Comparative analyses of extinction risk in vertebrates

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Title: Comparative analyses of extinction risk in vertebrates
Authors: Fritz, Susanne
Item Type: Thesis or dissertation
Abstract: Measures of current extinction risk imply that a high proportion of the world’s species are threatened with global extinction in the near future, stressing the need for thorough understanding of extinction processes. In this thesis, I investigate three aspects of current global species extinction risk, using novel phylogenetic and spatially-explicit comparative methods. First, I develop a new measure of the phylogenetic-signal strength in extinction risk, and use it to show that the nonrandomness in global mammalian extinction risk differs with threatening processes. These results imply that the biological traits which increase species’ susceptibility depend on the anthropogenic threat experienced. Secondly, I investigate the focus of current extinction risk, both spatially and in terms of biological traits increasing risk. I model regional extinction-risk correlates for mammals across the globe, finding strong geographical variation in the influence of biological traits on risk, and in trait interactions with anthropogenic impacts. I also compare biological and anthropogenic correlates of global extinction risk across and within mammals, birds and frogs. Results from this large-scale comparative study further confirm the strong heterogeneity of extinction processes, with taxon-specific traits playing a relatively large role in determining species’ fates. Finally, I estimate possible impacts of current extinction risk using three measures of global mammalian diversity: species richness, phylogenetic diversity and functional diversity. My results show that selective losses of large species will deplete functional variety in mammals, especially in the tropics. Loss of functional diversity is much higher than expected under random species loss, and there is low congruence with losses of species richness and phylogenetic diversity. The selectivity of current extinction risk means that we stand to lose a very biased sample of global diversity, with potentially severe consequences for ecosystem functioning.
Issue Date: 2009
Date Awarded: Aug-2009
URI: http://hdl.handle.net/10044/1/5275
Supervisor: Purvis, Andy
Owens, Ian
Sponsor/Funder: Marie Curie fellowship of the European Commission
Author: Fritz, Susanne
Funder's Grant Number: MEST-CT-2005-020561
Department: Biology
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Biology PhD theses



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