ASSESSING THE PHENOTYPE

Systematic paleontology is largely based on the assumption that preservable skeletal hard parts serve as a proxy for biological species. An understanding of the relationships between genetic and environmental sources of morphological variation is essential for meaningful application of species concepts to broader studies of paleobiology. The degree to which variation in physical environmental factors can affect the phenotype within and among closely related populations can help shape fossil species concepts.

Methods applied in modern analyses of morphology and variation have their roots in the 1960's movement toward quantification in paleontology, typified by the school of “numerical taxonomy.” Although purely phenetic classifications are no longer considered adequate in phylogentic studies, the methods of selecting and treating morphological characters and the application of advanced statistical methods, especially ordination and variance-covariance, serve as the starting point for modern morphometric and analysis of phenotypic variation.

The hierarchical influence of large and small scale environmental variation on skeletal morphology of the anascan bryozoan Electra pilosa L. is evaluated in modern populations through hierarchical scales of environmental variation (50 cm to 300 km). Completely random nested analysis of variance was used to assess sources of phenotypic variation. Relationships are observed graphically with principal component analyses. Results suggest that more systematic variation occurs within colonies than among colonies at a single locality (ultra-microenvironmental differences and packing constraints). More variation occurs among colonies over small spatial scales (50 cm) than at mid-scale (10m to 1km) or large scale (20 to 300 km). It is likely that this small scale variation reflects genotypic differences among colonies. No systematic variation was observed among colonies at the 10 m to 1 km scale (i.e. no systematic variation within sedimentary facies). Small, but significant differences were recognized among specimens at the 20 to 300 km scale (among facies)are attributed to extremes of wave dominated to protected environments.