Chasmogamy and entomophily in Burmannia disticha (Burmanniaceae)

Burmannia shows a set of floral traits that suggest elaborate mechanisms of animal-mediated pollen transfer. These include flower coloration, septal nectaries and a long and narrow floral chamber. The stamens are synorganized with the common style restricting the entrance to the floral chamber, sometimes forming a gynostegium. Contrary to this apparent zoophilous floral syndrome, several species of Burmannia were reported to perform self-pollination via cleistogamy. Understanding of reproductive systems in Burmannia is complicated by scarcity of available results of direct observations on pollination process. Here we present data on pollination biology of B. disticha obtained during field investigations in Vietnam followed by laboratory analyses of ecologically important floral traits and the captured flower visitors. We found that the anthetic perianth is open, i.e. the flower is chasmogamous. The flowers are visited by various Diptera, Hymenoptera, Lepidoptera and Orthoptera. Of them, the bumblebees (Bombus burmensis), a bee (Coelioxys sp.) and some lepidopterans were revealed to carry pollen of B. disticha. Based on the amount of carried pollen, insect behavior during the visits and general knowledge on biology of these insect taxa, we concluded that the bumblebees act as the principal pollinators of B. disticha, whereas the lepidopterans are considered as its possible pollinators. We compared the lengths of proboscises of the captured insects to the depth of the floral chamber, and found that only the bumblebees and lepidopterans should be able to reach the nectar. Finally, we estimated the pollen-ovule ratio of B. disticha as 6.84, which is comparable to the ratio known in autogamous angiosperms. Based on its flower organization and pollination mechanism, we consider B. disticha an entomophilous and predominantly xenogamous species. Its gynostegium is likely an adaptation for pollen transfer by insects with long proboscises. At the same time, earlier investigations together with pollen-ovule ratio indicate that B. disticha possesses a labile pollination strategy, and autogamy sometimes occurs. Since Burmannia is one of the few angiosperm genera that comprise both mycoheterotrophic (achlorophyllous) and autotrophic (green) species, our study provides important evidence for reconstructions of ecological and morphological evolutionary pathways in relation to the mode of organic nutrition

The First Genome from the Basal Monocot Family Has Been Misnamed: Taxonomic Identity of Acorus tatarinowii (Acoraceae), a Source of Numerous Chemical Compounds of Pharmaceutical Importance

The basalmost monocot genus Acorus is well-known for its use in traditional oriental medicine. It comprises the groups of A. calamus and A. gramineus. A recent study recognized three species in the latter group, A. gramineus, A. macrospadiceus, and A. tatarinowii. The material currently known as A. tatarinowii has been extensively studied as a source of various chemical compounds and for producing the first published genome of Acorus, which is important for understanding the origin and evolution of monocots. Using the data from morphology, anatomy, and biogeography, we argue that the type material of A. tatarinowii does not match the interpretation of the species name as adopted in the current literature and herbarium collections (to a taxon of the A. gramineus group from Southeast Asia) but rather belongs to the A. calamus group. Moreover, the name A. macrospadiceus also cannot be used because it was invalidly published. Under a narrow species concept, other appropriate species names should be found or proposed for the plants currently named A. tatarinowii and A. macrospadiceus. However, we discourage the use of a narrow species concept in the A. gramineus group as insufficiently justified and suggest recognizing a single polymorphic species, A. gramineus s.l., at least until a comprehensive taxonomic revision of the group is available. Apart from the presentation of our revised taxonomic framework, we update the geographical distributions of Acorus species in Vietnam, Laos, and Thailand

Structure and Development of Flowers and Inflorescences in Burmannia (Burmanniaceae, Dioscoreales)

Species of the genus Burmannia possess distinctive and highly elaborated flowers with prominent floral tubes that often bear large longitudinal wings. Complicated floral structure of Burmannia hampers understanding its floral evolutionary morphology and biology of the genus. In addition, information on structural features believed to be taxonomically important is lacking for some species. Here we provide an investigation of flowers and inflorescences of Burmannia based on a comprehensive sampling that included eight species with various lifestyles (autotrophic, partially mycoheterotrophic and mycoheterotrophic). We describe the diversity of inflorescence architecture in the genus: a basic (most likely, ancestral) inflorescence type is a thyrsoid comprising two cincinni, which is transformed into a botryoid in some species via reduction of the lateral cymes to single flowers. Burmannia oblonga differs from all the other studied species in having an adaxial (vs. transversal) floral prophyll. For the first time, we describe in detail early floral development in Burmannia. We report presence of the inner tepal lobes in B. oblonga, a species with reportedly absent inner tepals; the growth of the inner tepal lobes is arrested after the middle stage of floral development of this species, and therefore they are undetectable in a mature flower. Floral vasculature in Burmannia varies to reflect the variation of the size of the inner tepal lobes; in B. oblonga with the most reduced inner tepals their vascular supply is completely lost. The gynoecium consists of synascidiate, symplicate, and asymplicate zones. The symplicate zone is secondarily trilocular (except for its distal portion in some of the species) without visible traces of postgenital fusion, which prevented earlier researchers to correctly identify the zones within a definitive ovary. The placentas occupy the entire symplicate zone and a short distal portion of the synascidiate zone. Finally, we revealed an unexpected diversity of stamen-style interactions in Burmannia. In all species studied, the stamens are tightly arranged around the common style to occlude the flower entrance. However, in some species the stamens are free from the common style, whereas in the others the stamen connectives are postgenitally fused with the common style, which results in formation of a gynostegium

