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
