58-3 Changes in Multivariate Functional Space across the Richmondian Invasion in the Cincinnati Arch (Late Ordovician)

Session: Future Leaders in Paleontology

Presenting Author:

Madeline Ess

Authors:

Ess, Madeline P.¹, Banker, Roxanne M.W.², Maciech, Samantha³, Dineen, Ashley A.⁴, Roopnarine, Peter D.⁵, Tyler, Carrie L.⁶

(1) Miami University, Oxford, OH, USA, (2) Providence College, Providence, RI, USA, (3) UNLV, North Las Vegas, NV, USA, (4) UC Museum of Paleontology, Berkeley, CA, USA, (5) California Academy of Sciences, Invertebrate Zoology & Geology, San Francisco, CA, USA, (6) University of Nevada, Las Vegas, NV, USA,

Abstract:

Rising temperatures and globalization are enabling widespread biotic invasions in our world today, particularly in marine environments as biogeographical barriers break down. The fossil record can be used to assess the impacts of past invasions on ecosystem structure and functioning on evolutionary timescales to better manage invasions today. Here we use 1,273 species from benthic marine communities of the Cincinnati Arch (USA) to quantify the effects of non-native species on multivariate functional space during the Late Ordovician (Katian) Richmondian Invasion. Species from two 3rd order stratigraphic sequences, the pre-invasion C2 community to the post-invasion C7 community, were assigned five common functional traits: living habit, tiering, feeding mode, attachment method, and trophic rank. Traits were used to assess changes in multidimensional functional space across the invasion by quantifying functional richness, functional dispersion, and functional evenness. Functional richness declined from 0.887 to 0.746, suggesting a contraction in the breadth of occupied functional space, likely reflecting a loss of functionally unique taxa. Functional evenness remained low and effectively unchanged (0.049 to 0.048), indicating persistent clustering of taxa around certain trait combinations. In contrast, functional dispersion increased from 0.247 to 0.333, pointing to a rise in the overall spread of species around the community trait centroid. This suggests that although the overall functional richness decreased, the traits of the taxa that invaded or persisted across the invasion became more dissimilar, possibly reflecting the introduction or evolution of novel functional types after the invasion. Between C2 and C7 there were repeated influxes of invaders. However, invaders were likely occupying existing functional space upon arrival and may have outcompeted and replaced incumbents during establishment and integration, or adapted better to the changing conditions. These results are consistent with previous work documenting niche packing as a result of the invasion and suggest that this process did not lead to community-wide structural changes, bearing important implications for predicting the long-term effects of modern invasions. Despite changes in community composition, the Richmondian Invasion may not have substantially restructured the ecosystems, as we observed little change in multidimensional hyperspace. This emphasizes the importance of quantifying functional diversity in assessing the potential ecological impacts of marine invasions today. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9092

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