58-14 Assessing the environmental forces that shape the distribution of past species invasions to inform future projections

Session: Future Leaders in Paleontology

Presenting Author:

Authors:

Abstract:

The Pacific coast in southern California hosts rich biodiversity due to its complex oceanography and geographic variability, making it susceptible to climate-related perturbations such as species migration, range shifts, and extinctions. The sedimentary deposits of southern California contain valuable paleoecological records from glacial-interglacial cycles, revealing how past climatic shifts affected shallow marine benthic communities. Thermally anomalous species (extralimital) in the fossil records can indicate pre-anthropogenic (baseline) species invasion in response to warming and cooling cycles. Understanding the patterns of invasion during the last interglacial period—driven by natural climate variations—can provide valuable insights for monitoring these species under future warming conditions.

Our results indicate that nearly 20% of the ~800 species of mollusks known from the Late Pleistocene of southern California are represented by thermally anomalous occurrences, and can therefore be considered potential invaders. These extralimital occurrences include both warm- and cold-water species, although the former are more species-rich, frequent, and abundant. This is not surprising as the late Pleistocene includes both warm and cold climate perturbations. The spatial distribution of these extralimitals is notably patchy, reflecting the influence of a range of environmental conditions (e.g., temperature gradients, shelf exposure, substrate type). Our results include map-based depictions of habitat availability on both Pleistocene and modern coastlines. The distribution of rocky and soft-bottom habitats and wave exposure are heterogeneous through southern California. Similarly a strong temperature gradient dominates this region, but this was complicated by the presence of sheltered basins and embayments. Warm-water extralimital occurrences are concentrated within these sheltered (soft-bottom) regions, while cold-water extralimitals are more frequent in exposed (rocky) habitats.  Collectively these factors offer insight into why certain regions may have served as refugia for invaders in the past. These findings enhance our ability to identify and predict those taxa that will migrate, and particular geographic areas that will be impacted, under ongoing and future climate change.

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

doi: 10.1130/abs/2025AM-9427

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