8. plant systematics and evolution
Upcoming SlideShare
Loading in...5
×
 

8. plant systematics and evolution

on

  • 806 views

plants description

plants description

Statistics

Views

Total Views
806
Views on SlideShare
806
Embed Views
0

Actions

Likes
0
Downloads
15
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Adobe PDF

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    8. plant systematics and evolution 8. plant systematics and evolution Document Transcript

    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008C H A PT E R OU T L I N EEarly History of Classification 124 Carolus Linnaeus 124How Plants are Named 126 Common Names 126A CLOSER LOOK 8.1 The Language of Flowers 128 Scientific Names 129Taxonomic Hierarchy 130 Higher Taxa 130 What Is a Species? 131A CLOSER LOOK 8.2 Saving Species Through Systematics 133The Influence of Darwin’s Theory of Evolution 134 The Voyage of the HMS Beagle 134 Natural Selection 136Phylocode 137Chapter Summary 137Review Questions 137Further Reading 138K EY C O N CE P T S1. Scientific names are two-word names called binomials that are internationally recognized by the scientific community.2. Carolus Linnaeus, an eighteenth-century Swedish botanist, started the binomial system and is therefore known as the Father of Taxonomy.3. With the publication in 1859 of On the Origin of Species, Charles Darwin proposed that species are not static entities but are works in progress that evolve in response to environmental pressures.4. Natural selection favors the survival and reproduction of those individuals in C H A P T E R a species that possess traits that better adapt them to a particular environment. 8 Plant Systematics and Evolution Fossils, such as this 160 million year old arucarian pine cone from Argentina, were part of the evidence Charles Darwin used to formulate his theory of evolution of species by means of natural selection. 123
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008124 UNIT II Introduction to Plant Life: Botanical PrinciplesP lant systematics is the branch of botany that is con- Carolus Linnaeus (fig. 8.1) was born in May 1707, in cerned with the naming, identification, evolution, and southern Sweden, the son of a clergyman. He became inter- classification (arrangement into groups with common ested in botany at a very young age through the influence ofcharacteristics) of plants. In a strict sense, plant taxonomy his father, who was an avid gardener and amateur botanist. Itis the science of naming and classifying plants; however, in was expected that Linnaeus would also become a clergyman,this book the terms taxonomy and systematics are used inter- but in school he did not do well in theological subjects. Hechangeably. The simplest form of classification is a system did, however, excel in the natural sciences and entered thebased on need and use; early humans undoubtedly classified University of Lund in 1727 to pursue studies in natural sci-plants into edible, poisonous, medicinal, and hallucinogenic ence and medicine. (At this time medical schools were thecategories. centers of botanical study because physicians were expected to know the plant sources of medicines in use.) After one year he transferred to the University of Uppsala, the most presti-EARLY HISTORY OF gious university in Sweden. It was here that he published hisCLASSIFICATION first botanical papers, which laid the foundations for his later works in classification and plant sexuality. In 1732, he under-The earliest known formal classification was proposed by took a solo expedition to Lapland to catalog the natural his-the Greek naturalist Theophrastus (370–285 B.C.), who was a tory of this relatively unknown area. He later published Florastudent of Aristotle. In his botanical writings (Enquiries into Lapponica, a detailed description of the plants of this area.Plants and The Causes of Plants), he described and classified Linnaeus received his medical degree in 1735 from theapproximately 500 species of plants into herbs, undershrubs, University of Harderwijk in the Netherlands. Soon he cameshrubs, and trees. Because his influence extended through the under the patronage of George Clifford, a director of the DutchMiddle Ages, he is regarded as the Father of Botany. East India Company and one of the wealthiest men in Europe. Two Roman naturalists who also had long-lasting impacts He served as Clifford’s personal physician and as curatoron plant taxonomy were Pliny the Elder (A.D. 23–79) and of his magnificent gardens, which housed specimens fromDioscorides (first century A.D.). Both described medicinal around the world. The 3 years he spent in the Netherlandsplants in their writings, and Dioscorides’s Materia Medicaremained the standard medical reference for 1,500 years.From this period through the Middle Ages, little new botani-cal knowledge was added. Blind adherence to the Greek andRoman classics prevailed, using manuscripts painstakinglycopied by hand in monasteries throughout Europe. The revival of botany after its stagnation in the MiddleAges began early in the Renaissance with the renewed inter-est in science and other fields of study. The invention of theprinting press in the middle of the fifteenth century allowedbotanical works to be more easily produced than ever before.These richly illustrated books, known as herbals, dealt largelywith medicinal plants and their identification, collection, andpreparation. The renewal of interest in taxonomy can be tracedto the work of several herbalists; in fact, this period of botanicalhistory from the fifteenth through the seventeenth centuries isknown as the Age of Herbals. Another factor in the revival oftaxonomy was the global exploration by the Europeans duringthis period, which led to the discoveries of thousands of newplant species. In less than 100 years more plants were intro-duced to Europe than in the previous 2,000 years.Carolus LinnaeusBy the beginning of the eighteenth century, it was commonto name plants using a polynomial (see fig. 8.4), whichincluded a single word name for the plant (today called thegenus name), followed by a lengthy list of descriptive terms,all in Latin. This system had flaws. It was not standardized;different polynomials existed for the same plant; and it wascumbersome to remember some of the longer polynomials, Figure 8.1 Statue of Carolus Linnaeus (1707–1778) holdingwhich could be a paragraph in length. This was the state of flowers of Indian blanket (Gaillardia pulchella) at the Linnaeustaxonomy during the time of Linnaeus. Teaching Garden, Tulsa, OK.
