Characterization Of Biodiversity
2Characterization of BiodiversityFA. BISBYLead Authors:F.A. Bisby and J. Coddington (Chapter 2.1); J.P Thorpe, J. Smartt (Chapter 2.2);R. Hengeveld, P.J. Edwards, S.J. Duffield (Chapter 2.3)Contributors:/. Cracraft, D.L. Hawksworth, D. Lipscomb, N.R. Morin, P. Munyenyembe, G.J. Olsen,D.LJ. Quiche, MM. V van Regenmortel, Y.R. Rostov (Chapter 2.1); A.L Alkock,M. Chauvet, K.A. Crandall, D.R. Given, S.J.G. Hall, J.M. Iriondo, T.M. Lewinsohn,S.M. Lynch, G.M. Mace, A.M. Sole-Cava, E. Stackebrandt, A.R. Templeton, RC. Watts(Chapter 2.2); M.T. Kalin-Arroyo, J. Bullock, R.G.H. Bunce, E.A. Norse, A. Magurran,K. Natarajan, S.L Pimm, R.E. Ricklefs (Chapter 2.3)
CONTENTSElective Summary252.1.6.1 Evaluating taxonomic isolation of272.1.6.2 Measuring taxonomic diversity of biotaindividual species2.0 Introduction to the characterization of biodiversity2.0.1 What is biodiversity?2.0.2 What components of biodiversity are to becharacterized?2.0.3 What is meant by characterizing biodiversity?or ecosystems272753References532.2 Genetic diversity as a component of biodiversity2.2.0 Introduction272.1.0 Introduction: patterns of living organisms classification and evolution27612.2.1.1 Analysis of karyotypic variation632.2.1.1.1 Karyotypic variation analysistechniques29what taxonomists do312.1.1.1 The role of specimens in taxonomy312.1.1.2 Stability of scientific names33preparing Floras, handbooks and keys332.1.2.1 The amount of research work involved3467of minisatellite loci68of minisatellite loci682.2.1.2.5 Gene cloning and poly me rasechain reaction (PCR)682.2.126 Nucleotide sequences6936382.2.1.2.7 Applications of PCR69382.2.1.2.8 Conclusions69402.2.2 Patterns of differentiation under domestication702.1.4.2 The biological species concept412.1.4.4 The pluralistic approach6536412.1.5 The power of taxonomy and taxonomic products652.2.1.2.! Allozymes2.2.1.2.4 Single-locus DNA fingerprinting2.1.4.1 The morphological species concept2.1.4.3 The phylogenetic species conceptof genetic diversity352.1.3.2 From phylogenetic trees to formal2.1.4 Charac;enzing species64polymorphism (RFLP)2.1.3.1 Analysing systematic data to reconstructclassifications2.2.1.1.3 Assessment2.2.1.2.3 Multi-locus DNA fingerprinting2.1.3 Characterizing systematic patterns: the species,2.1.3.3 Why do classification schemes change?632.2.1.2.2 Restriction fragment length2.1.2.2 Modem developments: databases andevolutionary history632.2.1.1.2 Genetic diversity studies2.2.1.2 Molecular methods for assessing levels2.1.2 Characterizing flora, fauna and microbiota:their evolution and their classification57species level2 1.1 The basics of taxonomic characterization:expert identification systems572.2.1 Partitioning of genetic variability below the2.1,0.1 Folk classifications and the origin ofscientific taxonomy532.1,7 Conclusion272.1 Biodiversity from a taxonomic and evolutionaryperspective512.2.2.1 Characterizing biodiversity withindomesticated species73432 2 2 2 The genetic basis of cultivarsand breeds75442.2.2.3 Species complexes and gene flow762.2.2.4 Future developments77462.2.3 Investigating genetic diversity2.1.5.1 Taxonomic products: an essential77technological infrastruciure for2.2.3.1 Type of biological material available79biotechnology, natural resources2.2.3.2 Research and development79management, and regulation46in studies of wiihtn-species and between-2.1.5.2 As a summary of biodiversity andevoluiionary patterns2.1.5.3 As a basis for prediction2.1.5.4 Other uses of taxonomic techniques' Taxonomic measures of species diversity2.2.4 Case studies of the use of genetic techniques47species diversity79492.2.4.1 Pctrtula792.2.4.2 Aiutlis815051References82
\Characterization of Biodiversity242.3 Biodiversity from an ecological perspective2.3.1 Introduction2.3.2 Diversity within areas2.3.2.1 Species richness and species diversity2.3 2.1.1 Comparing diversity acrossspecies groups: coherence ofpatterns2.3.2.1.2 Comparing areas of differentsixes8S SS'XI'Mi2.3.2.1.3 The relative abundance of species 912.3.2.2 Taxic diversity2.3.2.3 Functional diversity2.3.2.3.1 Autecological diversity (speciesin isolation)2 3.2.3.2 Synecological diversity (speciesin communities)919292932 3.3 Diversity between areas2.3.3.1 The general difficulties in classifyingecological communities2.3.3.2 Classifications based on speciescomposition2.3.3.2.1 Phytosociology2.3.3.2.2 Global classifications ofspecies distribution2.3.3.3 Global classifications of ecosystems2.3.3.4 Characterising and classifying landscapes2.3.3.5 Diversity in ecological systems2.3.3.6 The importance of better ecologicalclassifications2.3,4 ConclusionsReferences M949697100102102102103j104\
