DOCSLIB.ORG

Gene Genealogies and Population Variation in Plants

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Gene Genealogies and Population Variation in Plants Colloquium Gene genealogies and population variation in plants Barbara A. Schaal* and Kenneth M. Olsen Department of Biology, Washington University, St. Louis, MO 63130 Early in the development of plant evolutionary biology, genetic selection. Morphology, karyotypes, and fitness components are drift, fluctuations in population size, and isolation were identified central traits for understanding evolution and adaptation, but as critical processes that affect the course of evolution in plant they limit which evolutionary processes can be studied. In his species. Attempts to assess these processes in natural populations book, Stebbins discusses such events as fluctuations in popula- became possible only with the development of neutral genetic tion size, random fixation (genetic drift), and isolation as all markers in the 1960s. More recently, the application of historically affecting the process of evolution (see passage quoted above; ref. ordered neutral molecular variation (within the conceptual frame- 1). However, the study of these mechanisms requires markers work of coalescent theory) has allowed a reevaluation of these that are not under selection. microevolutionary processes. Gene genealogies trace the evolu- In the years after the publication of Stebbins’ book, among tionary relationships among haplotypes (alleles) with populations. the first major technical advances in evolutionary biology were Processes such as selection, fluctuation in population size, and the development of protein electrophoresis and the identifi- population substructuring affect the geographical and genealog- cation of allozyme variation in natural populations. Many ical relationships among these alleles. Therefore, examination of allozymes are selectively neutral, and thus, for the first time, these genealogical data can provide insights into the evolutionary evolutionary biologists could attempt to assess the amount of history of a species. For example, studies of Arabidopsis thaliana neutral genetic variation within species as well as its spatial have suggested that this species underwent rapid expansion, with distribution. Plant species were found to vary widely, both in populations showing little genetic differentiation. The new disci- levels of genetic variation and in the apportionment of this pline of phylogeography examines the distribution of allele gene- variation within and among populations. These observations alogies in an explicit geographical context. Phylogeographic stud- spurred researchers to examine the mechanisms underlying the ies of plants have documented the recolonization of European tree process of genetic differentiation in plants. One of the most species from refugia subsequent to Pleistocene glaciation, and such common approaches for doing this analysis has been to look for studies have been instructive in understanding the origin and correlations between the life history characteristics of a species domestication of the crop cassava. Currently, several technical (e.g., mechanisms of pollen and seed dispersal, system of limitations hinder the widespread application of a genealogical mating, and generation length) and patterns of population approach to plant evolutionary studies. However, as these tech- genetic differentiation (2). Neutral allelic variation from allo- nical issues are solved, a genealogical approach holds great prom- zymes also can be used to estimate levels of gene flow among ise for understanding these previously elusive processes in plant populations. The population genetic theory developed by evolution. Wright, Fisher, and Malecot (among others) established that, for a group of populations at equilibrium, the level of genetic n the following succinct statements, G. L. Stebbins presents differentiation is roughly inversely proportional to the level of Iwhat would become the framework for the study of plant interpopulation gene flow per generation. This relationship is evolutionary mechanisms for the next 50 years (1). expressed by Wright’s (3) familiar equation for estimating gene Ϸ ͞ ϩ flow under an island model: FST 1 (4Nem 1), where FST Individual variation, in the form of mutation and gene is the standardized variance in allele frequencies among recombination, exists in all populations;...themolding populations, Ne is the effective population size, and m is the of this raw material... into variation on the level of migration rate. populations by means of natural selection, fluctuation in The use of allozymes has led to more than 30 years of insight population size, random fixation and isolation is suffi- into how plant populations evolve. However, inferring popu- cient to account for all of the differences, both adaptive lation structure solely from allele frequencies has its limita- and non-adaptive, which exist between related races and tions. Allozyme alleles (or their DNA analogs, restriction species.... fragment length polymorphisms, amplified fragment length polymorphisms, and microsatellites) are unordered, meaning The problem of the evolutionist is...evaluating on the that the genealogical pattern of relationships among alleles basis of all available evidence the role which each of cannot be easily inferred. As a result, these data cannot be used these known forces has played in any particular evolu- in directly assessing genetic change over time but rather tionary line.... require indirect approaches based on models that often assume A central thesis of Stebbins’ seminal book, Variation and Evolu- equilibrium conditions. For example, Wright’s equation tioninPlants(1), is