Biosystematic studies on the genus Isoetes (Isoetaceae) in Japan. II. Meiotic behavior and REPRODUCTIVE MODE OF EACH CYTOTYPE

Meiotic behaviors and reproductive modes of Japanese Isoetes were studied. The hexaploid (2n = 66) and the octaploid (2n = 88) of I. japonica consistently formed 33 and 44 bivalents, respectively, at diakinesis and/or metaphase I in both micro- and megaspore mother cells. The tetraploid (2n = 44) of I. sinensis formed 22 bivalents and its hexaploid made 33 bivalents in both types of spore mother cells. At diakinesis and/or metaphase I of microspore mother cells in I. asiatica with 2n = 22, 11 bivalents were detected. Because behaviors of meiosis in all cytotypes mentioned above were quite regular and plants yielded normal-appearing spores, they should reproduce sexually. Aneuploids of I. japonica with 2n = 87 formed 43 bivalents and one univalent, and I. sinensis with 2n = 65 formed 32 bivalents and one univalent in microspore mother cells. Meiosis of both cytotypes was almost regular and yielded microspores of normal appearance. In the heptaploid (2n = 77) of I. japonica, a configuration of 22 bivalents and 33 univalents was detected in micro- and megaspore mother cells, and various irregularities were observed throughout the meiotic divisions. Therefore, the genomic formula of the heptaploid is symbolized as AABBCDE, and the heptaploid is a sterile F, hybrid between the hexaploid (AABBCC) and the octaploid (AABBDDEE) of I. japonica. Since diploid and even-numbered polyploids regularly formed bivalents and odd-numbered ones displayed irregularities, allopolyploidy should act as a significant speciation mechanism in this genus.     

Isoëtes sabatina (IsoëtaceaeLycopodiophyta), a new aquatic species from central Italy

The new species Isoëtes sabatina is described and illustrated. Morphological, anatomical, and ecological characters are given. It differs from the similar I. echinospora by several characters, such as megaspore ornamentation and size, microspore size, velum extension and form, and also for its ecology. A table showing the main differential characters of the new species compared with those of the other European aquatic species is presented. So far, the species is known from a single locality (Bracciano Lake, central Italy), having a peculiar ecology and within the Mediterranean bioclimate.     

中国水韭属两个四倍体新种

水韭属(Isoëtes)是起源最为古老的水生维管植物,全属物种均被列为国家一级重点保护植物。通过对全国水韭属植物的调查和研究发现,不同产地的四倍体植株在形态上存在显著差异。基于形态学、孢粉学和细胞学证据,将分布于中国湖南省长沙地区和怀化地区的四倍体居群分别命名为隆平水韭(Isoëtes longpingii)和湘妃水韭(I. xiangfei),并详细描述了其形态特征。隆平水韭形态上与中华水韭(I. sinensis)相似,不同之处在于其大孢子具小的瘤状或冠状纹饰,叶细长而柔弱,长达60 cm; 该种也与六倍体东方水韭(I. orientalis)相似,不同之处在于其染色体44条,大孢子具瘤状或冠状纹饰。湘妃水韭的大孢子纹饰虽与二倍体云贵水韭(I. yunguiensis)相似,但在小孢子纹饰、孢子囊形状和染色体数目方面却不同。隆平水韭仅少数植株生长于湖南省宁乡市一处池塘,完全沉水生长,而湘妃水韭则分布于怀化市通道县和会同县的湿地。由于这两个新种的分布区狭窄,野生居群数量和个体数较少,栖息地环境受到人为干扰,因此根据IUCN红色名录评估标准,将隆平水韭评为极危(CR)等级,湘妃水韭评为易危(VU)等级。所编制的中国已知水韭属物种的分种检索表,为本属物种的鉴定和保护工作提供了重要参考。     

Genetic Diversity and Population Structure of Juniperus rigida (Cupressaceae) and Juniperus coreana

