Dr. Alistair Seddon
I submitted my D.Phil thesis in October 2010 (thesis title: "Palaeoecology, Biogeography and Evolution of Galapagos Diatoms”). I have a BA in Geography from the University of Oxford and am currently a lecturer in Physical Geography at Brasenose, St Catherine's and Hertford College, Oxford.
I am interested in explaining patterns of biodiversity through time and space. For my D.Phil research, I have 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. My research has consisted of three major themes; ecological responses to palaeoenvironmental change; taxonomy; and biogeographical patterns and process.
Ecological Response to Palaeoenvironmental Change:
Here, my 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 timescales are necessary for speciation events to occur?
Taxonomy involves the description and classification of species according to their morphological and ecological characteristics. During my D.Phil research I discovered 10 new species of diatom from one coastal lagoon, leading me 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, where-as 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? I have 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.
Seddon, A.W.R (2012) CDF Checklist of Galapagos Diatoms - FCD Lista de especies de Diatomeas de Galápagos. In: Bungartz, F., Herrera, H., Jaramillo, P., Tirado, N., Jiménez-Uzcátegui, G., Ruiz, D., Guézou, A. & Ziemmeck, F. (eds.). Charles Darwin Foundation Galapagos Species Checklist - Lista de Especies de Galápagos de la Fundación Charles Darwin. Charles Darwin Foundation / Fundación Charles Darwin, Puerto Ayora, Galapagos: http://checklists.datazone.darwinfoundation.org/algae/bacillariophyta/ Last updated 20 May 2012
Seddon, A.W.R. (2012) “Paleoecology.” In Oxford Bibliographies Online: Ecology. Ed. David Gibson. New York: Oxford University Press.
Seddon, A.W.R, Froyd C.A., Leng M.J., Milne G.A., Willis K.J. (2011) Ecosystem Resilience and Threshold Response in the Galápagos Coastal Zone. PLoS ONE 6(7): e22376. doi:10.1371/journal.pone.0022376
Seddon, A.W.R., Froyd, C.A. and Witkowski, A. (2011), Diatoms (Bacillariophyta) of isolated islands: New taxa in the genus Navicula sensu stricto from the Galápagos Islands. Journal of Phycology, 47: 861–879. doi: 10.1111/j.1529-8817.2011.01026.x
Seddon, A.W.R., Froyd, C.A., Witkowski, A, and Willis, K.J. (in preparation). Local endemics or ecological specialists? Are the Galapagos geographically isolated for diatoms?
Seddon, A.W.R., Froyd, C.A., Witkowski, A, and Willis, K.J. (in preparation). Assessing the response of coastal diatom assemblages to environmental variability in the Galápagos Islands.