COMPARING FUNCTIONAL SPACE DURING THE RICHMONDIAN INVASION (LATE ORDOVICIAN) USING A MULTIFACETED FUNCTIONAL DIVERSITY APPROACH

Invasions are becoming more common as modern sea temperatures rise and biogeographical barriers break down. During the Late Ordovician (Katian), the fossil record provides a record of biotic interactions and can be used to understand the impacts of biotic invasion on ecosystem structure and functioning over evolutionary timescales. Functional traits are at the forefront of modern ecology research as they are linked to ecosystem processes (e.g., nutrient cycling and sediment transport). Here we examine 1,279 species from shallow benthic marine communities of the Cincinnati Arch (USA) to quantify the effects of non-native species on functional space. Species were grouped by common functional traits readily identifiable in fossil taxa: living habit, tiering, and feeding mode. Changes in functional space were quantified across six stratigraphic sequences using multivariate analyses of functional diversity comparing C2 (pre-invasion) and C7 (post-invasion). Both the C2 and C7 functional space overlaps entirely suggesting that invaders occupy pre-existing functional space and perform similar functions to incumbents. Functional richness decreased from C2 to C7 (0.89 to 0.68) across the invasion. In addition, functional evenness decreased slightly from 0.074 in C2 to 0.064 in C7. This is consistent with functional homogenization with less functional diversity overall post invasion. These results are consistent with previous work documenting niche packing caused by the invasion, which has important implications for predicting the long-term effects of modern invasions.