#-EXECUTIVE SUMMARY. jhe recognition and characterization of biodiversitydepends critically on the work of three scientificdisciplines. Taxonomy provides the reference system anddepicts the pattern or tree of diversity for all organisms(Chapter 2.1). Genetics gives a direct knowledge of thegene variations found within and between species (Chapter2.2). Ecology provides knowledge of the varied ecologicalsystems in which taxonomic and genetic diversity islocated, and of which it provides the functionalcomponents (Chapter 2.3). There appear to be no short cuts to full examinationof biodiversity. All three disciplines report inthis assessment that, having characterized only part ofthe world's biological diversity, it will be necessaryto undertake similar work to survey the remainder.While predictions can be made, they are no substitutefor full enumeration. It is in the nature of biodiversitythat surprises and uniqueness abound: predictivemethods, such as the use of indicator species,latitudinal gradients, and mapping of hotspots, are oflimited value, Taxonomy provides the core reference system andknowledge-base on which all discussion of biodiversityhinges: the framework within which biodiversity isrecognized and in which species diversitycharacterization occurs. The most commonly used unitsof biological diversity are species, the basic kindsof organisms.* Taxonomic characterization of the world's organisms is amammoth but essential strategic task with which onlylimited progress has been made: just I 75 of the estimated13 to 14 million species have so far been described, andmost of these are still poorly known in biological terms.There is not even a comprehensive catalogue of these 1.75million known species.* Despite its universal usage as a basic unit of taxonomy, itis difficult to agree on an exact definition of whatconstitutes a species. As a result there is considerablevariation in concept and usage which may be reflected indiffering classifications and species totals- Taxonomists have the task of enumerating which speciesexist and placing them in a taxonomic hierarchy. Thistaxonomic hierarchy serves both as a classification used forreference purposes and as a summary of the evolutionarytree. It can also be used to predict properties of certainorganisms. The hierarchy is characterized by observation ofthe patterns of resemblances in comparative features suchas morphology, anatomy, chemistry (including moleculardata), behaviour and life-history. Systematic and evolutionary studies provide valuableknowledge about the evolutionary origins and patterns oflife, the scientific map of diversity. This is the map thatmust be used in planning conservation, prospecting,exploitation, regulation, and sustainable use. It is considered important that assessments used in theevaluation of resources and conservation options makeadequate use of taxic diversity measures which take intoaccount not just numbers of species but their taxonomicpositions and the differing contributions that differentspecies make. The map or tree of diversity is occupied byvery varied densities of species: in some parts there arethousands of species, in others just one or two. It followsthat the very few species in certain parts of the pattern areof exceptionally high scientific value,* Genetic diversity is the diversity of the sets of genescarried by different organisms: it occurs not only on a smallscale between organisms of the same population, but on aprogressively larger scale between organisms in differentpopulations of the same species, between closely relatedspecies such as those in the same genus, and between moredistantly related species, those in different families, orders,kingdoms and domains. Genetic diversity may becharacterized by a range of techniques: by observation ofinherited genetic traits, by viewing under the microscopethe chromosomes that carry the genes, and by reading thegenetic information carried on the chromosomes usingmolecular techniques.* Genes transmit features from one generation to the next,so determining by inheritance and in interaction with theenvironment, the pattern of variation realized in features