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008 CHAPTER 8 Plant Systematics and Evolution 125 He returned to Sweden in 1738 and soon married Sara Elisabeth Moraea. After setting up a medical practice in Stockholm, he was appointed physician to the Swedish Admiralty, specializing in the treatment of venereal diseases. In 1741, he returned to the University of Uppsala as professor of medicine and botany, a position he retained until retire- ment in 1775. Linnaeus was a popular teacher who attracted students from all over Europe. Many of his students became famous professors in their own right; others traveled to distant lands collecting unknown specimens for Linnaeus to classify. After suffering several strokes, he died in January 1778. One of Linnaeus’s achievements was his sexual system of plant classification, which did much to popularize the study of botany. This system was based on the number, arrangement,Figure 8.2 Frontispiece of Systema Naturae, one of the writings and length of stamens and thus divided flowering plants intoof Linnaeus, in which he expounded on his ideas of classification. 24 classes. Using this system, it was possible for anyone to identify and name unknown plants. At the time, his lan- guage was risqué because he compared floral parts to humanwere the most productive period in his life. During that time, sexuality, with stamens referred to as husbands and pistils∗he completed several books and papers including Systema as wives; for example, “husband and wife have the sameNaturae, Fundamenta Botanica, and Genera Plantarum, bed” meant stamens and pistils in the same flower (fig. 8.3).which expanded on his ideas of classification (fig. 8.2). ∗ Note that the older term of pistil, rather than carpel, has been used in this key. Vegetable Kingdom Key of the Sexual System Marriages of plants Florescence Public marriages Flowers visible to every one In one bed Husband and wife have the same bed All the flowers hermaphrodite: stamens and pistils in the same flower Without affinity Husbands not related to each other Stamens not joined together in any part With equality All the males of equal rank Stamens have no determinate proportion of length 1. One male 4. Four males 7. Seven males 10. Ten males 2. Two males 5. Five males 8. Eight males 11. Twelve males 3. Three males 6. Six males 9. Nine males 12. Twenty males 13. Many males With subordination Some males above others Two stamens are always lower than the others 14. Two powers 15. Four powers With affinity Husbands related to each other Stamens cohere with each other, or with the pistil 16. One brotherhood 18. Many brotherhoods 17. Two brotherhoods 19. Confederate males In two beds 20. Feminine males Husband and wife have separate beds (b) Male flowers and female flowers in the same species 21. One house 22. Two houses 23. Polygamies Clandestine marriages Flowers scarce visible to the naked eye (a) 24. Clandestine marriagesFigure 8.3 (a) Linnaeus’s sexual system related floral parts to human sexuality. (b) Hibiscus in the Mallow Family (Malvaceae) keys out tofeminine males because the stamens are attached to the style.
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008126 UNIT II Introduction to Plant Life: Botanical PrinciplesDr. Johann Siegesbeck, a contemporary of Linnaeus anddirector of the botanical garden in St. Petersburg, wasshocked at the analogies and said such loathsome harlotry as several males to one female would not be permitted in the vegetable kingdom by the Creator . . . . Who would have thought that bluebells, lilies, and onions could be up to such immorality? Despite the opposition of some, the Linnaean sexualmethod was easy to understand and simple for even the ama-teur botanist to use. This method, however, was an artificialsystem grouping together clearly unrelated plants (in his sys-tem, cherries and cacti were grouped together); by the earlynineteenth century it was abandoned in favor of systems thatreflected natural relationships among plants. Linnaeus’s greatest accomplishment was his adoptionand popularization of a binomial system of nomenclature.When he described new plants, he conformed to the currentpractice of using a polynomial. For convenience, however, hebegan to add in the margin a single descriptive adjective thatwould identify unequivocally a particular species (fig. 8.4).He called this adjective the trivial name. This combinationlater developed into the two-word scientific name, or bino-mial, described in the next section. Linnaeus used this systemconsistently in Species Plantarum, published in 1753. Thiswork contains descriptions and names of 5,900 plants, all theplants known to Linnaeus. The binomial system simplifiedscientific names and was soon in wide use. In 1867, a groupof botanists at the International Botanical Congress in Parisestablished rules governing plant nomenclature and classifi-cation. They established Species Plantarum as the startingpoint for scientific names. Although the rules (formalized Figure 8.4 A photograph from Species Plantarum illustrates thein the International Code of Botanical Nomenclature) have beginning of the binomial system. Note the trivial names in thebeen modified over the years, the 1753 date is still valid, margin next to the polynomial description for each species. The trivial name was later designated as the species epithet, which,and many names first proposed by Linnaeus are still in use together with the generic, forms the binomial.today. Linnaeus’s contributions were not limited to botany sincethe binomial system is used for all known organisms. He is Common Namescredited with naming approximately 12,000 plants and ani- A close look at common names often reveals a keen sense ofmals; for all his contributions to the field of taxonomy, he is observation, a fanciful imagination, or even a sense of humor:known as the Father of Taxonomy. trout lily, milkweed, Dutchman’s pipe, Texas bluebonnet, ragged sailor, and old maid’s nightcap (table 8.1). Sometimes the names even convey feelings or emotions (see A Closer Look 8.1—The Language of Flowers).HOW PLANTS ARE NAMED Names have evolved over centuries but are sometimesNames are useful because they impart some information only used in a limited geographical area. Even short dis-about a plant; it may be related to flower color, leaf shape, fla- tances away, other common names may be used for thevor, medicinal value, season of blooming, or location. Names same plant. Consider, for example, the many names for theare necessary for communication; “if you know not the name, tree that many people call osage orange (Maclura pomifera)knowledge of things is wasted.” (fig. 8.5a): bodeck, bodoch, bois d’arc, bow-wood, osage This discussion begins with a look at common names, or apple tree, hedge, hedge apple, hedge osage, hedge-plantwhat plants are called locally, and follows with an examina- osage, horse apple, mock orange, orange-like maclura, osagetion of internationally recognized scientific names. apple, and wild orange.
