Nature and Human Society The Quest for a Sustainable World (1997) / Chapter Skim
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2 Less Well-Known Individual Forms of Life
2 Less Well-Known Individual Forms of Life
Pages 115-222
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From page 117... ...
At most only a few of these microor' ganisms would be known to us; only about 5,000 noneukaryotic organisms have been formally described (Bull and others 1992) in contrast with the half million described insect species.
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From page 118... ...
However, the pure~culture approach to the study of the microbial world seriously constrained the view of microbial diversity because most microorganisms defy cultivation by standard methods. Moreover, the morphological and nutritional criteria used to describe microorganisms failed to provide a natural taxonomy, ordered according to evolutionary relationships.
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From page 119... ...
: Ze: CrJ/ptomonas~ EUCARYA ~ z ~ ~= 3 At' ~ {D ~ ~ ~to ~ ~ ~ ARCHAEA At, 0.1 changes/site FIGURE 1 Universal phylogenetic tree based on small-subunit ribosomal RNA sequences. Sixty-four rRNA sequences representative of all known phylogenetic domains were aligned, and a tree was produced with FASTDNAML (Barns and others 1996; Maidak and others 1997~.
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From page 120... ...
Nonetheless, the order of occurrence of branchings in the trees can be interpreted as a genealogy, and intriguing insights into the evolution of cells are emerging. A sobering aspect of large-scale phylogenetic trees like that shown in figure 1 is the graphic recognition that most of our legacy in biological science, historically based on large organisms, has focused on a narrow slice of biological diversity.
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From page 121... ...
THE METABOLIC DIVERSITY OF LIFE The molecular-phylogenetic perspective, as depicted in figure 1, is a reference framework within which to describe microbial diversity; the sequences of genes can be used to identify organisms. That is an important concept for microbial biology.
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From page 122... ...
Molecular phylogeny now provides a framework within which we can relate organisms objectively and through which we can interpret the evolutionary flow of the metabolic machineries that constitute microbial diversity. Laboratory studies of microbial metabolism have focused mainly on such organ' isms as Escherichia cold and Bacillus subtilis.
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From page 123... ...
From that standpoint and on the basis of cultivated organisms, metabolic diversity seems to have flowered mainly among the Bacteria. Even here, however, reliance on organic nutrients probably was not ancestral.
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From page 124... ...
(Pitulle and others 1994~. Cultivated organisms from these deeply branching bacterial lineages also are all thermophilic and thus share two important physiological attributes with the deeply branching and slowly evolving Archaea; a Hz-based energy source and growth at high temperatures.
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From page 125... ...
Every nucleic acid-based study of natural microbial ecosystems so far performed has uncovered novel types of rRNA sequences, often representing major new lineages only distantly related to known ones. The discovery of rRNA sequences in the environment that diverge more deeply in phylogenetic trees than those of cultivated organisms is particularly noteworthy.
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From page 126... ...
. MICROBIAL DIVERSITY AND THE LIMITS OF THE BIOSPHERE Textbooks generally portray only a part of the global distribution of life the part that is immediately dependent on either the harvesting of sunlight or the
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From page 127... ...
Although the metabolic rate of this subterranean biosphere is likely to be far lower than in the more dynamic, photic environment, life is likely to be as pervasive in occurrence, and perhaps in cellular diversity, as we experience on the surface. The opportunities for discovery of new organisms and development of resources based on microbial diversity are greater than ever before.
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From page 128... ...
Proc Natl Acad Sci USA 91:4180-4.
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From page 129... ...
Proc Natl Acad Sci USA 95:6854-9. Woese CR.
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From page 130... ...
The hypothetical "gap fillers" to the surprise, perhaps, of many experimental biolo' gists but not of field and taxonomic protozoologists and phycologists turned out to be represented by the largely unicellular eukaryotic microorganisms, a huge assemblage (tens of thousands of species) of widespread but often poorly known forms that now can collectively be called the protists.
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From page 131... ...