the notion that to understand evolution we must (above) for quantifying gene flow under the island model examine its action at the level of populations within species. This assumes that populations have reached an equilibrium be- reasoning may seem obvious to contemporary readers, but at the tween gene flow and random genetic drift. This equilibrium time of Stebbins’ writing, the importance of population-level pro- perspective can be biologically misleading, particularly for cesses for evolution was far from apparent. Stebbins’ elucidation of this connection is one of his most enduring contributions to plant This paper was presented at the National Academy of Sciences colloquium ‘‘Variation and evolutionary biology. Evolution in Plants and Microorganisms: Toward a New Synthesis 50 Years After Stebbins,’’ Fifty years ago, the study of plant evolution was necessarily held January 27–29, 2000, at the Arnold and Mabel Beckman Center in Irvine, CA. concerned with the phenotype, much of which is subject to *To whom reprint requests should be addressed. E-mail: [email protected]. 7024–7029 ͉ PNAS ͉ June 20, 2000 ͉ vol. 97 ͉ no. 13 Downloaded by guest on September 27, 2021 species in which recent history is a major determinant of population structure. We speculate that very few plant species have reached, or will ever reach, a gene flow-drift equilibrium. Many plants, both temperate and tropical, have altered their range subsequent to glaciations in the last 20,000 years, a recent event on an evolutionary time scale. Likewise, many plant species have a metapopulation structure with subpopu- lations continually being colonized, dispersing migrants, and going extinct. Such metapopulations may reach a system-wide equilibrium in which probabilities of extinction and recoloni- zation are constant given enough time, but such a situation is unlikely considering the relatively short time frame of global climatic changes in the past. Equilibrium in plants is for the most part a theoretical construct with little relation to reality. We would argue that the second major development since the publication of Stebbins’ work has been the application of or- dered, genealogical data to the study of population-level pro- cesses. This development, which has begun to reach its potential only in the last decade, was predicated on two major advances, one technical and the other conceptual. The technical advance has been the widespread availability of ordered genetic variation at the intraspecific level, typically in the form of DNA sequence variation or mapped restriction-site data. For such data, muta- tional differences among genetic variants indicate the patterns of relationship among variants. These data therefore provide the raw information needed to reconstruct genealogical relation- ships among alleles (i.e., gene trees). The conceptual advance has been the application of coalescent theory to the study of microevolutionary processes (for a recent review, see ref. 4). For a population of constant size, new alleles are continually arising through mutation, and others are going extinct over successive generations (assuming neutrality). There- fore, the extant alleles of a gene in a population are all derived from (i.e., coalesce to) a single common ancestral allele that existed at some point in the past (Fig. 1). Coalescent theory provides a framework for studying the effects of population-level processes (e.g., population size fluctuations, selection, and gene flow) on the expected time to common ancestry of alleles within a gene tree. The application of gene genealogies to population genetics has allowed the study of population-level processes within a temporal, nonequilibrium framework. Thus, microevo- lution can be studied as a dynamic, historical process, changing over time within a species. COLLOQUIUM At the foundation of all genealogical analyses is the gene tree, which represents the inferred genealogical relationships among alleles
Load more

Recommended publications
  • Plant Evolution an Introduction to the History of Life
    Plant Evolution An Introduction to the History of Life KARL J. NIKLAS The University of Chicago Press Chicago and London CONTENTS Preface vii Introduction 1 1 Origins and Early Events 29 2 The Invasion of Land and Air 93 3 Population Genetics, Adaptation, and Evolution 153 4 Development and Evolution 217 5 Speciation and Microevolution 271 6 Macroevolution 325 7 The Evolution of Multicellularity 377 8 Biophysics and Evolution 431 9 Ecology and Evolution 483 Glossary 537 Index 547 v Introduction The unpredictable and the predetermined unfold together to make everything the way it is. It’s how nature creates itself, on every scale, the snowflake and the snowstorm. — TOM STOPPARD, Arcadia, Act 1, Scene 4 (1993) Much has been written about evolution from the perspective of the history and biology of animals, but significantly less has been writ- ten about the evolutionary biology of plants. Zoocentricism in the biological literature is understandable to some extent because we are after all animals and not plants and because our self- interest is not entirely egotistical, since no biologist can deny the fact that animals have played significant and important roles as the actors on the stage of evolution come and go. The nearly romantic fascination with di- nosaurs and what caused their extinction is understandable, even though we should be equally fascinated with the monarchs of the Carboniferous, the tree lycopods and calamites, and with what caused their extinction (fig. 0.1). Yet, it must be understood that plants are as fascinating as animals, and that they are just as important to the study of biology in general and to understanding evolutionary theory in particular.
