Ellesmeris sphenopteroides,gen. ET SP. NOV., a new zygopterid fern from the Upper Devonian (Frasnian) of Ellesmere,N.W.T., Arctic Canada

A new fern-like fossil plant is described from the lower Upper Devonian of southern Ellesmere Island, Canadian Arctic Archipelago. The plant occurs in an Archaeopteris-dominated flora preserved in the Nordstrand Point Formation (Mid-Late Frasnian) near Bird Fiord. The plant has a pinnate vegetative system with three branch orders and laminate sphenopteroid pinnules. Primary pinnae usually diverge from the main axis in distichous pairs (quadriseriate), but can depart singly (biseriate). Each primary pinna bears a basal catadromic aphlebia. Anatomically, the plant exhibits a mesarch, bipolar protostele that is ribbon- to clepsydropsoid-shaped in the main axis. Primary pinna traces are also initially bipolar and crescent-shaped, but may become four-ribbed before dividing into a pair of bipolar traces. The morphology and anatomy of this plant are nongymnospermous and are most similar to Zygopteridales (particularly Rhacophytaceae and Zygopteridaceae). The Frasnian age of Ellesmeris shows that laminated foliage had evolved in some zygopterid ferns much earlier than previously recognized. The Sphenopteris-like pinnules of Ellesmeris indicate the need for caution when attributing such a convergent foliar design to other plant groups, such as the Devonian gymnosperms.     

Air humidity as key determinant of morphogenesis and productivity of the rare temperate woodland fern Polystichum braunii

(1) Most ferns are restricted to moist and shady habitats, but it is not known whether soil moisture or atmospheric water status are decisive limiting factors, or if both are equally important. (2) Using the rare temperate woodland fern Polystichum braunii, we conducted a three‐factorial climate chamber experiment (soil moisture (SM) × air humidity (RH) × air temperature (T)) to test the hypotheses that: (i) atmospheric water status (RH) exerts a similarly large influence on the fern's biology as soil moisture, and (ii) both a reduction in RH and an increase in air temperature reduce vigour and growth. (3) Nine of 11 morphological, physiological and growth‐related traits were significantly influenced by an increase in RH from 65% to 95%, leading to higher leaf conductance, increased above‐ and belowground productivity, higher fertility, more epidermal trichomes and fewer leaf deformities under high air humidity. In contrast, soil moisture variation (from 66% to 70% in the moist to ca. 42% in the dry treatment) influenced only one trait (specific leaf area), and temperature variation (15 °C versus 19 °C during daytime) only three traits (leaf conductance, root/shoot ratio, specific leaf area); RH was the only factor affecting productivity. (4) This study is the first experimental proof for a soil moisture‐independent air humidity effect on the growth of terrestrial woodland ferns. P. braunii appears to be an air humidity hygrophyte that, whithin the range of realistic environmental conditions set in this study, suffers more from a reduction in RH than in soil moisture. A climate warming‐related increase in summer temperatures, however, seems not to directly threaten this endangered species.     

福建梅花山自然保护区蕨类植物区系研究

通过野外调查和资料整理,统计分析梅花山自然保护区蕨类植物区系组成和分布区类型,比较其与周边相邻4个自然保护区的蕨类植物区系的相似性。结果表明:(1)梅花山自然保护区共有蕨类植物42科83属189种,科、属组成优势现象明显,区系起源古老。(2)分布区类型在科、属级水平上以泛热带分布和世界分布为主,种级水平以热带亚洲分布、东亚分布和中国特有分布为主,热带亲缘明显,具有由热带向温带过渡的性质。(3)在地理亲缘关系上,梅花山与梁野山的蕨类植物区系联系最为紧密,与圭龙山的关系次之,与热带区系性质较强的南靖南亚热带雨林自然保护区和典型的中亚热带性质的武夷山自然保护区的种子植物区系联系较为疏远,具有从南亚热带向中亚热带过渡的明显特点。     

Species richness of sawfly–host plant associations at higher taxonomic levels

Insect–plant interactions are important to understanding the evolutionary mechanisms responsible for most of the diverse plant‐feeding insects. We aggregated data on sawfly–host plant associations and other resource associations from existing sources to address the following questions: (i) Is there a general correlation between host diversity and sawfly species richness? (ii) Is the pattern of host plant use consistent across sawfly lineages? and (iii) Is there a phylogenetically significant shift in species richness among sawflies? Our analysis comprised 8567 sawfly species, including 2087 species with host plant and other records. In total, there were 2126 records of host usage for sawflies, the overwhelming majority of which were sawflies using angiosperms as resources. Rosales are used by most of the species in sawfly families or subfamilies. We found that there was a strong correlation between the number of host plant orders and the species richness of sawfly families and subfamilies. To examine the points at which sawflies have experienced significant shifts in species richness, we compared sister taxon species richness. Several positive and negative shifts in species richness among sawflies were related to their range of host plant usage and specialized niche, respectively. In general, we found that most of the sawfly families and subfamilies used several orders as host plants, but mainly core eudicots, although some families or subfamilies were specialized on pteridophytes or gymnosperms.     

