Abstract:
To reduce the accelerating rate of phylogenetic diversity loss, many studies have searched for mechanisms that could
explain why certain species are at risk, whereas others are not. In particular, it has been demonstrated that species might be
affected by both extrinsic threat factors as well as intrinsic biological traits that could render a species more sensitive to
extinction; here, we focus on extrinsic factors. Recently, the International Union for Conservation of Nature developed a new
classification of threat types, including climate change, urbanization, pollution, agriculture and aquaculture, and harvesting/
hunting. We have used this new classification to analyze two main factors that could explain the expected future loss of
mammalian phylogenetic diversity: 1. differences in the type of threats that affect mammals and 2. differences in the
number of major threats that accumulate for a single species. Our results showed that Cetartiodactyla, Diprotodontia,
Monotremata, Perissodactyla, Primates, and Proboscidea could lose a high proportion of their current phylogenetic diversity
in the coming decades. In contrast, Chiroptera, Didelphimorphia, and Rodentia could lose less phylogenetic diversity than
expected if extinctions were random. Some mammalian clades, including Marsupiala, Chiroptera, and a subclade of
Primates, are affected by particular threat types, most likely due solely to their geographic locations and associations with
particular habitats. However, regardless of the geography, habitat, and taxon considered, it is not the threat type, but the
threat diversity that determines the extinction risk for species and clades. Thus, some mammals might be randomly located
in areas subjected to a large diversity of threats; they might also accumulate detrimental traits that render them sensitive to
different threats, which is a characteristic that could be associated with large body size. Any action reducing threat diversity
is expected to have a significant impact on future mammalian phylogeny.