    [Show full text]
  • Construct a Plant Evolution Timeline
    Constructing a Timeline of Plant Evolution Use this photo as a guide to creating an interactive timeline. Refer to Geologic Time Scale charts. A good resource is http://www.ucmp.berkeley.edu/help/timeform.php Use the “Plant Timeline Cards” found at the end of this document. Attach pictures with Velcro to allow for manipulation by students, and to “build” the timeline in increments. Teachers will need to find and print photos for “seed ferns” or omit that step in the timeline. Cut and paste the text below under each picture. Cyanobacteria: Also known as blue- Mosses: These have the first identifiable green algae, these are bacteria transport systems for water (xylem), and (prokaryotes – no nucleus) that can reproduce via spores, which encase sex photosynthesize. cells to prevent desiccation. They still need to live near water. First eukaryotes (cell nucleus): Scientist think that eukaryotes evolved via Hornworts: These developed the cuticle symbiosis, with one bacteria engulfing (waxy coating to prevent water loss) and another, but not digesting it. stomata (openings in the cuticle to allow Chloroplasts were originally for gas exchange.) All land plants except cyanobacteria engulfed by another liverworts have these two features. bacterium. Development of a true vascular system Anabaena: These water organisms allowed for better transport of water evolved from being unicellular to more and provided structural support for the complex, multicellular organisms. Their plant to grow taller. specialized cells help with nitrogen fixation. Club mosses: These were the first plants to have true leaves with veins. They also Stoneworts: Scientists think that developed roots as an anchoring system colonization of land occurred only once, to allow plant to grow taller.
    [Show full text]
  • The Big Bloom—How Flowering Plants Changed the World
    The Big Bloom—How Flowering Plants Changed the World Written by Michael Klesius Republished from the pages of National Geographic magazine -- July 2002 In the summer of 1973 sunflowers appeared in my father's vegetable garden. They seemed to sprout overnight in a few rows he had lent that year to new neighbors from California. Only six years old at the time, I was at first put off by these garish plants. Such strange and vibrant flowers seemed out of place among the respectable beans, peppers, spinach, and other vegetables we had always grown. Gradually, however, the brilliance of the sunflowers won me over. Their fiery halos relieved the green monotone that by late summer ruled the garden. I marveled at birds that clung upside down to the shaggy, gold disks, wings fluttering, looting the seeds. Sunflowers defined flowers for me that summer and changed my view of the world. Flowers have a way of doing that. They began changing the way the world looked almost as soon as they appeared on Earth about 130 million years ago, during the Cretaceous period. That's relatively recent in geologic time: If all Earth's history were compressed into an hour, flowering plants would exist for only the last 90 seconds. But once they took firm root about 100 million years ago, they swiftly diversified in an explosion of varieties that established most of the flowering plant families of the modern world. Today flowering plant species outnumber by twenty to one those of ferns and cone-bearing trees, or conifers, which had thrived for 200 million years before the first bloom appeared.
