Molecular phylogeny and habitat diversification of the genus Farfugium (Asteraceae) based on nuclear rDNA and plastid DNA

Impact on the scape of Farfugium japonicum var. japonicum (Asteraceae) under strong wind conditions based on morphological and mechanical analyses

Adaptation of Farfugium japonicum (L.) Kitam. var. japonicum (Asteraceae) to the strong wind environment of coastal areas has been shown to reduce lamina size and shorten petioles; however, their effects on other traits of this species remain unknown. Our morphological analyses showed that shortening of the scape of this species is correlated with shortening of the petiole in coastal areas. The results suggested that when the height of the scapes became higher than that of the petioles, the wind stress on the scapes became stronger and their growth was suppressed. Therefore, the populations in coastal areas with strong winds had significantly shorter scapes than inland populations, and the height of petioles and scapes in the coastal populations were correlated. Further mechanical analysis by three-point bending tests revealed that the scapes had higher strength than the petioles. This species is evergreen and can produce new leaves regardless of the season, even if it loses its leaves by strong winds; however, because scapes only develop above ground for a limited period of the year, the loss of the scapes by strong winds has a significant impact on reproduction in that year. Therefore, even though the scapes were stronger than the petiole, shortening the scapes plays an important role in reducing strong wind stress in coastal areas.

Biogeographical patterns and speciation of the genus Pinguicula (Lentibulariaceae) inferred by phylogenetic analyses

Earlier phylogenetic studies in the genus Pinguicua (Lentibulariaceae) suggested that the species within a geographical region was rather monophyletic, although the sampling was limited or was restricted to specific regions. Those results conflicted with the floral morphology-based classification, which has been widely accepted to date. In the current study, one nuclear ribosomal DNA (internal transcribed spacer; ITS) and two regions of chloroplast DNA (matK and rpl32-trnL), from up to ca. 80% of the taxa in the genus Pinguicula, covering all three subgenera, were sequenced to demonstrate the inconsistency and explore a possible evolutionary history of the genus. Some incongruence was observed between nuclear and chloroplast topologies and the results from each of the three DNA analyses conflicted with the morphology-based subgeneric divisions. Both the ITS tree and network, however, corresponded with the biogeographical patterns of the genus supported by life-forms (winter rosette or hibernaculum formation) and basic chromosome numbers (haploidy). The dormant strategy evolved in a specific geographical region is a phylogenetic constraint and a synapomorphic characteristic within a lineage. Therefore, the results denied the idea that the Mexican group, morphologically divided into the three subgenera, independently acquired winter rosette formations. Topological incongruence among the trees or reticulations, indicated by parallel edges in phylogenetic networks, implied that some taxa originated by introgressive hybridisation. Although there are exceptions, species within the same geographical region arose from a common ancestor. Therefore, the classification by the floral characteristics is rather unreliable. The results obtained from this study suggest that evolution within the genus Pinguicula has involved; 1) ancient expansions to geographical regions with gene flow and subsequent vicariance with genetic drift, 2) acquirement of a common dormant strategy within a specific lineage to adapt a local climate (i.e., synapomorphic characteristic), 3) recent speciation in a short time span linked to introgressive hybridisation or multiplying the ploidy level (i.e., divergence), and 4) parallel evolution in floral traits among lineages found in different geographical regions (i.e., convergence). As such, the floral morphology masks and obscures the phylogenetic relationships among species in the genus.

Phylogeographic and demographic modeling analyses of the multiple origins of the rheophytic goldenrod Solidago yokusaiana Makino

Understanding adaptation mechanisms is important in evolutionary biology. Parallel adaptation provides good opportunities to investigate adaptive evolution. To confirm parallel adaptation, it is effective to examine whether the phenotypic similarity has one or multiple origins and to use demographic modeling to consider the gene flow between ecotypes. Solidago yokusaiana is a rheophyte endemic to the Japanese Archipelago that diverged from Solidago virgaurea. This study examined the parallel origins of S. yokusaiana by distinguishing between multiple and single origins and subsequent gene flow. The haplotypes of noncoding chloroplast DNA and genotypes at 14 nuclear simple sequence repeat (nSSR) loci and single-nucleotide polymorphisms (SNPs) revealed by double-digest restriction-associated DNA sequencing (ddRADseq) were used for phylogeographic analysis; the SNPs were also used to model population demographics. Some chloroplast haplotypes were common to S. yokusaiana and its ancestor S. virgaurea. Also, the population genetic structures revealed by nSSR and SNPs did not correspond to the taxonomic species. The demographic modeling supported the multiple origins of S. yokusaiana in at least four districts and rejected a single origin with ongoing gene flow between the two species, implying that S. yokusaiana independently and repeatedly adapted to frequently flooding riversides.

