The origin of Darwin’s “abominable mystery”

The phrase “Darwin’s abominable mystery” is frequently used with reference to a range of outstanding questions about the evolution of the plant group today known as the angiosperms. Here, I seek to more fully understand what prompted Darwin to coin the phrase in 1879, and the meaning he attached to it, by surveying the systematics, paleobotanical records, and phylogenetic hypotheses of his time. In the light of this historical research, I argue that Darwin was referring to the origin only of a subset of what are today called angiosperms: a (now obsolete) group equivalent to the “dicotyledons” of the Hooker and Bentham system. To Darwin and his contemporaries, the dicotyledons’ fossil record began abruptly and with great diversity in the Cretaceous, whereas the gymnosperms and monocotyledons were thought to have fossil records dating back to the Carboniferous or beyond. Based on their morphology, the dicotyledons were widely seen by botanists in Darwin’s time (unlike today) as more similar to the gymnosperms than to the monocotyledons. Thus, morphology seemed to point to gymnosperm progenitors of dicotyledons, but this hypothesis made the monocotyledons, given their (at the time) apparently longer fossil record, difficult to place. Darwin had friendly disagreements about the mystery of the dicotyledons’ abrupt appearance in the fossil record with others who thought that their evolution must have been more rapid than his own gradualism would allow. But the mystery may have been made “abominable” to him because it was seen by some contemporary paleobotanists, most notably William Carruthers, the Keeper of Botany at the British Museum, as evidence for divine intervention in the history of life. Subsequent developments in plant systematics and paleobotany after 1879 meant that Darwin’s letter was widely understood to be referring to the abrupt appearance of all angiosperms when it was published in 1903, a meaning that has been attached to it ever since.     

The origin of angiosperms

The claim of monophyletic origin of angiosperms arose from the confusion of phylogenetic and taxonomic concepts. Unpreconceived studies of extant angiosperms point to more than one archetype. Several lines of angiosperms have simultaneously entered the fossil record; the monocotyledons, proto-Hamamelidales, proto-Laurales and “proteophylls” (possibly ancestral to the Rosidae) are recognized among them. Three groups of Mesozoic seed plants — the Caytoniales, Czekanowskiales and Dirhopalostachyaceae — are distinguished as major sources of angiosperm characters (proangiosperms). Other Mesozoic lineages probably also contributed to the angiosperm character pool. Angiospermization is related to Mammalization and other processes involved in development of the Cenozoic lithosphere and biosphere.     

Mikromorphologie und Orientierungsmuster epicuticularer Wachs-Kristalloide: Ein neues systematisches Merkmal bei Monokotylen

Based on SEM examinations of some 1600 species of monocotyledons out of 61 families the characteristics of their epicuticular waxes are described in this preliminary paper and illustrated by 20 SEM micrographs. Four basic types of waxes are recognized. Two of them occur throughout the monocotyledonous and dicotyledonous orders of angiosperms; two others are of high systematic significance and restricted to particular orders of the monocotyledons: The “Convallaria-Type” is characterized by fine wax platelets with parallel orientation, forming a pattern around the stomata reminiscent of electromagnetic field lines. This type is restricted to the three liliiflorous ordersAsparagales, Liliales, andBurmanniales. The “Strelitzia-Type” is characterized by massive compound wax rodlets; it is restricted to the superordersAreciflorae, Commeliniflorae, Zingiberiflorae, plus the two liliiflorous ordersBromeliales andVelloziales. The data are compared with the classifications ofDahlgren & Clifford (1982); they tentatively indicate the exclusion ofBromeliales, Velloziales, andTyphales from theLiliiflorae.     

A revised system of classification of the angiosperms

A new system of classification of the angiosperms is presented. Like that of Dahlgren, 1975, it is shown as a two-dimensional diagram or frame-work, but differs in numerous major and minor features. In the new classification the angiosperms represent a class divisible into two subclasses corresponding to the di- and monocotyledons. The dicotyledons are divided into 24 ruperorders, viz . the Magnoliiflorae, Nymphaeiflorae, Ranunculiflorae, Caryophylliflorae, Polygoniflorae, Malviflorae, Violiflorae, Theiflorae, Primuliflorae, Rosiflorae, Podostemoniflorae, Fabiflorae, Proteiflorae, Myrtiflorae, Rutiflorae, Santaliflorae, Balanophoriflorae, Araliiflorae, Asteriflorae, Solanifloirae, Corniflorae, Loasiflorae, Gentianiflorae and Lamiiflorae, while the monocotyledons are divided into reven superorders, the Alismatiflorae, Ariflorae, Triuridiflorae. Liliiflorae, Zingiberiflorae, Commeliniflorae and Areciflorae. The higher categories are not defined here, but some general features in the classification are mentioned, and the distribution of some attributes is shown in the diagram.     

The "new" chemosystematics: phylogeny and phytochemistry

For almost a decade it has been acknowledged that the flowering plant dichotomy of monocotyledons and dicotyledons does not reflect the evolution of angiosperms. Despite this, conclusions in the field of chemosystematics are still drawn from, and rely on, non-phylogenetic botanical classifications such as those of Cronquist, Dahlgren and Takhtajan. In this paper the two alkaloids colchicine and camptothecin are used as examples of how phylogenetic systematics may be applied to alkaloid chemosystematics.     

MAJOR CLADES OF THE ANGIOSPERMS

Abstract— Our knowledge of fundamental angiosperm interrelationships is still very incomplete. The absence of a narrowly circumscribed gymnosperm outgroup, ideally the sister group, makes character evaluation, necessary for a cladistic analysis, difficult. According to current views the superorder Magnoliiflorae with a number of other groups, for example the monocotyledons, may represent a complex of families near the base of the angiosperms. Interrelationships of groups within the monocotyledons are much better understood than those between groups within the dicotyledons. A cladogram of monocotyledon orders based on earlier work by R. Dahlgren, H. T. Clifford, and F. N. Rasmussen is presented. A data matrix for a sample of the angiosperms with 61 characters for 49 taxa, mostly magnoliifloran and related families, is presented. The characters are polarized mainly according to the current view that the primitive angiosperm morphotype is a woody dicotyledon with strobiloid flowers. As an alternative the matrix is adjusted following W. C. Burger's conjecture that the primitive angiosperm was a herbaceous monocotyledon with trimerous flowers. Both matrices were run in a computerized parsimony analysis, resulting in numerous equally parsimonious solutions. This result is illustrative of the great homoplasy in the available character information, and also of how little actually is known about fundamental angiosperm interrelationships or phylogeny.     

An updated angiosperm classification

DAHLGREN, C, 1989. An updated angiosperm classification. A new two-dimensional diagram, reflecting the system of classification of the angiosperms, is presented. It combines the dicotyledon diagram in G. Dahlgren (1989) and an adapted monocotyledon diagram after that in Dahlgren (1985) in a single diagram. An updated monocotyledon taxonomy is presented and the classification is appended.     

A critique on the “Eight_Class System” of the classification of Angiosperms proposed by Wu et al.

Some critical comments are made on the “Eight-Classs System” of the classification of angiosperms recently proposed by Wu et al., which the aut hors claimed to be a “polyphyletic-polytopic” system. This system is established based on the hypothesis that there have existed eight principal lineages of angiosperms by the end of the Early Cretaceous. However, this hypothesis has not been supported by any neobotanical and paleobotanical evidence. There lationship among the eight lineages and their relationship with the common ances tor of angiosperms are not clearly clarified in the system. Having failed to follow the principle of common ancestry in the reconstruction of angiosperm phylogeny and having misinterpreted the concepts of monophyly and polyphyly, the “Eight-Class System” of the classification of angiosperms is considered to be an artificial one.     

Investigation of the Presence of Phenolic Compounds in Monocotyledonous Cell Walls, using UV Fluorescence Microscopy

Harris and Hartley (1976, 1980) demonstrated the presence offerulic acid in cell walls of certain monocotyledons using UVfluorescence microscopy (fluorescing green after treatment withammonium hydroxide solution). The presence or absence of thistype of fluorescence is apparently critical in higher levelsystematics of monocotyledons. In order to evaluate the significanceof this character, cell wall fluorescence was investigated ina range of monocotyledon species, particularly the AustralianXanthorrhoeaceae sensu lato (Bedford et al., 1986), which werenot investigated in earlier studies. This family is widely regardedas polyphyletic and was divided into several families by Dahlgren,Clifford and Yeo (1985). Some of its constituent genera, suchas Dasypogon, Kingia and Calectasia, have been linked with bothcommelinoid and non-commelinoid monocotyledons, and are of obscureaffinity. Some genera of Xanthorrhoeaceae sensu lato (Baxteria,Calectasia, Dasypogon and Kingia) show this type of green cellwall fluorescence and may therefore be more closely linked withthe commelinoid monocotyledons, rather than the Lilianae-Asparagales,as previously placed (Dahlgren et al., 1985).Copyright 1994,1999 Academic Press Asparagales, Dasypogonaceae, fluorescence, Hanguana, monocotyledons, systematics, Xanthorrhoeaceae     

