Skip to main content Accessibility help

Observed phenotypic variation in a Paleozoic bryozoan

  • Steven J. Hageman (a1)


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.



Hide All
Abbott, M. B. 1973. Intra- and intercolony variation in populations of Hippoporina neviani (Bryozoa-Cheilostomata). Pp. 223245in Boardman, R. S. and Cheetham, A. H., eds. Animal colonies. Development and function through time. Dowden, Hutchinson & Ross, Stroudsburg, Penn.
Anstey, R. L., Pachut, J. F., and Prezbindowski, D. R. 1976. Morphogenetic gradients in Paleozoic bryozoan colonies. Paleobiology 2:131146.
Boardman, R. S. 1954. Morphologic variation and mode of growth in Devonian trepostomatous Bryozoa. Science 120:322323.
Boardman, R. S., and Cheetham, A. H. 1983. Glossary of morphological terms. Pp. 304320in Robison, R. A., ed. Treatise on invertebrate paleontology, part G, Bryozoa revised. Geological Society of America and University of Kansas, Lawrence.
Boardman, R. S., Cheetham, A. H., and Cook, P. L. 1970. Intracolony variation and the genus concept in Bryozoa. Pp. 294320in Yochelson, E. L., ed. Proceedings of the North American Paleontological Convention, September 1969, Part C, Chicago.
Boardman, R. S., Cheetham, A. H., and Cook, P. L. 1983. Introduction to the Bryozoa. Pp. 349in Robison, R. A., ed. Treatise on invertebrate paleontology, Part G, Bryozoa revised. Geological Society of America and University of Kansas, Lawrence.
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 56:12071212.
Cheetham, A. H. 1986. Tempo of evolution in a Neogene bryozoan: rates of morphologic change within and across species boundaries. Paleobiology 12:190202.
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 47:15261538.
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 48:360375.
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.
Foster, A. B. 1984. The species concept in fossil hermatypic corals: a statistical approach. Palaeontographica Americana 34:5869.
Foster, A. B. 1985. Variation within coral colonies and its importance for interpreting fossil species. Journal of Paleontology 59:13591381.
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.
Hageman, S. J. 1991. Approaches to systematic and evolutionary studies of perplexing groups: an example using fenestrate Bryozoa. Journal of Paleontology 65:630647.
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.
Hageman, S. J. 1994. Microevolutionary implications of clinal variation in the Paleozoic bryozoan Streblotrypa. Lethaia 27:209222.
Holdener, E. J.In press. Numerical taxonomy of fenestrate bryozoans: evaluation of methodology and applicability to analyses of microevolution. Journal of Paleontology.
Jackson, J. B. C., and Cheetham, A. H. 1990. Evolutionary significance of morphospecies: a test with cheilostome Bryozoa. Science 248:579583.
Key, M. M. Jr. 1987. Partition of morphologic variation across stability gradients in Upper Ordovician trepostomes. Pp. 145152in Ross, J. R. P., ed. Bryozoa: present and past. Western Washington University, Bellingham.
Lidgard, S., and Buckley, G. A. 1994. Toward a morphological species concept in cheilostomes: phenotypic variation in Adeonellopsis yarraensis (Waters). Pp. 101105in Ryland, J. and Hayward, P., eds. Biology and palaeobiology of bryozoans.
McKinney, F. K., and Boardman, R. S. 1985. Zooidal biometry of Stenolaemata. Pp. 193203in Nielsen, C. and Larwood, G. P. eds. Bryozoa: Ordovician to Recent. Olsen and Olsen, Fredensborg, Denmark.
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 67:343354.
Pachut, J. F. 1982. Morphologic variation within and among genotypes in two Devonian bryozoan species: an independent indicator of paleostability. Journal of Paleontology 56:703716.
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 65:213233.
Schopf, T. J. M. 1976. Environmental versus genetic causes of morphologic variability in bryozoan colonies from the deep sea. Paleobiology 2:156165.
Snyder, E. M. 1991. Revised taxonomic procedures and paleoecological applications for some North American Mississippian Fenestellidae and Polyporidae (Bryozoa). Palaeontographica Americana 57:1351.
Taylor, P. D. 1988. Colony growth pattern and astogenetic gradients in the Cretaceous cheilostome bryozoan Herpetopora. Palaeontology 31:519541.
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 52:10931102.
Winston, J. E. 1977. Feeding in marine bryozoans. Pp. 233271. in Woollacott, R. M. and Zimmer, R. L., eds. The biology of bryozoans. Academic Press, New York.
Winston, J. E. 1978. Polypide morphology and feeding behavior in marine ectoprocts. Bulletin of Marine Science 28:131.
Winston, J. E. 1981. Feeding behavior of modern bryozoans. Pp. 121in Broadhead, T. W., ed. Lophophorates: notes for a short course. University of Tennessee Department of Geological Sciences Studies in Geology 5.
Zar, J. 1984. Biostatistical analysis. Prentice-Hall, Englewood Cliffs, New Jersey.

Related content

Powered by UNSILO

Observed phenotypic variation in a Paleozoic bryozoan

  • Steven J. Hageman (a1)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed.