Resistence and resilience: quantifying relative extinction risk in a diverse assemblage of Australian tropical rainforest vertebrates
Isaac, JL and Vanderwal, J and Johnson, CN and Williams, SE, Resistence and resilience: quantifying relative extinction risk in a diverse assemblage of Australian tropical rainforest vertebrates, Diversity and Distributions, 15, (2) pp. 280-288. ISSN 1366-9516 (2009) [Refereed Article]
Assessing the relative vulnerability of species within an assemblage to extinction
is crucial for conservation planning at the regional scale. Here, we quantify relative
vulnerability to extinction, in terms of both resistance and resilience to environmental
change, in an assemblage of tropical rainforest vertebrates.
Wet Tropics Bioregion, north Queensland, Australia.
We collated data on 163 vertebrates that occur in the Australian Wet
Tropics, including 24 frogs, 33 reptiles, 19 mammals and 87 birds. We used the ‘seven
forms of rarity’ model to assess relative vulnerability or resistance to environmental
change. We then develop a new analogous eight-celled model to assess relative
resilience, or potential to recover from environmental perturbation, based on
reproductive output, potential for dispersal and climatic niche marginality.
In the rarity model, our assemblage had more species very vulnerable and
very resistant than expected by chance. There was a more even distribution of species
over the categories in the resilience model. The three traits included in each model
were not independent of each other; species that were widespread were also habitat
generalists, while species with narrow geographical ranges tended to be locally
abundant. In the resilience model, species with low reproductive output had a
narrow climatic niche and also a low capacity to disperse. Frogs were the most
vulnerable taxonomic group overall. The model categories were compared to current
IUCN category of listed species, and the product of the two models was best correlated
with IUCN listings.
The models presented here offer an objective way to predict
the resistance of a species to environmental change, and its capacity to recover from
disturbance. The new resilience model has similar advantages to the rarity model, in
that it uses simple information and is therefore useful for examining patterns in
assemblages with many poorly known species.