Enzyme electrophoresis was used to estimate genetic diversity and population structure of Juniperus rigida (Cupressaceae) and Juniperus coreana in Korea. In J. rigida, 16 of the 22 loci (72.7%) showed detectable polymorphism. Genetic diversity (0.224) was higher than average values for species with similar life history traits. The endemic species (J. coreana) was found to have fewer alleles per locus (1.39 vs. 1.61), fewer alleles per polymorphic locus (2.42 vs. 2.63), lower percent polymorphic locus (54.6 vs. 72.7%), and lower diversity (0.199 vs. 0.224) than J. rigida. These genetic diversity parameters indicated that J. coreana was genetically depauperate relative to its presumptive progenitor, J. rigida. Analysis of fixation indices showed a substantial deficiency of heterozygotes relative to Hardy–Weinberg expectations suggesting inbreeding in J. coreana. The G _ST values of J. rigida and J. coreana were 0.173 and 0.118 respectively. The indirect estimate of gene flow based on mean G _ST was moderate (Nm = 1.19 for J. rigida and 1.86 for J. coreana). This revised version was published online in July 2006 with corrections to the Cover Date.     

Spore morphology of Isoëtes (Isoëtaceae) from China

Micromorphological characters of mega- and microspores of five Isoëtes species from China were observed under scanning electron microscope (SEM). Megaspores of I. hypsophila have a levigate ornamentation, and are 358 µm in diameter (mean, n=30), microspores of this species have a gyrus ornamentation, and are 22 µm in length (mean, n=30); megaspores of I. yunguiensis have a cristate-reticulate ornamentation, with a size of 390 µm in diameter (mean, n=30), while microspores nearly smooth with some fine granulates, and with a size of 22 µm in length (mean, n=30); megaspores of I. taiwanensis are tuberculate and 312 µm in diameter (mean, n=30), echinate microspores are 24 µm in length (mean, n=30); cristate megaspores of I. sinensis are 409 µm in diameter (mean, n=30), and echinate microspores are 28 µm in length (mean, n=30); megaspores of I. orientalis have a cristate-reticulate ornamentation, with diameter of 420 µm (mean, n=30), microspores of this species have an echinate-tuberculate ornamentation with a size of 34 µm in length (mean, n=30). Based on the morphological characters of spores and chromosome numbers among taxa, it was found that mean spore size in each species of Isoëtes generally reflected the ploidy level. I. hypsophila, I. yunguiensis and I. taiwanensis, with smaller mean spore size, are diploidy with 2n=22; I. sinensis (2n=44) and I. orientalis (2n=66), with larger mean spore size, are polyploidy. The spore morphology of Isoëtes still plays an important role in identification and classification of Isoëtes from China.     

Micromorphological approach to the systematics of Mediterranean Isoëtes species (Isoëtaceae,Lycopodiophyta): analysis of the megaspore surface

Megaspore ornamentation is one of the few morphological characters used in the taxonomy of the genus Isoëtes. In the present work, we test the application of this character for distinguishing some Isoëtes species occurring in the Mediterranean: Isoëtes sicula, which according to some authors should be included as a variety in I. histrix, and the recently described I. todaroana, whose affinity with other taxa is currently unknown. Two additional species (I. duriei, I. velata) were also included in the analysis. The megaspores were studied using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy and chemical treatment. In all species, the megaspore surface is covered by a siliceous coating; removal of this coating reveals an underlying three-dimensional network of fused rodlets. A unique pattern of this network occurs in I. sicula, supporting its separation from I. histrix. Comparison between the patterns observed in the examined Mediterranean species shows that I. todaroana is most similar to I. histrix.     

