How does biogeography determine species extinction?

Dr Alexander Dunhill
Research Fellow 2012

Dr Alexander Dunhill
University of Bath

Geographically widespread animals are less likely to become extinct than animals with smaller geographic ranges. Ecological theory states that a large geographic range, spanning multiple ecosystems, offers insurance against regional environmental catastrophes. However, during mass extinctions when environmental catastrophes affect the entire globe, it is claimed that this insurance is likely to become ineffectual.

Alex’s research shows that although large geographic ranges do offer insurance against extinction, this insurance disappeared across a mass extinction event that occurred around 200 million years ago. In the first study to analyse the relationship between geographic range and extinction in the terrestrial fossil record he found that organisms with larger geographic ranges were less likely to become extinct than those with smaller ranges during most of the Triassic-Jurassic. However, this pattern disappears near the Triassic-Jurassic boundary (around 200 million years ago) when the world experienced a catastrophic mass extinction event associated rapid climate change which caused the demise of around 80% of species on the planet.


“These results shed light on the likely outcome of the current biodiversity crisis caused by human activity" Dr Alex Dunhill

During the course of the fellowship Alex also developed a new method for quantifying biogeographic connectedness by adapting methods from Network Theory and applied new methods for analysing the relationship between rock and fossil record biases derived from Information Theory.

Alex has been awarded a 3-year Early-Career Research Fellowship from the Leverhulme Trust to continue his work on ecological and geographical determinants of extinction in the fossil record.