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University of Oxford
School of Geography and the Environment

 School of Geography and the Environment

Dr Alistair Seddon

Academic Profile

Ali completed his DPhil thesis, entitled "Palaeoecology, Biogeography and Evolution of Galapagos Diatoms", in December 2010. He has a BA in Geography from the University of Oxford and is currently a lecturer in Physical Geography at St Catherine's and Hertford Colleges, Oxford. Ali works in the Long-term Ecology Laboratory in Department of Zoology, Oxford.

Current Research

Ali is interested in explaining patterns of biodiversity through time and space. For his DPhil research, he studied the ecological and evolutionary changes in diatoms (unicellular algae) from coastal lagoons in the Galapagos Islands and their interrelationships with environmental change and biogeographical isolation. His research has consisted of three major themes; ecological responses to palaeoenvironmental change; taxonomy; and biogeographical patterns and process.

Ecological Response to Palaeoenvironmental Change

In this theme, Ali's research involves reconstructing past abiotic variables (climate, sea-level changes, volcanics) and ecological changes in sediment cores using a variety of biological and geochemical proxies. A number of statistical and theoretical approaches are then applied to help resolve key questions regarding the ecological processes which have occurred in response to past abiotic change. Are ecological changes linear or non-linear? Do thresholds exist which determine the type of ecosystem response? What temporal scale results in speciation events?

Taxonomy

Taxonomy involves the description and classification of species according to their morphological and ecological characteristics. During his DPhil research Ali discovered 10 new species of diatom from one coastal lagoon, leading him to investigate a number questions with regards to their origins and evolution. What species have colonized the Galapagos lagoons during the past 3,000 years? Are they endemic to Galapagos and is there evidence for in situ speciation? Future work in this field involves investigating genetic variability in these taxa, identifying differences between morphological and genetic diversity and examining the impacts this has on species definitions.

Biogeographical Patterns and Process

Abiotic factors generally determine the characteristics of species assemblages on larger temporal and spatial scales, whereas biotic processes (speciation, extinction) operate on the local scale and are enhanced in geographically isolated islands such as the Galapagos. However, the relative importance of these two processes are less well known for diatoms. Is geographical isolation important for organisms that can reproduce rapidly and are easily dispersed? Ali has used biogeographical methods to compare diatom diversity at the global level. Future research involves improving the scope of the global data sets, and refining the statistical techniques used to enable a better understanding of abiotic and biotic processes.

Teaching

Ali teaches aspects of the undergraduate Physical Geography course. Preliminary Examination topics include Ecology, Geomorphology, Climatology, and Statistics. For the Final Honour School he teaches the Geographical Environment I, including: past / future environmental change; biodiversity; coastal processes; tipping points and non-linear systems; and hazards.

Selected Publications

  • Seddon, A., Froyd, C.A., Leng, M.J. and Willis, K.J. (in review) Ecosystem resilience and threshold response in the Galapagos coastal zone.
  • Seddon, A., Froyd, C.A., Witkowski, A. and Willis, K.J. (in review) Ecological turnover or evolutionary change? Assessing the response to coastal diatoms to environmental variability in the Galapagos Islands.
  • Seddon, A., Froyd, C.A., Witkowski, A. and Willis, K.J. (in review) Local endemics or ecological specialists? Are the Galapagos geographically isolated for diatoms?
  • Seddon, A., Froyd, C.A. and Witkowski, A. (in press) Diatoms (Bacillariophyta) of isolated islands I. New taxa in the genus Navicula sensu stricto from the Galapagos Islands.