But it is increasingly clear that much further work is required to assess the multiple roles of protists in natural ecosystems. To speak quantitatively about the numbers of known protistan species, a main aim of this paper, we must first have some idea of the qualitative nature of pro' fists: what are they, and how can they be defined and classified?
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From page 132... ...
The single-celled species are wholly independent organisms: the two terms cell and organism are thus not mutually exclusive descriptors (Corliss 1989a; Hausmann and Bradbury 1996~. Major habitats of free-living forms include soils and bodies of freshwater and salt water; and ectosymbiotic and endosymbiotic species are found in association with numerous animal and some plant species and even other protists.
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From page 133... ...
and thus sidestepping a number of high level taxonomic problems. A second is to view groups of protists as simply mostly independent evolutionary lines or lineages, again leaving aside attempts to define high level taxonomic interrelationships among such lines; cladistically de' rived phylogenetic trees (such as those constructed from collected molecular bio' logical data)
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From page 134... ...
PROTOZOA (literally meaning "first animals") traditionally has embraced spe' cies belonging not only to the phyla listed in Protozoa in table 1 but also to other major taxa no longer included there, most notably Cryptomonada, Haptomonada, Labyrinthomorpha, Opalinata, and some lower taxa of Bicosoecae, Chrysophyta, and Dictyochae; I consider these seven phyla to belong to the kingdom Chromista.
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From page 135... ...
In much of its composition, the kingdom Chromista of table 1 resembles the rather similar assemblage widely known today as the stramenopiles (Patterson 1989, 1994; Sogin and Hinkle 1997~. Both circumscribed groups, chromists and stramenopiles, contain predominantly species of the old and large heterokont algal assemblage of the past botanical and phycological literature (see historical reviews in Corliss 1984, 1994a)
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From page 136... ...
. · The justification of new species continually being described in the literature on practically all protistan taxonomic groups (see the Zoological Record and relevant botanical and algal lists and monographs)
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From page 137... ...
Yet, as habitats and niches in diverse geographic and ecological areas (including new host species for symbiotic forms) are more thoroughly explored (perhaps even for the first time)
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From page 138... ...
come next; spore~forming parasitic taxa (sporozoa and the former "cnidosporidian" groups) are then treated; and finally the ciliates, a large collection of species that represents one of the most circumscribed and noncontroversial protistan taxa of all, are mentioned.
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From page 139... ...
Rhizopoda (synonym Amoebozoa, in part, of Corliss 1984~: Predominantly typical amoeboid forms, including ones with tests, shells, or thecae, but some small heterotrophic flagellates here as well (see Patterson and Zolffel 1991~. Some workers put the enigmatic algal Chlorarachnion here; others, 40 or more species of plasmodiophorans (endoparasitic slime molds)
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From page 140... ...
It is treated here under "Algae," below. It is assigned to the kingdom CHROMISTA.
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From page 141... ...
About half the described species have been found as fossils, exclusive of 400 genera of acritarchs (a fossil group also assigned here by some workers) but including the small taxa of ebriideans and ellobiophyceans.
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From page 142... ...
There are more than 5,000 species, some questionable today because of inadequate past accounts; but parasitologists predict numerous yet-to-be-described species. Levine (1973)
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From page 143... ...
rank, eight of which I assign to the kingdom CHROMISTA, six to PLANTAE, and two to PROTOZOA (Euglenozoa, Dinozoa: see above)
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From page 144... ...
. These species are assigned to the kingdom PLANTAE with other green algae.
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From page 145... ...
These were formerly placed within Chrysophyta. The group is assigned to the kingdom CHROMISTA and contains about 40 species.
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From page 146... ...
: Small group of yellow-green algae, from freshwater and salt-water habitats, formerly placed in Chrysophyta by some workers. The group is assigned to the kingdom CHROMISTA.
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From page 147... ...
Both groups are assigned to the kingdom CHROMISTA. These small but numer' ous freshwater "water molds," whose zoospores have an anteriorly projecting fla' gellum bearing mastigonemes, parasitize hosts ranging from other protists and aquatic plants to fishes and, via the soil, grapes and potatoes.
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From page 148... ...