Characterization of Biodiversity26seen within and between species. Similarly alterations inthe genes carried forward to future generations mark thepath of evolution. Yet scientists observe that in neither caseis there a strictly one-to-one relationship between geneticdiversity and the realized diversity of organismscharacterized by taxonomists.zones differ taxonomically in the flora and fauna present,even between areas of similar physical environment (e.g.within the same ecoregion) or similar physiognomy (e.g.within the same biome). Conversely, the physiognomicdifferences between bionics within one biogeographic zoneare para I led by those within another. Genetic analysis, including molecular techniques.provides a formidable tool for gaining access to precisegene differences both within and be!ween species. Withinspecies genetic details can characterise the traits and thepopulations on which natural selection and the process ofevolution is acting. Between closely related species genecomparisons can reveal details of speciation andcolonization. All existing global classifications of ecological systemsare to some extent inadequate, either in their methodologyor in their spatial coverage, or in both. A robustclassification of the world's ecosystems which can be usedto map the distribution of ecological resources is urgentlyneeded. It is selection acting on genetic diversity that carriesforward both ecological adaptation and microevolution: tolimit or reduce the genetic diversity within a species is tolimit or reduce its potential or actual role in the ecologicaland evolutionary development of the biosphere. The food plants, animals, fungi and other microorganisms on which all humankind depend arise fromgenetic variants of originally wild organisms. The geneticresources in both wild and domesticated organisms thusrepresent a patrimony of resources for future use. Even thepresent well-developed food crops and animal resources areconstantly at risk because of the rapid adaptation of pestsand diseases: skilful and extensive manipulation of geneticresources is needed even to maintain agriculturalproductivity, Organisms are not evenly distributed: they occur in anintricate spatial mosaic, classified on a world scale intobiogeographic zones, biomes, ecoregions and oceanicrealms, and at a variety of smaller scales within landscapesinto ecosystems, communities and assemblages. In terrestrial systems the community found at any onepoint can be characterized by the physical environment(ecoregion), the physiognomic type (biome), and thefloristic/faunistic (biogeographic) zone in which it occursIn marine systems communities are characterized in termsof the physical environment and the faunistic(biogeographic) zone. The units of classification used on a global scale differ inhow they are recognised and consequently in thedistinctions between their subdivisions. Biogeographic The biodiversity within an area can be characterized bymeasures of species richness, species diversity, taxicdiversity and functional diversity - each highlightingdifferent perspectives.(a)Species richness (also called a-diversity) measuresthe number of species within an area, giving equalweight to each species.(b)Species diversity measures the species in an area,adjusting for both sampling effects and speciesabundance.(c)Taxic diversity measures the taxonomic dispersion ofspecies, thus emphasizing evolutionarily isolatedspecies that contribute greatly to the assemblage offeatures or options.(d)Functional diversity assesses the richness offunctional features and interrelations in an area,identifying food webs along with keystone speciesand guilds, characterised by a variety of measures,strategies and spectra. A serious limitation on all measures of species diversityin an ecosystem is our inability to survey all organisms atany site: only a few taxonomic groups are sufficientlyknown for complete field surveys to be made. At the smaller scale, landscapes are composed of areascharacterised as ecosystems or communities. The diversitybetween areas is measured as ( -diversity, the change inspecies present. Systems diversity is assessed as the richness of ecologicalsystems in a region or landscape.
