Plant Systematics and Evolution最新文献

Species are fundamental biological units and can be treated as testable scientific hypotheses. Historically, species in the genus Coccoloba have been published based only on classical morphology. One of these species, Coccoloba laevis, contains many specimens with strong morphological differences. We here test the hypothesis that these morphological variations are consistent with the circumscription of C. laevis as a single taxonomic entity. In addition to classical morphology, we used linear morphometry, vascular anatomy, and potential geographic distribution to delineate a distinctive morphotype of C. laevis from the remainder of C. laevis s.s. Statistical analysis showed significant differences for all ten morphometric variables. Petiole and midrib anatomy also pointed to differences in both shape and arrangement of vascular bundles between the distinctive morphotype and the remainder of C. laevis s.s. The potential distribution model yielded a wide distribution for C. laevis s.s. in the coastal zone of northeastern Brazil. The distinctive morphotype, however, had a contiguous and restricted distribution within this range. Based on our results, we here reestablish Coccoloba candolleana at the species level, which has been previously treated as a synonym of C. laevis. Both species differ morphologically mainly by habit, and the shape and size of ochrea, leaf, petiole, inflorescence, pedicel, and fruit. Because of its restricted distribution in a coastal ecosystem associated with strong anthropogenic disturbance, we consider C. candolleana as endangered.

Despite many studies conducted over a period of nearly two centuries since Reboul, who was the first to classify tulips as subgeneric level, there is still no consensus among researchers regarding the infrageneric classification of tulips. Nevertheless, in recent years, efforts to solve this taxonomic problem have been increasing. However, phylogenetic studies covering all species of a genus or at least with species representatives of all subgeneric taxonomy worldwide are very scarce. The main difference of the current study from previous studies is that it is a larger study focused on solving this problem by considering all perspectives together, covering many geographical areas and species in global distribution. For this purpose, we examined the phylogenetic relationships of the genus Tulipa with 82 accessions from 45 Tulipa species and six accessions from two Amana and three Erythronium species, and we positioned our results by discussing them in light of previous morphological, geographical, molecular and anatomical data. We investigated the phylogenetic relationships in the genus using DNA sequences from the internal transcribed spacer region of nuclear ribosomal DNA. The 45 species of Tulipa formed a monophyletic clade. Genera Amana and Erythronium were clustered as outgroups. In the genus Tulipa, two major clades were obtained; the first clade belonged to subgenus Orithyia. The second clade separated subgenus Tulipa and subgenera Eriostemones+Clusianae. Then, Eriostemones and Clusianae subgenera formed two separate clusters. Subgenus Eriostemones separated two main clusters; section Biflores and section Sylvestres. On the other hand, all previously proposed sections and series under the subgenus Tulipa were grouped into a single clade. This situation agrees with previous biosystematic data highlighting the morphological overlap of most of the sections and with previous molecular data showing that many sections are not monophyletic. Consequently, we propose a taxonomic concept consisting of four subgenera and two sections.

Phyllanthus emblica is a well-known medicinal and non-timber forest product species, widely distributed in the Indian subcontinent. Multiple disturbances like intensive fruit harvest, the spread of invasive species such as Lantana camara and Taxillus tomentosus, and other anthropogenic disturbances threaten population viability by altering ecological and genetic processes. Studying the genetic diversity and population structure of species harvested intensively and subjected to anthropogenic disturbances is crucial for evaluating their ability to survive under future environmental changes and for establishing conservation strategies. The genetic diversity and population structure of twelve populations of P. emblica that are harvested across three protected areas of the Western Ghats, the world’s most densely populated biodiversity hotspot was evaluated. Three hundred sixty samples were genotyped with nine simple sequence repeat markers. The changes in genetic diversity and genetic structure were assessed between generations by analyzing adults, seedlings, and juvenile samples. Despite intensive harvesting, the results found high genetic diversity in all the populations (mean/pop: Ho = 0.626; Hs = 0.722). However, genetic differentiation was significant between the study regions as well as between adult and seedling populations. The study also indicated a clear clustering of the twelve populations into three distinct genetic clusters. Neighbor-joining tree and hierarchical clustering analysis also showed the same pattern. The genetic data from the study provide information on how local disturbances including harvesting affect the population's genetic diversity and structure, which can provide a basis for implementing programs for conserving and sustainable utilization of P. emblica genetic resources in the future.