In this paper, I append only two protistan phyla to the kingdom ANIMALIA (see above, under convert' tional "protozoan" phyla) , namely the Choanozoa (controversially)
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From page 149... ...
Uncertain taxonomic boundaries Most symbionts kinetoplastideans Symbionts few but important Nearly all intestinal parasites Nearly all intestinal parasites No nonparasitic form identifiable? Only few parasitic in primates Some saprotrophic on dead tissue Some saprotrophic on dead tissue Nonpigmented heterotrophs The silicoflagellates Nonheterokontic group Prymnesiophytes of phycologists Many species uncertain?
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From page 150... ...
forms from their estimates with' out clearly informing their readers of the fact? For the radiozoa, are about half the 11,650 described species now to be considered by protozoologists to be invalid or uncertain?
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From page 151... ...
Biod Cons 1:267-92. Andersen RA.
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From page 152... ...
1986. The kingdom Chromista: origin and systematics.
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From page 153... ...
1992. Microbial Diversity 2: biodiversity amongst microorganisms and its relevance.
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From page 154... ...
Proc Natl Acad Sci USA 95:9720-3. Muller M
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From page 155... ...
Annals NY Acad Sci 503:1-16. Taylor FJR (ed)
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From page 156... ...
But why in particular do we need to measure fungal diversity? Why do we even want to know which fungi are present in an ecosystem?
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From page 157... ...
Oxydothis previously had 27 species names, but the number was increased to 42 after publication of the monograph of Hyde (1994) , and a further 23 species have since been found on palms in Australia, Brunei, Ecuador, and Hong Kong (Frohlich 1997~.
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From page 158... ...
Those findings indicate that a ratio of 1:6 for vascular plants to fungi might be low, at least in the tropics. MEASURING FUNGAL BIODIVERSITY Why Should We Measure Fungal Diversity Rapidly?
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From page 159... ...
. Once some site inventories are complete, protocols for accurate measurement of fungal diversity can be developed and tested in them.
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From page 160... ...
Five to eight years of coordinated effort across forest regions would be required to allow the identification of suitable predictor microhabitats and then to provide methods for rapid evalua' tions of fungal diversity in different regions. Rapid Biodiversity Assessment In rapid biodiversity assessment or RBA (Beattie and others 1993)
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From page 161... ...
Over a period of 7 weeks, sites in Tai Po Kau Nature Reserve and on the University of Hong Kong campus were visited during the wet season. Representative collections of all macromycetes were made on each visit and sorted into recognizable species units.
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From page 162... ...
Identification to genus, species, or other recognizable units is relatively easy for paratechnicians. Because the fruiting bodies of these fungi are tough and persistent, they can provide a better comparative measure of fungal diversity than is the case with the more ephemeral, larger basidiomycetes.
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From page 163... ...
The results generated by both the endophytic and saprobic studies indicate a decrease in species numbers on palms when they are outside their natural range, unless they are in equivalent habitats with in the case of palms, for instance a source of fungi from other palm hosts. SELECTED HABITATS FOR RAPID BIODIVERSITY ASSESSMENT As a complement to selecting particular groups of fungi to subject to RBA, we suggest that particular habitats be examined in addition to selected groups.
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From page 164... ...
It should be returned to the laboratory and incubated for a few days. The hyphomycetes present on the material should sporulate quickly and can be identified to provide a measure of fungal diversity.
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From page 165... ...
However, large numbers of pathogens occur in gardens, nurseries, or monocultured crops. Other Habitats for Rapid Biodiversity Assessment The habitats suggested above are those we have worked on, and they have proved to be excellent sources of fungal diversity.
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From page 166... ...
MYCODIVERSITY TECHNICIANS It is unlikely that trained mycologists will always be available for or have the time to devote to measuring fungal diversity in a given habitat, but it can be pos' sible to use mycodiversity technicians (Hyde 1997; Hyde and Hawksworth 1997~. Mycodiversity technicians (a kind of "parataxonomist")
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From page 167... ...