Characterization of Biodiversity20 introduction to the characterization of biodiversity2.0.1 What is biodiversity?As explained in Section I, biodiversity means thevariability among living organisms from all sources and theecological systems of which they arc a part; this includesdiversity within species, between species and ofecosystems. Were life to occur on other planets, or livingorganisms to be rescued from fossils preserved millions ofyears ago, the concept could include these as well. It can bepartitioned, so that we can talk of the biodiversity of acountry, of an area, or of an ecosystem, of a group oforganisms, or within a single species.Biodiversity can be set in a time frame so that speciesextinctions, the disappearance of ecological associations, or theloss of genetic variants in an extant species can all be classedas losses of biodiversity. New elements of life - by mutation,by natural or artificial selection, by speciation or artificialbreeding, by biotechnology, or by ecological manipulation- can similarly be viewed as additions to biodiversity.2.0.2 What is meant by characterizing biodiversity?The scientific characterization of biodiversity involveswhat may seem like two different processes, theobservation and characterization of the main units ofvariation {e.g. genes, species and ecosystems), and thequantification of variation within and between them(genetic distance, taxonomic relatedness, etc.). In realitythey are part of the same process: the analysis of patterndefines the units as well as characterizing their variation.In each of the three chapters that follow an assessment ismade both of the reference framework and units used, andof the methods for quantifying variation. Chapter 2.1 dealswith the central issue of characterizing species ortaxonomic diversity. Chapter 2.2 assesses genetic diversitythat occurs both within and between species. Chapter 2.3introduces the diversity of ecological systems in which thisspecies and genetic diversity occurs, a theme furtherdeveloped in Sections 5 and 6.A number of techniques described here are of wideapplication both in characterizing diversity and in topicsaddressed in later sections. The molecular techniquesdescribed as part of genetic diversity (Chapter 2.2) arewidely used in taxonomic analysis (2.1) and inbiotechnology (Section 10). The taxic diversity measuresdescribed in 2.1 are increasingly of interest in thecomparison of ecological systems (2.3). No attempt ismade to appraise cultural diversity: with its humanand cultural dimensions, this is left until Sections 11and 12.Lastly, we should comment that this assessment ofcharacterization units and techniques leaves rather adissected view of biodiversity at different levels ofdescription. It is for other sections to assess our knowledgeof how the system works as a whole.272.1 Biodiversity from a taxonomic and evolutionaryperspectiveThis chapter contains an introduction to the taxonomic andevolutionary characterization biodiversity (2.1.0-2.1.4).This is followed by an overview of the power and utility oftaxonomic products in general biodiversity usage (2.1.5),and in the particular context of species diversity assessment(2.1.6).2.1.0 Introduction: patterns of living organisms classification and evolutionThe study of the different kinds of living organisms, thevariations among and between them, how they aredistinguished one from another, and their patterns ofrelationship, is known as taxonomy or biosystematics (seeBox 2.1-1 for strict definitions). Taxonomy is thusfundamental in providing the units and the pattern tohumankind's notion of species diversity. Indeed, the firstestimates of global biodiversity were those made bytaxonomists.At one end of the range of taxonomic studies are ratherpractical operations such as naming and cataloguing whatkinds of organisms exist (including the preparation ofchecklists, plant Floras, animal handbooks, computerizedidentification tools, etc.), the information science aspect oftaxonomy. At the other end are sophisticated studies of thebranching tree and geographic patterns of evolution bydescent (known as phytogeny) and taxonomic measures ofbiodiversity. Simple introductory texts are provided byRoss (1974), Jeffrey (1982), Heywood (1976) andLiorente-Bousquets (1990).Despite the sometimes bewildering complexity of formsobserved, biosystematists have succeeded in most