Vietnam and are here described and illustrated. Colour photographs, preliminary conservation assessment, and tables comparing these two new species against two closely related species are also presented.

Background and Aims Reproductive interference may reduce fitness of either of the involved species, with potentially important ecological and evolutionary consequences. Except for the effect of shared pollinators on reproductive success, however, mechanisms underlying reproductive interference have been little studied, even though the severity of its impact may depend on the specific mechanism. The aim of this study was therefore to explore the mechanisms of reproductive interference between Taraxacum japonicum (native to Japan) and Taraxacum officinale (alien). Methods In a field survey, the association between alien species density and seed set in T. japonicum, and whether pollinator behaviour indicated a preference for the alien, were examined. Effects of heterospecific pollen deposition were measured in a series of hand pollination experiments, including mixed pollination experiments in which the order of application of conspecific and heterospecific pollen was varied. Finally, to investigate hybridization frequency, the parentage of seedlings produced following natural, mixed or heterospecific pollination was compared. Key Results Alien species density did not negatively affect native seed set, nor did pollinators appear to have a preference for alien flowers. The hand pollination experiments showed that heterospecific pollen deposition adversely affected native seed set, especially when alien pollen was applied before conspecific pollen. No viable hybrids were found following natural pollination, which suggests that hybridization might be a rare event. Conclusion Among the examined mechanisms, heterospecific pollen deposition might have the largest deleterious effect on the native species. This effect is frequency dependent; thus, a positive feedback loop may cause the effect on the population dynamics to increase over time, with the result that the alien might eventually displace the native in a population. Effects of the examined mechanisms on population dynamics should be investigated further to improve understanding of the impact of reproductive interference on the structure of plant communities.

The new species of Clusiaceae, Calophyllum honbaense V.S. Dang, H. Toyama & Tagane, sp. nov., was discovered in the Hon Ba Nature Reserve of southern Vietnam and is here described and illustrated.

A new species of Gentiana (Gentianaceae), G. laotica Soulad., Tagane & Yahara, from Phou Khao Khouay National Protected Area, Vientiane Province, central Laos, is described. Photographs, vernacular name, DNA barcodes of rbcL, matK and ITS, and preliminary conservation status are provided for the new species.

A new species, Garcinia hopii H.Toyama & V.S.Dang is described from Bidoup Nui Ba National Park, southern Vietnam. This species is similar to Garcinia hendersoniana Whitmore but differs from that species in having larger leaves, clustered pistillate flowers, a greater number of sterile anthers and a larger stigma of young fruits. A description, preliminary conservation assessment, illustration, photographs and DNA barcodes of the new species are provided, as well as an updated key to Garcinia sect. Hebradendron in Indochina.

Two species of Araliaceae, Heteropanax thaiensis Tagane, Suddee & Rueangr., a new species from Phu Kradueng National Park, Loei Province, and Schefflera wrayi (King) R.Vig., from Khao Luang National Park, Nakhon Si Thammarat, formerly known only from Malaysia, are added to the flora of Thailand. Descriptions and illustrations, as well as DNA barcodes of rbcL and matK are provided based on our newly collected specimens.

Background and AimsHeterospecific pollen transfer may reduce the fitness of recipient species, a phenomenon known as reproductive interference. A theoretical study has predicted that distributions of species pairs affected by reproductive interference may be syntopic under negligible reproductive interference, sympatric but with partitioning at small spatial scale (i.e. allotopic) under weak interference, or exclusive when reproductive interference is strong. Verifying these predictions is essential for evaluation of the applicability of reproductive interference as a general assembly rule of biological communities. The aim of this study was to test these predictions in two sympatrically distributed wild Geranium species, G. thunbergii and G. wilfordii.MethodsTo measure the effect of reproductive interference, the associations between the relative abundance of the counterpart species and seed set in the focal species, and seed set reduction following mixed pollination, were analysed. The possibility of hybridization with viable offspring was examined by genotyping plants in the field and after mixed pollination. Fertility of putative hybrids was based on their seed set and the proportion of pollen grains with apertural protrusions. A transect study was conducted to examine spatial partitioning, and possible influences of environmental conditions (canopy openness and soil moisture content) on partitioning between the species were analysed.Key ResultsNeither abundance of the counterpart species nor heterospecific pollen deposition significantly affected seed set in the focal species, and hybridization between species was almost symmetrical. Putative hybrids had low fertility. The two species were exclusively distributed at small scale, although environmental conditions were not significantly different between them.ConclusionsThe allotopy of the two species may be maintained by relatively weak reproductive interference through bidirectional hybridization. Re-evaluation of hybridization may allow ongoing or past reproductive interference to be recognized and provide insight into the distributional relationships between the interacting plants.