. Although inconclusive, this pilot expert' merit indicates that · mycodiversity technicians can be used in fungal diversity assessment; · further studies are required to establish whether a single visit to a site to assess fungal diversity is representative; and · further studies are required to establish how many visits to a site are required to collect an adequate representation of the macromycete species present.
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From page 168... ...
The set can be tested, procedures can be added, and others can be removed, until we establish a robust mechanism for estimating fungal diversity across a range of glo' teal habitats. For the purposes of this exercise, we assume that appropriate hu' man resources are not available and that specialized help will be provided by mycodiversity technicians.
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From page 169... ...
A short period of training provides mycodiversity technicians with the skill to collect logs and ex' amine them for fungi in the laboratory. The plot of 50-100 m2 can be used, but in this case 20 logs can be randomly collected during a wet period and then incubated in moist chambers.
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From page 170... ...
Endophytes It is relatively easy for mycodiversity technicians to carry out standard procedures to recover endophytic fungi. The methods will depend on the host plant, and pilot studies need to be undertaken to develop optimal sampling and surface sterilization techniques.
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From page 171... ...
Fungi on Pandanus Dead Pctudctnus leaves support a high diversity of fungi, and we suggest these for biodiversity assessment. Numerous dead leaves can be found on the floor or attached to the plants, and these can be randomly collected.
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From page 172... ...
In the exploration of fungal diversity, much attention has been focused on obtaining data on species richness in different systematic groups or in particular niches or substrates. Such studies have been important in vindicating hypoth' eses regarding the richness of the world's mycota, but we believe that it is now time to focus on securing comparative data on the richness of fungi in different sites.
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From page 173... ...
1999. Options anc constraints in rapid Biodiversity assessments in natural ecosystems.
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From page 174... ...
1997. Can we rapidly measure fungal diversity?
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From page 175... ...
Hong Kong: Hong Kong Univ Pr.
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From page 176... ...
More than 85 years ago, Cobb (1914) eloquently noted that "if all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes, and oceans represented by a film of nematodes." "So little do we know of this vast multitude of soil-inhabiting nematodes that the first spadeful of earth we lift is practically certain to contain kinds never seen before", and 'There exists...a greater disproportion between the known and the unknown than exists in almost any other class of organisms." With respect to Cobb's characterization of our knowledge of nematode diversity, relatively little has changed during the last 85 years.
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From page 177... ...
Most microbivorous nematodes are of unnamed species, but these poorly characterized taxa play an important role in decomposition of organic matter and nutrient cycling in all eco' systems (Freckman 1988; Peterson and Luxton 1982~. Nonparasitic nematodes are commonly the most abundant microinvertebrates of terrestrial (Nielsen 1949)
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From page 178... ...
A One of larger plant-parasitic nematodes, Hoplolaimus columbus, propped on human hair.
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From page 179... ...
Although hundreds of named nematode species in four orders are known to be associated with insects, they probably represent a small fraction of the existing species, considering insect diversity and nematode specialization on such hosts. It is very likely that this pool of largely unexplored parasites is rich in potential biocontrol agents and management tools for medical, veterinary, and agricultural insect pests.
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From page 180... ...
A potential source of error that has been more difficult to assess is the degree to which morphotypic uniqueness is a good estimator for ontologically real species; the integration of molecular data in nematode systematics provides an independent line of evidence to help address this problem (Adams 1998; Szalanski and others 1997; Thomas and others 1997~. Current systematics practice emphasizes that discovery and description of new nematode species requires phylogenetic context for many taxonomic decisions, including reevaluation of previously described species and their relationships.
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From page 181... ...
Such geographic limits would be difficult to explain through introductions or biogeography; it is much more likely that more-extensive surveys will demonstrate a broad distribution of these species beyond California and South Africa. Some parasitic nematodes have broad host ranges and are distributed nearly worldwide; an example is the root knot nematode, Meloidogyne incognita, one of the most destructive plant pathogens of agriculture and widespread in relatively undisturbed habitats (Eisenback and Triantaphyllou 1991~.
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From page 182... ...