中国水韭属植物的染色体数目及其分类学意义

利用细胞学方法观察统计了中国4种水韭属Isoestes植物的染色体数目。结果发现4个种的染色体基数均为x=11,其中高寒水韭I．hypsophila Hand.-Mazz．为2n=22,为首次报道;台湾水韭 I．taiwanensis DeVol为2n=22;中华水韭I．sinensis Palmer 2n=44为四倍体;而产于云南贵州一带并一直被当作是宽叶水韭I．japonica A．Br．的水韭属植物2n=22,与文献报道的宽叶水韭(2n=66,67,77,87,88,89)完全不同,应重新予以认识和评价。依据本文和其他相关的研究结果,对东亚水韭属植物进行了分类处理。     

Mychophilus palmatus, a new species (Copepoda: Cyclopoida: Ascidicolidae) associated with the compound ascidian Botryllus leachi Savigny, with remarks on congeneric species and related genera

Presently two species of the genus Mychophilus Hesse, 1865 are known: Mychophilus roseus Hesse, 1865 and Mychophilus fallax Stock, 1967. A hitherto unknown species is described herein as Microphilus palmatus n. sp. The new species is characterized by its urosome much exceeding the cephalosome-metasome in length, the ornamentation of the labrum, the shape of the palp of the first maxilla, the ornamentation of the legs 1–4 and shape of the caudal rami. These and other features of the genus Mychophilus are compared with those from other related genera of the family Ascidicolidae Thorell, 1859.     

Description of a New Helicopsyche Species from China (Trichoptera: Helicopsychidae)

Helicopsyche zhejiangensis sp. n. from southeastern China is described and figured, representing the first record of this family in China. The species has a general resemblance with Helicopsyche species known from the Oriental Region, and the East Palaearctic species Helicopsyche coreana Mey from North Korea.     

Studies on male and female meiosis in Indian Allium

Frequency and position of chiasmata at diplotene were studied in pollen mother cells and megaspore mother cells of the same plants of two wild Allium species (A. consanquineum and A. kachrooi) and two cultivated species (a. cepa and A. nigrum), all diploid with 2n=16. Contrary to most reports on sex differences in recombination, chiasma frequencies were higher in male than in female meiosis in all cases. Chiasmata were non-localised except in A. kachrooi megaspore mother cells where they were proximally localised.     

云贵水韭雌配子体发育及其濒危机制的研究

为了解云贵水韭(Isoetes yunguiensis)的生殖过程和濒危原因,采用人工培养获得其雌配子体,用半薄切片法观察雌配子体发育过程。结果表明,云贵水韭的大孢子萌发率约为26%;雌配子体异养,终生都在大孢子细胞壁内发育;颈卵器发育只有2枚颈沟细胞而无腹沟细胞。雌配子体发育停止在游离核时期、颈壁细胞数量偏少或排列紊乱、颈沟细胞异常、卵细胞凋亡等可能是导致生殖濒危的原因。同时,游离核是水韭生殖生物学研究和系统学研究的重要环节之一;缺失腹沟细胞可能是水韭类简化性进化的特征之一。     

浙江乌岩岭国家级自然保护区凤尾藓属物种多样性研究

报道了浙江省乌岩岭国家级自然保护区12种凤尾藓属(Fissidens)植物,其中内卷凤尾藓济州岛变种(F.involutus Wilson ex Mitt.var.jejuensis Y.-J.Yoon,B.C.Tan&B.-Y.Sun)为中国首次报道,该变种此前只分布在日本和韩国,其特征是背翅基部明显下延,鞘部细胞的...     

四川雅安地区13种凤仙花属植物花粉形态及其分类学意义

采用扫描电镜观察了中国四川雅安地区13种凤仙花属植物的花粉形态,并对其花粉形态进行了主成分分析和聚类分析,基于孢粉学和SRAP聚类结果的比较,讨论不同孢粉学特征对分类结果的影响。结果显示:(1)雅安地区13种凤仙花属植物花粉粒均为中等大小,花粉粒形状从超扁到扁球形变化,花粉粒极面观形状从矩形和椭圆形到四边形、圆形、三角型变化,且只有湖北凤仙、峨眉凤仙和匙叶凤仙是三沟花粉粒,其余种均为四沟花粉粒;外壁纹饰仅扭萼凤仙和齿萼凤仙为细小网状,其余均为网状纹饰。(2)依据不同指标进行的孢粉学聚类均将13种凤仙花属植物划分为3个类群,而SRAP聚类结果则将13种凤仙花属植物划分为5个类群;不同孢粉学聚类结果的相似率只有30.77%。(3)孢粉学聚类并未与分子聚类显示严格的对应关系,以花粉大小和形状、外壁纹饰为指标进行的孢粉学分类与SRAP分类的相似率最高(69.23%)。研究认为,选择不同的花粉形态特征作指标对分类的准确性影响较大,花粉大小和形状、外壁纹饰这2个指标对凤仙花属植物分类具有意义,而萌发沟的特征则很难作为分类的依据,花粉形态特征在分类上有局限性;进行该属植物孢粉学分类需要选择有价值的分类指标,并结合形态学、分子生物学等综合研究。     

