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Implications of intracolonial variation in a Paleozoic bryozoan

  • Eric J. Holdener (a1) and Steven J. Hageman (a2)


Relative differences between environmentally controlled variation and genetically controlled variation are important when investigating morphologic variation in general, especially when establishing species concepts. The colonial nature of bryozoans provides a means for distinguishing between the two sources; variation can be partitioned into within-colony (microenvironmental) and among-colony (environmental + genetic) components. For the Paleozoic order Cryptostomata, biologically and taxonomically significant morphologic characters are well defined and methods for recognizing morphotaxa are well established.

The importance of within-colony variation to the morphometric treatment of fenestrate species was assessed after the discovery of a large specimen of Hemitrypa sp. Variation within the colony was compared to variation among and within two congeneric species. The distribution of study segments across the colony allowed assessment of variation both along the growth axis and laterally between segments of approximately equivalent generational age. Repeatability of methods was assessed using data measured independently from identical segments by three workers.

Variation within the large colony is less than variation among congeneric species, indicating that genetic differences among species exceed variation resulting from combined phenotypic and genotypic sources within species. Neither astogenetic nor ontogenetic morphologic gradients are recognized. Variation between data collected from identical segments by pairs of workers falls within the range of variation for the entire colony. Thus, multiple workers can reproduce data to the finest level of meaningful resolution. Cryptostome morphospecies concepts are validated.

The potential for partitioning genotypic versus environmental variation in reduced, multidimensional morphospace is reinforced. Studies of microevolution and speciation may be designed that account for these factors.



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Anstey, R. L., and Perry, T. G. 1970. Biometric procedures in taxonomic studies of Paleozoic bryozoans. Journal of Paleontology, 44:383398.
Anstey, R. L., Pachut, J. F., and Prezbindowski, D. R. 1976. Morphogenetic gradients in Paleozoic bryozoan colonies. Paleobiology, 2:131146.
Boardman, R. S., Cheetham, A. H., and Cook, P. L. 1983. Introduction to the Bryozoa, p. 348. In Robinson, R. A., (ed.), Treatise on Invertebrate Paleontology, Part G, Bryozoa Revised. The Geological Society of America and the University of Kansas, Boulder, Colorado and Lawrence, Kansas.
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., 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. 1995. Quantitative genetics of bryozoan phenotypic evolution. III. Phenotypic plasticity and the maintenance of genetic variation. Evolution, 49:290296.
Elias, M. K. 1964. Stratigraphy and paleoecology of some Carboniferous bryozoans. Cinquieme Congres International de Stratigraphie et de Geologie du Carbonifere, Compte Rendu, 1:375382.
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 morphologic variation of a rhabdomesine bryozoan, Streblotrypa (Streblascopora) prisca (Gabb and Horn). The University of Kansas Paleontological Contributions, New Series, Number 4, 13 p.
Hageman, S. J. 1994. Microevolutionary implications of clinal variation in the Paleozoic bryozoan Streblotrypa. Lethaia, 27:209222.
Hageman, S. J. 1995. Observed phenotypic variation in a Paleozoic bryozoan. Paleobiology, 21:314328.
Hageman, S. J., and Blake, D. B. 1992. Microenvironmental effects on intracolonial morphology in Bryozoa. Geological Society of America Abstracts with Programs, 24(7):A99.
Holdener, E. H. 1994. Numerical taxonomy of fenestrate bryozoans: evaluation of methodologies and recognition of intraspecific variation. Journal of Paleontology, 68:12011214.
Key, M. M. Jr. 1987. Partitioning of morphological variation across stability gradients in Upper Ordovician trepostomes, p. 145152. In Ross, J. R. P. (ed.), Bryozoa: Present and Past. Western Washington University, Bellingham.
McKinney, F. K. 1980. The Devonian fenestrate bryozoan Utropora Pocta. Journal of Paleontology, 54:241252.
McKinney, F. K., and Boardman, R. S. 1985. Zooidal biometry of Stenolaemata, p. 193203. In Nielsen, C. and Larwood, G. P. (eds.), Bryozoa: Ordovician to Recent. Olsen and Olsen, Fredensborg, Denmark.
McKinney, F. K., and Kriz, J. 1986. Lower Devonian Fenestrata (Bryozoa) of the Prague Basin, Barrandian area, Bohemia, Czechoslovakia. Fieldiana, Geology, New Series, Number 15, 90 p.
McKinney, F. K., and Stedman, T. G. 1981. Constancy of characters within helical portions of Archimedes, p. 151157. In Larwood, G. P. and Nielsen, C. (eds.), Recent and Fossil Bryozoa. Olsen and Olsen, Fredensborg, Denmark.
McKinney, F. K., Taylor, P. D., and Zullo, V. A. 1993. Lyre-shaped hornerid bryozoan colonies: homeomorphy in colony form between Paleozoic Fenestrata and Cenozoic Cyclostomata. Journal of Paleontology, 67:343354.
Miller, T. G. 1962. On Hemitrypa hibernica M'Coy. Geological Magazine, 99:313321.
Neff, N. A., and Marcus, L. F. 1980. A Survey of Multivariate Methods for Systematics. Privately published, New York, 243 p.
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. 1984. Taxonomy, functional morphology, and paleoecology of the Fenestellidae and Polyporidae (Fenestelloidea, Bryozoa) of the Warsaw Formation (Valmeyeran, Mississippian) of the Mississippi Valley. Unpublished , , 802 p.
Snyder, E. M. 1991. Revised taxonomic procedures and paleoecological applications for some North American Mississippian Fenestellidae and Polyporidae (Bryozoa). Palaeontographica Americana, 57, 275 p.
Stedman, T. G. 1982. Astogeny of fenestrate bryozoans and their potential use in biostratigraphy. Unpublished , , 129p.
Stratton, J. F., and Horowitz, A. S. 1977. Astogenetic variability in a frond of Polypora laevinodata (Hall). Proceedings of the Indiana Academy of Sciences, 86:290292.
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, p. 233271. In Woollacott, R. M. and Zimmer, R. L. (eds.), Biology of Bryozoans. Academic Press, New York.

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Implications of intracolonial variation in a Paleozoic bryozoan

  • Eric J. Holdener (a1) and Steven J. Hageman (a2)


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