Mature Phloem of Perennial Monocotyledons

Structural aspects of differentiating and mature sieve elements of perennial monocotyledons in general and of palms in particular are presented. As in other angiosperms, an immature sieve element undergoes a profound modification of the protoplast during differentiation. Intact, mature sieve elements lack nuclei, possess a parietal cytoplasm, empty lumen and sieve-plate pores that are free of obstructions. Such a structure is in general agreement with the physiological data obtained from exuding inflorescences of woody monocotyledons. Structural evidence and some tracer experiments indicate that sieve elements in perennial monocotyledons are long-lived and apparently function throughout the lifetime of the organ or the plant.     

南昌市不同植物类群叶片氮磷浓度及其化学计量比

对南昌大学前湖校区89种主要植物叶片的N、P浓度及其化学计量比进行了研究,结果表明:乔灌、常绿、针叶、种子、裸子和单子叶植物类群的N浓度分别低于相对应的草本、落叶、阔叶、蕨类、被子和双子叶植物类群,而C3和C4植物差异不显著;乔灌、常绿和裸子植物类群的P浓度含量分别低于相对应的草本、落叶和被子植物类群,而针叶和阔叶、蕨类和种子、单子叶和双子叶、C3和C4植物类群间差异不显著;乔木、阔叶、被子和双子叶植物类群叶片N/P分别高于相对应的灌草、针叶、裸子和单子叶植物类群,而常绿和落叶、蕨类和种子、C3和C4植物类群之间差异不显著.可见,不同类型植物对N和P的吸收利用存在差异,且对不同养分供应采取不同的适应对策.结合研究区土壤养分现状,建议优先选择常绿、针叶、裸子和单子叶植物类群作为城市园林植物.     

单子叶植物科级分类阶元形态性状分支分析

基于93个形态形状,采用13个被子植物基部类群做为外类群,对49个单子叶植物科级分类阶元进行了分支系统学分析。经过简约性分析,得到了1684棵同等最大简约分支树。严格一致树的分支结构图表明：1）古草本类植物和单子叶植物是姐妹群关系;2）具有网状脉的类群,薯蓣科,菝葜科,百部科是单子叶植物的最基部类群。由于性状状态间存在着较多的平行和逆转进化,这在一定程度上影响了系统发育重建的准确性;所选择的性状状态之间的演化很可能是平行的、多次的或者是特化的状态,因此这样复杂的演化关系的探索关键在于找到一些能确切反映其系统演化关系的形态性状。目前很难通过简约化的形态分支分析来解开整个单子叶植物的起源和演化之谜。为了避开对系统学分析造成干扰的误导性状,形态数据结合DNA序列分析很可能是必需的。     

Nuclear DNA content of monocotyledons and related taxa

Nuclear DNA content of 62 species of angiosperms including 52 monocotyledons and ten dicotyledons has been estimated by flow cytometry using Nicotiana tabacum var. Xanthi as the internal standard. These data, considered together with previous data on diploid species, suggest the following: 1) Most families and orders of monocotyledons have small genomes. Contrary to the general impression that monocotyledons are a group characterized by large genomes, genomes of over 20 pg/2C nucleus occur only in the Liliiflorae, Commelinales, Alismatales, and Araceae. 2) Variation within families ranges from two- to 56-fold, but is two- to fivefold in most families. Thus extraordinary variation in genome size appears to be limited to particular lineages, perhaps owing to some shared feature that facilitates such variation. 3) Endopolyploidy is not observed in the leaves of the species studied, although it has been reported to occur in the roots of several monocotyledons. This suggests that an examination of the basis for this difference between the roots and leaves of monocotyledons may provide clues to the mechanisms that regulate endopolyploidization in these organs.     

