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About Turn for Supercontinents System NEWS AND VIEWS Illuminated view the known fungal species, much less Hawksworth discusses their significance WEAK binding processes are hard to those yet unknown. The International in the evolution of organic diversity, analyse because the free ligand is Mycological Institute at Kew, for inst­ suggesting that they were crucial to land perforce always in large excess over the ance, holds a reference collection of colonization by plants, and - especially bound. C. L. Poglitsch eta/. · about 31,500 species, which occupy through the development of mutualisms (Biochemistry 30, 6662-6671, 1991) 1,456 metres of shelving in compactors. - to the subsequent radiation of other now demonstrate the virtues of a new An equivalent collection of Hawks­ groups, particularly vascular plants and method which they use to quantitate the worth's global total of 1.6 million species many insects. Like Rodney Dangerfield, weak interaction between an lgG and an would run to over 70 km of shelving. they deserve more respect. 0 Fe receptor in vitro. The receptor is The need to computerize the data, pre­ incorporated into liposomes, which are ferably on CD-ROM disks with graphic Robert M. May is in the Department of then deposited on a quartz plate and Zoology, University of Oxford, South Parks and picture-storing capability, is evident, Road, Oxford OX1 3PS, UK. fused into a continuous bilayer. This is even though the costs are high in com­ placed in contact with a solution of parison with the traditions of this 1. Erwin, T. L. Co/eopt. Bull. 36, 74-82 (1982). fluorescein-labelled antibody and 10 discipline (but not in comparison. with 2. Stork, N. E. Bioi. J. Linn. Soc. 35, 321~337 (1988). 3. May, R. M. Proc. R. Soc. Lond. 6330, 293-304 (1990). examined by fluorescence, excited by a other areas seen as 'big science'). As for laser at a glancing angle to give total 4. Hawksworth, D. L. Myco/. Res. 95, 641-655 (1991). conservation of species endangered by 5. Whittaker, R. H. Science 163, 157~160 (1969). internal reflection. The light penetrates 6. Hawksworth, D. L. eta/. Ainsworth and Bisby's Dictionary less than 100 nm into the solution and habitat loss or other environmental of the Fungi, 7th edn (Commonwealth Mycological changes, it is sufficient to note that ex Institute. Kew, 1983). so excites only surface-bound 7. Hodkinson, I. D. & Casson, D. Bioi. J. Linn. Soc. 43, fluorophores. Binding isotherms of situ collections of living fungal cultures 109-109 (1991). enviable precision deliver an association include fewer than 12,000 species, or 8. Esslinger, T. L. Systematic Botany Monographs 38, 1~111 (1989). 5 1 around one sixth of known species. constant of a mere 3 x 10 M~ . 9. Corner, E. J. H. Boletus in Malaysia (Government Print­ Fungi lack the appeal of the panda, or ing Office, Singapore, 1972). even of the average beetle, but they are 10. Hawksworth, D. L. & Mound, L.A. in The Importance of Unnatural gas Microorganisms and Invertebrates in the Maintenance CooL astrophysical clouds are known to key players in most ecosystems, especial­ of Sustainable Agriculture (ed. D. L. Hawksworth) contain all kinds of organic molecules, ly as decomposers and soil-developers. 230-250 (CAB International, Wallingford, 1991). so it comes as a bit of a surprise to see PlATE TECTONICS------------------ J. H. Lacy eta/. (Astrophys. J. 376, 556-560; 1991) announcing the first detection of methane, the simplest saturated hydrocarbon, outside the Solar About turn for supercontinents System. Many other simple Chris J. H. Hartnady hydrocarbons have been found, but the weakness of methane's molecular lines THE supercontinent Pangaea, which ex­ eration of plate tectonics over the grea­ allowed it to elude detection until now. isted about 200 million years ago, was ter part of Earth history has probably Lacy eta/. distinguish both gaseous and formed by the (not much) earlier colli­ led, via the so-called 'Wilson Cycle', to solid methane (the latter presumably a sion of two smaller land masses, Gond­ the episodic disruption and re-assembly mantle on dust grains) in the spectra of wanaland to the south and Laurasia to molecular clouds around young stars. of continental fragments into a number the north. Was there also an ancient of varied mosaical configurations at The presence of either form is not hard 7 to explain, but their coexistence is more supercontinental ancestor to these different times . Indeed, the alternative problematic. There is less gas than blocks; and if so, what did it (or they) view of Gondwanaland's origin is that it would be expected if the grain mantles actually look like? These are among the formed not by rifting from a larger evaporate by stellar irradiation. The issues addressed in a series of related whole, but by a collision between the 2 authors speculate that gaseous papers by Moores\ Dalziel , and putative, smaller West Gondwanaland 3 8 methane must be vulnerable to gas­ Hoffman , with fresh perspectives on the and East Gondwanaland blocks . The phase reactions in the dense molecular evolution of Gondwanaland and the con­ high-grade metamorphic Mozambique clouds. figuration of its precursor supercontinent Belt of East Africa and Madagascar is during the Late Proterozoic era (900-530 usually considered to be the zone of Rats' tales million years ago). The answers that are collisional mountain construction RATs resistant to warfarin pay a huge emerging may surprise - not least the (orogeny) within which the cryptic su­ price for the privilege. Warfarin is an suggestion that Gondwanaland arose ture between the two halves of Gond­ anticoagulant, thought to work by when its predecessor "turned inside­ wanaland is concealed. inhibiting an enzyme called vitamin K out"3 on the spherical surface of our The hypothesis of a geological connec­ epoxide reductase which is involved in planet. This suggests that continental tion between southwest United States the production of blood clotting factors. rifting and accretion by continent­ and East Antarctic ("SWEAT")1 was The drawback is that mutant enzymes continent collision are two facets of the inspired by an earlier matching of late are almost as unresponsive to vitamin K, same plate-tectonic process. Precambrian rocks between western their co-factor, as to warfarin itself. The The essential palaeogeography of Canada and South Australia on stratig­ result is that the protected rats are Gondwanaland was established in 1937 raphic, metallogenetic and palaeomagne­ deficient in vitamin K. They are also 4 9 by Du Toit , and a geological wall-map tic grounds . Before their separation by smaller then their susceptible cousins. 5 now exists of the continent . A common sea-floor ~preading, only about 50 mil­ but expenditure of extra energy in view is that it originated by rifting of a lion years (Myr) ago, continental East patching up the defect may not be the 6 reason. P. Smith eta/. (Functional unitary Proterozoic supercontinent , Antarctica was previously attached to Ecology 5, 441-447; 1991) note that a which also spawned its counterpart in the stable cratonic shield of Australia. reduced version of vitamin K is essential the Northern Hemisphere, Laurasia. But Therefore, when the Pacific-facing mar­ for maintaining high concentrations of the idea that, through most of geological gins of a combined East Antarctica­ the bone growth promoter osteocalcin, time, a single primal supercontinent Australia block are reconstructed in and suggest that it is this aspect of drifted more or less rigidly over the their possible pre-Gondwana configura­ vitamin K deficiency that stunts growth. surface of the globe is open to serious tion against the conjugate western mar­ challenge. Instead, the continuous op- gin of the North America continental 476 NATURE · VOL 352 · 8 AUGUST 1991 .
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