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008 CHAPTER 8 Plant Systematics and Evolution 127 Table 8.1 Some Common Names and Their Meanings Names in CommemorationDouglas-fir David Douglas, plant collector (1798–1834)Camellia Georg Josef Kamel, pharmacist (1661–1706)Gerber daisy Traugott Gerber, German explorer (?–1743)Freesia Friedrich H. T. Freese, German physician (?–1876) (a) Names That Describe Physical QualitiesDusty miller White woolly leavesDutchman’s breeches Shape of flowerGoldenrod Shape and color of inflorescenceIndian pipe Shape of flower with stemCattail Inflorescence of carpellate flowersLady’s slipper Shape of this orchid’s flowerMilkweed Milky juice when plant is cutSkunk cabbage Fetid odor of inflorescenceCheeses Fruit resembles a round head of cheeseSmoke tree Plumelike pedicelsShagbark hickory Shedding barkRedbud Color of flower budsQuaking aspen Rustling leavesBluebell Color and shape of flowerCrape myrtle Wavy edges of petalsScientific Names That Have Become Common NamesHydrangea AbeliaVanilla NarcissusCoreopsis Gladiolus Names That Indicate UseDaisy fleabane Gets rid of fleasBoneset A tonic from this plant can heal bonesFeverwort Medicinal property to reduce feverKentucky coffee tree Seeds roasted for coffee substitute (b)Belladonna Juice used to beautify by producing pallid skin and dilated, mysterious eyes Figure 8.5 Mock orange is a common name shared by (a) the tree Maclura pomifera and (b) the shrub Philadelphus lewisii—two Names That Indicate Origin, Location, or Season entirely different species of plants.Pacific yew Grows along northern Pacific coastSpring beauty One of the first flowers of springMarshmallow Found in wet, marshy habitatDaylily Flowers last only a dayFour-o’clock Flowers open in late afternoonJapanese honeysuckle Country of origin is Japan
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008 A CLOSER LOOK 8.1 The Language of FlowersThrough traditions, some flowers became symbolic ofcertain emotions and feelings. This was sometimes evenreflected in their common names; two straightforwardexamples are forget-me-not flowers, which conveyed thesentiment “remember me,” and bachelor’s button, whichindicated the single status of the wearer. This symbolismreached its peak during the Victorian era, when almost everyflower and plant had a special meaning. In Victorian times, itwas possible to construct a bouquet of flowers that imparteda whole message (box fig. 8.1). A Victorian suitor might senda bouquet of jonquils, white roses, and ferns to his intended,which indicated that he desired a return of affection, he wasworthy of her love, and he was fascinated by her. This “lan-guage” became so popular that dictionaries were printed tointerpret floral meanings. One of the most popular dictionar-ies was the Language of Flowers (1884) by Kate Greenaway,a well-known illustrator of children’s books. Following is asmall sampling of some common flowers and plants and whatthey symbolized:Amaryllis: prideApple blossom: preferenceBachelor’s buttons: celibacyBluebell: constancyButtercup: ingratitudeYellow chrysanthemum: slighted loveDaffodil: regardDaisy: innocence Box Figure 8.1 Flowers convey a message all their own.Dogwood: durabilityElm: dignityGoldenrod: caution Dwarf sunflower: adorationHolly: foresight Tall sunflower: haughtinessHoneysuckle: generous and devoted affection Yellow tulip: hopeless loveIvy: fidelity Blue violet: faithfulnessLavender: distrust Wild grape: charityLichen: dejection Zinnia: thought of absent friendsLily of the valley: return of happinessLive oak: liberty Even today, several plants have well-known symbolicMagnolia: love of nature meanings. Red roses convey passionate love; a four-leaf clo-Marigold: grief ver means luck; orange blossoms symbolize weddings; andMock orange: counterfeit an olive branch indicates peace. Floral colors can also com-Oak leaves: bravery municate feelings, with red indicating passion; blue, security;Palm: victory yellow, cheer; white, sympathy; and orange, friendship. WithPansy: thoughts some thought, it is possible to find the right flower and colorSpring crocus: youthful gladness to express the exact message.128
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008 CHAPTER 8 Plant Systematics and Evolution 129 On the other hand, different plants may share the samecommon name. Although mock orange is one of the common Table 8.2names for osage orange, the name mock orange is usually Genus Names and Their Meaningsassociated with a completely unrelated group of floweringshrubs (Philadelphus spp.) (fig. 8.5b). These examples point Names in Commemorationout the difficulties with common names; one plant may be Begonia Michel Begon, patron of botany (1638–1710)known by several different names, and the same name mayapply to several different plants. The need to have one univer- Forsythia William Forsyth, gardener at Kensington Palace (1737–1804)sally accepted name is fulfilled with scientific names. Bougainvillea Louis Antoine de Bougainville, explorer and scientist (1729–1811)Scientific Names Fuchsia Leonhard Fuchs, German physician andEach kind of organism is known as a species, and similar spe- herbalist (1501–1566)cies form a group called a genus (pl., genera). Each species Zinnia Johann Gottfried Zinn (1727–1759)has a scientific name in Latin that consists of two elements; Wisteria Caspar Wistar, American professor of plantthe first is the genus and the second is the specific epithet. anatomy (1761–1818)Such a name is a binomial, literally two names, and is alwaysitalicized or underlined; for example, Maclura pomifera is Names That Describe Physical Qualitiesthe scientific name for osage orange. A rough analogy of the Myriophyllum Finely divided leavesbinomial concept can be seen in a list of names in a telephone Chlorophytum Green plantdirectory, where the surname “Smith” (listed first) representsthe genus and the first names (John, Frank, and Mary) define Lunaria Moon, refers to appearance of podsparticular species within the genus. Helianthus Sunflower In the binomial, the first name is a noun and is capital- Zebrina Zebra, refers to striped leavesized; the second, written in lower case, is usually an adjective. Trillium Floral parts in threesAfter the first mention of a binomial, the genus name can be Tetrastigma Four-lobed stigmaabbreviated to its first letter, as in M. pomifera, but the spe- Ribes Acid tasting; refers to fruitcific epithet can never be used alone. The genus name, how- Polygonum Many knees; refers to jointed stemsever, can