majorgroups in recognizing the patterns of variation andoccurrence that are observed. The patterns can be depictedgraphically as nested hierarchies, boxes within boxes, orbranching trees (Figure 2.1-1) which, as we shall see later,can be thought of either as a nested classification or as atree of descent. This practice originated simply as a humanmethod of organizing knowledge, as in Aristotle's principleof Logical Division (Turrill 1942), where organisms aredivided into contrasted classes: A, not A; useful, not useful;woody, not woody. Similarly, in Diderot's Encyclopedic(Diderot 1751-65) all "knowledge, including both biologyand many other topics, is connected on a hierarchical treeprinted inside the book's covers. But since the acceptanceof Darwin's theory of evolution by descent withmodification (Darwin 1859), the success of using ahierarchy is attributed to organisms having evolved bydescent with modification through time, a process thatproduces a branching tree. The pattern of life actually isintrinsically tree-like and hierarchical in variation pattern.At the lowest level of this hierarchy are individualorganisms which live and die fe.g. a particular dog, a
Characterization of Biodiversity28Box 2.1-1: Definitions of taxonomy and biosystematics.A distinction between taxonomy and biosystematicsTaxonomy in the strict sense refers lo all information science aspects of handling the different sets of organisms. Theword is sometimes used in contexts outside biology so, strictly, one should speak of biological taxonomy. Mayr(1969) defines it thus:Taxonomy is the theory and practice of classifying organisms.It can be thought of as having four components (Bisby 1984: Abbott el ai. 1985; R ad ford 1986: Hawksworlh andBisby 1988):(i) the classification(it) the nomenclature(iii) circumscriptions or descriptions(iv) identification aidsBiosystematics is a broader topic, which includes taxonomy, but also includes the full breadth and richness ofassociated biological disciplines, including elements of evolution, phytogeny, population genetics and biogeography(Hawksworth and Bisby 1988; Quicke 1993). In the late 1930s the term systematics was used in Britain to emphasizethe move away from classical taxonomy, as in the phrase 'The New Systematics', and the establishment of 'TheSystematics Association'. Simpson (1961) and Mayr (1969) define it thus:Systematics is the scientific study of the kinds and diversity of organisms and of any and all relationships amongthem.Again the word is used in non-biological contexts: biosystematics makes clear the biological context.particular tree, a particular bacterium). Individuals occurusually as members of more-or-less continuously existingpopulations, which can be variously characterized,depending on their breeding systems, either as being relatedby the process of mating amongst their immediateancestors (as among humans, among beetles and amongpalm trees), or as having a common descent from a singlerecent ancestor (as in the HIV virus). These populationsthemselves fall into patterns, some being clearly similarand of the same species, others being different to varyingdegrees and thus of different species e.g. species of rats:Norway rat (Rattus norvegicus), roof rat (Rattus rattus);species of Prunus: plum, cherry, peach, apricot; species oflarge cats: lion, jaguar, leopard, tiger. Even though theexact definition of a species is a matter for debate, thespecies is used universally as the basic category of theclassification.As the common names sometimes imply, some speciesare clearly members of recognizable larger aggregations (orthe descendants of a common ancestral form) known asgenera (singular, genus): e.g. date palm, canary date palm,dwarf date palm - species in the date palm genus Phoenix.This process of aggregating similar or related forms can becontinued to form larger aggregations. Genera areaggregated into families, families into orders, and so on upthe hierarchy as shown in Table 2.1-1. The highercategories of the hierarchy, such as families and orders, arevitally important for communication; they permitdiscussion, generalization and information retrieval aboutparticular sets of organisms. The overall result is ahierarchical classification going the whole way fromspecies (or even subspecies, or human-made varietiescalled cuitivars or breeds, within species) up to the majorkingdoms