Lasianthus honbaensis V.S. Dang, Tagane & H. Toyama sp. nova (Rubiaceae) is described and illustrated from Hon Ba Nature Reserve, Khanh Hoa Province, southern Vietnam. It resembles L. inodorus and L. inodorus subsp. pubescens in leaf morphology, but differs from them in having shorter stipules, calyx tubes and corolla, and orange fruits. It is also similar to L. latifolius and L. calycinus in deeply disected calyx lobes and orange fruits, but differs from them by having persistent bracts and shorter calyx tubes. A table comparing the new species with its closest allies is provided.

A new species of Hamamelidaceae, Eustigma honbaense H.Toyama, Tagane & V.S.Dang, sp. nov., is described from Hon Ba Nature Reserve, Vietnam. This species is similar to Eustigma oblongifolium Gardner & Champ., but differs from it in having entire leaves, longer infructescences, capsules with a longer apical part and seeds with a larger hilum. A description, preliminary conservation assessment, illustration and photographs of the new species are provided, as well as an updated key to the genus Eustigma.

A new species, Glycosmis suberosa H.Toyama & Rueangr. is described from Khao Luang National Park, Nakhon Si Thammarat Province, Thailand. This species is distinguished from the other Glycosmis species by its characteristic corky branches.

Two new species of Lasianthus (Rubiaceae), L. thuyanae V.S. Dang & Naiki from Ba Vi National Park, Ha Noi City, northern Vietnam, and L. tamdaoensis V.S. Dang from Tam Dao National Park, Vinh Phuc Province, northern Vietnam, are described and illustrated. Lasianthus thuyanae is closely related to L. curtisii but differs from it by having larger stipules and corollas, and a differently coloured calyx. Lasianthus tamdaoensis resembles L. filipes and L. longipedunculatus but differs from them by having longer petioles and larger corolla lobes.

A new species, Aporosa tetragona Tagane & V. S. Dang, sp. nov., is described and illustrated from Mt. Hon Ba located in the Khanh Hoa Province, South Vietnam. This species is characterized by tetragonal pistillate flowers and fruits, which are clearly distinguishable from the other previously known species of the genus. The morphology and phylogeny based on rbcL and matK of this species indicated that the new species belongs to section Appendiculatae Pax & K. Hoffm.

A new species, Lasianthus bidoupensis V.S. Dang & Naiki (Rubiaceae) is described and illustrated from Bidoup Nui Ba National Park, Lam Dong Province, southern Vietnam. It resembles L. yaharae which was recently discovered from Mt. Hon Ba and L. dalatensis which is endemic to Dalat, southern Vietnam. However, L. bidoupensis differs from them by having larger leaves and bracts, longer petioles, stipules, calyx and corolla tubes, and deep-red mature fruits.

Croomia is a small monocotyledonous genus with eastern Asian–eastern North American floristic disjunction. The Croomia species are endangered and in urgent need of conservation. In this study, we report the development and characterization of 11 polymorphic compound microsatellite markers from Croomia japonica. Moreover, transferability and polymorphism of these primers was tested across Croomia heterosepala and Croomia pauciflora. All of them were transferable and polymorphic in these species. The number of alleles per locus ranged from 2 to 14 (mean: 7.7), 2 to 20 (mean: 7.3) and 2 to 16 (mean: 8.2), while the observed (and expected) heterozygosities ranged from 0.053 to 1.000 (0.053–0.918), 0.000 to 1.000 (0.656–0.945) and 0.190 to 0.905 (0.251–0.937) in populations of C. japonica, C. heterosepala and C. pauciflora, respectively. Most loci in the Croomia populations deviated significantly from the HWE expectations. Significant heterozygosity deficiency was found but no bottleneck was detected in Croomia. These polymorphic markers will be useful tool to study the genetic diversity and the population genetic structure, evolution of Croomia species and for establishment of effective conservation strategies.