Comparative analysis of plastid genomes in the non-photosynthetic genus Thismia reveals ongoing gene set reduction

Heterotrophic plants provide intriguing examples of reductive evolution. This is especially evident in the reduction of their plastid genomes, which can potentially proceed toward complete genome loss. Several milestones at the beginning of this path of degradation have been described; however, little is known about the latest stages of plastome reduction. Here we analyze a diversity of plastid genomes in a set of closely related non-photosynthetic plants. We demonstrate how a gradual loss of genes shapes the miniaturized plastomes of these plants. The subject of our study, the genus Thismia, represents the mycoheterotrophic monocot family Thismiaceae, a group that may have experienced a very ancient (60–80 mya) transition to heterotrophy. In all 18 species examined, the plastome is reduced to 14–18 kb and is highly AT-biased. The most complete observed gene set includes accD, seven ribosomal protein genes, three rRNA, and two tRNA genes. Different clades of Thismia have undergone further gene loss (complete absence or pseudogenization) compared to this set: in particular, we report two independent losses of rps2 and rps18

Checklist to the Elatostema (Urticaceae) of Vietnam including 19 new records, ten new combinations, two new names and four new synonyms

Elatostema (Urticaceae) comprises several hundred herbaceous species distributed in tropical and subtropical Africa, Asia, Australia and Oceania. The greatest species richness occurs on limestone karst in Southeast Asia. Taxonomic revisions of Elatostema are largely out of date and contradict each other with respect to the delimitation of Elatostema and Pellionia. Most herbaria in SE Asia and worldwide contain significant amounts of unidentified material. As part of a broader revision of Elatostema in SE Asia, we present an updated checklist for Vietnam based on field visits, a review of specimens in herbaria worldwide, a review of type material and nomenclature. We recognize 77 taxa (75 species and two infraspecific taxa) of Elatostema in Vietnam, 23 of which were previously ascribed to Pellionia. Nineteen of these are new records for the country, i.e., E. attenuatoides, E. austrosinense, E. backeri, E. brunneinerve, E. crassiusculum, E. crenatum, E. fengshanense, E. glochidioides, E. malacotrichum, E. nanchuanense, E. oblongifolium, E. obtusum, E. oppositum, E. pergameneum, E. prunifolium, E. pseudolongipes, E. pycnodontum, E. salvinioides and E. xichouense. We place E. baviensis in synonymy of E. platyphyllum, E. colaniae in synonymy of E. myrtillus, P. macroceras in synonymy of E. hookerianum, and P. tetramera in synonymy of E. dissectum for the first time. Fourteen taxa (18% of all the recognized taxa) are endemic to Vietnam, which makes Elatostema one of the richest genera for endemic species in this country; this level of endemism is comparable to levels observed in Orchidaceae. Our checklist suggests that the highest diversity and endemism of Elatostema occurs in northern Vietnam, and that there is the greatest floristic similarity of northern Vietnam to SW China. The relationship among floristic regions is also investigated. We could find no records of Elatostema for 33 out of 63 provincial units of Vietnam, including all the southernmost provinces. We propose that further studies on the diversity of Elatostema in central and southern Vietnam are severely needed

Patterns of Diversity of Floral Symmetry in Angiosperms: A Case Study of the Order Apiales