be used alone, especially when referring to severalspecies within a genus; for example, Philadelphus refers to Zanthoxylum Yellow woodover 50 species of mock orange. The specific epithet can be Sagittaria Arrow; refers to arrowhead leavesreplaced by an abbreviation for species, “sp.” (or “spp.” plu- Names from Aboriginal or Classic Originsral), when the name of the species is unknown or unnecessaryfor the discussion. In the previous example, Philadelphus sp. Avena Oats (Latin)refers to one species of mock orange whereas Philadelphus Triticum Wheat (Latin)spp. refers to more than one species. Allium Garlic (Greek) Scientific names may be just as descriptive as common Catalpa Catalpa (North American Indian)names, and translation of the Latin (or latinized Greek) is Vitis Grape vine (Latin)informative (table 8.2). Sometimes either the genus name or Ulmus Elm (Latin)the specific epithet is commemorative, derived from the nameof a botanist or other scientist. Some specific epithets are Pinus Pine (Latin)frequently used with more than one genus, and knowledge of Names That Indicate Usetheir meanings will provide some insight into scientific namesencountered later in this text (table 8.3). Solidago Make whole or strengthen A complete scientific name also includes the name or Angelica Angelic medicinal propertiesnames of the author or authors (often abbreviated) who first Cimcifuga Repel bugsdescribed the species or placed it in a particular genus. For Saponaria Soap; refers to soap that can be made fromexample, the complete scientific name for corn is Zea mays the plantL.; the “L” indicates that Linnaeus named this species. On the Pulmonaria Lung; used to treat infections of the lungother hand, the complete name for osage orange is Maclura Potentilla Powerful; refers to its potent medicinalpomifera (Raf.) Schneid. This author citation indicates that propertiesRafinesque-Schmaltz first described the species, giving it Names That Indicate Locationthe specific epithet pomifera, but Schneider later put it in the Elodea Grows in marshesgenus Maclura. In this text, the author citations are omittedfor simplicity. Petrocoptis Break rock; refers to habit of growing in rock crevices
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008130 UNIT II Introduction to Plant Life: Botanical Principles A scientific name is unique, referring to only one spe- Table 8.3 Common Scientific cies and universally accepted among scientists. It is the key Epithets and Their Meanings to unlocking the door to the accumulated knowledge about acidosus, -a, -um Sour a plant. Imagine the confusion if only common names were aestivus, -a, -um Developing in summer used and a reference was made to mock orange. Would albus, -a, -um White this reference allude to Maclura pomifera or to a species of Philadelphus? alpinus, -a, -um Alpine annus, -a, -um Annual arabicus, -a, -um Of Arabia arboreus, -a, -um Treelike TAXONOMIC HIERARCHY arvensis, -a, -um Of the field In addition to genus and species, other taxonomic categories biennis, -a, -um Biennial exist to conveniently group related organisms. As pointed out, Linnaeus used an artificial system; however, today scientists campester, -tris, -tre Of the pasture use a phylogenetic system to group plants. In a phylogenetic canadensis, -is, -e From Canada system, information is gathered from morphology, anatomy, carolinianus, -a, -um From the Carolinas cell structure, biochemistry, genetics, and the fossil record to chinensis, -is, -e From China determine evolutionary relationships and, therefore, natural coccineus, -a, -um Scarlet groupings among plants. deliciosus, -a, -um Delicious dentatus, -a, -um Having teeth Higher Taxa domesticus, -a, -um Domesticated Species that have many characteristics in common are edulis, -is, -e Edible grouped into a genus, one of the oldest concepts in taxonomy esculentus, -a, -um Tasty (fig. 8.6). In almost every society, the concept of genus has europaeus, -a, -um From Europe developed in colloquial language; in English the words oak, fetidus, -a, -um Bad smelling maple, pine, lily, and rose represent distinct genera. These intuitive groupings reflect natural relationships based on floridus, -a, -um Flowery shared vegetative and reproductive characteristics. Many of foliatus, -a, -um Leafy the scientific names of genera are directly taken from the hirsutus, -a, -um Hairy ancient Greek and Roman common names for these genera japonicus, -a, -um From Japan (Quercus, old Latin word for oak). lacteus, -a, -um Milky white The next higher category, or taxon (pl., taxa), above littoralis, -is, -e Growing by the shore the rank of genus is the family. Families are composed of luteus, -a, -um Yellow related genera that again (as in a genus) share combinations of morphological traits. In the angiosperms, floral and fruit mellitus, -a, -um Honey-sweet features are often used to characterize a family. Ideally, the niger, -ra, -um Black family represents a natural group with a common evolution- occidentalis, -is, -e Western ary lineage; some families may be very small while others odoratus, -a, -um Fragrant are very large, but still cohesive, groups. A few common officinalis, -is, -e Used medicinally angiosperm families that have special economic importance robustus, -a, -um Hardy are listed in Table 8.4. According to the International Code ruber, -ra, -rum Red of Botanical Nomenclature, each family is assigned one name, which is always capitalized and ends in the suffix saccharinus, -a, -um Sugary -aceae. The old established names of several well-known sativus, -a, -um Cultivated families present exceptions to this rule. Both the tradi- silvaticus, -a, -um Of the woods tional and standardized names are used for these families sinensis, -is, -e Chinese (table 8.5). The taxa above the rank of family and their speciosus, -a, -um Showy appropriate endings are presented in Table 8.6. The higher tinctorius, -a, -um Used for dyeing the taxonomic category, the more inclusive the grouping utilis, -is, -e Useful (fig. 8.7). Families are grouped into orders, orders into classes, classes into divisions (phyla)*, and divisions into vernalis, -is, -e Spring flowering kingdoms. A domain is above the kingdom level and is the virginianus, -a, -um From Virginia vulgaris, -is, -e Common *Either division or phylum (sing.; phyla, plural) may be used to indicate the taxonomic rank that is composed of a group of related classes. Traditionally, division has been the term preferred by botanists and will be used throughout this textbook.