Heterostyly is a genetically controlled sexual polymorphism promoting outcrossing by animal pollinators. The occurrence of heterostyly in angiosperms was investigated, and 199 genera in 28 families in 15 orders were recognized as taxa that contain heterostylous species. A correlation between the occurrence of heterostyly and ploidy level was found in some limited groups in Primulaceae and Rubiaceae. In such taxa, individuals with a lower ploidy level tended to have heterostyly and individuals with a higher ploidy level tended to have monomorphic flowers. It appears reasonable that the first step of the breakdown of heterostyly was the recombination of the supergene in a diploid heterostylous plant, and then poyploidization incidentally occurred. Polyploidization itself does not necessarily appear to have direct effects on the breakdown of heterostyly.

Five new species of Syzygium (Myrtaceae), S. honbaense, S. phamhoangii and S. yersinii from Khanh Hoa Province, Vietnam, S. phoukhaokhouayense from Phou Khao Khouay National Protected Area, Vientiane Province, Laos, and S. scabrum from Bung Khla, Phu Wua Wildlife Sanctuary, Buengkan Province, Thailand, are described and illustrated. Photographs, vernacular names and preliminary conservation assessments are provided for them.

Erythroxylum calyptratum, sp. nov. (Erythroxylaceae), from Mt. Fansipan, Hoang Lien National Park, Lao Cai Province, northern Vietnam, is newly described. The new species is characterized by thinly chartaceous leaves with 2–3 mm long petiole, 1–3 flowered inflorescences, downward facing white flowers, well-developed petal appendages (1/3–1/2 length of petals) and entirely free 3 styles. A description, illustrations, DNA barcodes of rbcL and matK and a key to the species of Erythroxylum in Indochina are provided.

Lecanorchis Blume (1856: 188) comprises about 30 species of mycoheterotrophic orchids (Seidenfaden 1978, Hashimoto 1990, Szlachetko & Mytnik 2000, Govaerts et al. 2017) characterized by having numerous, long, thick, horizontal roots produced from a short rhizome, presence of a calyculus (i.e. a cup-like structure located between the base of the perianth and apex of the ovary) and an elongate column with a pair of small wings on each side of the anther (Seidenfaden 1978, Hashimoto 1990). The genus is distributed across a wide area including China, Korea, India, Indonesia, Japan, Laos, Malaysia, New Guinea, Pacific islands, the Philippines, Taiwan, Thailand and Vietnam (Seidenfaden 1978, Hashimoto 1990, Pearce & Cribb 1999, Szlachetko & Mytnik 2000, Averyanov 2011, 2013).

Platycrater arguta (Hydrangeaceae) is a small deciduous shrub of the Sino-Japanese floristic region, where it occurs in montane sites mostly covered with warm-temperate deciduous forest. This sole representative of its genus contains two varieties disjunctly distributed between East China (var. sinensis) and South Japan (var. arguta). To illuminate the biogeographic and demographic history of this rare species, we conducted a survey of chloroplast DNA (cpDNA) sequence variation (trnD-trnE, trnH-psbA) within and among twelve populations (four from China, eight from Japan, 129 individuals in total) representing the overall distributional range of the species. Based on a total of 19 haplotypes identified, P. arguta was found to harbor surprisingly high levels of haplotype and nucleotide diversity (h T = 0.882; π T = 0.00475), possibly associated with its long evolutionary history. Spatial analysis of molecular variance found two regional phylogroups, corresponding to var. sinensis and var. arguta, and supported by genealogical (unrooted network) analysis of haplotypes. Using a coalescent-based model of 'divergence by isolation with migration', the likely vicariant origin of these varieties was dated to the mid-Pleistocene (ca. 0.89 mya). Very similar haplotype mismatch distributions indicate that var. sinensis and var. arguta underwent past demographic growth almost simultaneously (dated to ca. 0.43 and 0.45 mya, respectively), suggesting climate-induced expansion. However, var. sinensis likely experienced a mere demographic expansion in a narrowly circumscribed mountain range, while var. arguta underwent a spatial northward expansion that might have consisted of a series of bottlenecks, leading to genetically impoverished populations that most likely derived from initial population(s) in southern Kyushu. Our results endorse the recognition of two 'evolutionarily significant units' within P. arguta, corresponding to var. sinensis from East China and var. arguta from South Japan.