such as plants, animals and fungi.To give some idea of our progress in understanding lifeon Earth a comprehensive, detailed classification of livingorganisms on earth compiled into a single work (Parker1982) recognizes 4 kingdoms, 64 phyla, 146 classes, 869orders and about 7000 families. However, recent advancesin the study of cell organdies and DNA sequences have ledto rapid changes in the topmost categories: Whittaker(1969) and Margulis and Schwartz (1982) propose fivekingdoms and Woese (1994) places three domains abovethe kingdoms (as depicted in Figure 2.1-5). The total of1.75 million species thought to have been described to thepresent day represents a small fraction of the 13 to 14million species estimated to exist in total. There is atpresent no comprehensive catalogue even of these 1.75
29Characterization of BiodiversityRosaccac (Rose Family)(a)RubuPrunusPlum(b)PeachApricotBlackberry RaspberryRosaccac (Rose Family}PrunusPlum(c)PlumPeachPeachRubusBlackberry RaspberryApricotBlackberry RaspberryApricotRosaceae (Rose Family)Figure 2.1-1: Three graphical representations of the laxonomic hierarchy of some members of the Rosaceae: (a) nested hierarchy; (b)box-within-box, and (c) a branching tree.million species (see Chapter 3.1 for further discussion andTables 3.1.2-1 and 3.1.2-2 for species counts)Two properties of the taxonomic hierarchy are pivotal toits value in characterizing species diversity. First, thehierarchy provides a reference system that permits thesummary, storage and retrieval of information aboutall organisms (Simpson 1961: Blackwelder 1967; Mayr1969; Farris 1979; Bisby 1984), Secondly, the hierarchyatletnpts to be natural, by reflecting the presumed pathwayof evolution and the pattern of resemblances amongthe organisms (Darwin 1859; Haeckcl 1866; Cam 1954;Simpson 1961; Mayr 1963, Davis and Heywood 1963;Hennig 1966).2.1.0.! Folk classifications and the origin of scientifictaxonomyThroughout history humans have classified organisms. Wcuse our innate classificatory abilities every day: we eat ricein quantity but not peppercorns. In supermarkets manyfoods are arranged by species. All human societies havefolk taxonomies - traditional classifications of organismsoften associated with cultural, survival and culinarypractices (Berlin 1992). The limit of Fast Hudson Bayrecognize two major kinds of animals, umajitq which aregame animals, and umajuquts which are domestic ones(Atran 1990). The Tzeltal Indians of Chiapas, Mexico, usefour life-forms - trees, herbs, grasses and vines (Table 2.1-2;Berlin el al. 1974), a system winch contains logicalstructures (generic tax a) analogous to the genus and speciesof scientific taxonomy.ft is from these folk classifications that scientifictaxonomy emerged, initially in Europe, bringing togetherthe more formalized cataloguing of medicinal herbs, worldwide collecting expeditions, particularly by the seafaringnations, and the dawn of scientific discovery in biology.Mediaeval herbals contained descriptions of herbal extracts
Characterization oj BiodiversityJOTable 2.1-1: Major taxonomic categories.Categories (in descending rank}ExamplesInformal category above kingdomDomainLucaryaEucaryaEucaryaforma! categories recognizedKingdom*Animal iaPlaniaeProtect istaPhylum (Division)*Chord ataTrac heo p h y taCiliophoraClass (Super-, Sub-)*MammaliaAngiospermaeOligohymenophoraOrder (Super-, Sub-)*PrimatesFabalesHymenostomatidaFamily (Super-, Sub-)*HominidaeLegu mi n osaeParameciidaeTribe ( Super-, Sub-)*HomininiVicieaeGenus (Super-, Sub-)*HomoPisttmParaineciumPismn sativumParamecium caudaiumSection (Sub-)*Species (Super-, Sub-)*Homo sapiensVariety (also Form)P sativum var. sativumCultivar Group, Cultivar(Sugar Pea Groups cv. 'Olympia'Further informal categories usedSpecial formPathovarRaceBreed* These categories are often subdivided still further by the addition of the prefixes sub- or super- in addition to the stem ranksthemselves, e.g. a superfamily may contain several families, and a family several subfamilies.Table 2.1-2; Folk taxonomy of the Tzeltal Indians ofand crude illustrations of the plants from which they came,Chiapas, Mexico (from Berlin etal. 1974).often with a number of animal extracts and even inanimateitems alongside. The thoughtless copying of such worksCategoryNumber of generic taxaand the attempts to shoe-horn into them new discoveriesfrom all over the