    [Show full text]
  • Evidence for Natural Selection Acting on Genes Affecting Lignin and Cellulose Biosynthesis in Eucalyptus Globulus
    Evidence for Natural Selection acting on Genes Affecting Lignin and Cellulose Biosynthesis in Eucalyptus globulus Sara Hadjigol (BSc) Submitted in fulfilment of the requirements for the Degree of Master of Philosophy School of Plant Science, University of Tasmania July 2011 i Declaration This thesis contains no material which has been accepted for a degree or diploma by the University or any other institution, except by way of background information and duly acknowledged in the thesis. To the best of my knowledge and belief, this thesis contains no material previously published or written by another person, except where due acknowledgement is made in the text of the thesis, nor does the thesis contain any material that infringes copyright. This thesis may be made available for loan and limited copying in accordance with the Copyright Act 1968. Sara Hadjigol July 2011 ii ABSTRACT Eucalyptus globulus (Myrtaceae) is a forest tree species that is native to South-eastern Australia, including the island of Tasmania. It is the main eucalypt species grown in pulpwood plantations in temperate regions of the world and is being domesticated in many breeding programs. The improvement of its wood properties is a major objective of these breeding programs. As many wood properties are expensive to assess, there is increasing interest in the application of molecular breeding approaches targeting candidate genes, particularly those in the lignin and cellulose biosynthesis pathways. To assist in the identification of genes and allelic variants likely to have important phenotypic effects, this study aimed to determine whether there was a signature in the genome indicating that natural selection had caused differentiation amongst the races of E.
    [Show full text]
  • Lntrogression and Its Consequences in Plants Loren H
    Botany Publication and Papers Botany 1993 lntrogression and Its Consequences in Plants Loren H. Rieseberg Rancho Santa Ana Botanic Garden Jonathan F. Wendel Iowa State University, [email protected] Follow this and additional works at: http://lib.dr.iastate.edu/bot_pubs Part of the Botany Commons, Evolution Commons, and the Plant Breeding and Genetics Commons Recommended Citation Rieseberg, Loren H. and Wendel, Jonathan F., "lntrogression and Its Consequences in Plants" (1993). Botany Publication and Papers. 8. http://lib.dr.iastate.edu/bot_pubs/8 This Book Chapter is brought to you for free and open access by the Botany at Iowa State University Digital Repository. It has been accepted for inclusion in Botany Publication and Papers by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. lntrogression and Its Consequences in Plants Abstract The or le of introgression in plant evolution has been the subject of considerable discussion since the publication of Anderson's influential monograph, Introgressive Hybridization (Anderson, 1949). Anderson promoted the view, since widely held by botanists, that interspecific transfer of genes is a potent evolutionary force. He suggested that "the raw material for evolution brought about by introgression must greatly exceed the new genes produced directly by mutation" ( 1949, p. 102) and reasoned, as have many subsequent authors, that the resulting increases in genetic diversity and number of genetic combinations promote the development or acquisition of novel adaptations (Anderson, 1949, 1953; Stebbins, 1959; Rattenbury, 1962; Lewontin and Birch, 1966; Raven, 1976; Grant, 1981 ). In contrast to this "adaptationist" perspective, others have accorded little ve olutionary significance to introgression, suggesting instead that it should be considered a primarily local phenomenon with only transient effects, a kind of"evolutionary noise" (Barber and Jackson, 1957; Randolph et al., 1967; Wagner, 1969, 1970; Hardin, 1975).