中国西双版纳傣族与泰国泰族民间植物命名方法与土著名字的相似性探讨

通过对中国西双版纳与泰国都有分布和栽培的641种植物的傣、泰土著名字相似性比较,发现这两个民族具有基本相同的民间植物命名的"双名法"。西双版纳傣族与泰国的兰纳地区、北—东北部和其它地区泰族的植物土著名相同、相似的分别占0.69、0.57和0.37,主要包括药用植物在内的经济植物和与南传上座部佛教文化密切相关的植物。其主要成因包括他们的语言文字、宗教信仰、生活习俗等的傣、泰历史渊源及其所具有的传统文化密切程度相关。其中,兰纳地区地处泰国北部,它不仅邻近西双版纳,而且在历史上,它们曾经同属于"兰纳王国",两地的边界曾是"犬牙交错",成为"曼比勐农"(兄弟之邦)。这样,使包括土著名字在内的佛教植物、野生植物和栽培植物等的交流比泰国其它地区更加密切,相似性便最高。西双版纳傣族和兰纳泰族被视为尚存的标准"Tai"人区。因此,该研究对于中国Dai、泰国Thai、缅甸Siam和老挝Laos等国家民族的科学文化交流及其植物资源的利用和保护等具有重要的意义。     

The impact of heat waves on children’s health: a systematic review

Young children are thought to be particularly sensitive to heat waves, but relatively less research attention has been paid to this field to date. A systematic review was conducted to elucidate the relationship between heat waves and children’s health. Literature published up to August 2012 were identified using the following MeSH terms and keywords: “heatwave”, “heat wave”, “child health”, “morbidity”, “hospital admission”, “emergency department visit”, “family practice”, “primary health care”, “death” and “mortality”. Of the 628 publications identified, 12 met the selection criteria. The existing literature does not consistently suggest that mortality among children increases significantly during heat waves, even though infants were associated with more heat-related deaths. Exposure to heat waves in the perinatal period may pose a threat to children’s health. Pediatric diseases or conditions associated with heat waves include renal disease, respiratory disease, electrolyte imbalance and fever. Future research should focus on how to develop a consistent definition of a heat wave from a children’s health perspective, identifying the best measure of children’s exposure to heat waves, exploring sensitive outcome measures to quantify the impact of heat waves on children, evaluating the possible impacts of heat waves on children’s birth outcomes, and understanding the differences in vulnerability to heat waves among children of different ages and from different income countries. Projection of the children’s disease burden caused by heat waves under climate change scenarios, and development of effective heat wave mitigation and adaptation strategies that incorporate other child protective health measures, are also strongly recommended.     

花同源异型MADS-box 基因在被子植物中的功能保守性和多样性

MADS-box基因家族成员作为转录调控因子在被子植物花发育调控中发挥关键作用。本文以模式植物拟南芥(Arabidopsis thaliana) 和水稻 (Oryza sativa)为例, 综述了近10年来对被子植物(又称有花植物)两大主要类群——核心真 双子叶植物和单子叶植物花同源异型MADS-box基因的研究成果, 分析MADS-box基因在被子植物中的功能保守性和多样性,同时探讨双子叶植物花发育的ABCDE模型在多大程度上适用于单子叶植物。     

Congruence between independent character systems across a hybrid zone: patterns in geographic space

The hybrid zone between eastern and western grass snakes, which has been independently hypothesized to be due to secondary contact, is investigated using univariate and multivariate analysis of a large number of independent, quantitative characters. Investigation of the patterns of geographic variation show that 5 out of 6 character systems show a congruent pattern of “stepped clinal” change across the zone. Insofar as this case is concerned, secondary contact ‘hybrid’ zones are associated with concordant changes in many character systems and “speciation” involves the origin of a large number of small differences in most character systems rather than the major reorganisation of a single system.     

