Hostname: page-component-8448b6f56d-t5pn6 Total loading time: 0 Render date: 2024-04-24T07:34:37.164Z Has data issue: false hasContentIssue false
  • English
  • Français

Observed phenotypic variation in a Paleozoic bryozoan

Published online by Cambridge University Press:  08 February 2016

Steven J. Hageman
Steven J. Hageman*
Affiliation:
Department of Geology and Geophysics, University of Adelaide, South Australia 5005
Get access Rights & Permissions [Opens in a new window]

Abstract

Documentation of morphologic variation within and among fossil species (and larger clades) provides fundamental data needed for studies of evolution, paleoecology, and the systematic foundation required for most fields of paleobiology. In paleontological (and, frequently, biological) studies, morphologic variation is used as a general proxy for genetic variation. Although the occurrence of ecophenotypic variation is well appreciated in these studies, it is only with the use of colonial (clonal) organisms that the scope and significance of phenotypic variation can be evaluated directly. Systematic evaluation of intracolonial morphologic variation (transects through growth series) can yield insights about ecophenotypic variation in bryozoans and suggest the most appropriate methods for data collection in paleobiologic and taxonomic studies.

In this study, morphological conservatism is documented within local segments of bryozoan colonies; each zooid is generally more similar to adjacent zooids than to distant zooids within the same colony. One region of a colony, therefore, can be more similar to a region of a different colony than to a distant region of its own colony. Variation within one colony does not, however, represent the total variation among a group of specimens, indicating a colonial level of morphologic control (genetic or macroenvironmental) over morphogenesis. Directional morphogenetic gradients (associated with successive ontogenetic histories) are not recognized in these specimens, but fluctuating trends within colonies (some cyclic), were observed and are indicative of changing microenvironmental influence during skeletal formation. In order to best document morphologic variation within a population, for any type of paleobiological study, individual measurements should be widely distributed over large colony fragments and (or) a minimal number of measurements collected from each of a large number of smaller fragments.

Direct extrapolation of these results to non-colonial organisms is not appropriate at this time. However, additional, related studies with bryozoans and other colonial organisms (e.g., corals, graptolites), should provide a greater, general appreciation of relationships between morphology and genetics.

Type
Articles
Information
Paleobiology , Volume 21 , Issue 3 , Summer 1995 , pp. 314 - 328
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