Floral symmetry is widely known as one of the most important structural traits of reproductive organs in angiosperms. It is tightly related to the shape and arrangement of floral parts, and at the same time, it plays a key role in general appearance (visual gestalt) of a flower, which is especially important for the interactions of zoophilous flowers with their pollinators. The traditional classification of floral symmetry divides nearly all the diversity of angiosperm flowers into actinomorphic and zygomorphic ones. Within this system, which is useful for ecological studies, many variations of symmetry appear to be disregarded. At the same time, the diversity of floral symmetry is underpinned not only by ecological factors, but also by morphogenetic mechanisms and constraints. Sometimes it is not an easy task to uncover the adaptive or developmental significance of a change of the floral symmetry in a particular lineage. Using the asterid order Apiales as a model group, we demonstrate that such changes can correlate with the merism of the entire flower or of its particular whorl, with the relative orientation of gynoecium to the rest of the flower, with the presence of sterile floral elements and other morphological characters. Besides, in some taxa, the shape and symmetry of the flower change in the course of its development, which should be taken in consideration in morphological comparisons and evaluations of synapomorphies in a particular clade. Finally, we show that different results can be obtained due to employment of different approaches: for instance, many flowers that are traditionally described as actinomorphic turn out to be disymmetric, monosymmetric, or asymmetric from a more detailed look. The traditional method of division into actinomorphy and zygomorphy deals with the general appearance of a flower, and mainly considers the shape of the corolla, while the geometrical approach handles the entire three-dimensional structure of the flower, and provides an exact number of its symmetry planes

Vietorchis furcata (Orchidaceae, Vietorchidinae) - a New Species from Southern Vietnam

Vietorchis furcata, an achlorophyllous orchid, discovered in southern Vietnam is described and illustrated as new for science. This is the second species of the genus regarded earlier as monotypic. A key for identification of both species of the genus and short notes on their taxonomy and biology are provided. Closely related genera - Vietorchis and Silvorchis are segregated in rank of subtribe Vietorchidinae due to their isolated taxonomical position

The First Genome from the Basal Monocot Family Has Been Misnamed: Taxonomic Identity of Acorus tatarinowii (Acoraceae), a Source of Numerous Chemical Compounds of Pharmaceutical Importance

The basalmost monocot genus Acorus is well-known for its use in traditional oriental medicine. It comprises the groups of A. calamus and A. gramineus. A recent study recognized three species in the latter group, A. gramineus, A. macrospadiceus, and A. tatarinowii. The material currently known as A. tatarinowii has been extensively studied as a source of various chemical compounds and for producing the first published genome of Acorus, which is important for understanding the origin and evolution of monocots. Using the data from morphology, anatomy, and biogeography, we argue that the type material of A. tatarinowii does not match the interpretation of the species name as adopted in the current literature and herbarium collections (to a taxon of the A. gramineus group from Southeast Asia) but rather belongs to the A. calamus group. Moreover, the name A. macrospadiceus also cannot be used because it was invalidly published. Under a narrow species concept, other appropriate species names should be found or proposed for the plants currently named A. tatarinowii and A. macrospadiceus. However, we discourage the use of a narrow species concept in the A. gramineus group as insufficiently justified and suggest recognizing a single polymorphic species, A. gramineus s.l., at least until a comprehensive taxonomic revision of the group is available. Apart from the presentation of our revised taxonomic framework, we update the geographical distributions of Acorus species in Vietnam, Laos, and Thailand

Citronella suaveolens, a new generic record for Vietnam, with a key to Vietnamese Cardiopteridaceae.

Citronella suaveolens is reported from Quang Nam Province in southern Vietnam, representing the first record of this species and the genus Citronella in the country and in mainland Southeast Asia in general. Detailed photographic illustrations of studied specimens are provided. A key to the Vietnamese genera and species of Cardiopteridaceae is presented. Diversity of Citronella in the Malesian region is discussed. Floristic affinities of Malesia and Eastern Indochina are highlighted by a list of illustrative examples

The First Genome from the Basal Monocot Family Has Been Misnamed: Taxonomic Identity of <i>Acorus tatarinowii</i> (Acoraceae), a Source of Numerous Chemical Compounds of Pharmaceutical Importance

The basalmost monocot genus Acorus is well-known for its use in traditional oriental medicine. It comprises the groups of A. calamus and A. gramineus. A recent study recognized three species in the latter group, A. gramineus, A. macrospadiceus, and A. tatarinowii. The material currently known as A. tatarinowii has been extensively studied as a source of various chemical compounds and for producing the first published genome of Acorus, which is important for understanding the origin and evolution of monocots. Using the data from morphology, anatomy, and biogeography, we argue that the type material of A. tatarinowii does not match the interpretation of the species name as adopted in the current literature and herbarium collections (to a taxon of the A. gramineus group from Southeast Asia) but rather belongs to the A. calamus group. Moreover, the name A. macrospadiceus also cannot be used because it was invalidly published. Under a narrow species concept, other appropriate species names should be found or proposed for the plants currently named A. tatarinowii and A. macrospadiceus. However, we discourage the use of a narrow species concept in the A. gramineus group as insufficiently justified and suggest recognizing a single polymorphic species, A. gramineus s.l., at least until a comprehensive taxonomic revision of the group is available. Apart from the presentation of our revised taxonomic framework, we update the geographical distributions of Acorus species in Vietnam, Laos, and Thailand