BIOTIC RESPONSE TO THE CLARKSVILLE PHASE OF THE RICHMONDIAN INVASION: A SYNECOLOGICAL PERSPECTIVE

This study establishes how biodiversity, niche differentiation, ecospace utilization, and community composition were impacted by the first successful phase of the Richmondian Invasion. The Richmondian Invasion has been the subject of many past studies in the Cincinnati Arch Region, which have identified general ecological and evolutionary patterns across the entire invasion interval. However, there were discrete pulses within the larger invasion that have received less attention (e.g. Clarksville Phase), largely due to the temporal constraints of the existing stratigraphic framework. However, recently published sequence stratigraphic revisions by Brett et al. provide a framework for individual invasion pulses to be studied.

The biotic impact of the Clarksville Phase was analyzed using species abundance data collected from the Waynesville Formation. The preinvasion data was collected from the Fort Ancient Member and the post-invasion data was collected from the Clarksville Member. Abundance data were collected for a diverse suite of invertebrate taxa using a quadrat sampling method, in which a 100 cm² quadrant was utilized. Data were analyzed using cluster analysis, detrended correspondence analysis, nonmetric multidimensional scaling, and seriation to establish paleocommunity composition and test for the presence of underlying ecological gradients. Depth distribution of taxa, richness and evenness, and guild membership were also considered.

Clear patterns of community structure change were observed before and after the Clarksville Phase. This analysis has improved our understanding of how the Clarksville Phase impacted the niche parameters of native taxa, community composition and structure, alpha diversity, and ecospace utilization. Understanding how this invasion pulse impacted the biota not only improves our understanding of this event but contributes to our broader knowledge of biotic invasions.