PHENOTYPIC VARIATION AND ENVIRONMENTAL HIERARCHY IN THE BRYOZOAN ELECTRA PILOSA L

The phenotype of an individual organism can be partitioned into the portion that is controlled by its genetic composition and the portion attributable to the environmental conditions under which it grew. Variation in physical environmental factors (and their interaction with the genotype) can affect the degree of phenotypic variation within and among closely related populations. Environmentally controlled variation can have implications for species-level taxonomic distinctions. The purpose of this study was to evaluated the degree to which phenotypic variation (five morphometric characters) is induced by hierarchical spatial variation (scale 50 cm to 300 km) correlates with morphologic variation in a single extant species (Electra pilosa L.) in modern inter-tidal settings. Completely random nested analysis of variance was used to access these questions. Relationships among environmental and phenotypic variation can be observed graphically in principal component analyses. Results are summarized. 1). More systematic variation occurs within colonies than among colonies at a single locality (due to packing, growth and ultra-microenvironmental variation). 2). More variation occurs over small spatial scales (50 cm) than at mid-scale (10 m to 1 km) or large scale (20 to 300 km). This is most likely due to differences among individual genotypes, but could also reflect microenvironmental variation. 3). Virtually no systematic variation occurs among specimens at the 10 m to 1 km scale (i.e., no systematic variation within facies). 4). A small, but significant amount of systematic variation occurs among widely dispersed sample localities. Differences are attributable to environmental difference (wave-dominated vs. protected vs. tidal currents) rather than genetic partitioning among populations. 5). Differences exist between the degrees of significance for characters associated with length versus width of individual zooids and their level in the spatial hierarchy. This study may provide insights for the interpretation of morphological patterns associated with varying scales within and among facies in the paleontolgical record.