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The improbability of animal phyla with few species

Published online by Cambridge University Press:  08 April 2016

Richard R. Strathmann  and
Montgomery Slatkin
Richard R. Strathmann
Affiliation:
Friday Harbor Laboratories NJ-22 and Department of Zoology NJ-15, University of Washington, Seattle, Washington 98195
Montgomery Slatkin
Affiliation:
Friday Harbor Laboratories NJ-22 and Department of Zoology NJ-15, University of Washington, Seattle, Washington 98195
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Abstract

At present there are many animal phyla that contain only a few species. The existence of these small phyla can be used to test assumptions about speciation and extinction in multicellular animals.

We first model the number of species in a monophyletic clade with a birth and death process that assumes rates of speciation and extinction are constant. If no new phyla have evolved since the Cambrian and speciation and extinction rates for minor phyla are similar to or greater than those estimated from fossils, then our model shows that the probabilities of minor phyla surviving to the present are small. Random variation in extinction and speciation rates does not improve the chances for persistence. If speciation rates exceed extinction rates at the initial radiation of the clade, but before the clade becomes large, speciation rates come to equal extinction rates and both are low, persistence from before the Ordovician up to the present becomes likely. These models show that if speciation and extinction rates are independent of the number of species in a clade, then conditions before the Ordovician strongly influence today's distribution of species among taxa.

We also discuss a model in which speciation and extinction rates depend on the number of species in a clade. This alternative model can account for the persistence of phyla with few species to the present and predicts a short duration for phyla that did not exceed a threshold number of species.

Type
Research Article
Information
Paleobiology , Volume 9 , Issue 2 , Spring 1983 , pp. 97 - 106
Copyright
Copyright © The Paleontological Society 

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References

Literature Cited

Brasier, M. D. 1979. The Cambrian radiation event. Pp. 103–159. In: House, M. R., ed. The Origin of Major Invertebrate Groups. Academic Press, New York.Google Scholar
Conway Morris, S. 1979. The Burgess Shale (Middle Cambrian) fauna. Annu. Rev. Ecol. Syst. 10:327–349.Google Scholar
Conway Morris, S. and Crompton, D. W. T. 1982. The origins and evolution of the Acanthocephala. Biol. Rev., Cambridge, 57:85–115.Google Scholar
Emig, C. C. 1979. British and Other Phoronids. Synopses of the British Fauna No. 13. Academic Press, London. 57 pp.Google Scholar
Feller, W. 1968. An Introduction to Probability Theory and Its Applications. Vol. 1. Wiley, New York.Google Scholar
Goodman, L. A. 1967. The probabilities of extinction for birth-and-death processes that are age-dependent or phase-dependent. Biometrika 54:579–596.Google Scholar
Hochberg, F. G. Jr. 1982. The “kidneys” of cephalopods: a unique habitat for parasites. Malacologia 23:121–134.Google Scholar
House, M. R. 1979. The Origin of Major Invertebrate Groups. Academic Press, New York.Google Scholar
Jagers, P. 1975. Branching Processes with Biological Applications. Wiley, New York.Google Scholar
Keiding, N. 1975. Extinction and exponential growth in random environments. Theoret. Popul. Biol. 8:49–63.CrossRefGoogle ScholarPubMed
MacArthur, R. H. and Wilson, E. O. 1967. The Theory of Island Biogeography. Princeton University Press, Princeton.Google Scholar
Raup, D. M. 1978. Cohort analysis and survivorship. Paleobiology 4:1–15.Google Scholar
Raup, D. M., Gould, S. J., Schopf, T. M., and Simberloff, D. S. 1973. Stochastic models of phylogeny and the evolution of diversity. J. Geol. 81:525–542.Google Scholar
Richter-Dyn, N. and Goel, N. S. 1972. On the extinction of colonizing species. Theoret. Popul. Biol. 3:406–433.Google Scholar
Schopf, T. J. M. 1982. A critical assessment of punctuated equilibria. I. Duration of taxa. Evolution 36:1144–1157.Google ScholarPubMed
Sepkoski, J. J. Jr. 1979. A kinetic model of Phanerozoic taxonomic diversity. II. Early Phanerozoic families and multiple equilibria. Paleobiology 5:222–251.CrossRefGoogle Scholar
Stanley, S. M. 1979. Macroevolution. Freeman, San Francisco.Google Scholar
Stanley, S. M., Signor, P. W. III, Lidgard, S., and Karr, A. F. 1980. Natural clades differ from “random” clades: simulations and analyses. Paleobiology 7:115–127.Google Scholar
Van Valen, L. 1973. Are categories in different phyla comparable? Taxon 22:333–373.Google Scholar
Yule, G. U. 1924. A mathematical theory of evolution, based on the conclusions of Dr. J. C. Willis, F.R.S. Phil. Trans. R. Soc., London 213B:21–87.Google Scholar