New Zealand is home to 16 endemic species of Lepidium (Brassicaceae), including two species considered to have become extinct since European colonisation and an additional species shared with Australia. Previous meiotic chromosome counts suggest at least some are high polyploids. A hybrid origin has been proposed for several of them, with African and American species implicated as parents. We generated amplicon sequence data for 15 genes derived from targeted enrichment data from a selection of species endemic to New Zealand, and of African, American, and Australian origin naturalised in New Zealand. These were analysed, along with publicly available genomic data from other Lepidium species. Our results are consistent with earlier work in supporting two main groups of endemic New Zealand Lepidium, corresponding to different dominant nrDNA sequences. Our data suggest that these two groups differ in ploidy (one octoploid, the ploidy of the other uncertain). The octoploid species combine four distinguishable subgenomes and the other species may be the products of allopolyploidisation between octoploid species and a diploid species closely related to, if not, L. africanum. Previously proposed links to American Lepidium are also supported, with at least two Australasian Lepidium subgenomes related to subgenomes present in American polyploid species. The affinities of two further subgenomes present in Australasian Lepidium remain to be determined, but they may also be of American origin. One New Zealand endemic species, L. naufragorum, displays sequences broadly consistent with it being the octodecaploid product of hybridisation between octoploid and decaploid New Zealand groups.

Identification of natural hybrids considered as endangered species is of vital importance in taxonomy and biodiversity conservation, as natural hybrids will usually waste the conservation resource and efforts. During field surveys in the Sanqing Mountain, we found the endangered endemic species, Ilex sanqingshanensis, strictly co-occurred with I. ficoidea and I. pernyi and then hypothesized a hybrid origin for this taxon. Combing molecular analyzes of the nrDNA ITS and cpDNA (petA-psbJ + psbA-trnH) with morphological analyzes of eight leaf characters, we confirmed that this taxon is truly a hybrid between I. ficoidea and I. pernyi and we therefore to rename it as I. × sanqingshanensis. Despite the presence of intermediate morphological characteristics, this hybrid is sharply distinct from the two parents in almost all tested traits, misleading botanists who treated it as a species. Considering the inadequacies of morphological distinctions in distinguishing holly hybrids, we have emphasized the necessity of molecular evidence for erecting Ilex species.

Amino acid substitution model is a key component to study the plant evolution from protein sequences. Although single-matrix amino acid substitution models have been estimated for plants (i.e., Q.plant and NQ.plant), they are not able to describe the rate heterogeneity among sites. A number of multi-matrix mixture models have been proposed to handle the site-rate heterogeneity; however, none are specifically estimated for plants. To enhance the study of plant evolution, we estimated both time-reversible and time non-reversible multi-matrix mixture models QPlant.mix and nQPlant.mix from the plant genomes. Experiments showed that the new mixture models were much better than the existing models for plant alignments. We recommend researchers to use the new mixture models for studying the plant evolution.

Ficus microcarpa, belonging to Moraceae, is an evergreen tree that can grow on tropical or subtropical rocky coasts. Recently, dwarf F. microcarpa individuals have been found on Nakanokamishima Island, Okinawa, Japan, but it remains unclear whether this dwarf trait is based on environmental plasticity or represents an intermediate stage of ecological speciation. To clarify the morphological and genetic traits of dwarfism and consider the process of ecological divergence, we conducted a common garden experiment and performed population genetic and structure analyses using 11 microsatellite markers. Moreover, we conducted a coalescent analysis to estimate the demographic parameters of two genetic clusters: dwarf and tree groups. Common garden experiments clearly classified the samples into two groups: dwarf and tree. In the STRUCTURE analysis, the highest ΔK value was obtained when K = 2, suggesting the existence of two genetic clusters: A and B. All samples collected on Nakanokamishima Island were classified into cluster B. Most samples from the other islands were classified into cluster A. Additionally, it was found that dwarf and tree lineages had diverged from an ancestral population hundreds or thousands of years ago. These results indicate that the dwarfism of F. microcarpa can be considered an ecotype defined as the intermediate stage of ecological speciation, and that dwarf individuals diversified very recently from an ancestral population with the existence of gene flow.

