Hostname: page-component-cd9895bd7-gvvz8 Total loading time: 0 Render date: 2024-12-27T08:54:05.220Z Has data issue: false hasContentIssue false
  • English
  • Français

Approximate evolutionary stasis for bivalve morphology over millions of years: a multivariate, multilineage study

Published online by Cambridge University Press:  08 April 2016

Steven M. Stanley  and
Xiangning Yang
Steven M. Stanley
Affiliation:
Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, Maryland 21218
Xiangning Yang
Affiliation:
Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, Maryland 21218
Get access Rights & Permissions [Opens in a new window]

Abstract

We have calculated rates of evolution for 19 lineages of Neogene bivalves over time intervals ranging from 1 ma to 17 ma. Our morphometric comparisons are based on 24 variables, for which we have made more than 43,000 individual measurements normalized for shell size. We initially assessed evolutionary changes in shape for 19 early Pliocene (4 ma old) species of bivalves by comparing these forms to their closest living relatives, which in 12 cases have traditonally been assigned to the same species. To make our study unbiased and comprehensive, we included all species that met certain predetermined guidelines and that offered suitable fossil material for measurement. We compared early Pliocene and Recent populations using (1) all 24 variables treated separately, (2) multivariate distance (Mahalanobis' D), based on the full set of variables, and (3) eigenshapes for shell outlines. For these comparisons, we used as a yardstick the same measures of morphologic distance applied to pairs of geographically separated Recent populations that belong to eight of the living species to which the fossil populations were compared. As it turns out, with minor exceptions, the distribution of morphologic distances between 4 ma old and Recent populations resembled the distribution of distances between conspecific Recent populations.

We calculated net rates of evolution separating pairs of populations that belong to single lineages. For all intervals of time, the distribution of differences between population means for individual variables is remarkably similar to a comparable distribution representing the comparison of pairs of conspecific Recent populations from separate geographic regions. Because morphologic differences between populations do not vary greatly with evolutionary time, measured “rates” of evolution, on the average, decrease with interval of measurement. Because these differences resemble intraspecific variability, however, the rates do not represent significant evolution. Evolution has followed a weak zigzag course, yielding only trivial net trends.

The weak and reversible “trends” that we measured yield net rates averaging less than 10 millidarwins, which is much lower than most rates previously reported for marine invertebrates (average ~200 millidarwins for a 1 ma interval and ~60 millidarwins for a 10 ma interval). We attribute this disparity (1) to the fact that most previously published rates have been calculated when a significant amount of evolution was recognized in advance (often for a poorly documented lineage) and (2) to the fact that most measured variables have represented nothing more than some measure of body size. We conclude that shape, as opposed to size, has been highly stable in bivalve evolution over millions of years and 106–107 generations. We conclude that to characterize rates or evolution for any group of organisms, one must employ a large, unbiased sample of measurements for numerous well-documented lineages, and one must segregate data depicting shape from data depicting size.

Type
Articles
Information
Paleobiology , Volume 13 , Issue 2 , Spring 1987 , pp. 113 - 139
Copyright
Copyright © The Paleontological Society 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Literature Cited