We examined variation in Cinnamomum camphora (L.) J. Presl (Lauraceae) leaf domatium morphology with respect to domatium inhabitants in the tree's natural habitats. Canonical discriminant analysis revealed that domatium morphology could be classified into four different types: pouch type, domatia with a narrow (about 0.06 mm) pubescent opening; pubescent pit type, domatia with a wider (about 0.21 mm) pubescent opening; glabrous pit type, domatia similar to the pubescent pit type but with a glabrous opening; and dish type, domatia with a wide (about 0.26 mm) glabrous opening. These four domatium types were found in different positions on a leaf, and domatia with narrower openings tended to occur in or near the position between the midrib and basal secondary veins. The four domatium types were associated, respectively, with herbivorous Eriophyidae mites and herbivorous or fungivorous Tarsonemidae mites; with carnivorous Stigmaeidae mites; with Stigmaeidae mites and egg shells or excuviae of carnivorous Phytoseiidae mites; and with egg shells or excuviae of Phytoseiidae mites. These results suggest that different mites use different domatia, even on the same C. camphora leaf. This conclusion may explain the different results in previous reports about domatium fauna. It suggests that ecological interactions within the plant–herbivore–carnivore system are complicated.Key words: carnivorous mite, Cinnamomum camphora, domatia, herbivorous mite, inhabitant, morphology.

Somatic chromosomes were observed in 661 individuals of 14 taxa, nine species and five varieties, of Damnacanthus (Rubiaceae). Chromosome numbers are reported for the first time for 13 taxa. Diploid (2n = 22) and tetraploid (2n = 44) counts were obtained. Distyly is reported for the first time for four species, D. angustifolius, D. henryi, D. labordei, and D. officinarum. A strong correlation exists between chromosome number and occurrence of distyly. Regardless of taxa in Damnacanthus, distylous populations are diploid, and monomorphic populations are tetraploid. Flowers of the monomorphic populations observed have a long style and short stamens with few exceptions. Polyploidization may have caused the breakdown of distylous to monomorphic flowers. In D. indicus, leaves from the tetraploid populations tend to be larger than those from the diploid populations. Populations of tetraploid D. indicus were distributed in more northern areas than those of the diploid. Three types of sympatric distribution were found for the varieties of D. indicus in Japan: diploid and tetraploid, two diploids, and two tetraploids. Based on the present chromosome number study, the taxonomy of the varieties of D. indicus should be revised.

Herein, Mussaenda recurvata, a new species from Hon Ba Nature Reserve, southern Vietnam, is described and illustrated. This species is morphologically similar to M. longipetala, distributed from southern China to northern Vietnam, in having recurved stipules and densely pilose and puberulent hairs throughout, but differs in its strongly recurved calyx lobes, a shorter corolla tube, and ovate corolla lobes. The species is morphologically heterostylous and it appears to be functionally dioecious. An updated key to Mussaenda species in Vietnam, Laos, and Cambodia is also provided.

The floral morphology and reproductive ecology of a scandent shrub species, Mussaenda parviflora Miq. (Rubiaceae), were studied on Iriomote and Amami Ohshima Islands, Japan. The morphological study demonstrated that M. parviflora was gynodioecious. Crossing experiments, however, revealed that it was functionally dioecious. The flowers were visited mainly by butterflies in the daytime and mainly by crepuscular hawkmoths in the evening. Dioecy in this species is thought to have evolved from distyly. Dioecy of this species, which is pollinated by long-tongued Lepidoptera, is unusual as the evolution of dioecy from distyly in plants with long corolla tubes is thought to have been triggered by a pollinator shift from long- to short-tongued insects. In this species, however, two floral morphological features may have caused the evolution. The first feature is the presence of many upward-facing hairs covering the inner surface of the upper part of the corolla tube; these hairs appear to have impeded pollen flow from long- to short-styled flowers. The second feature is the overlap in anther height between the two types of flowers, which may have reduced seed set by clogging stigma with incompatible pollen grains. Accordingly, male sterility in long-styled plants may have evolved.