    [Show full text]
  • Evolution of Land Plants P
    Chapter 4. The evolutionary classification of land plants The evolutionary classification of land plants Land plants evolved from a group of green algae, possibly as early as 500–600 million years ago. Their closest living relatives in the algal realm are a group of freshwater algae known as stoneworts or Charophyta. According to the fossil record, the charophytes' growth form has changed little since the divergence of lineages, so we know that early land plants evolved from a branched, filamentous alga dwelling in shallow fresh water, perhaps at the edge of seasonally-desiccating pools. The biggest challenge that early land plants had to face ca. 500 million years ago was surviving in dry, non-submerged environments. Algae extract nutrients and light from the water that surrounds them. Those few algae that anchor themselves to the bottom of the waterbody do so to prevent being carried away by currents, but do not extract resources from the underlying substrate. Nutrients such as nitrogen and phosphorus, together with CO2 and sunlight, are all taken by the algae from the surrounding waters. Land plants, in contrast, must extract nutrients from the ground and capture CO2 and sunlight from the atmosphere. The first terrestrial plants were very similar to modern mosses and liverworts, in a group called Bryophytes (from Greek bryos=moss, and phyton=plants; hence “moss-like plants”). They possessed little root-like hairs called rhizoids, which collected nutrients from the ground. Like their algal ancestors, they could not withstand prolonged desiccation and restricted their life cycle to shaded, damp habitats, or, in some cases, evolved the ability to completely dry-out, putting their metabolism on hold and reviving when more water arrived, as in the modern “resurrection plants” (Selaginella).
    [Show full text]
  • Sow Thistle Chloroplast Genomes: Insights Into the Plastome Evolution and Relationship of Two Weedy Species, Sonchus Asper and Sonchus Oleraceus (Asteraceae)
    G C A T T A C G G C A T genes Article Sow Thistle Chloroplast Genomes: Insights into the Plastome Evolution and Relationship of Two Weedy Species, Sonchus asper and Sonchus oleraceus (Asteraceae) Myong-Suk Cho 1, Jin Hyeong Kim 1 , Chang-Seok Kim 2, José A. Mejías 3 and Seung-Chul Kim 1,* 1 Department of Biological Sciences, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Korea; [email protected] (M.-S.C.); [email protected] (J.H.K.) 2 Highland Agriculture Research Institute, National Institute of Agricultural Sciences, Rural Development Administration (RDA), Gangwon-do 25342, Korea; [email protected] 3 Department of Plant Biology and Ecology, Universidad de Sevilla, 41004 Seville, Spain; [email protected] * Correspondence: [email protected]; Tel.: +82-31-299-4499 Received: 20 September 2019; Accepted: 1 November 2019; Published: 1 November 2019 Abstract: Prickly sow thistle, Sonchus asper (L.) Hill, and common sow thistle, Sonchus oleraceus L., are noxious weeds. Probably originating from the Mediterranean region, they have become widespread species. They share similar morphology and are closely related. However, they differ in their chromosome numbers and the precise relationship between them remains uncertain. Understanding their chloroplast genome structure and evolution is an important initial step toward determining their phylogenetic relationships and analyzing accelerating plant invasion processes on a global scale. We assembled four accessions of chloroplast genomes (two S. asper and two S. oleraceus) by the next generation sequencing approach and conducted comparative genomic analyses. All the chloroplast genomes were highly conserved. Their sizes ranged from 151,808 to 151,849 bp, containing 130 genes including 87 coding genes, 6 rRNA genes, and 37 tRNA genes.