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008 CHAPTER 8 Plant Systematics and Evolution 131 (a) Quercus phellos (b) Quercus rubra (willow oak) (red oak)Figure 8.6 A genus is a group of species that share many characteristics in common. Although willow oak (Quercus phellos) and red oak(Quercus rubra) are clearly distinct species, they are both recognizable as belonging to the oak (Quercus) genus by the presence of acorns.most inclusive taxonomic category. The complete classifi- which defines a species as “a group of interbreeding popula-cation of a familiar species is also illustrated in Table 8.6. tions reproductively isolated from any other such group ofIn addition to the categories already described, biologists populations.”also recognize intermediate categories with the “sub” This definition presents problems when defining plantfor any rank; for example, divisions may be divided into species. Many closely related plant species that are distinctsubdivisions, and species may be divided into subspecies morphologically are, in fact, able to interbreed; this is true(varieties and forms are also categories below the rank of for many species of oaks and sycamores. By contrast, aspecies). single plant species may have diploid and polyploid (more Although the International Code of Botanical than the diploid number of chromosomes) individuals thatNomenclature has rules that govern the assignment of names may be reproductively isolated from each other. It is esti-and define the taxonomic hierarchy, it does not set forth any mated that as many as 40% of flowering plants may beparticular classification system. As a result, there are several polyploids, with the evening primrose group a thoroughlyorganizational schemes that have supporters. These systems studied example; an even higher percentage of polyploiddiffer in the numbers of classes, divisions, kingdoms, and even species occurs in ferns. Because of these limitations, alter-domains and how they are related to one another. Presently natives to the biological species concept have been sug-most biologists use a three-domain, six-kingdom system, gested. The ecological species concept recognizes a specieswhich will be described fully in Chapter 9. There is general through its role in the biological community as defined byagreement about the use of a three-domain, six-kingdom sys- the set of unique adaptations within a particular species totem, but biologists still debate the definition of a species. its environment. The availablity of molecular sequence data for nucleic acids and proteins had led to the development of the genealogical species concept. Proponents utilize theWhat Is a Species? distinct genetic history of organisms to differentiate species.As indicated previously, each kind of organism is known Despite the lack of an all-inclusive botanical definition, theas a species. Although this intuitive definition, based on concept of “species” facilitates the naming, describing, andmorphological similarities, works fairly well in many cir- classifying of plants in a uniform manner. An inventory ofcumstances, it is limited; scientists have given much thought the world’s species is the first step in preserving biodiver-to the biological basis of a species. Many accept the biologi- sity, as discussed in A Closer Look 8.2—Saving Speciescal species concept first proposed by Ernst Mayr in 1942, through Systematics.
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008132 UNIT II Introduction to Plant Life: Botanical Principles Table 8.4 Economically Important Angiosperm Families Scientific Family Name Common Family Name Economic Importance Aceraceae Maple Lumber (ash, maple), maple sugar Apiaceae Carrot Edibles (carrot, celery), herbs (dill), poisonous (poison hemlock) Arecaceae Palm Edibles (coconut), fiber oils and waxes, furniture (rattan) Asteraceae Sunflower Edibles (lettuce), oils (sunflower oil), ornamentals (daisy) Brassicaceae Mustard Edibles (cabbage, broccoli) Cactaceae Cactus Ornamentals, psychoactive plants (peyote) Cannabaceae Hemp Psychoactive (marijuana), fiber plants Cucurbitaceae Gourd Edibles (melons, squashes) Euphorbiaceae Spurge Rubber, medicinals (castor oil), edibles (cassava), ornamentals (poinsettia) Fabaceae Bean Edibles (beans, peas), oil, dyes, forage, ornamentals Fagaceae Beech Lumber (oak), dyes (tannins), ornamentals Iridaceae Iris Ornamentals Juglandaceae Walnut Lumber, edibles (walnut, pecan) Lamiaceae Mint Aromatic herbs (sage, basil) Lauraceae Laurel Aromatic oils (bay leaves), lumber Liliaceae Lily Ornamentals, poisonous plants Magnoliaceae Magnolia Ornamentals, lumber Malvaceae Mallow Fiber (cotton), seed oil, edibles (okra), ornamentals Musaceae Banana Edibles (bananas), fibers Myrticaceae Myrtle Timber, medicinals (eucalyptus), spices (cloves) Oleaceae Olive Lumber (ash), edible oil and fruits (olive) Orchidaceae Orchid Ornamentals, spice (vanilla) Papaveraceae Poppy Medicinal and psychoactive plants (opium poppy) Piperaceae Pepper Black pepper, houseplants Poaceae Grass Cereals, forage, ornamentals Ranunculaceae Buttercup Ornamentals, medicinal and poisonous plants Rosaceae Rose Fruits (apple, cherry), ornamentals (roses) Rubiaceae Coffee Beverage (coffee), medicinals (quinine) Rutaceae Citrus Edible fruits (orange, lemon) Salicaceae Willow Ornamentals, furniture (wicker), medicines (aspirin) Solanaceae Nightshade Edible (tomato, potato), psychoactive, poisonous (tobacco, mandrake) Theaceae Tea Beverage (tea) Vitaceae Grape Fruits (grapes), wine
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008A CLOSER LOOK 8.2Saving Species through SystematicsEarth is blessed with a tremendous variety of living organ- plants and animals. Commercial fishing is in essence theisms. About 1.4 million living microbes, fungi, plants, and hunting of wild fish populations. Blueberries and maple syrupanimals have been identified by systematics. The number of are just two examples of foods gleaned from nature in theyet undescribed species is much greater, with estimates rang- United States. Wood and wood pulp are other products har-ing between 10 million and 100 million. Biodiversity is an vested from biodiversity resources. Biodiversity in itself is ainventory of the number and variety of organisms that inhabit major economic force, as evidenced by the increasing popu-Earth. We are currently in the midst of a biodiversity crisis; larity of ecotourism. Sport fishing, hunting, and bird-watchingthe variety of living species is declining owing to an acceler- are other examples of economically profitable activities thatated extinction rate. Human activities are responsible for this depend on the preservation of biodiversity. Lastly, nearly halfterrible loss. Over 6.6 billion people at present inhabit Earth, of the medicinals now in use originated from a wild plant, andand this number is expected to increase to over 9 billion in it has been estimated that between 35,000 and 70,000 spe-the next 50 years. Population pressures cause natural areas cies of plants are used directly as medicines worldwide.to be cleared for agriculture or expanding urbanization. More Knowledge of systematics has many practical applications.people also results in more pollution that fouls the land, sea, There has been a movement to reduce our dependenceand air. All of these human-induced changes translate into a upon chemical pesticides and instead rely more heavily ondeath toll upon the world’s biodiversity. biological controls to manage nuisance organisms. Biological Consider the tropical rain forests of the world. These control methods depend upon proper identification of a pest,forests are some of the most biologically diverse areas on the knowledge of its life cycle, and correct identification of itsplanet, home to approximately 70% of the world’s species. predators and susceptibility to disease. Misidentification canUnfortunately, these forests have been subjected to massive be