Abbott, M. B. 1973. Intra- and intercolony variation in populations of Hippoporina neviani (Bryozoa-Cheilostomata). Pp. 223–245in Boardman, R. S. and Cheetham, A. H., eds. Animal colonies. Development and function through time. Dowden, Hutchinson & Ross, Stroudsburg, Penn.Google Scholar
Anstey, R. L., Pachut, J. F., and Prezbindowski, D. R. 1976. Morphogenetic gradients in Paleozoic bryozoan colonies. Paleobiology 2:131–146.CrossRefGoogle Scholar
Boardman, R. S. 1954. Morphologic variation and mode of growth in Devonian trepostomatous Bryozoa. Science 120:322–323.CrossRefGoogle ScholarPubMed
Boardman, R. S., and Cheetham, A. H. 1983. Glossary of morphological terms. Pp. 304–320in Robison, R. A., ed. Treatise on invertebrate paleontology, part G, Bryozoa revised. Geological Society of America and University of Kansas, Lawrence.Google Scholar
Boardman, R. S., Cheetham, A. H., and Cook, P. L. 1970. Intracolony variation and the genus concept in Bryozoa. Pp. 294–320in Yochelson, E. L., ed. Proceedings of the North American Paleontological Convention, September 1969, Part C, Chicago.Google Scholar
Boardman, R. S., Cheetham, A. H., and Cook, P. L. 1983. Introduction to the Bryozoa. Pp. 3–49in Robison, R. A., ed. Treatise on invertebrate paleontology, Part G, Bryozoa revised. Geological Society of America and University of Kansas, Lawrence.Google Scholar
Brande, S., and Bretsky, S. S. 1982. Avoid improper statistical analysis in bryozoans: analysis of variance is suitable for study of hierarchical variation. Journal of Paleontology 56:1207–1212.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.CrossRefGoogle Scholar
Cheetham, A. H., Jackson, J. B. C., and Hayek, L. C. 1993. Quantitative genetics of bryozoan phenotypic evolution. I. Rate tests for random change versus selection in differentiation of living species. Evolution 47:1526–1538.CrossRefGoogle ScholarPubMed
Cheetham, A. H., Jackson, J. B. C., and Hayek, L. C. 1994. Quantitative genetics of bryozoan phenotypic evolution. II. Analysis of selection and random change in fossil species using reconstructed genetic parameters. Evolution 48:360–375.CrossRefGoogle ScholarPubMed
Cheetham, A. H., Jackson, J. B. C., and Hayek, L. C.In press. Quantitative genetics of bryozoan phenotypic evolution. III. Phenotypic plasticity and the maintenance of genetic variation. Evolution.Google Scholar
Foster, A. B. 1984. The species concept in fossil hermatypic corals: a statistical approach. Palaeontographica Americana 34:58–69.Google Scholar
Foster, A. B. 1985. Variation within coral colonies and its importance for interpreting fossil species. Journal of Paleontology 59:1359–1381.Google Scholar
Gabb, W. M., and Horn, M. D. 1862. Monograph of the fossil Polyzoa of the Secondary and Tertiary formations of North America. Journal of the Academy of Natural Sciences of Philadelphia, new series V.Google Scholar
Hageman, S. J. 1991. Approaches to systematic and evolutionary studies of perplexing groups: an example using fenestrate Bryozoa. Journal of Paleontology 65:630–647.CrossRefGoogle Scholar
Hageman, S. J. 1993. Effects of nonnormality on studies of morphological variation of a rhabdomesine bryozoan, Streblotrypa (Streblascopora) prisca (Gabb and Horn). University of Kansas Paleontological Contributions new series no. 4.Google Scholar
Hageman, S. J. 1994. Microevolutionary implications of clinal variation in the Paleozoic bryozoan Streblotrypa. Lethaia 27:209–222.CrossRefGoogle Scholar
Holdener, E. J.In press. Numerical taxonomy of fenestrate bryozoans: evaluation of methodology and applicability to analyses of microevolution. Journal of Paleontology.Google Scholar
Jackson, J. B. C., and Cheetham, A. H. 1990. Evolutionary significance of morphospecies: a test with cheilostome Bryozoa. Science 248:579–583.CrossRefGoogle ScholarPubMed
Key, M. M. Jr. 1987. Partition of morphologic variation across stability gradients in Upper Ordovician trepostomes. Pp. 145–152in Ross, J. R. P., ed. Bryozoa: present and past. Western Washington University, Bellingham.Google Scholar
Lidgard, S., and Buckley, G. A. 1994. Toward a morphological species concept in cheilostomes: phenotypic variation in Adeonellopsis yarraensis (Waters). Pp. 101–105in Ryland, J. and Hayward, P., eds. Biology and palaeobiology of bryozoans.Google Scholar
McKinney, F. K., and Boardman, R. S. 1985. Zooidal biometry of Stenolaemata. Pp. 193–203in Nielsen, C. and Larwood, G. P. eds. Bryozoa: Ordovician to Recent. Olsen and Olsen, Fredensborg, Denmark.Google Scholar
McKinney, F. K., Taylor, P. D., and Zullo, V. A. 1993. Lyreshaped hornerid bryozoan colonies: homeomorphy in colony form between Paleozoic Fenestrata and Cenozoic Cyclostomata. Journal of Paleontology 67:343–354.CrossRefGoogle Scholar
Pachut, J. F. 1982. Morphologic variation within and among genotypes in two Devonian bryozoan species: an independent indicator of paleostability. Journal of Paleontology 56:703–716.Google Scholar
Pachut, J. F., Cuffey, R. J., and Anstey, R. L. 1991. The concepts of astogeny and ontogeny in stenolaemate bryozoans, and their illustration in colonies of Tabulipora carbonaria from the Lower Permian of Kansas. Journal of Paleontology 65:213–233.CrossRefGoogle Scholar
Schopf, T. J. M. 1976. Environmental versus genetic causes of morphologic variability in bryozoan colonies from the deep sea. Paleobiology 2:156–165.CrossRefGoogle Scholar
Snyder, E. M. 1991. Revised taxonomic procedures and paleoecological applications for some North American Mississippian Fenestellidae and Polyporidae (Bryozoa). Palaeontographica Americana 57:1–351.Google Scholar
Taylor, P. D. 1988. Colony growth pattern and astogenetic gradients in the Cretaceous cheilostome bryozoan Herpetopora. Palaeontology 31:519–541.Google Scholar
Taylor, P. D., and Furness, R. W. 1978. Astogenetic and environmental variation of zooid size within colonies of Jurassic Stomatopora (Bryozoa, Cyclostomata). Journal of Paleontology 52:1093–1102.Google Scholar
Winston, J. E. 1977. Feeding in marine bryozoans. Pp. 233–271. in Woollacott, R. M. and Zimmer, R. L., eds. The biology of bryozoans. Academic Press, New York.CrossRefGoogle Scholar
Winston, J. E. 1978. Polypide morphology and feeding behavior in marine ectoprocts. Bulletin of Marine Science 28:1–31.Google Scholar
Winston, J. E. 1981. Feeding behavior of modern bryozoans. Pp. 1–21in Broadhead, T. W., ed. Lophophorates: notes for a short course. University of Tennessee Department of Geological Sciences Studies in Geology 5.Google Scholar
Zar, J. 1984. Biostatistical analysis. Prentice-Hall, Englewood Cliffs, New Jersey.Google Scholar