    [Show full text]
  • Allopolyploidy, Diversification, and the Miocene Grassland Expansion
    Allopolyploidy, diversification, and the Miocene grassland expansion Matt C. Estepa,b,1, Michael R. McKaina,c,1, Dilys Vela Diaza,d,1, Jinshun Zhonga,e,1, John G. Hodgea,c, Trevor R. Hodkinsonf, Daniel J. Laytona,c, Simon T. Malcomberg, Rémy Pasqueth,i,j, and Elizabeth A. Kellogga,c,2 aDepartment of Biology, University of Missouri–St. Louis, St. Louis, MO 63121; bDepartment of Biology, Appalachian State University, Boone, NC 28608; cDonald Danforth Plant Science Center, St. Louis, MO 63132; dDepartment of Biology, Washington University, St. Louis, MO 63130; eDepartment of Plant Biology, University of Vermont, Burlington, VT 05405; fDepartment of Botany, Trinity College Dublin, Dublin 2, Ireland; gDivision of Environmental Biology, National Science Foundation, Arlington, VA 22230; hInternational Centre of Insect Physiology and Ecology (icipe), Nairobi, Kenya; iUnité de Recherche Institut de Recherche pour le Développement 072, Laboratoire Évolution, Génomes et Spéciation, 91198 Gif-sur-Yvette, France; and jUniversité Paris-Sud 11, 91400 Orsay, France Edited* by John F. Doebley, University of Wisconsin–Madison, Madison, WI, and approved July 29, 2014 (received for review March 4, 2014) The role of polyploidy, particularly allopolyploidy, in plant di- inference of polyploidization events from chromosome numbers. versification is a subject of debate. Whole-genome duplications Although unavoidable, inferences from chromosome numbers precede the origins of many major clades (e.g., angiosperms, require assumptions about which numbers represent polyploids Brassicaceae, Poaceae), suggesting that polyploidy drives diversi- and when the polyploids arose. fication. However, theoretical arguments and empirical studies Phylogenetic trees of nuclear genes can reliably identify allo- suggest that polyploid lineages may actually have lower specia- polyploidization events (17–21) because they produce charac- tion rates and higher extinction rates than diploid lineages.
    [Show full text]
  • Evolution of the Life Cycle in Land Plants
    Journal of Systematics and Evolution 50 (3): 171–194 (2012) doi: 10.1111/j.1759-6831.2012.00188.x Review Evolution of the life cycle in land plants ∗ 1Yin-Long QIU 1Alexander B. TAYLOR 2Hilary A. McMANUS 1(Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA) 2(Department of Biological Sciences, Le Moyne College, Syracuse, NY 13214, USA) Abstract All sexually reproducing eukaryotes have a life cycle consisting of a haploid and a diploid phase, marked by meiosis and syngamy (fertilization). Each phase is adapted to certain environmental conditions. In land plants, the recently reconstructed phylogeny indicates that the life cycle has evolved from a condition with a dominant free-living haploid gametophyte to one with a dominant free-living diploid sporophyte. The latter condition allows plants to produce more genotypic diversity by harnessing the diversity-generating power of meiosis and fertilization, and is selectively favored as more solar energy is fixed and fed into the biosystem on earth and the environment becomes more heterogeneous entropically. Liverworts occupy an important position for understanding the origin of the diploid generation in the life cycle of land plants. Hornworts and lycophytes represent critical extant transitional groups in the change from the gametophyte to the sporophyte as the independent free-living generation. Seed plants, with the most elaborate sporophyte and the most reduced gametophyte (except the megagametophyte in many gymnosperms), have the best developed sexual reproduction system that can be matched only by mammals among eukaryotes: an ancient and stable sex determination mechanism (heterospory) that enhances outcrossing, a highly bimodal and skewed distribution of sperm and egg numbers, a male-driven mutation system, female specialization in mutation selection and nourishment of the offspring, and well developed internal fertilization.
    [Show full text]
  • Natural Selection and Repeated Patterns of Molecular Evolution
    RESEARCH ARTICLE Natural selection and repeated patterns of molecular evolution following allopatric divergence Yibo Dong1,2†, Shichao Chen3,4,5†, Shifeng Cheng6, Wenbin Zhou1, Qing Ma1, Zhiduan Chen7, Cheng-Xin Fu8, Xin Liu6*, Yun-peng Zhao8*, Pamela S Soltis3*, Gane Ka-Shu Wong6,9,10*, Douglas E Soltis3,4*, Qiu-Yun(Jenny) Xiang1* 1Department of Plant and Microbial Biology, North Carolina State University, Raleigh, United States; 2Plant Biology Division, Noble Research Institute, Ardmore, United States; 3Florida Museum of Natural History, University of Florida, Gainesville, United States; 4Department of Biology, University of Florida, Gainesville, United States; 5School of Life Sciences and Technology, Tongji University, Shanghai, China; 6Beijing Genomics Institute, Shenzhen, China; 7State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China; 8Laboratory of Systematic & Evolutionary Botany and Biodiversity, College of Life Sciences, Zhejiang University, Hangzhou, China; 9Department of Biological Sciences, University of Alberta, Edmonton, Canada; 10Department of Medicine, University of Alberta, Edmonton, Canada *For correspondence: [email protected] (XL); Abstract Although geographic isolation is a leading driver of speciation, the tempo and pattern [email protected] (Y-Z); of divergence at the genomic level remain unclear. We examine genome-wide divergence of [email protected] (PSS); putatively single-copy orthologous genes (POGs) in 20 allopatric species/variety pairs from diverse [email protected] (GK-SW); angiosperm clades, with 16 pairs reflecting the classic eastern Asia-eastern North America floristic [email protected] (DES); disjunction. In each pair, >90% of POGs are under purifying selection, and <10% are under positive [email protected] (Q-Y(J)X) selection.