Akers, W. H. 1972. Planktonic foraminifera and biostratigraphy of some Neogene formations, Northern Florida and Atlantic coastal plain. Tulane Stud. Geol. Paleontol. 9:1–139.Google Scholar
Akers, W. H. 1974. Age of Pinecrest Beds, South Florida. Tulane Stud. Geol. Paleontol. 11:103–104.Google Scholar
Bender, M. L. 1973. Helium-uranium dating of corals. Geochim. Cosmochim. Acta. 37:1229–1247.Google Scholar
Blackwelder, B. W. 1981. Later Cenozoic stages and Molluscan zones of the U.S. middle Atlantic coastal plain. Paleontol. Soc. Mem. 12:1–34.Google Scholar
Cheetham, A. H. 1986. Tempo of evolution in a Neogene bryozoan: rates of morphologic change within and across species boundaries. Paleobiology. 12:190–202.Google Scholar
Dall, W. H. 1895. Tertiary fauna of Florida. Trans. Wagner Free Inst. Sci. Philadelphia. Vol. 3, pt. III, pp. 484–947.Google Scholar
Eldredge, N. and Gould, S. J. 1972. Punctuated equilibria: an alternative to phyletic gradualism. Pp. 82–115. In: Schopf, T. J. M., ed. Models in Paleobiology Freeman Cooper; San Francisco.Google Scholar
Fisher, R. A. 1930. The Genetical Theory of Natural Selection. 291 pp. Oxford Univ. Press; Oxford.Google Scholar
Gingerich, P. D. 1983. Rates of evolution: effects of time and temporal scaling. Science. 222:159–161.CrossRefGoogle ScholarPubMed
Gould, S. J. 1984. Smooth curve of evolutionary rate: a psychological and mathematical artifact. Science. 226:994–995.CrossRefGoogle Scholar
Haldane, J. B. S. 1949. Suggestions as to quantitative measurement of rate of evolution. Evolution. 3:51–56.Google Scholar
Hallam, A. 1975. Evolutionary size increase and longevity in Jurassic bivalves and ammonites. Nature. 285:493–496.Google Scholar
Hallam, A. 1978. How rare is phyletic gradualism and what is its evolutionary significances? Evidence from Jurassic bivalves. Paleobiology. 4:16–25.Google Scholar
Krishtalka, L. and Stucky, R. K. 1985. Revision of the Wind River faunas, Early Eocene of Central Wyoming. Pt. 7. Revision of Diacodexis (Mammalia, Artiodactyla). Ann. Carnegie Mus. 54:413–486.CrossRefGoogle Scholar
Lerman, A. 1965. On rates of evolution of unit characters and character complexes. Evolution. 19:16–25.Google Scholar
Lohmann, G. P. 1983. Eigenshape analysis of microfossils: a general morphometric procedure for describing changes in shape. Math. Geol. 15:659–672.Google Scholar
Malmgren, B. A. and Kennett, J. P. 1981. Phyletic gradualism in a Late Cenozoic planktonic foraminiferal lineage; DSDP site 284, Southwest Pacific. Paleobiology. 7:230–240.Google Scholar
Mather, P. M. 1976. Computational Methods of Multivariate Analysis in Physical Geography. 532 pp. Wiley; New York.Google Scholar
Maynard Smith, J. 1981. Macroevolution. Nature. 289:13–14.Google Scholar
Mayr, E. 1970. Populations, Species and Evolution. 797 p. Harvard Univ. Press; Cambridge, Mass.Google Scholar
Petuch, E. J. 1982. Notes on the molluscan paleoecology of the Pinecrest Beds at Sarasota, Florida with the description of Pyruella, a stratigraphically important new genus (Gastropoda: Melongenidae). Proc. Acad. Nat. Sci. Philadelphia. 134:12–30.Google Scholar
Pimentel, R. 1979. Morphometrics: The Multivariate Analysis of Biological Data. 276 pp. Kendall/Hunt Publishing Co.; Iowa.Google Scholar
Raffi, S., Stanley, S. M., and Marasti, R. 1985. Biogeographic patterns and Plio-Pleistocene extinction of Bivalvia in the Mediterranean and southern North Sea. Paleobiology. 11:368–389.Google Scholar
Schopf, T. J. M. 1982. A critical assessment of punctuated equilibria. I. Duration of taxa. Evolution. 36:1147–1157.Google Scholar
Schopf, T. J. M. 1984. Rates of evolution and the notion of “living fossils.” Ann. Rev. Earth Planet. Sci. 12:215–292.Google Scholar
Siegel, A. F. and Benson, R. H. 1982. A robust comparison of biological shapes. Biometrics. 38:341–350.Google Scholar
Stanley, S. M. 1970. Relation of shell form to life habits in the Bivalvia (Mollusca). Geol. Soc. Am. Mem. 125. 296 pp.Google Scholar
Stanley, S. M. 1975. Why clams have the shape they have: an experimental analysis of burrowing. Paleobiology. 1:48–58.Google Scholar
Stanley, S. M. 1979. Macroevolution: Pattern and Process. 332 pp. W. H. Freeman; San Francisco.Google Scholar
Stanley, S. M. 1981. Infaunal survival: alternative functions of shell ornamentation in the Bivalvia (Mollusc). Paleobiology. 7:384–393.CrossRefGoogle Scholar
Stanley, S. M. 1982. Macroevolution and the fossil record. Evolution. 36:460–473.Google Scholar
Stanley, S. M. 1985. Rates of evolution. Paleobiology. 11:13–26.CrossRefGoogle Scholar
Stanley, S. M. 1986. Anatomy of a regional mass extinction: Plio-Pleistocene decimation of the western Atlantic bivalve fauna. Palaios. 1:17–36.Google Scholar
Van Valen, L. 1974. Two modes of evolution. Nature. 252:298–300.Google Scholar
Vokes, H. E. 1972. On the presence of Acopagia (Johnsonella) fausta (Pulteney), with observations on that species. Tulane Stud. Geol. Paleontol. 10:34–40.Google Scholar
Wright, S. 1931. Evolution in Mendelian populations. Genetics. 16:97–159.Google Scholar
Wright, S. 1977. Evolution and the Genetics of Populations. Vol. 3. Experimental Results and Evolutionary Deduction. 613 pp. Univ. Chicago Press; Chicago.Google Scholar