58-2 The Effects of Invasive Species on Late Ordovician Shallow Marine Food Web Structure During the Richmondian Invasion

Session: Future Leaders in Paleontology

Presenting Author:

Samantha Maciech

Authors:

Maciech, Samantha A.¹, Ess, Madeline P.², Banker, Roxanne M.W.³, Dineen, Ashley A.⁴, Roopnarine, Peter D.⁵, Tyler, Carrie L.⁶

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

Abstract:

Although invasions can alter fundamental ecosystem properties, such as nutrient cycling and productivity, the effects of invasive species on native communities remain difficult to quantify as neontological data before invasions are rare. However, the fossil record can be used to shed light on the long-term impacts of invasive species on community structure and functioning. The well-defined stratigraphy and excellent fossil preservation in the Cincinnati Arch in Ohio, USA documents the Richmondian Invasion from the Late Ordovician (Katian). The invasion consists of a large influx of invasive species and major changes in species composition over approximately five million years. Here we model 30 species-level food webs for each of the six stratigraphic sequences (C2 through C7) to assess changes in ecosystem structure and functioning across the invasion. We find that invasive species contribute to new trophic groups that change the interaction dynamics between species, and also occupy established trophic groups with incumbent species, potentially leading to competition, displacement, or extinctions. The network trophic position (ntp) of persistent guilds also fluctuated across the invasion, and the mean ntp of species in both C2 and C4 were significantly higher from both mean ntp in C6 and C7 (F = 7.26; p << 0.001), while mean maximum chain length was higher between C2 and C6 (F = 2.48; p = 0.03). Interestingly, increases in trophic position corresponded to longer chain lengths with a positive relationship between mean guild ntp and mean maximum chain length per sequence (R = 0.546 to 0.831; p << 0.001). Differences in trophic structure before and after the invasion suggest that the arrival of invaders altered ecosystem structure and functioning. The integration and establishment of invaders led to trophic contraction and ultimately shorter food chains. Further analysis of the influence of the Richmondian invaders on food web structure will provide modern ecologists better means to predict what will happen to ecosystems experiencing invasive species today.

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

doi: 10.1130/abs/2025AM-8961

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