The genus Disporum (Colchicaceae) comprises approximately 20 species distributed throughout Asia, of which four species (Disporum sessile, D. smilacinum, D. uniflorum, and D. viridescens) are currently recognized in Korea. Mixed-ploidy variations, including odd-ploidy levels within the same species, are important in evolution as they enable backcrosses with their parental cytotypes. However, Korean Disporum species have not been examined in detail with regard to ploidy variation and pollen fertility. Therefore, we document the occurrence of diploids and triploids among the Disporum spp. in Korea and report for the first time that D. sessile and D. smilacinum are both diploid (2n = 2x = 16) and triploid (2n = 3x = 24), though they were previously known as diploids from Korean natural populations. The total haploid chromosome length is variable, ranging from 67.32 µm in diploid D. smilacinum to 108.11 µm in triploid D. smilacinum; however, the karyotypes of the investigated species are similar regardless of the ploidy levels. The occurrence of fertile pollen grains from triploid individuals is approximately two-thirds that from diploid species, but triploid plants show no pollen tube germination compared to their diploid counterparts. Overall, this study presents the first comprehensive chromosomal and pollen fertility data for Korean Disporum species, and thus lays the foundation for better understanding the evolution and diversification of morphologically and cytologically variable plant groups.

Abstract

Some plant species have a kind of mixed pollination system—ambophily—which rely both on biotic and abiotic (most commonly wind) as pollen vectors. Ambophily remains poorly addressed in the pollination literature and may have been overlooked because existing studies do not quantify the wind contribution in animal-pollinated species. After observing pollen transport by the wind in an Orobanchaceae species with ornithophilous floral phenotype, we hypothesize that this species could be ambophilous. Esterhazya eitenorum Barringer is a (sub-)shrub endemic to a high-altitude grassland (campos de altitude) area in southeastern Brazil. Pollinated mainly by hummingbirds and secondarily by large bees, it presents features generally associated with ornithophily. Bird-pollinated species are not expected to be ambophilous, due to their high resource investment in floral construction and maintenance. However, here we detect ambophily in E. eitenorum by testing the potential for pollen export by the wind as well as seed set after floral visitor exclusion and spontaneous self-pollination treatments, and comparing these with natural conditions. Esterhazya eitenorum has an ambophilous pollination system, with effect size analyses between floral visitor exclusion treatments and natural conditions revealing significant contributions from both abiotic and biotic components. Although its floral phenotype corresponds to the main pollinator, the occurrence of ambophily in E. eitenorum underscores the need for an independent approach to the association of floral phenotypes with pollination vectors, in particular for the detection and better understanding of the evolution of mixed pollination systems.

This paper presents a biomechanical study of stems of two liana species, Clematis vitalba and Vitis vinifera, investigates the mechanical performance of these two liana species and attempts to enhance the understanding of structure–function relationships. The investigation involved mechanical testing of whole plant stems, supplemented by X-ray micro-CT (X-ray computed tomography at micron voxel size) imaging and 2D microscopic images of stained cross sections of the plant stems, to derive structure–function relationships with potential for application in bioinspired composite materials. The micro-CT images were compared to the microscopic images of stained cross sections, in order to show benefits and potential drawbacks of the X-ray micro-CT method with respect to traditional methods. The high-resolution 3D imaging capacity of micro-CT is exploited to explain the structural functionality derived from the mechanical testing. A simple finite element model is developed based on the plant topology derived by the micro-CT images and proved accurate enough to model the plant’s mechanical behaviour and assess the influence of their structural differences. The two plants exhibit different to each other physical and mechanical properties (density, strength and stiffness) due to their common growth form. Anatomical cross-sectional observation and X-ray micro-CT provide complementary information. The first method allows the identification of the lignified parts, supposedly more resistant mechanically, of these structures, while the second one provides a full 3D model of the structure, admittedly less detailed but providing the spatial distribution of density contrasts supposed to be important in the mechanical properties of the plant. The proposed methodological approach opens new perspectives to better understand the mechanical behaviour of the complex structure of plants and to draw inspiration from it in structural engineering.