    [Show full text]
  • The Evolution of Plants: a Major Problems for Darwinism — Bergman Papers
    Papers pollen must penetrate in order to fertilize the seed.22 The evolution of Angiosperms, in turn, are divided into monocotyledons (plants with seeds that have one cotyledon such as grains, grasses, and certain flowers, including orchids and lilies), plants: and dicotyledons (plants with seeds with two cotyledons, which includes most angiosperms). Went concludes that a major problem botanists have used a seemingly insignificant character— viz., the number of seedling leaves (cotyledons)—to classify the estimated 250,000 types of flowering plants. for Darwinism Categorizing the 300 different groups of flowering plants Jerry Bergman into families is enormously difficult because the ‘ … individual species are so numerous that they A major problem for Neo-Darwinism is the complete have never yet been listed in any one book, or even lack of evidence for plant evolution in the fossil re- in one series of books. Such a listing would have cord. As a whole, the fossil evidence of prehistoric to describe about a quarter million known plants; to plants is actually very good, yet no convincing tran- compile it, all the taxonomic botanists in the world sitional forms have been discovered in the abundant would have to work together for years and years, plant fossil record. This fact has been recognized and the finished product would have perhaps half a million pages, enough to cover a whole wall in a by both creationists and evolutionists as providing 23 strong evidence for abrupt appearance theory. If library.’ The basic groups for which Darwinists must macroevolution were true, some evidence of plant 24 evolution should exist in the abundant plant fossil demonstrate the existence of transitional forms include: record.
    [Show full text]
  • Feedbacks and the Coevolution of Plants and Atmospheric CO2 David J
    Feedbacks and the coevolution of plants and atmospheric CO2 David J. Beerling*† and Robert A. Berner‡ *Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, United Kingdom; and ‡Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, CT 06520-8109 Contributed by Robert A. Berner, November 23, 2004 The coupled evolution of land plants, CO2, and climate over the last and arrows with bull’s-eyes indicate inverse responses. For half billion years has maintained atmospheric CO2 concentrations example, an increase in CO2 leads to an increase in global mean within finite limits, indicating the involvement of a complex surface temperature due to the atmospheric greenhouse effect network of geophysiological feedbacks. But insight into this im- (plain arrow i). Conversely, an increase in rock weathering leads portant regulatory network is extremely limited. Here we present to CO2 consumption and a decrease in atmospheric CO2 (bull’s- a systems analysis of the physiological and geochemical processes eyed arrow g). Closed pathways linked together by an even involved, identifying new positive and negative feedbacks be- number of arrows with bull’s-eyes, or by no arrows with bull’s- tween plants and CO2 on geological time scales. Positive feedbacks eyes, represent positive feedback loops (PFLs), and those with an accelerated falling CO2 concentrations during the evolution and odd number of arrows with bull’s-eyes represent negative feed- diversification of terrestrial ecosystems in the Paleozoic and en- back loops (NFLs). hanced rising CO2 concentrations across the Triassic–Jurassic Our systems analysis identifies five important previously boundary during flood basalt eruptions.
    [Show full text]