High-resolution evolution: calibration and application of fossil foraminifera in evolutionary time series

Abstract

Many evolutionary processes are well-studied on generational and macroevolutionary time scales, but much less is known about the processes bridging short- and long-term biotic change. This is commonly due to a lack of sufficiently-high-resolution fossil records over long microevolutionary time scales. The work presented in this thesis describes new calibrations and applications of planktonic foraminifera in evolutionary biology. The high-resolution fossil archives of planktonic foraminifera enable construction of continuous, long-term microevolutionary time series of large numbers (>10,000) of individuals.In Chapter 2 I study the repeatability of traits commonly used in studies describing foraminifera evolution. The results show that some traits are reliable, whereas others are very susceptible to small mounting-induced errors and should be used with caution.Chapter 3 deals with various representations of foraminifera body size, and whether these proxies remain accurate in a lineage undergoing morphological change. This was shown to be the case for foraminifera shell area as measured from a two-dimensional image, but less so for shell diameter.In Chapter 4 I study within- and among-population allometries during an interval of global climatic upheaval. When climate remains constant the within-population allometries predict evolutionary change from one time-step to the next. However, the evolutionary allometry measured across step-wise environmental change deviates significantly from the static evolutionary allometries.Changes in biodiversity are often linked to climate change, usually represented by global temperature. However, climate consists of many interacting variables, and species likely respond to the entire climate system as opposed to individual variables. In Chapter 5 I show that evolutionary response in two species of planktonic foraminifera is indeed best explained by combinations of environmental parameters.Chapter 6 presents evolutionary time series of two species of planktonic foraminifera from six sites along an Atlantic transect over 600,000 years. The results show that temporal dynamics do not match spatial variation, implying that care should be taken when extrapolating one population’s predicted response to another location.

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ORCID for Paul Wilson: orcid.org/0000-0001-6425-8906

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