costly. Mealybugs are noxious pests that can cause mas-destruction. Scientists have calculated that species loss in the sive damage to crops. A species of mealybug was identified astropical rain forests is currently 1% to 5% per decade and will the culprit in the devastation of coffee plantations in Kenya.increase to 2% to 8% by the year 2015. This rate translates Biological control methods were employed using the naturalto an average loss of 9,000 species per year, or a heartbreak- enemies of the identified species of mealybug but were inef-ing 225,000 extinctions between 1990 and 2015. fective. Further investigation revealed that the mealybug had Why should we care about biodiversity? Biodiversity been misidentified. Once the correct species was assigned,is the basis for the necessary essentials to human existence: natural pests of the mealybug were brought in from its nativefood, fiber, fuel, and shelter. Of the estimated more than habitat in Uganda, and the mealybug infestation was soon250,000 species of angiosperms, nearly 20,000 have been brought under control. Knowledge of systematics can beused at one time or another as food for humans. Advances in used to predict economic uses of little known but relatedagriculture are dependent upon the interaction between sys- species. Researchers identified anticancer compounds fromtematics and biodiversity. Since the 1960s, world crop yields Kenyan populations of Maytenus buchananii. There was ahave increased two- to four-fold. Part of this increase is due problem, however; the species was rare in this locality.to the creation of improved crop varieties through breeding Knowledge of systematics suggested that closely related spe-programs and more recently through genetic engineering. cies would probably possess the same chemical compounds.Locating and identifying relatives of crop species have been This proved to be the case when a population of the sameof critical importance to agricultural research in breeding for genus but different species was collected from India.desirable characteristics. With the advent of genetic engi- Clearly, the preservation of biodiversity should be ofneering, nearly any plant species is a potential source of genes utmost importance to everyone. Systematic research is fun-for transfer to agricultural crops. Ironically, the conversion damental to learning about the characteristics and dimensionsof native ecosystems to agricultural lands in an attempt to of biodiversity. Systematics is necessary to identify localitiesaccommodate the food demands of an exponentially grow- of high species diversity or rare species. Baseline data musting human population may eliminate the very organisms on be collected to ascertain which species are declining in num-which agriculture depends for its future. Fertile soil, obvi- bers or those whose range is becoming limited. Knowledgeously essential for the vitality of agricultural crops, is also a of systematics will determine if exotic pests are moving intoby-product of biodiversity because it is formed through the new areas and threatening native species. Without scientificinteractions of a number of soil organisms: fungi, earthworms, identification and mapping, valuable habitats and the speciesbacteria, plant roots, and burrowing mammals. Species loss found there will be lost. In fact, Systematics Agenda 2000 iscould result in soils unable to support vegetation. an ongoing global initiative by the scientific community to dis- Not all of the world’s supply of food comes from cul- cover, describe, and classify the world’s species in an efforttivated sources. There is still a substantial harvest of wild to understand and conserve biodiversity. 133
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008134 UNIT II Introduction to Plant Life: Botanical PrinciplesKingdom: Plantae Plant kingdom Figure 8.7 Major ranks in the taxonomic hierarchy. Note that the higher the ranking, the broader the defining characteristics and the more inclusive the group. Table 8.5 Traditional and Standardized Names for Some Common Families Family Traditional Standardized Name Name Name Division: Magnoliophyta Flowering plants Sunflower Compositae Asteraceae Mustard Cruciferae Brassicaceae Grass Gramineae Poaceae Mint Labiatae Lamiaceae Pea Leguminosae Fabaceae Palm Palmae Arecaceae Carrot Umbelliferae Apiaceae Class: Liliopsida Monocots Table 8.6 The Taxonomic Hierarchy and Standard Endings Standard Rank Ending Example Division (Phylum) -phyta Magnoliophyta Class -opsida Liliopsida Order -ales Liliales Family -aceae Liliaceae Order: Liliales Genus Lilium Species Lilium superbum L. Family: Liliaceae Lily family THE INFLUENCE OF DARWIN’S THEORY OF EVOLUTION The theory of evolution by means of natural selection was to irrevocably change the way biologists view species. Instead of unchanging organisms and generations created all alike, it Genus: Lilium Lilies was realized that species are dynamic and variable, continu- ally evolving through the mechanism of natural selection in which adaptions are refined to a changing environment. The Voyage of the HMS Beagle Species: Lilium Turk’s Cap Lily Charles Robert Darwin (fig. 8.8) was born in England in superbum L. 1809 to a family of distinguished naturalists and physi- cians. His grandfather was Erasmus Darwin, a well-known poet and physician, and his father, Robert Darwin, was a successful country doctor. At 15 years of age, Charles was sent to the University of Edinburgh Medical School to study medicine. Not finding it to his liking, he transferred after
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008 CHAPTER 8 Plant Systematics and Evolution 135 2 years to Cambridge University to study theology. While at Cambridge, he spent much of his free time with the students and professors of natural history. This association later proved invaluable. In 1831, at the age of 22, Darwin graduated from Cambridge with a degree in theology. Shortly thereafter he was recommended as ship naturalist by John Henslow, one of the natural history professors at Cambridge. The ship in ques- tion was the HMS Beagle, commissioned by King William IV to undertake a voyage around the world for the purpose of charting coastlines, particularly that of South America, for the British navy. The voyage of the Beagle began on December 27, 1831, and was to last 5 years (fig. 8.9). During his time on the Beagle, Darwin collected thousands of plants and other specimens from South America, the Galápagos Islands (off the coast of Ecuador), Australia, and New Zealand. He stud- ied geological formations and noted fossil forms of extinct species. He found that some fossils of extinct species bore a striking resemblance to extant species, as though the former had given rise to the latter. Darwin spent some time studying the species found on the Galápagos Islands. He noted that animals and plants found in the Galápagos were obviously similar to species found in South America, but there were distinct differences. These observations led Darwin to ques- tion the fixity of species concept. According to this concept, widely held at the time of Darwin, species were acts of Divine Creation, unchanging over time. When the Beagle returned to England in 1836, DarwinFigure 8.8 Charles Darwin (1809–1882) published The Origin married his cousin Emma Wedgwood (of the famousof Species in 1859. British Isles Europe North Azores America Atlantic Asia Ocean Canary Islands Pacific Cape Verde Ocean Islands Africa Galápagos Islands Bahia South Tahiti America Cocos Rio de Islands Australia Janeiro Sydney Valparaíso Montevideo Cape of King George Good Hope Sound New Falkland Tasmania Zealand Islands Cape HornFigure 8.9 The 5-year voyage of the HMS Beagle. Darwin’s observations on the geology and distributions of plants and animals inSouth America and the Galápagos Islands were the groundwork for the development of the theory of evolution by means of naturalselection.