This problem is no doubt more acute for some nematode groups than others, but recent molecular investigations show promise for investigating potential synonymies. For example, a study of nucleotide sequences indicated that three described species of vertebrate parasites (Teladorsagia spp.)
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From page 183... ...
In addition, assessing geographic distributions of nematode parasites of ver' tebrates is made more difficult by the fact that nematodes are typically not uni' formly distributed among individuals of a host species; instead many hosts remain uninfected while a few individuals harbor many nematodes (overdispersion)
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From page 184... ...
of Described Author Habitat Type Location Species Johnson and others 1972 Forest Indiana, US 175 Yeates 1972 Forest Denmark 75 Lawton and others 1996 Forest Cameroon 204 Hodda and Wanless 1994 Grassland England 154 Freckman and Huang 1998 Grassland Central Plains 118 Niles 1991 Freckman and Ettema 1993 Agroecosystem Agroecosystem Freckman and Mankau 1986 Hot desert Freckman and Virginia 1989 Hot desert Freckman and Virginia 1997 Cold desert Hope 1987 Dinet and Vivier 1977 Jensen 1988 Lambshead 1993 Marine sediments Marine sediments Marine sediments Marine sediments Number of Species Per Habitat Type, Globally Author Habitat Type Experimental Range LTER, Colorado, US Indiana, US 94 Kellogg Biological Station 132 LTER, Michigan, US Nevada, US 23 Jornada LTER, US 18 Dry Valleys, Antarctica East Pacific Rise Bay of Biscay Norwegian Sea San Diego Trough Described Species 148 316 92 116 Total No. of Species Andrassy 1992 Continental 5,600 Marine 5,450 Lambshead 1993 Marine sediments 4,000 1o6_1o8 Hoberg 1997 Helminthic parasites > 12,000 of vertebrates Number of Species Across All Habitats of Globe Author Habitat Type Described Species Total No.
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From page 185... ...
estimated the highest number of marine nematode spe' cies alone to be 100,000,000. A fundamental problem encountered in estimating regional or global nematode species diversity is that many of the traditional diversity methods might not be applicable to such a group as poorly described and as varied as nematodes.
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From page 186... ...
Assessment and conservation of nematode species diversity are confounded by an inadequate taxonomic and phylogenetic framework. The situation is exacerbated by the need for a new generation of nematode taxonomists with broad training in a range of classical and molecular tools in a rigorous phylogenetic context (Barker 1994; Ferris 1994; Hyman and Powers 1991; Systematics Agenda 2000 1994~.
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From page 187... ...
have received expanded attention in recent years because of their potential as biological control agents of insect pests; but only about 25 specialists worldwide work on these nematodes. From the perspective of advancing knowledge of nematode biodiversity, more taxonomic emphasis should be placed on understanding nonparasitic taxa, particularly aquatic species.
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From page 188... ...
Nematology's base of classical taxono' mists with their wealth of information on nematode structure, diagnoses, and natural history has been seriously eroded over the last 15 years. Although mo' lecular systematists are applying modern approaches that offer much promise to advance the discipline, the most fruitful outcomes will come from collaborative efforts of classically trained Hematologists, molecular systematists, and other sci' enlists who can apply novel tools that enhance our ability to address complex problems in biodiversity.
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From page 189... ...
1990. Pattern of nematode species diversity in temperate and tropical subtidal sediments.
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From page 190... ...
. Global biodiversity assessment.
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From page 191... ...
1984. Distribution and species diversity of deep-sea nematodes in the Venezuela Basin.
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From page 192... ...
B HALLIDAY Australian National Insect Collection, CSIRO Entomology, GPO Box 1700, Canberra Act 2601, Australia B
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From page 193... ...
We use these data as the basis of an extrapolation to an estimate of the number of species that remain to be described in these regions and then, more speculatively, to an estimate of the total world fauna of mite species. Previous estimates of the number of described mite species are summarized in table 1, and our current estimate is 48,200 described species.