world soon led to chaos. It was againstthis background that the cataloguing energies of thefe ' trees'178eighteenth century Swedish naturalist Carl Linnaeus, andwamat 'herbs'1 19the first attempts at natural classification by the French?ak 'grasses'35?ak 'vines':MUnaffiliaied taxa97Ambiguous taxaIBnaturalists, were so badly needed.For a long time species were named using a descriptiveLatin phrase, but no formal system was widespread. It wasLinnaeus who adopted the binomial system in later editionsof his master catalogues Systema Naturae (Linnaeus 1735)and Species Plamarum (Linnaeus 1753), and a system ofTotal471nomenclature broadly similar to his has continued to thepresent day. It is now formally embodied in the various
Characterization of Biodiversity31Table 2.1-3: The Codes and Committees dial define rules and recommendations for the scientific names oftaxa.AbbreviationRelevant publication or authorityInternational Code of Zoological NomenclatureLatest editioniCZNICZN 1985iCBNGreuter et at. 1994international Code of Nomenclature of Bacteria 1CNBSneath 1992International Committee on the Taxonomy of Viruses1CTVFrankiefo/ 1990; Mayo 1994International Code of Nomenclature of Cultivated PlantsICNCPBrickcll et ai. 19801International Code of Botanical Nomenclature11. Blue-green algae (Cyanobacteria) have variously been treated as plants or bacteria, giving rise to confusing applications of bothICBN and ICNB.2 Fungi are covered by the ICBN/as are Cyanobacteria and certain Protozoa.international rules for nomenclature and almost universallyendorsed as the scientific names of organisms. Starting inthe same period, much of the classification that we usetoday was put in place by de Jussieu, Adanson, Cuvier,Lamarck and Geoffroy Saint-Hilaire. It was they whorecognized the major natural groupings of animals andplants, albeit without Darwin's insights into evolution ortoday's understanding of phylogenetic taxonomy. Theclassification and nomenclature system has developedcontinuously from that time and now enables workers in allsorts of professions from all over the world to communicatereasonably effectively about the same organisms, be theyplants, animals, fungi or other microorganisms.2.1.1 The basics of taxonomic characterization: whattaxonomists doThere are common elements to nearly all taxonomic studiesdespite the different practices relevant to different groupsof organisms (Blackwelder 1967; Davis and Heywood1963). Most studies start from the examination of live orpreserved specimens, either because newly discoveredspecimens do not fit the known patterns, or becausespecimens are being re-examined to solve a problem in theexisting taxonomy. Some specimens are found to belong toalready-known species. They are identified and the dataassociated with the specimen are added to thedocumentation for the species, possibly adding newlocalities, or variations in the description Others prove tobe of a previously unnamed organism. After carefulresearch in the literature, and thorough examination of thenew taxon, a new species, subspecies or variety isdescribed and named using the international codes ofnomenclature (see Table 2.1-3).Ideally most taxonomic studies would be revisions of anentire group of organisms over its complete geographicalrange - a whole genus, family or order - but this is difficultto achieve both because of the labour involved and becauseof the logistics needed to see specimens or cultures andstudy the organisms over several continents. Depending onthe size of the group and its distribution, it may takeanything from three to ten years of full-time work, inextreme cases even a lifetime, for a taxonomist to complete.The advantage is that all species can
2.0.1 What is biodiversity? 27 2.0.2 What components of biodiversity are to be characterized? 27 2.0.3 What is meant by characterizing biodiversity? 27 2.1 Biodiversity from a taxonomic and evolutionary perspective 27 2.1.0 Introduction: patterns of living organisms - classification and evolution
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Chapter Outline 47.1: The Biodiversity Crisis 47.2: The Importance of Biodiversity to Human Life 47.3: Threats to Biodiversity 47.4: Preserving Biodiversity Introduction In the 1980s, biologists working in Lake Victoria in Africa discovered one of the most extraordin
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