A test of environmental and paleocommunity stability within the Ambocoelia-Chonetes biofacies
Zambito, James Joseph, IV
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The coordinated stasis hypothesis suggests that biofacies are stable ecological units which track a preferred habitat such that species resist morphological change. A community's inability to track its preferred habitat results in geologically rapid turnover in which speciation and community reorganization occurs. This study focuses on the appropriate sampling and statistical regimes for comparing Ambocoelia-Chonetes biofacies compositions, and then, tests the hypothesis of habitat tracking. This case study demonstrates that a sampling effort accounting for within-outcrop patchiness is adequate for testing differences in sample composition across a basinal gradient. Multinomial models are recommended for analyzing bulk sample data as they determine the relative likelihood of competing hypotheses of population distributions; ANOSIM determines the significance of a single clustering against a null hypothesis of lack-of-structure. Habitat tracking by this biofacies through several sea level cycles is shown to be both statistically significant and more likely than temporal changes in community membership.