Phenotypic Variation In The Bryozoan Leioclema Punctatum (Hall, 1858) From Mississippian Ephemeral Host Microcommunities

ASU Author/Contributor (non-ASU co-authors, if there are any, appear on document)
Steven J. Hageman Ph.D., Professor (Creator)
Appalachian State University (ASU )
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Abstract: The morphologic expression of microenvironmental variation is difficult to document in fossil ecosystems and therefore is poorly understood. However, documentation of environmental sources of variation in the phenotype is essential for meaningful studies of microevolution and speciation. A fossil assemblage from the Mississippian (Valmeyeran) Warsaw Formation near St. Louis, Missouri, provides necessary conditions to evaluate microenvironmentally induced phenotypic variation in the Paleozoic trepostome bryozoan Leioclema punctatum (Hall, 1858). Specimens of L. punctatum, found as fragments in 22 discrete piles, were collected in their entirety from a weathered surface. Each pile contained 20-200+ branch fragments of L. punctatum, which were all originally attached to large, soft-bodied hosts (sponges?). Multiple attachment bases were found in most piles, indicating that 1) multiple L. punctatum colonies (genotypes) are represented in each pile, and 2) each pile represents a near contemporaneous, relatively short-lived microcommunity. Morphological characters were measured (four per section) from two branches for each of two specimens from five separate piles. Results from completely random, nested, one-way ANOVA indicate that no highly significant differences exist among microcommunities or between colonies for any measured characters, but that significant variation exists within colonies and among colonies in the same microcommunity (pile). That is, submicroenvironmental variation, within and among colonies, can play a greater role in morphogenesis than environmental heterogeneity within a given environmental setting (undifferentiated facies). Microenvironmental factors affect the size and shape of mesopores (space-filling structures) more than other morphological characters. Results are encouraging for the general application of the preserved fossil phenotypes as proxies for biological species. This conclusion is based on the absence of systematic variation at microenvironmental levels, measurable here, but not normally distinguishable in paleontological and sedimentological studies.

Additional Information

Steven J. Hageman, Jennifer A. Sawyer. Phenotypic variation in the bryozoan Leioclema punctatum (Hall, 1858) from Mississippian ephemeral host microcommunities. Journal of Paleontology. 2006;80(6):1047-1057. doi:10.1666/0022-3360(2006)80[1047:PVITBL]2.0.CO;2. Publisher version of record available at:
Language: English
Date: 2006
biometry, Bryozoa, Leioclema punctatum, Mississippian, morphology, principal components analysis, phenotypes

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