The extinction vortex

25 08 2008

One for the Potential list:

vortexFirst coined by Gilpin & Soulé in 1986, the extinction vortex is the term used to describe the process that declining populations undergo when”a mutual reinforcement occurs among biotic and abiotic processes that drives population size downward to extinction” (Brook, Sodhi & Bradshaw 2008).

Although several types of ‘vortices’ were labelled by Gilpin & Soulé, the concept was subsequently simplified by Caughley (1994) in his famous paper on the declining and small population paradigms, but only truly quantified for the first time by Fagan & Holmes (2006) in their Ecology Letters paper entitled Quantifying the extinction vortex.

Fagan and Holmes compiled a small time-series database of ten vertebrate species (two mammals, five birds, two reptiles and a fish) whose final extinction was witnessed via monitoring. They confirmed that the time to extinction scales to the logarithm of population size. In other words, as populations decline, the time elapsing before extinction occurs becomes rapidly (exponentially) smaller and smaller. They also found greater rates of population decline nearer to the time of extinction than earlier in the population’s history, confirming the expectation that genetic deterioration contributes to a general corrosion of individual performance (fitness). Finally, they found that the variability in abundance was also highest as populations approached extinction, irrespective of population size, thus demonstrating indirectly that random environmental fluctuations take over to cause the final extinction regardless of what caused the population to decline in the first place.

What does this mean for conservation efforts? It was fundamentally the first empirical demonstration that the theory of accelerating extinction proneness occurs as populations decline, meaning that all attempts must be made to ensure large population sizes if there is any chance of maintaining long-term persistence. This relates to the minimum viable population size concept that should underscore each and every recovery and target set or desired for any population in trouble or under conservation scrutiny.

CJA Bradshaw

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15 07 2017
Radical Overhaul Needed To Halt Earths Sixth Great Extinction Event – Para-SciFi

[…] numbers, population fragmentation, inbreeding and reduced genetic variation can lead to a fatal extinction vortex. In this sense, our planet is currently accumulating a large extinction debt that must eventually […]

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27 02 2017
The sexual frustration of the isolated tree | Biodiversity Revolution

[…] Following population genetic theory, we can make several predictions for the future genetic health of isolated trees. The first is that the genetic diversity of trees inhabiting small isolated fragments will decrease over time, as the pool and diversity of individuals decreases. The second prediction is that individuals inhabiting small isolated patches will become more genetically different from each other over time due to a reduction in the exchange of genes via pollen and seed, a process termed genetic drift. It is this gene exchange, or gene flow, that maintains the genetic connection between individuals and populations. The third prediction is that individuals will become more inbred over time as individuals are forced to mate with related individuals. Remember your cousin living up the street? The key problem with inbreeding is that it can increase the frequency of some maladaptive characters – remember your neighbour with that genetic condition? This reduction in vigour of populations due to inbreeding is known as inbreeding depression. These three forces, loss of genetic diversity, increasing genetic differences and increasing inbreeding, can also interact synergistically to drive the populations inhabiting such genetic ghettos towards an extinction vortex. […]

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8 01 2017
Radical Overhaul Needed To Halt Earth’s Sixth Great Extinction Event | Technology News and Reviews | A2Z Support

[…] numbers, population fragmentation, inbreeding and reduced genetic variation can lead to a fatal “extinction vortex”. In this sense, our planet is currently accumulating a large extinction debt that must […]

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20 11 2016
Paul Ehrlich: Radical overhaul needed to halt earth’s sixth great extinction – Ecologise

[…] numbers, population fragmentation, inbreeding and reduced genetic variation can lead to a fatal “extinction vortex”. In this sense, our planet is currently accumulating a large extinction debt that must […]

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9 11 2016
Radical overhaul needed to halt Earth’s sixth great extinction event | Everyday News Update

[…] Extinctions rarely happen instantly, but the conspiracy of declining numbers, population fragmentation, inbreeding and reduced genetic variation can lead to a fatal “extinction vortex“. […]

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9 11 2016
Radical overhaul needed to halt Earth’s sixth great extinction event – Enjeux énergies et environnement

[…] numbers, population fragmentation, inbreeding and reduced genetic variation can lead to a fatal “extinction vortex”. In this sense, our planet is currently accumulating a large extinction debt that must […]

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1 11 2016
The world's vanishing wild places are vital for saving species - News blog

[…] this could make Cheetahs perilously vulnerable to an “extinction vortex”. The vortex starts with a population crash, perhaps from a newly-introduced disease, habitat […]

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23 08 2016
The Plight of the Passenger Pigeon | Ranging Far

[…] be unable to recover naturally as other processes start to take hold. This has since been termed an Extinction Vortex, and it pushes declining populations into greater decline. The point at which it comes into effect […]

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28 05 2016
Coral reefs are dying out, and coastal communites will go with them | mfjsreporterspring2016b

[…] in multiple populations declining, genetic diseases and extinction, related in a concept called the extinction vortex. Coral reefs, as a major part of the world’s oceanic ecosystems, are already stating […]

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29 03 2013
Keryn Gedan

I like your extinction vortex graphic – where did you get it?

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31 07 2012
Extintos en vida - Esceptica

[…] Tomando en cuenta que esto se puede aplicar a todos los demás genes y que la interacción entre ellos llega a ser mucho más compleja, estaríamos hablando de mermas en rasgos que participan en la supervivencia o reproducción, resultando en una menor capacidad de adaptarse a los cambios ambientales. A todo esto le sumamos la endogamia que acelera todo este proceso de erosión génica. Como la selección natural opera de manera menos eficiente en poblaciones reducidas, se van acumulando mutaciones desfavorables. Llega un punto donde la población está condenada, cayendo por un círculo vicioso, más bien representado por un espiral, llamado “Vortex de extinción”. […]

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11 02 2009
Rare just tastes better « ConservationBytes.com

[…] The poor record of species over-exploitation by humans arising from the Tragedy of the Commons (Hardin 1968) is compounded by this new information. This anthropogenic Allee effect (Courchamp et al. 2006) provides a novel example mechanism for how small populations are driven ever-downward because low densities ensure declining fitness. Many species may follow the same general rules, from bluefin tuna, Napoleon wrasse lips and shark fins, to reptile skins and Tibetan antelope woollen shawls. Gault and colleagues warn that as the human population continues to expand and more people enter the luxury-goods market, more wildlife species will succumb to this Allee effect-driven extinction vortex. […]

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15 09 2008

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