Do all mass extinctions represent an ecological crisis? Evidence from the Late Ordovician

Geological Journal - Tập 36 Số 3-4 - Trang 329-340 - 2001
P. J. Brenchley1, James D. Marshall1, Charlie J. Underwood2
1Department of Earth Sciences, University of Liverpool, Liverpool, UK
2School of Earth Sciences, Birkbeck College, London, UK

Tóm tắt

AbstractThe high rate of species extinction in recent decades is seen by many ecologists as heralding an extinction of catastrophic magnitude in the near future. The ecological consequences of such a biodiversity crisis are hard to predict, but some indication of likely effects can be gained from the knowledge of mass extinctions in the past. The Late Ordovician extinction was one of the five great extinctions in the geological record. It occurred in two phases about 0.5–1million years (Ma) apart and resulted from climatic and related environmental changes associated with the rapid growth and decay of the large Gondwanan ice cap. Overall, an estimated 86% of species became extinct, 61% of genera and 12–24% of families, but few or no orders or higher taxa. The extinction severely affected both marine benthos and plankton. Using brachiopod data as a measure of ecological change, it can be seen that the number of within‐habitat species (alpha diversity) was severely reduced and the number and distinctness of benthic communities (beta diversity) on marine shelves also declined sharply. Concurrently the number of palaeogeographic provinces fell from ten to five, possibly as a result of a loss of endemic species and preferential survival of cosmopolitan species. At the peak of extinction, following the second extinction phase, the ecological structure of both benthic and planktonic ecosystems had been severely disrupted and downgraded in complexity as a wide variety of niches were ‘vacated’. In spite of the profound biodiversity and ecological crisis within this ‘survival’ interval, communities returned to their pre‐extinction levels of alpha and beta diversity during the subsequent ‘recovery’ interval. In spite of the large amount of vacant ecospace to be filled there was very little innovation in terms of adaptive strategy, so that the structure of the emerging Silurian communities was similar to that of the Ordovician. In these terms the ecological recovery was remarkable, but it was also prolonged over about 4–5 Ma. On a geological time scale the biosphere returned to ‘normal’, but on a human time scale the mass extinction produced a very severely degraded biosphere. Copyright © 2001 John Wiley & Sons, Ltd.

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Tài liệu tham khảo

10.1111/j.1502-3931.1987.tb00763.x

Baarli BG, 1986, Relic Ordovician brachiopod faunas in the Lower Silurian of Asker, Oslo District, Norway, Norsk Geologisk Tiddskrift, 66, 87

10.1126/science.7701342

Berry WBN, 1996, Biotic Recovery from Mass Extinction Events, 119

Boucot AJ, 1975, Evolution and Extinction Rate Controls

Brenchley PJ, 1999, Quo vadis Ordovician?, 187

10.1130/0091-7613(1994)022<0295:BAIEFA>2.3.CO;2

Brenchley PJ, 1995, Environmental changes associated with the ‘first strike’ of the late Ordovician mass extinction, Modern Geology, 20, 69

10.1111/j.1502-3931.1993.tb01507.x

Briggs DEG, 1988, Extinction and Survival in the Fossil Record, 171

Chen X, 1999, Quo vadis Ordovician?, 233

10.1017/S0094837300014111

Cocks LRM, 1988, Brachiopods across the Ordovician–Silurian boundary, Bulletin of the British Museum of Natural History (Geology), 43, 311

10.1007/BF00426428

Copper P, 1991, A global review of coral reefs, Special Papers in Palaeontology, 44, 225

10.1126/science.240.4855.996

Droser M L, 1995, Fieldtrip Guidebook and Volume for the Seventh International Symposium on the Ordovician System, 64

10.1130/0091-7613(1997)025<0167:ETEAOM>2.3.CO;2

10.1130/0091-7613(2000)28<675:DOTAES>2.0.CO;2

Erdtman BD, 1976, The Ordovician System: Proceedings of the Palaeontological Symposium, Birmingham, 1995, 621

10.1111/j.1558-5646.1987.tb02459.x

10.2307/3514628

10.1130/0091-7613(1999)027<0215:LOMEAN>2.3.CO;2

10.1098/rstb.1989.0092

10.1111/1475-4983.00080

Harper DAT, 1995, Patterns of change in the brachiopod faunas through the Ordovician–Silurian interface, Modern Geology, 20, 83

Harris MT, 1997, Carbonate sequences and fossil communities from the Upper Ordovician–Lower Silurian of the Eastern Great Basin, Brigham Young University Geology Studies, 42, 105

10.1126/science.253.5021.754

Jablonski D, 1996, Mass extinctions: Persistent problems and new directions, Geological Society of America, 307, 1

Legrand P, 1986, Palaeoecology and Biostratigraphy of Graptolites, 145

Loydell DK, 1991, Isolated graptolites from the Llandovery of Kallholen, Sweden, Palaeontology, 34, 653

10.1139/e89-147

Mu E‐Z, 1988, A Global Analysis of the Ordovician–Silurian Boundary, 117

Owen AW, 1995, Ecological changes during the end‐Ordovician extinction, Modern Geology, 20, 21

10.4095/132187

Pickerill RK, 1991, Benthic macrofossils as paleoenvironmental indicators in marine siliciclastic facies, Geoscience Canada, 18, 119

10.1126/science.215.4539.1501

10.1080/10292389109380396

10.1017/S026359330001436X

10.1002/(SICI)1099-1034(199911/12)34:4<321::AID-GJ809>3.0.CO;2-I

10.1144/pygs.51.3.177

10.1017/S0094837300006539

10.1017/S0094837300003778

10.1017/S0094837300011969

Sepkoski JJ, 1990, Palaeobiology: A Synthesis, 37

Sepkoski JJ, 1995, Ordovician Odyssey: Short Papers for the Seventh International Symposium on the Ordovician System, 393

10.1017/S0022336000040026

10.1111/j.1502-3931.1973.tb01188.x

10.1017/S0094837300002396

Sheehan PM, 1982, Brachiopod macroevolution at the Ordovician–Silurian boundary, Proceedings of the Third North American Paleontological Convention, 2, 477

10.1016/S0031-0182(96)00086-7

Sheehan PM, 1990, Palaeozoic Palaeogeography and Biogeography, 181

Skelton PW, 1994, Radiations and extinctions in the history of life: “what turns the wheel of fortune”?, European Palaeontological Newsletter (Europal), 6, 15

10.1111/j.1502-3931.1998.tb00487.x

10.1144/gsjgs.154.4.0709

10.1016/S0031-0182(98)00070-4

10.1017/S0094837300005686

Walker KR, 1970, Congruent fossil communities from the Ordovician and Devonian carbonates of New York, Journal of Paleontology, 44, 928

10.2307/3515138

10.1016/0031-0182(84)90041-5

10.1007/BFb0011136

10.1017/S0016756800021269

10.1111/j.1502-3931.1968.tb01724.x

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Geological Journal

Tập 36 Số 3-4

329-340

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