A new species of Primulaceae from Thailand, Lysimachia kraduengensis, is described and illustrated. It is morphologically similar to L. engleri, L. lancifolia, L. laxa and L. sikokiana in having solitary and axillary flowers, a yellow corolla, relatively long pedicels and basifixed anthers. The new species can be distinguished by the combination of its height, leaf texture, petiole, calyx and anther length, and brown coloration on the flowers. In addition, the conservation status, an updated key to Lysimachia species in Thailand, and discussion of the systematic placement of the new species based on the trnL-F marker of chloroplast DNA are provided.

Smilax Linnaeus (1753: 1028) is the only genus of Smilacaceae, comprising ca. 210 species, which are lianas, shrubs, and herbs (Cameron & Fu, 2006; Qi et al. 2013a). The genus shows a near-cosmopolitan distribution (Qi et al. 2013a). In the large genus, Smilax sect. Heterosmilax (Kunth 1850: 270) Judd (1998: 158), formerly treated as an independent genus Heterosmilax Kunth in Smilacaceae, has 12 species and is distributed only in Asian and Malesian regions (Judd 1998, Qi et al. 2013b). All species of the section have slender stem without pricks, cordate leaves, and tendrils in bronze color. Especially, flowers with connate perigone are one of the most important characteristics to distinguish the section from the other sections (Koyama 1984, Qi et al. 2013a).

Pollen morphology of the genus Skimmia was studied. Of six species of the genus, five species were investigated by light microscopy and scanning electron microscopy. Pollen grains of Skimmia had striate to striate-reticulate sculpture and variable aperture number (3–7), and these characters differed from even the phylogenetically closest relatives such as Dictamnus and Casimiroa which have 3-colporate pollen grains with reticulate exine. In Skimmia laureola, pollen dimorphism is suggested in the aperture number in accordance with the floral system. Pollen grains of Skimmia japonica, a morphologically very variable species, were extensively surveyed covering its whole distribution area. The grains were also striate to striate-reticulate, and the exine sculpture was not different between varieties. However, the aperture number of S. japonica showed a geographical variation ranging from 4 to 6; in Sakhalin, Hokkaido, most part of Honshu and Taiwan, grains with 4–5 apertures were dominant, while in the southern part of Japan, including the Ryukyu Islands and the Izu Islands, those with 5–6 apertures were common.

A karyotypic analysis of three species of Skimmia (Rutaceae) in East Asia was performed that examined 88 individuals from 53 localities. Chromosome numbers of S. japonica, S. reevesiana and S. arisanensis were 2n=30, 31, 32 (=30+0−2B), 2n=60 and 2n=60, respectively. The chromosome number of S. arisanensis was reported for the first time. All species had a large chromosome pair or quartet (the first pair or quartet) with a median–submedian centromere in the karyotype. In S. japonica the arm ratio of this first pair was considerably variable and showed a geographical pattern. In the northern half of the distribution range, Sakhalin, Hokkaido, Honshu, Shikoku and part of Kyushu, the arm ratio was 1–1.2, while in the southern half, part of Kyushu, Ryukyu and Taiwan, the arm ratio was very variable and ranged from 1.2 to 2.4. In S. japonica the first pair was sometimes rather heteromorphic; however, the heteromorphism was not related to sex of the plant.

We document distyly in Damnacanthus (Rubiaceae) and investigate pollen morphology in the genus. Within nine taxa in Japan (four species, four varieties and one form), five show distyly. Non-distylous taxa of Damnacanthus always have a long style and short stamens. We examined the pollen morphology of all taxa of Damnacanthus in Japan. The pollen grains of Damnacanthus are 3- to 5-orthocolporate or sometimes loxocolporate. Polymorphic pollen is sometimes observed even within a single flower. Pollen dimorphism is associated with distyly; pollen grains from short-styled (thrum) flowers are significantly larger than those from long-styled (pin) flowers, and the muri are smooth in pin flowers whereas the pollen grains of thrum flowers have minute granules on the top and/or on the sides. In non-distylous taxa, in which the style is longer than stamens, the muri are always provided with minute granules. Interestingly, the pollen grains with granules in the non-distylous taxa contrast with the pollen of the distylous taxa, because granulate pollen grains are found only in thrum flowers. Although Damnacanthus is a stenopalynous genus, the number of colpi is useful for delimiting taxa. Based on palynological characters, we conclude that Damnacanthus should be revised.