General aspects of angiosperm evolution and macrosystematics

Taxonomy makes increasing use of significant results from many fields of research including the rapidly developing fields of micro– and macromolecular chemistry, ultrastructure and micromorphology in combination with macromorphology, anatomy, embryology, cytology, paleontology, biological interaction and distribution. Some of these results have contributed to make the current systems of classifications more concordant. Recent studies on Cretaceous fossils are related to present–day angiosperms and their floral types. It is concluded that pleiomerous flowers with helically arranged parts (corresponding to the Magnolia type, though probably less elaborate), on the basis of recent evidence can still be regarded as the probably earliest floral type in angiosperms. But the trimerous flowers must also have appeared very early, at least in the Albian. There is also evidence that the monocotyledons had differentiated as a separate group at that time. Similarities between certain extant monocotyledons and certain dicotyledons, in particular between some Dios–coreales and some Annonales–Aristolochiales, indicate that the monocotyledons had their roots in early Cretaceous pro–Magnoliiflorae. Fossil petaliferous flowers from Cenomanian layers, and later of a variety of flower types, such as the obdiplostemo–nous, petaliferous, epigynous Scandianthus (similar to extant saxifragaceous genera), or flowers with secondarily pleiomerous androecia of the theaceous type are discussed in relation to the distribution of corresponding floral types in extant dicotyledons. The main features of the author's classification of angiosperms are outlined with notes on important, though often neglected, aspects and critical problems. Finally, an updated table of classification down to family rank is presented.     

The Other Edge of Ockham’s Razor: The A-PR Hypothesis and the Origin of Mind

Charles Darwin’s theory of evolution characterized all life as engaged in a “struggle for existence”. To struggle requires internal data processing to detect and interpret patterns to guide behavior, a mechanism to struggle for existence. The cognitive bootstrapping A-PR cycle (Autonomy | Pattern Recognition) couples the origin of life and mind, enabling their symbiotic co-evolution. Life processes energy to create order. Mind processes data to create meaning. Life and mind co-evolve toward increased functional effectiveness, using A-PR feedback cycles that reflect the two Laws deduced from Ockham’s Razor. The Law of Parsimony is only one of two laws that have emerged from debate about Ockham’s Razor. Less well known is the “other edge of Ockham’s Razor”, the Law of Succinctness which, when viewed through the lens of Charles Darwin’s theory of evolution, enables the A-PR Hypothesis to fulfill the criteria of Ockham’s Razor.     

New evidence from the ultrastructural and micromorphological fields in angiosperm classification

Based on TEM investigations of some 1850 species and SEM examinations of about 6000 species of the Angiospermae, this is a survey of ultrastructural and micromorphological data (excluding pollen wall characters) which contribute valuable information for the classification of angiosperms. TEM characters predominately relate to phloem features, such as sieve–element plastids and crystalline P–protein, and to those equally present in other tissues, e.g. nuclear protein crystals and dilated ER–cisternae (DC). Of these, the sieve–element plastids with their types and subtypes (S, PI–PVI) and their over 20 forms represent the most thoroughly investigated TEM character. SEM characters mainly relate to epidermal surface features and can be grouped into four categories: (1) Cellular arrangement or cellular pattern; (2) Shape of cells (the “primary sculpture” of a surface); (3) Relief of outer cell walls (“the secondary sculpture” superimposed on the primary sculpture), caused mainly by cuticular striations and superficially visible wall inclusions and wall thickenings; (4) Epicuticular secretions (the “tertiary sculpture” superimposed on the secondary sculpture), i.e. mainly waxes and related substances. Ultrastructural evidence from sieve–element plastids for the classification of Mag–noliiflorae, Caryophylliflorae, Fabiflorae and the unity of the Monocotyledoneae is discussed, while further plastid data are listed for single families (e.g. Buxaceae, Cyrillaceae, Erythroxylaceae, Eucryphiaceae, Gunneraceae, Rhizophoraceae, Vitaceae). Crystalline P–protein dominates in Malviflorae, Violiflorae and Fabiflorae. Nuclear protein crystals are a specific feature of sieve elements of Boraginaceae. DC characterize Capparales s.lat. Micromorphological evidence derived from specific trichomes is presented as an aid to the characterization of Urticales and Loasales, while a detailed analysis of the micromorphology of the seed coat of Cactaceae and Orchidaceae provided new information for the classification of these families at the tribal and generic levels. As a completely new systematic feature for the classification of the Monocotyledoneae first results of micromorphological differences in wax crystalloids and their orientation patterns are presented: The Liliiflorae s. str. are clearly separated against the Zingiberiflorae–Commeliniflorae (incl. Velloziales, Bromeliales, Typhales) and Areciflorae, both characterized by two mutually exclusive and very specific wax types and delimited against taxa with unspecific waxes in the rest of the monocotyledons and all dicotyledons.