Quantitative Paleobiogeographic Analysis of Habitat Tracking Patterns in the Cincinnati Arch Following the Late Ordovician Richmondian Invasion

The C5 sequence (Late Ordovician) in the Cincinnati region (Indiana, Kentucky, Ohio) records basin wide ecologic changes following the introduction of invader taxa from Canada and the Western United States occurred at the onset of the Richmondian stage. The goal of this project is to assess paleobiogeographic patterns of native and invasive brachiopod species across three time intervals in the sequence. Hypotheses to tested are 1) if brachiopod species track their preferred environments as sea level falls and facies belts shift 2) if species maintain constant geographic range size during sea level change. 3) if statistical differences in habitat tracking or range size exist between native vs. invasive taxa. Analyses are conducted using ecological niche modeling (ENM) to model species' ranges based on environmental parameters.

Two sets of data are used for analysis: 1) species occurrences, 2) environmental parameters. Data were collected from literature, museum collections, and targeted field work to ensure even data coverage in areas poorly represented in museum or literature sources. Estimates of the fundamental niche for individual brachiopod species were modeled using the ENM program GARP. GARP identifies non-random associations between species occurrence and environmental variables, creates a rule set for an environmental parameter, and then tests each rule through an iterative process to determine the statistically best niche model. Estimated niches are projected into geographic space using ArcGIS, and ranges are quantified with Spatial Analyst.

Statistically significant patterns of brachiopod habitat tracking and range size shifts were recovered. Analyses of the differential response of native and invasive brachiopod species of the C5 sequence can provide a better understanding of the long term impact of invasive species. These results may have implications for understanding how modern shallow marine benthic organisms will track their environments as they shift due to climatic variability and human-induced environmental changes.