The Contribution of Regional Variability to Beta Diversity: A Case Study of the Deep-water Marine Communities of the Middle Upper Ordovician of Eastern Laurentia

Open Access
Perkons, Eriks
Graduate Program:
Master of Science
Document Type:
Master Thesis
Date of Defense:
February 18, 2016
Committee Members:
  • MARK E PATZKOWSKY, Thesis Advisor
  • Peter Daniel Wilf, Thesis Advisor
  • Michael Allan Arthur, Thesis Advisor
  • Paleontology
  • Paleoecology
  • Geobiology
  • Ordovician
  • Trenton
  • Gradient
  • Biofacies
  • Beta diversity
  • Salona
  • Coburn
The structure and recurrence of marine invertebrate communities along depth gradients have been recent and productive research subjects among paleobiologists studying evolutionary patterns and biostratigraphic correlation. However, the extent to which these communities vary across regional spatial scales (beta diversity) has received comparatively little attention despite being a potential source for the observed increase in gamma diversity through the Paleozoic. The fauna of the middle Upper Ordovician Salona and Coburn Formations of the Trenton group carbonates were investigated to quantitatively study community compositions along a deep subtidal to offshore gradient. The deep subtidal through offshore biofacies have previously been under-sampled, so detailed examination of these strata provides much needed quantitative community data. High resolution (5 cm scale) stratigraphic analysis, coupled with extensive fossil collection from several exposures in central Pennsylvania, allows for identification of biofacies through cluster analysis, and faunal depth preferences through detrended correspondence analysis (DCA). These biofacies, and the ecologic preferences of their taxa, were then compared with previously reported collections from the Trenton Falls area of New York, and central Kentucky near Frankfort. While several comparable biofacies were identified, most did not have obvious counterparts in other collections. Those that were comparable varied greatly between locales, despite a high degree of taxonomic overlap. Ecological parameters of individual taxa were similarly not highly conserved, and all three locales contained numerous endemic taxa. Taxonomic dissimilarity between locations increases with greater geographic distance. Variations occurred over regional geographic scales, but not all correlate directly with distance, suggesting that regional and local variation may be a potential underappreciated source of diversity within provinces.