Scaling the extinction vortex: Body size as a predictor of population dynamics close to extinction events
Data files
Mar 31, 2022 version files 126.12 KB
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BayesianAnalyses.R
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Humbert_function.R
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modelling_data.csv
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phylogeny.tre
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population_data.csv
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readme.txt
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StateSpace.R
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Abstract
- Mutual reinforcement between abiotic and biotic factors can drive small populations into a catastrophic downward spiral to extinction – a process known as the ‘extinction vortex.’ However, empirical studies investigating extinction dynamics in relation to species’ traits have been lacking.
- We assembled a database of 35 vertebrate populations monitored to extirpation over a period of at least ten years, represented by 32 different species, including 25 birds, five mammals and two reptiles. We supplemented these population time series with species-specific mean adult body size to investigate whether this key intrinsic trait affects the dynamics of populations declining towards extinction.
- We performed three analyses to quantify the effects of adult body size on three characteristics of population dynamics: time to extinction, population growth rate, and residual variability in population growth rate.
- Our results provide support for the existence of extinction vortex dynamics in extirpated populations. We show that populations typically decline non-linearly to extinction, while both the rate of population decline, and variability in population growth rate increase as extinction is approached. Our results also suggest that smaller-bodied species are particularly prone to the extinction vortex, with larger increases in rates of population decline and population growth rate variability when compared to larger-bodied species.
- Our results reaffirm and extend our understanding of extinction dynamics in real-life extirpated populations. In particular, we suggest that smaller-bodied species may be at greater risk of rapid collapse to extinction than larger-bodied species, and thus management of smaller-bodied species should focus on maintaining higher population abundances as a priority.