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008136 UNIT II Introduction to Plant Life: Botanical PrinciplesWedgwood china family) and settled, at age 27, in the Englishcountryside. He continued his work in natural history, con-ducting experiments, writing papers, and corresponding with Concept Quizother naturalists. Among his works was a four-volume trea- Darwin identified four conditions that are necessary if evo-tise on the classification and natural history of barnacles. lution is to occur: genetic variation, overproduction of off- In 1842, he began putting his thoughts together on what spring, competition for limited resources, and reproductionwas to become his theory of evolution by natural selection. of the fittest.Darwin continued to expand and fine-tune his thoughts over Imagine a plant population that reproduces entirely by asexualthe next 16 years. In June of 1858, he received a manuscript methods, such as spreading by underground stems. Althoughfrom Alfred Russel Wallace (1823–1913), a young British there are many individual plants in the population, they arenaturalist working in Malaysia. Wallace’s work was entitled essentially a single plant genetically; that is, they are clones. CanOn the Tendency of Varieties to Depart Indefinitely from natural selection act on a population of clones? Is this populationthe Original Type; Wallace had independently arrived at capable of evolving? Explain.the concept of natural selection. Wallace and Darwin jointlypresented their ideas on July 1, 1858, at a meeting of theLinnean Society in London. During the next few months,Darwin completed writing what was to become one of themost influential texts of all time. With the publication on In addition to natural selection, humans have long usedNovember 24, 1859 of On the Origin of Species by Means of artificial selection, natural selection as practiced by humansNatural Selection, or the Preservation of Favoured Races in (see Chapter 11), to shape the characteristics of crop plants tothe Struggle for Life by Charles Darwin, biological thought suit the needs of humanity. The most serious flaw in Darwin’swas changed forever. Theory of Evolution was the mechanism of heredity. Darwin had not worked out the source of variation in species, norNatural Selection did he understand the means by which traits are passed downThere are four underlying premises to Darwin’s theory of from generation to generation. It would take an Austrianevolution by natural selection: monk, Gregor Mendel (see Chapter 7), working in relative obscurity with pea plants, to come up with the answers to1. Variation: Members within a species exhibit individual Darwin’s questions about inheritance. differences, and these differences are heritable. A well-known example of natural selection is the case2. Overproduction: Natural populations increase geometri- of heavy-metal tolerance in bent grass, Agrostis tenuis. cally, producing more offspring than will survive. Certain populations of bent grass were found growing near3. Competition: Individuals compete for limited resources, the tailings, or soil heaps, excavated from lead mines in what Darwin called “a struggle for existence.” Wales despite the fact that mine soils had high concentra-4. Survival to reproduce: Only those individuals that are tions of lead and other heavy metals (copper, zinc, and better suited to the environment survive and reproduce nickel). When mine plants were transplanted into uncon- (survival of the fittest), passing on to a proportion of their taminated pasture soil, all survived but were small and offspring the advantageous characteristics. slow growing. A nearby population of bent grass from uncontaminated pasture soil exhibited no such tolerance Offspring that inherit the advantageous traits are selected when transplanted into mine soil; in fact, most (57 out offor survival and many will live to reproductive age passing on 60) of the pasture plants died in the lead-contaminatedthe desirable attributes. Those that do not inherit these traits soil. The survival of the three pasture plants in mine soil isare not likely to survive or reproduce. Gradually, the species significant; undoubtedly these three possessed an advanta-evolves, or changes, as more and more individuals carry these geous trait, the ability to tolerate heavy-metal soil. A traittraits. Darwin gave this example: that promotes the survival and reproductive success of an If the number of individuals of a species with plumed organism in a particular environment is an adaptation. The seeds could be increased by greater powers of dis- mine plants had descended from bent grass plants that pos- semination within its own area (that is, if the checks sessed the adaptation that conferred tolerance to the mine to increase fell chiefly on the seeds), those seeds soil; over time (less than 100 years in this case) populations which were provided with ever so little more down, of Agrostis tolerant to heavy metal evolved from those few would in the long run be most disseminated; hence tolerant individuals. a greater number of seeds thus formed would ger- Although Darwin’s theory of natural selection is the minate, and would tend to produce plants inheriting foundation of modern evolutionary concepts, biologists today the slightly better-adapted down. are still learning about the forces that shape evolution.