A CONTRIBUTION TO THE EARLY TERTIARY FOSSIL RECORD OF THE SALVINIACEAE

Megaspores and massulae of Azolla, Azollopsis, and Salvinia are recorded from the Paleocene and Eocene of Montana and the Dakotas. Three new species of Azolla are described and two species of Azolla are redescribed. The columella of the floating apparatus of the megaspore apparatuses of Azolla appears to be a phylogenetic localization of the perispore around the megaspore. A new section of Azolla (section Kremastospora) is created for species whose megaspore apparatuses have many floats and whose massulae have hooked (anchor-shaped) glochidia. Salvinia preauriculata is based only on leaf remains from the Eocene of North America. Megaspores and massulae which probably are conspecific with the leaf remains are described. The megaspores and massulae of the fossil species are much smaller than those of the living species, S. auriculata, with which S. preauriculata has been compared. The similar size of the megaspores and massulae of the fossil species suggests a less specialized condition than in living species, where these two structures differ greatly in size. Azollopsis tomentosa, previously known from the late Cretaceous, has been found in the Eocene.     

Mallomonas jejuensis sp. nov. (Synurophyceae) from Jeju Island,South Korea

A new species of Mallomonas (Synurophyceae), Mallomonas jejuensis sp. nov., has been found in Jeju Island, South Korea. This species is placed in the series Mangoferae (section Torquatae) because it has a collar of elongated domed scales, domeless body scales, rear scales with spines and all scales ornamented with papillae. The morphological characteristics of the scales and bristle of the new species are described by EM and compared with those reported for the other species of the series Mangoferae.     

Formation of first division restitution (FDR) 2n-megaspores through pseudohomotypic division in ds-1 (desynapsis) mutants of diploid potato: routine production of tetraploid progeny from 2xFDR × 2xFDR crosses

Summary The level and mode of 2n megaspore formation was studied in full-sib diploid potato clones with either normal or desynaptic (ds-1ds-1) meiosis. Cytological analysis revealed that functional 2n megaspores produced by normal and desynaptic clones originate exclusively from second division restitution (SDR) and first division restitution (FDR), respectively. SDR 2n megaspores resulted from the omission of the second meiotic division following chromosome doubling after anaphase I, whereas FDR 2n megaspores resulted from a direct equational division of univalent chromosomes at anaphase I (pseudohomotypic division). Comparative data strongly indicated that the observed mechanisms of SDR and FDR 2n megaspore formation are extremes of a continuum that is being brought about by common genes for precocious chromosome division. Depending on the relative timing of cell cycle and chromosome division, this precocious chromosome division may impose postreductional (SDR) or prereductional (FDR) restitution of the sporophytic chromosome number under normal synaptic and desynaptic conditions, respectively. The observed frequencies of 2n megaspores closely correlated with seed set, following pollination by tetraploid varieties and by desynaptic diploid clones with exclusive FDR 2n pollen formation. Up to 54.0 and 21.5 seeds/ fruit were obtained from normal synaptic (SDR) and desynaptic (FDR) progeny, respectively. The high frequency of segregants with either SDR or FDR 2n megaspore formation (78.0 and 45.2%, respectively) supports the hypothesis that sexual polyploidization is the driving force behind the origin and evolution of polyploid Solanum species. The present identification of diploid potato clones with consistent FDR 2n megaspore formation extends the opportunities for direct transfer of enhanced diploid germ plasm to tetraploids, and particularly advocates the feasibility of 2x(ds-1; FDR)×2x(ds-1; FDR) breeding schemes in cultivar development and the production of relatively vigorous and uniform true potato seed (TPS) varieties. Its potential value and limitations for breeding and the experimental induction of diplosporic apomixis are discussed.     

