How do environment, ecology and evolution
regulate the self-assembly of marine plankton communities?

Visualisation of a plankton community network built from eukaryotic, prokaryotic and viral subnetworks and their relationship with carbon export (from    Guidi et al. Nature, 2016   ).

Visualisation of a plankton community network built from eukaryotic, prokaryotic and viral subnetworks and their relationship with carbon export (from Guidi et al. Nature, 2016).

Four-year PhD studentship at the University of Southampton.
Funded by the Royal Society.

Advisory Panel:

Application Deadline: 30th June 2019

Motivation

Recent global surveys have unveiled enormous levels of diversity in marine microbial communities, with molecular analysis suggesting the existence of up 150,000 genera of marine eukaryotes in the photic layer of the ocean alone (1). These diverse - but now measurable - communities support almost all life in the ocean and play a central role in the regulation of Earth’s climate. While these ecological and climate functions are thought to be disproportionately attributable to a limited number of keystone species, we do not yet have a clear idea of why these particular species emerge from a much larger background of less influential species, and how sensitive the system might be to their loss. A key issue is that environmental change can drive the restructuring or even collapse of biological communities, with knock-on effects on their ecological and climate function. Prediction of these responses depends on understanding how marine ecosystems emerge and self-organise as a consequence of their environment, ecology and evolutionary history (2, 3). The aim of this project is to quantify the relative influence of these different factors in setting the structure, function and sensitivity to change of marine ecosystems.

In particular…

  • What is the relative importance of species dispersal, ecological interaction and natural selection with regard to the emergence of an ecologically and evolutionarily stable community?

  • How do these factors affect an ecosystem’s resilience to (and potential recovery from) environmental change?

  • And can small chance events in the evolutionary history of a community impact its ultimate composition and function?

Methodology

The proposed PhD studentship will address the evolution and resilience of diverse plankton communities using bioinformatic data and computer modelling. Previously, numerical models of diverse planktonic ecosystems have focussed on how communities emerge from among a predetermined range of potentially viable species (3). Such models neglect the evolutionary emergence of new species and can provide only a limited description of community assembly. In contrast, this project will work with a new model of the marine ecosystem that allows diverse trophic food-webs to develop from a single ancestral species. Environmental dispersal, ecological selection and the adaptive generation of new phenotypes can be manipulated within the model, allowing assessment of their influence on community assembly, biodiversity and the ecosystem-level resistance/resilience to environmental change. Insights from the model will be tested against original analysis of metagenomic data from the Tara Oceans project (1). These data describe the global distribution of millions unique DNA tags (or ‘metabarcodes’) that have previously been sorted into five organismal size fractions and all known deep-branching eukaryotic and prokaryotic lineages. Analysis of this global dataset will be compared with model results to explore links between biogeography, ecological function and evolutionary history.

Training

The Graduate School provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted by the Ocean and Earth Science (OES) department within the National Oceanography Centre Southampton. The student will be associated with the marine biogeochemistry group at OES and will have the opportunity to interact with researchers studying multiple aspects of oceanic systems using a diverse range of observational and modelling tools. Specific training will include (i) eco-evolutionary theory and numerical modelling, (ii) genomic analysis of global biodiversity, and (iii) paleoceanographic reconstructions of the biodiversity of past ecosystems. Beyond the exchanges associated with graduate school, we anticipate the student travelling to the US and France to work with project collaborators Mick Follows (MIT) and Colomban de Vargas (CNRS).

Details

Start date: October 2019

Contact: b.a.ward@soton.ac.uk for further details

References

  1. de Vargas C, Audic S and others (2015) Eukaryotic plankton diversity in the sunlit ocean. Science. 348(6237):1261605:-1–11.

  2. Louca S, Parfrey LW and Doebeli M (2016) Decoupling function and taxonomy in the global ocean microbiome. Science. 353(6305):1272.

  3.  Follows MJ, Dutkiewicz S, Grant S, Chisholm SW. (2007) Emergent Biogeography of Microbial Communities in a Model Ocean. Scienc e315:1843–1846.