The prevalence of eccentricity forcing on evolution and the carbon cycle

Key Questions

To what extent evolution of photosynthetic organisms, such as marine phytoplankton, is driven by variations in Earth orbit and whether this provides a fundamental pacing to the global carbon cycle.

Background

There are hints from the geological record that a link between variations in the Earth orbit and speciation events may have been persistent through geological time and leave an imprint on the carbon cycle3,4,5,6. This project aims to explore the extent to which evolution of photosynthetic organisms on land and in the ocean respond to orbital variations of the Earth around the sun and whether this provides a fundamental pacing to the carbon cycle.

Aims of the Project

This project aims to resolve to what extent variations in the Earth orbit are affecting population dynamics and evolutionary processes in major groups of photosynthesizing marine (diatoms, foraminifera) and terrestrial (e.g. boreal forest) organisms.

Project Description

Detailed morphological records of coccolithophores over the last 2 million years coupled with whole genome analysis have, for the first time, revealed that there is a strong 400 kyr periodicity to the speciation and evolution of these calcifying algae. There are hints from the geological record that a link between variations in the Earth orbit and speciation events may have been persistent through geological time and leave an imprint on the carbon cycle. This project aims to explore the extent to which evolution of photosynthetic organisms on land and in the ocean respond to orbital variations of the Earth around the sun and whether this provides a fundamental pacing to the carbon cycle.
Methodology
The observation that variations in the Earth orbit can affect evolution in calcifying plankton1 triggers a whole range of additional questions. Do all phytoplankton follow synchronous periodicity, as would be expected if it is driven by the same external factor, such as variations in Earth orbit? Do photosynthesisers on land follow the same pattern? Do the pulses in the extent of calcification and photosynthesis drive the carbon cycle in a systematic way? This project will bring together a novel blend of population genetics, with the marine fossil record and sedimentary geochemistry to explore the co-evolution of photosynthetic life and orbit.
This project aims to resolve to what extent variations in the Earth orbit are affecting population dynamics and evolutionary processes in major groups of photosynthesizing marine (diatoms, foraminifera) and terrestrial (e.g. boreal forest) organisms.
The project will benefit from a powerful combination of fossil- and DNA sequence-based analyses, as piloted in our recent work. Evolutionary genetic analyses of whole genome sequence data will be employed to reconstruct a record of past population size changes, which will be compared to species abundance in the fossil record. The phytoplankton species leave an enviable micorpalaeontological fossil record, while pollen records provide information about the past of the major photosynthesisers on land. The project will validate genomic inferences of past population size changes against the population sizes in the sedimentary record of marine and terrestrial photosynthesizers over the last 2 million years.
New data suggest that the increase in calcite productivity during the Brunhes 400 kyr acme of coccolithophore productivity, may not be restricted to one species, suggestive of some extrinsic forcing on enhanced calcite production such as weathering inputs to the ocean. The project will therefore generate new geochemical proxy records on a 2 million year timescales that may be sensitive to weathering to explore whether a 400 kyr signal is also sensed in weathering inputs to the ocean (including but not restricted to Si/particle, 10Be/9Be).

Timeline
Year 1: Training in sediment microseparation and microfossil identification
Selection and request of samples of ocean sites for sample preparation and analysis
Training in DNA extraction, sequencing
Years 2 and 3: Generation of population size reconstructions from genomes and the fossil record
Resolution of good age models for each record
Year 4: Synthesis of all data to explore whether orbit drives evolution of terrestrial biota, which drives weathering which drives evolution of phytoplankton or the orbital forcing is sense ubiquitously in photosynthetic organisms.
Training & Skills
Key skills and training in:
Microfossil identification
DNA extraction and whole genome analysis
Geochemical weathering proxies
Earth System linkages between marine and terrestrial biosphere
References & Further Reading

Methods to be used

Bioinformatic and evolutionary genetic analysis to reconstruct past population sizes and to compare with the inference from fossil record available for some of the mineralising phytoplankton groups (e.g. coccolithophores), as well as for land plants (from pollen records).

Specialised skills required

The project will involve processing and analysis of large amounts of high-throughput sequencing data, hence at least some bioinformatic skills are necessary.

Please contact Dmitry Filatov on dmitry.filatov@biology.ox.ac.uk and Ros Rickaby on rosalind.rickaby@earth.ox.ac.uk if you are interested in this project.