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From page 194... ...
essentially reported the results of a single collecting expedition by a single person, and many TABLE 2 Numbers of Described Mite Species in Selected Families before and after Modern Revisions, Australia No. Species Group Revision Before After Factor Water mites Cook 1986 133 334 2.51 Macrochelidae Halliday 1986a,b, 1988, 1990, 1993 25 64 2.56 Phytoseiidae Schicha 1987 31 97 3.13 Scutacaridae Mahunka 1967 4 19 4.75 Steganacaridae Niedbala 1987, 1989 6 63 10.5 Niedbala and Colloff 1997 Ascidae Walter and others 1993 17 45 2.65 Walter and Lindquist 1997 Halliday and others 1998 TOTAL 216 622 2.88
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From page 195... ...
Bearing all those factors in mind, we conservatively estimate that the Australian mite fauna is likely to exceed 20,000 species, more than seven times as many as the known described species. MITE FAUNA OF GREAT BRITAIN AND IRELAND On the basis of the checklists of Turk (1953)
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From page 196... ...
TABLE 3 Numbers of Described Mite Species in Selected Taxa before and after Modern Revisions, British Isles No. Species Group Revision Before After Factor Water mites Gledhill and Viets 1976 226 273 1.21 Halacaridae Green and Macquitty 1987 27 65 2.41 Eupodidae Baker 1987 5 24 4.8 Rhagidiidae Baker 1987 4 11 2.75 Parasitinae Hyatt 1980 21 36 1.71 Pergamasus Bhattacharyya 1963 13 32 2.46 Macrochelidae Hyatt and Emberson 1988 23 32 1.39 Phytoseiidae Baker pers.
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From page 197... ...
The prior published estimates would predict increase factors of 16.5 for the oribatids and 1.79 for the water mites. The much lower observed increase factor for the oribatids might be explained by the fact that the recent revisions dealt primarily with faunas occurring in boreal Canada, where species diversity might be expected to be lower than TABLE 4 Numbers of Described Mite Species in Selected Taxa before and after Modern Revisions, North America No.
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From page 198... ...
Later collecting at the same site has yielded an additional 25 undescribed species (OConnor, unpublished data)
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From page 199... ...
Similarly, the mites in many habitats and associations are poorly known, such as the soils of tropical rain forests and species associated with other arthropods (Welbourn 1983~. Taxonomic attention is sometimes focused on a group when its economic importance is recognized, with the resulting de' scription of huge numbers of new species.
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From page 200... ...
ACKNOWLEDGMENTS We thank Emma de Boise, Department of Entomology, The Natural History Museum, London, for help in the assessment of numbers of valid mite species and Dave Walter for generously providing access to unpublished information. REFERENCES Armine JW, Stasny TA.
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From page 201... ...
1979. Some data on the freshwater mites (Hydrachnellae and Limnohalacaridae, Acari)
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From page 202... ...
1989b. North American water mites of the family Momoniidae Viets (Acari: Arrenuroidea)
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From page 203... ...
1983. Potential use of trombidioid and erythraeoid mites as biological control agents of insect pests.
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From page 204... ...
(Current address: National Museum of Natural History, Smithsonian Institution, Washington, DC 20560-0105) THE CHALLENGE BIOLOGICAL RESOURCES are the basis of the prosperity of the developed world, yet the biologically rich underdeveloped nations of Africa are the economically poorest in the world.
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From page 205... ...
We seek to fill two key gaps in the understanding and use of the positive aspects of insects in African biodiversity. First, almost all research on insects in tropical Africa focuses on the negative aspects of insects for example, the problems in agriculture, forestry, livestock, and human health that are caused by less than 1% of the species of insects and ignores the remaining 99% of insect species.
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From page 206... ...
Thus, the involvement of the taxasphere, the international infrastructure for biological sys' tematics, including the natural history museums that hold most of the collections of specimens, is vital. We also expect to integrate our activities with those at smaller (for example, national or local)
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From page 207... ...
Second, a series of field projects will evaluate the use of insects as indicator organisms and will quantify their roles in ecosystem processes. In many cases, these projects will take approaches that have been successful in South Africa and the Northern Hemisphere and will apply them, with appropriate modifications, to tropical Africa.