Genetic consequence of restricted habitat and population decline in endangered Isoetes sinensis (Isoetaceae)

BACKGROUND AND AIMS: Isoetes sinensis (Isoeteaceae) is a critically endangered aquatic quillwort in eastern China. Rapid decline of extant population size and local population extinction have occurred in recent years and have raised great concerns among conservationists. METHODS: Amplified fragment length polymorphisms (AFLPs) were used to investigate the genetic variation and population structure of seven extant populations of the species. KEY RESULTS: Eight primer combinations produced a total of 343 unambiguous bands of which 210 (61.2 %) were polymorphic. Isoetes sinensis exhibited a high level of intra-population genetic diversity (H(E) = 0.118; hs = 0.147; I = 0.192; P = 35.2 %). The genetic variation within each of the populations was not positively correlated with their size, suggesting recent population decline, which is well in accordance with field data of demographic surveys. Moreover, a high degree of genetic differentiation (F(ST) = 0.535; G(ST) = 0.608; theta(B) = 0.607) was detected among populations and no correlation was found between geographical and genetic distance, suggesting that populations were in disequilibrium of migration-drift. Genetic drift played a more important role than gene flow in the current population genetic structure of I. sinensis because migration of I. sinensis is predominantly water-mediated and habitat range was highly influenced by environment changes. CONCLUSIONS: Genetic information obtained in the present study provides useful baseline data for formulating conservation strategies. Conservation management, including both reinforcement for in situ populations and ex situ conservation programmes should be carefully designed to avoid the potential risk of outbreeding depression by admixture of individuals from different regions. However, translocation within the same regional population should be considered as a measure of genetic enhancement to rehabilitate local populations. An ex situ conservation strategy for conserving all extant populations to maximize genomic representation of the species is also recommended.     

五种紫萁属植物的核型分析

研究了5种紫萁属Osmunda植物的核形态学特征, 其间期核属于复杂染色中心型, 有丝分裂前期染色体为中间型, 对有丝分裂前期染色体的动态变化过程和在细胞核内的自然排布情况进行了观察。核型公式为: 粗齿紫萁O. banksiifolia (Presl) Kuhn, 2n=4sm+10st+26t+4T; 紫萁O. japonica Thunb., 2n=2sm+8st+32t(2SAT)+2T;华南紫萁O. vachellii Hook., 2n=4sm+8st+28t+4T; 狭叶紫萁O. angustifolia Ching ex Ching &; Ch. H. Wang, 2n=2sm+4st+34t+4T; 粤紫萁O. mildei C. Chr., 2n=2sm+6st+33t+3T。所有染色体臂比均大于2, 核型类型均为4A, 后3种染色体为首次报道, 且对5种紫萁属植物的核型变异及演化关系进行了讨论, 推测Plenasium亚属3种紫萁属植物中粗齿紫萁核型类型最原始, 狭叶紫萁最进化, 其地理分布与核型不对称性有关联, 粤紫萁可能为一自然种间杂种。     

珠穆朗玛峰国家自然保护区蕨类植物区系研究

在野外实地调查和室内标本整理以及查阅文献的基础上,对珠穆朗玛峰自然保护区蕨类植物区系进行研究,为探讨喜马拉雅植物区系的起源以及该区生物多样性的保护提供资料。结果表明:(1)珠穆朗玛峰自然保护区共有蕨类植物193种,隶属于31科59属,其中优势科为鳞毛蕨科(51种)、水龙骨科(41种)、蹄盖蕨科(22种)、铁角蕨科(10种),优势属为耳蕨属(27种)、鳞毛蕨属(20种)、瓦韦属(17种)。(2)科的分布区类型有8种,以泛热带分布型(55.56%)为主;属的分布区类型有14种,以泛热带分布型(23.81%)、中国-喜马拉雅分布型(19.05%)为主;蕨类植物以土生(55.88%)为主,石生(24.35%)和附生(21.76%)也占有一定比例,缺乏水生蕨类。(3)珠穆朗玛峰自然保护区蕨类植物区系成分与南迦巴瓦峰地区联系最为密切,其次为横断山地区和尼泊尔,与九塞沟自然保护区、秦岭地区有一定的联系,与西双版纳地区的关系较为疏远。     

云南药山自然保护区蕨类区系研究

基于馆藏标本,对云南药山自然保护区蕨类进行区系分析.结果表明:该保护区共有蕨类30科、67属、177种及10变种;属的区系地理成分可划分为10个类型11个亚型;种的区系地理成分可划分为9个类型、20个亚型及7个变型;该保护区温带区系成分占优势;与相邻地区区系成分比较发现,蕨类区系与云南药山联系的紧密程度为:轿子雪山>梅里雪山及附近地区>玉龙雪山>黄山.     

浙江北雁荡山蕨类植物区系特征分析

通过标本和文献查阅以及野外调查,对浙江北雁荡山蕨类植物的区系组成和分布区类型进行了分析.结果显示:北雁荡山共有蕨类植物37科71属156种(含种下分类群);以单种和寡种分布的科和属所占比例最大,分别占总科数和总属数的75.7％和91.5％.该区域蕨类植物科的分布区类型以世界分布型和泛热带分布型为主,分别有14和20科,占总科数的37.8％和54.1％;热带成分总计22科,占总科数的59.5％,而温带成分仅1科.属的分布区类型可划分为9类型2亚型,包含世界分布型17属、热带分布型47属、温带分布型7属;其中,泛热带分布型属数量最多区28属),占总属数的39.4％.种的分布区类型以东亚分布型最多(93种),其中,中国-日本分布亚型有65种,占总种数的41.7％.中国特有种有21种(占总种数的13.5％),其中2种为仅分布于本区域的特有种,分布类型以华东-华南分布最多.由分析结果可见:北雁荡山蕨类植物具有组成丰富、区系起源古老、地理成分多样、热带区系特征明显及特有种数量匮乏等特点,但与周边区域蕨类植物分布有紧密联系.