Comparative analysis of spatial genetic structures in sympatric populations of two riparian plants, Saxifraga acerifolia and Saxifraga fortunei

PREMISE

The genetic structure between plant populations is facilitated by the spatial population arrangement and limited dispersal of seed and pollen. Saxifraga acerifolia, a local endemic species in Japan, is a habitat specialist that is confined to waterfalls in riparian environments. Its sister species, Saxifraga fortunei, is a generalist that is widely distributed along riverbanks. Here, we examined sympatric populations of the two Saxifraga species to test whether the differences in habitat preference and colonization process influenced regional and local genetic structures.

METHODS

To reveal genetic structures, we examined chloroplast microsatellite variations and genome-wide nucleotide polymorphisms obtained by genotyping by sequencing. We also estimated the gene flow among and within populations and performed landscape genetic analyses to evaluate seed and pollen movement and the extent of genetic isolation related to geographic distance and/or habitat differences.

RESULTS

We found strong genetic structure in the specialist S. acerifolia, even on a small spatial scale (<1 km part); each population on a different waterfall in one river system had a completely different predominant haplotype. By contrast, the generalist S. fortunei showed no clear genetic differentiation.

CONCLUSIONS

Our findings suggest that the level of genetic isolation was increased in S. acerifolia by the spatially fragmented habitat and limited seed and pollen dispersal over waterfalls. Habitat differentiation between the sister taxa could have contributed to the different patterns of gene flow and then shaped the contrasting genetic structures.

Bioactive phenolic compounds from the flowers of Farfugium japonicum (L.) Kitam. var. giganteum (Siebold et Zucc.) Kitam. (Asteraceae)

Farfugium japonicum (L.) Kitam. var. giganteum (Siebold et Zucc.) Kitam. is mainly distributed in the Kyushu and Shikoku Islands of Japan. The main aim of this study was to isolate and identify the chemical constituents of the 70% EtOH extract of the flowers of F. japonicum var. giganteum and to evaluate their tyrosinase inhibitory and free radical scavenging activities. Five phenolic compounds, namely petasiphenol (1), rosmarinic acid (2), 4,5-di-O-caffeoylquinic acid (3), 5-O-caffeoylquinic acid (4) and quercetin (5) were isolated and their structures were elucidated on the basis of NMR spectroscopic data. All these compounds were isolated for the first time from title plant. Among them, petasiphenol (1) showed potent tyrosinase inhibitory activity followed by quercetin (5) and 4,5-di-O-caffeoylquinic acid (3). All of these compounds showed potent free radical scavenging activity.

Differentiation of germination characteristics in Scutellaria rubropunctata (Lamiaceae) associated with adaptation to rheophytic habitats in the subtropical Ryukyu Islands of Japan

Seed germination characteristics of a facultative rheophyte Scutellaria rubropunctata, a perennial skullcap endemic to the subtropical Ryukyu Islands of Japan, were investigated at temperatures of 15 °C, 20 °C, 25 °C, and 30 °C. The rheophytic type of S. rubropunctata showed relatively simultaneous germination times and reached high germination rates under all temperatures tested. This characteristic may allow it to establish quickly without being influenced by temperature, giving a survival advantage in rheophytic habitats by avoiding seeds being washed away by the rising water. In contrast, the final germination rate of the terrestrial type of S. rubropunctata, as well as that of the congener S. indica var. parvifolia, was highest at 15 °C and declined drastically at 30 °C. Seeds of both of these plants that remained ungerminated at higher temperatures germinated soon after the temperature was changed to 15 °C, indicating that the germination suppression was a state of enforced dormancy that was released after transfer to the optimal temperature. These characteristics suggest an asynchronous germination which is thought to reduce the risk of disturbance in fluctuating environments. Our study may be the first to demonstrate the differentiation of seed germination characteristics in relation to adaptations to a rheophytic habitat. Because rheophytes occupy such a harsh environment under strong selective pressure, the adaptive differentiation of seed germination characteristics may occur in many other rheophytes.