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From page 208... ...
. Information Management An initiative for reviewing the literature and creating a database of specimens will repatriate 200 years' worth of information collected in sub-Saharan Africa and now housed in museums in the United Kingdom, France, Belgium, Germany, elsewhere in Europe, South Africa, Kenya, elsewhere in Africa, and the United States and Canada.
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From page 209... ...
Two other major activities are the enhancement of national capacities for the diffusion, adoption, and use of technology and the facilitation of the dissemination and exchange of information. EXAMPLES OF RESEARCH ON INSECT BIODIVERSITY IN AFRICA IN SUPPORT OF SUSTAINABLE DEVELOPMENT Recent research initiatives undertaken in Kenya have shown that basic research on the biodiversity of arthropods can contribute in substantial ways to sustainable agricultural development.
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From page 210... ...
Two of these inhibit egg-laying in Chilo, even at low concentrations. In contrast, Chilo's host plants (maize, sorghum, and Napier grass)
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From page 211... ...
The interest shown by authorities from national parks and by communities in East Africa is proof of the timeliness of this project and augurs well for the future of a strong conservation industry built around wild silk moths. CONCLUSION We expect that the foundation of knowledge and trained personnel that will be generated by this new initiative will enable sophisticated strategies of ecologi' cat monitoring and applications of sustainable development that draw on the strengths of the resource base of African arthropods.
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From page 212... ...
Cons Biol 1:344-6. World Conservation Monitoring Centre.
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From page 213... ...
Any meaningful assessment of the diversity of life on earth depends on estimates of both the number of named insect species and the number of insect species that are living but are yet unnamed or even undiscovered. Common sense might suggest that the number of described species would be a statistic that science would have available.
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From page 214... ...
; cur' rently accepted valid species, excluding synonyms but with or without names of subspecies; or the estimated currently extant species, including undescribed or even undiscovered species. In recent accounts, the estimated number of named species varies from 751,000 to 950,000, and the estimated number of living spe' cies ranges from 1 million to 100 million (Hammond 1994~.
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From page 215... ...
Given that some genera of insects, for example within the Ichneumonidae and Staphylinidae, include more than 1,000 species each, it is scarcely surprising that individual taxonomists have not had the resources to produce or maintain such massive checklists. Estimates of the possible number of living insect species originate essentially from two sources.
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From page 216... ...
imply that the world's insect fauna is 30 or more times that of the currently described subset. Current evidence from the major museum collections of sorted and labeled insect species, whether described or undescribed, does not support these larger estimates.
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From page 217... ...
made the point that better data on the total numbers of spe' cies could be obtained by conducting detailed studies of the numbers of both de' scribed and undescribed species from a number of specified sites; that is, data should be collected purposefully, with particular objectives. Similarly, Longino (1994)
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From page 218... ...
Arnett 1993 Arnett estimated about 250 species but indicated that many more probably remain to be discovered. Thysanura Smith and Watson 1991 About 370 species are known; this figure Ephemeroptera Arnett 1993 Odonata Arnett 1993 Plecoptera Arnett 1993 Theischinger 1991 Blattodea Roth 1991 Isoptera Arnett 1993 Watson and Gay 1991 Mantodea Arnett 1993 Balderson 1991 Grylloblattodea Storozhenko 1986 Dermaptera Orthoptera Arnett 1993 Rentz 1991 Rentz 1991 Arnett 1993 Phasmatodea Key 1991 presumably does not include any estimate of undescribed species.
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From page 219... ...
Estimated 350,000 named species. Stated that Australian fauna includes 20,000 described species of beetles; another 10,000 species likely exist.
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From page 220... ...
Indicated that if undescribed species are included, this order is likely to include at least 150,000 species. More than 7,000 species have been described but since tropical faunas generally have been sampled poorly, the worldwide total is likely to be considerably larger.
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From page 221... ...
1991a. The magnitude of global insect species richness.
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From page 222... ...
2nd ed. Carlton: Melbourne Univ Pr.
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