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008 CHAPTER 8 Plant Systematics and Evolution 137 indicates that the traditional dicots represent several evolution- ary lineages. Most of the dicots do comprise a clade and are nowConcept Quiz called the eudicots or true dicots. Approximately 75% of allNatural selection favors the survivorship of those individu- angiosperm species are now classified as eudicots. Traditionalals in a population that possess characteristics crucial for dicots excluded from the clade eudicot are called the paleodi-survival. cots (literally old dicots) by some authorities and include sev- eral ancient lineages in the evolution of angiosperms.You observe that trees in a part of a forest in which deer areplentiful have higher branches than the trees in a fenced-off partof the forest. Explain the different selective forces at work in CHAPTER SUMMARYthese two different environments. 1. Plant systematics has its origins in the classical works of Theophrastus of ancient Greece, who is generally regarded as the Father of Botany. The study of plants, as did many other intellectual endeavors, went into a decline duringPHYLOCODE the Dark Ages of Europe but was later revived owing to renewed interest in herbalism during the fifteenth to sev-The Linnaean system of nomenclature and the hierarchy of enteenth centuries.classification that has been presented in this chapter werecreated more than 250 years ago, before Charles Darwin and 2. Linnaeus, a Swedish botanist of the eighteenth century,Alfred R. Wallace had proposed their evolutionary theory is credited with the creation of the binomial, or scientificby means of natural selection. Linnaean nomenclature is an name. Although common names are often informative andartificial system based upon the appearance of organisms readily accessible, scientific names have the advantage ofthat often does not reflect their evolutionary relationships, or being recognized the world over and unique to a singlephylogeny. Currently, there is a movement to reject this pre- species.evolutionary taxonomy and replace it with a new system of 3. The taxonomic hierarchy includes the major ranks:nomenclature, called PhyloCode, that is truly phylogenetic. domain, kingdom, division (phylum), class, order, family, PhyloCode is based upon the work of the twentieth- genus, and species.century German entomologist Willi Hennig, who proposed 4. Biologists have wrestled with the concept of the species;that only shared derived characteristics should be used to the biological concept describes a species as a group ofdefine a group of related organisms. He further proposed that interbreeding populations, reproductively isolated fromeach group constructed should be monophyletic, or composed other populations.of only those organisms that can trace their descent from a 5. Charles Darwin and his theory of evolution by naturalcommon ancestor. These natural groupings are known as selection irrevocably changed the way biologists viewedclades. species. Natural selection favors those individuals that First introduced in 1983, the PhyloCode abandons the possess traits that better enable them to survive in theLinnaean ranks of the taxonomic hierarchy. In this system, environment. These individuals survive to reproduce, andas new information that may change a group’s ranking accu- many of their offspring will tend to have these adaptationsmulates, names are not changed, as they would be with the and pass them on to future generations. In this way, popu-Linnaean system, which associates different suffixes with lations change over time. The four underlying conditionsdifferent ranks. Instead of ranks, clades are the only groups of Darwin’s theory of evolution by natural selection arerecognized. Opponents fear that a complete abandonment of variation, overproduction of offspring, competition, andall ranks will result in a loss of comparative information and survival to reproduce.encourage a proliferation of names that, without any context,will serve only to confuse the nomenclature. Released in 1991, the APG (American Phylogeny Group) REVIEW QUESTIONSsystem compared the sequence data of select genes to clas- 1. List the common names of some of the wildflowers insify the flowering plants. The highest formal rank in this your area. Determine the type of information each nameclassification system is the order; higher categories are only imparts.identified as clades. As more data accumulated, APG II, anupdate of the classification, became available in 2003. In this 2. Using a plant dictionary (see Further Reading) look up thesystem, angiosperms are recognized as a clade, sharing several scientific names and their meanings for common house-distinct characteristics, such as ovules enclosed in a carpel plants and landscape plants in your area.and double fertilization. Within the angiosperms, all mono- 3. Briefly describe the concept of evolution by naturalcots appear to belong to a distinct clade, but molecular data selection.
    • Levetin−McMahon: Plants II. Introduction to Plant 8. Plant Systematics and © The McGraw−Hill and Society, Fifth Edition Life: Botanical Principles Evolution Companies, 2008138 UNIT II Introduction to Plant Life: Botanical Principles4. Why are only inherited traits important in the evolution- Laufer, Geraldine Adamich. 1996. Tussie-Mussies. The Herb ary process? Companion April/May: 48–53.5. How do mutations (Chapter 7) lead to the evolution of Litt, Amy. 2006. Origins of Floral Diversity. Natural History new species? 115(5): 34 –40.6. What was the lasting contribution of Linnaeus? How was Mayr, Ernst. 2000. Darwin’s Influence on Modern Thought. the binomial system an improvement over polynomials? Scientific American 283(1): 78–83.7. In what ways can systematics preserve biodiversity? Miller, Douglass R., and Amy Y. Rossman. 1995. Systematics, Biodiversity, and Agriculture. BioScience 45(10): 680–FURTHER READING 686.Blunt, Wilfrid. 1971. The Compleat Naturalist: A Life of Pennisi, Elizabeth. 2001. Linnaeus’s Last Stand? Science Linnaeus. The Viking Press, New York, NY. 291: 2304–2307.Briggs, David, and S. Max Walters. 1984. Plant Variation Piementel, David, Christa Wilson, Christine McCullum, and Evolution, 2nd Edition. Cambridge University Press, Rachel Huang, Paulette Dwen, Jessica Flack, Quynh Tran, Cambridge, MA. Tamara Saltman, and Barabara Cluff. 1995. EconomicCoombes, Allen J. 1994. Dictionary of Plant Names: Botanical and Environmental Benefits of Biodiversity. BioScience Names and Their Common Equivalents. Timber Press, 47(11): 747–757. Beaverton, OR. Quammen, David. 2004. Darwin’s Big Idea. NationalConniff, Richard. 2006/2007. Happy Birthday Linnaeus. Geographic 206(5): 2–35. Natural History 115(10): 42–47. Quammen, David. 2007. The Name Giver. NationalDarwin, Charles (author) and Edward O Wilson (editor) 2006. Geographic 211(6): 72–87. From So Simple A Beginning: The Four Great Books of Raby, Peter. 2001. Alfred Russel Wallace: A Life. Princeton Charles Darwin. W. W. Norton & Company, New York. University Press, Princeton, NJ.Friedman, William E. 2006. Sex Among the Flowers. Natural Savage, Jay M. 1995. Systematics and the Biodiversity Crisis. History 115(9): 48–53. BioScience 45(10): 673–679.Gilbert, Bil. 1984. The Obscure Fame of Carl Linnaeus. Schiebinger, Londa. 1996. The Loves of Plants. Scientific Audubon 86:102–115. American 274(2): 110–115.Greenaway, Kate. 1992. Language of Flowers. Dover Press, Sulloway, Frank J. 2005. The Evolution of Charles Darwin. New York, NY. Smithsonian 36(9): 58–69.Irvine, William. 1983. Apes, Angels, and Victorians: The Withgott, Jay. 2000. Is It “So Long, Linnaeus?” BioScience Story of Darwin, Huxley, and Evolution. University Press 50(8): 646–651. of America, New York, NY.Judd, Walter S., Christopher S. Campbell, Elizabeth A. Kellogg, Peter F. Stevens, and Michael J. Donoghue. 2002. Plant Systematics, A Phylogenetic Approach, 2nd ONLINE LEARNING CENTER Edition. Sinauer Associates, Sunderland, MA.Kohn, David. 2005. The Miraculous Season: The Historical Visit www.mhhe.com/levetin5e for online quizzing, web links to chapter-related material, and more! Darwin. Natural History 114(9): 38–40.Laufer, Geraldine Adamich. 1993. The Language of Flowers. Workman Publishing, New York, NY.