[Diversity of Plants Belonging to the Genus Ligularia (Asteraceae) Based on Terpenoids and Synthetic Studies on Some Terpenoids]

The terpenoid constituents of Ligularia virgaurea (30 samples), Ligularia pleurocaulis (8 samples), Ligularia dictyoneura (8 samples), Ligularia brassicoides (5 samples), Ligularia lingiana (1 sample), and Ligularia liatroides (1 sample)(all belonging to section Senecillis of Ligularia, Asteraceae and collected in Yunnan, Sichuan, Qinghai, and Gansu provinces, China), from which 220 compounds were isolated, including 113 novel ones, are reviewed. Five chemotypes were identified in L. virgaurea based on their chemical constituents, while three clades were detected from the base sequences. Although intra-specific diversity was found in L. virgaurea, more samples were needed of other species in order to reach a definite conclusion. Inter-specific diversity was also examined in section Senecillis but was restricted due to the scarcity of samples. Synthetic studies on chiral natural products to determine their absolute configurations, especially those of riccardiphenols A and B as well as crispatanolide, which were all isolated from the liverwort, are briefly reviewed.

Terpenoid Composition and Base Sequences of Ligularia virgaurea (Asteraceae) Grown in the Hengduan Mountain Area in China and a Comment on Drawing Structures

A chemical analysis of 30 samples of Ligularia virgaurea (Asteraceae) collected in Sichuan province and its adjacent territories in China was reviewed. These samples afforded 146 compounds, 73 of which were novel, and the chemical constituents were classified into 8 categories: (1) simple eremophilanes (without ring C) and eudesmanes including nor-derivatives, (2) furanoeremophilanes and lactones with a 1(10)-saturated bond, (3) furanoeremophilanes and lactones with a 1(10)-unsaturated bond, 1,10-epoxide, or 10-ol, (4) furanoeremophilanes and lactones with 1(10)-en-2-one, 1(10)-en-2-ol, or 1-en-3-one, (5) furanoeremophilanes and lactones with 1(10)-en-9-one, 1(10)-en-9-ol, or 1,10-epoxy-9-one, (6) cacalol and their derivatives, (7) bakkanes and their derivatives, and (8) others, as shown in Tables 1-7. In these studies, five chemotypes were identified in addition to three clades from the DNA sequences of L. virgaurea. The structural determination of some compounds was also discussed and a comment on how to express the real structure was proposed, particularly for spiro compounds.

Intraspecific karyotypic polymorphism is highly concordant with allozyme variation in Lysimachia mauritiana (Primulaceae: Myrsinoideae) in Taiwan: implications for the colonization history and dispersal patterns of coastal plants

BACKGROUND AND AIMS

Investigating intraspecific karyotypic and genetic variations jointly can provide unique insights into how historical, ecological and cytogenetic factors influence microevolution. A coastal herb, Lysimachia mauritiana, exhibits extensive karyotypic polymorphism and displays a complex cytogeographic pattern across the Ryukyus. To explore whether a similar degree of chromosomal variation exists south of the Ryukyus, and in an attempt to ascertain the mechanisms that may have generated the patterns, comprehensive sampling was conducted in Taiwan.

METHODS

Karyotypes were analysed at mitotic metaphase for 550 individuals from 42 populations throughout Taiwan Proper and its adjacent islands. In addition, genetic variation was estimated using 12 allozymes (21 loci) of 314 individuals sampled from 12 localities.

KEY RESULTS

Four chromosome numbers and eight cytotypes, including four endemic cytotypes, were detected. Cytotype distributions were highly structured geographically, with single cytotypes present in most populations and four major cytotypes dominating the north, east and south of Taiwan and the Penghu Archipelago. Allozyme variation was very low and F-statistics indicated an extremely high level of population differentiation, implying limited gene flow among populations. Cluster analysis of allozyme variation uncovered four geographic groups, each corresponding perfectly to the four dominant cytotypes. The geographic structure of cytotype distribution and allozyme variation probably resulted from severe genetic drift triggered by genetic bottlenecks, suggesting that Taiwanese populations were likely to be derived from four independent founder events. In the few localities with multiple cytotypes, cytogeographic patterns and inferences of chromosomal evolution revealed a trend of northward dispersal, consistent with the course of the Kuroshio Current that has been influential in shaping the coastal biota of the region.

CONCLUSIONS

The data elucidate the patterns of colonization and the effects of the Kuroshio Current on the distribution of L. mauritiana in Taiwan. These inferences are highly relevant to other coastal plant species in the region and will stimulate further studies.