| Popis: |
Type Cincinnatian strata are among the best preserved Upper Ordovician deposits in the world and record a range of depositional environments as well as various biotic and abiotic changes, making them an ideal natural laboratory in which to study biotic and abiotic processes. The most substantial biotic change in the Type Cincinnatian Series is abiotic invasion known as the Richmondian Invasion. The first pulse of the Richmondian Invasion is referred to as the Clarksville Phase (Aucoin and Brett, 2016) and is the focal point of this study which quantifies the impact the Clarksville Phase had on the ecology and diversity of the fauna of the Cincinnati basin. A suite of methods were employed to quantify the invader impact including detrended correspondence analysis, cluster analysis, rarefaction, Simpson’s index of dominance, guild analysis, and comparison of environmental preferences and tolerances through time. Results indicate the Clarksville Phase had numerous impacts on the fauna of the Cincinnati Sea including modification of occupied habitat, ecospace utilization, gradient structure, community structure, community composition, and biodiversity. Habitat occupation changed considerably following the introduction of the invaders with taxa shifting both their environmental tolerances and preferences. Ecospace utilization shifted as previously low diversity guilds were filled out with novel taxa. Faunal differentiation across the depth gradient increased with the introduction of the invaders. Generic richness increased within the basin, generic evenness decreased, and community composition became more complex. The results of this study contribute to our understanding of the Richmondian Invasion and our general understanding of earth history as well as provide new insights about the potential long term ecological and biodiversity impacts of biotic invasions today. |