A SYSTEMATIC REVISION OF PHYLLANTHUS SUBSECTION URINARIA (EUPHORBIACEAE)

The examination of several taxa from various tropical regions of the world, previously classified as Phyllanthus urinaria L., indicates that they do not belong to a single species. On the basis of morphology, cytology, genetics, and biometry, a new classification is presented in which the collective species P. urinaria, or “urinaria complex,” is elevated to the subsection level: Phyllanthus subsection Urinaria. Within the subsection, two subgroups may be recognized on the basis of seed coat ornamentation. Each of these lines is represented by two species which differ from each other in chromosome number: P. embergeri nov. spec. (2n = 100) and P. nozeranii nov. spec. (2n = 50) in the “spiraled” line, P. hookeri Muell. Arg. (2n = 100) and P. urinaria L. (2n = 50) in the “radiated” line. In the latter species, which has undergone diversification, two subspecies may be distinguished: P. urinaria urinaria and P. urinaria nudicarpus subspec. nova.     

STUDIES ON FOSSIL AZOLLA: PRIMITIVE TYPES OF MEGASPORES AND MASSULAE FROM THE CRETACEOUS

Fossil Salviniaceae are described from the Claggett Shale and Judith River Formation, late Cretaceous (Campanian stage) of Montana. A new genus, Parazolla, from the Claggett Shale, has megaspores in which the swimming apparatus is composed of a number of elongate floats attached to the megaspore body and invested by coiled hairs. The floats separate at maturity. Massulae (bearing microspores) have simple hair-like glochidia, many of which are knobbed at their tips. Glochidia tend to resemble the perisporial hairs of the megaspore body. This resemblance provides fossil evidence of the homology of these two hair-like structures among living species of Azolla. In Azolla simplex from the Judith River Formation the megaspore has a single cap-like so-called columellate float. Massulae, which have anchor-shaped glochidia, are associated with these megaspores. A. simplex is the oldest species of Azolla and Parazolla the oldest member of the Salviniaceae so far found.     

Different spore structures in sympatric Isoetes histrix populations and their relationship with gross morphology, chromosome number, and ribosomal nuclear ITS sequences

Traditionally, megaspores have supplied the most relevant character for the taxonomy of Isoetes at several systematic levels, including discriminant features usually used in species identification and diagnosis. Isoetes histrix Bory is a terrestrial circum-Mediterranean quillwort characterized by dark, shiny, and persistent phyllopodia with megaspore sporangia completely covered by a velum and tuberculate megaspores. Specimens of this species from Sardinian temporary wetlands showed the sympatric presence of two kinds of individuals with correlated variation in size, ornamentation, and radial ridges of megaspores, and in ornamentation of microspores. However, they showed the same diploid chromosome number (2n = 20), ITS ribotype, and macromorphological feature. No intermediate individuals, showing mixed characters of each spore types as well as malformed or aborted spores have been detected. These results suggest that the gene flow between both kinds of I. histrix plants is heavily restricted, if not limited at all. On the basis of the cytogenetic and molecular uniformity detected in I. histrix in this study, genomic incompatibilities do not seem to be the main reasons involved in the maintenance of the two kinds of I. histrix individuals. Prezygotic barriers involving changes in phenology (e.g. spore maturation) or differential gamete dispersal should be further assessed to gain insights in this topic. The presence of two kinds of individuals in I. histrix differing in significant spore features used in quillwort taxonomy, whatsoever the causes involved in its origin, could be the basis of an incipient differentiation process upon which selective pressures could ultimately lead to speciation.