The (in)consistency of links across traits, species and communities in planktic foraminifera during Plio-Pleistocene climate change

Abstract

This thesis aims to disentangle the roles of biotic and abiotic factors in driving extinction and shaping community dynamics in planktic foraminifera during the Plio-Pleistocene, a period characterised by a notable decline in species richness between 3.9 and 1.032 million years ago. Isolating biotic factors from environmental influences on planktic foraminiferal biodiversity remains challenging due to the complexity of environmental influence, difficulties in detecting biotic interactions from the fossil record, and the varying significance of measurements, even with large sample sizes. These factors, along with long-term evolutionary adaptations, make it difficult to clearly separate biotic influences from environmental pressures.

First, the thesis addresses the meaning of species and the challenges of their identification in deep time using Menardella limbata and Menardella multicamerata as exemplar case studies. Traditional methods, relying on qualitative traits, often lead to overlapping descriptions that complicate species differentiation rather than an evidence-based approach. Having defined what I mean by species in this chapter, this thesis further explores long-term ecological dynamics through extinction events.

Analysing 19 species extinctions of planktic foraminifera, the research uses Hill numbers to assess changes in community profiles across three extinction phases (pre-extinction, imminent-extinction, and post-extinction). Findings reveal how global temperature correlates with community structure differently in each phase, showing a loss of climate control closer to removing a constituent species. The final chapter extends this approach to examine the role of trait diversity in community dynamics during the same extinction events as the previous chapter. By integrating morphometric data from over 15,000 specimens, the research assesses how species size distributions impact key community metrics, offering insights into how trait diversity correlates with biodiversity dynamics and species identifications.

Overall, the thesis highlights the necessity of integrating trait, species, and community dynamics to comprehensively understand biodiversity changes. It provides valuable insights into the complex interactions driving ecological shifts and suggests directions for future research in understanding long-term biodiversity patterns.

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Identifiers

ORCID for Chloe Jones: orcid.org/0000-0003-0684-2404

ORCID for Tom Ezard: orcid.org/0000-0001-8305-6605

ORCID for Jenneke FA Brombacher: orcid.org/0000-0003-2310-047X

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