Population Size and Extinction: A Note on Determining Critical Population Sizes

Shaffer, Mark L.; Samson, Fred B.

doi:10.1086/284332

Cited by 147 publications

(83 citation statements)

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“…Concern about the long-term persistence of populations (Smith 1974;Geist 1975;Shaffer & Sampson 1985;Goodman 1987;Newmark 1987) has led to questions about the size a population should be to minimize its chances of extinction (Gilpin & Diamond 1980;Wilcox & Murphy 1985). Until now, only evidence from simulation models (Soulé et al 1979;Diamond 1984;Harris et al 1987;Iwasa & Mochhizuki 1988), from avian turnover rates (Pimm et al 1988), and of the historical loss of species of unknown population sizes (Brown 1971;Patterson 1984) has been available to suggest how long isolated mammalian populations persist, and it has not been possible to assess the generality of the models or conservation tactics (Lande 1988).…”

Section: Methods Sources Of Data and Limitationsmentioning

confidence: 99%

Persistence of Different‐sized Populations: An Empirical Assessment of Rapid Extinctions in Bighorn Sheep

Berger

1990

Conservation Biology

255

163

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Section: Methods Sources Of Data and Limitationsmentioning

confidence: 99%

Persistence of Different‐sized Populations: An Empirical Assessment of Rapid Extinctions in Bighorn Sheep

Berger

1990

Conservation Biology

255

163

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“…Some biologists have questioned this emphasis, and suggested that nongenetic factors such as demographic stochasticity and environmental factors that cause small population size have overriding importance in natural populations (Simberloff 1988, Caughley 1994, Caro and Laurenson 1994. Furthermore, theory indicates that, at the point populations are sufficiently small for inbreeding to become important, demographic and environmental stochasticity are likely to cause extinction regardless of inbreeding depression (Lande 1988, Schaffer and Samson 1985, Menges 1991. Other models linking genetic and demographic processes, however, indicate that these may interact to increase extinction risk of small populations (Mills and Smouse 1994, Tanaka 1997, Jaquie´ry et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Experimental separation of genetic and demographic factors on extinction risk in wild populations

Wootton

Pfister

2013

Ecology

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Abstract. When populations reach small size, an extinction risk vortex may arise from genetic (inbreeding depression, genetic drift) and ecological (demographic stochasticity, Allee effects, environmental fluctuation) processes. The relative contribution of these processes to extinction in wild populations is unknown, but important for conserving endangered species. In experimental field populations of a harvested kelp (Postelsia palmaeformis), in which we independently varied initial genetic diversity (completely inbred, control, outbred) and population size, ecological processes dominated the risk of extinction, whereas the contribution of genetic diversity was slight. Our results match theoretical predictions that demographic processes will generally doom small populations to extinction before genetic effects act strongly, prioritize detailed ecological analysis over descriptions of genetic structure in assessing conservation of at-risk species, and highlight the need for field experiments manipulating both demographics and genetic structure on long-term extinction risk.

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“…Even a few predators can have substantial impacts on prey demography (Nogales et al, 2004) and increase the risk of catastrophic extinction (Schoener et al, 2001), a concern on a hurricane-prone island. Because smaller populations often face a greater likelihood of extinction (Shaffer & Sampson, 1985), even the loss of a few birds can severely affect a species as rare as the Puerto Rican parrot.…”

mentioning

confidence: 99%

Monitoring invasive mammalian predator populations sharing habitat with the Critically Endangered Puerto Rican parrot Amazona vittata

Engeman¹,

Whisson²,

Quinn³

et al. 2005

Oryx

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Critically Endangered Puerto Rican parrots Amazona vittata are one of the rarest birds in the world. Several exotic mammal species capable of preying on Puerto Rican parrots cohabit the Caribbean National Forest with the only wild population of these parrots. We used tracking plates, monitoring blocks and trapping to index black rats, small Indian mongooses and feral cats in parrot habitat and in public-use areas in the same habitat type. We had high trap success for black rats at all sites (42% of all sites combined), among the highest reported in the world. Rat response to monitoring (nontoxic bait) blocks was universally high, regardless of ground or tree placement. Mongooses were present at all sites, with a greater proportion of plates tracked within the forest than at public-use sites. Cats were present at all forest sites and one of the public-use sites. Presence of the three species did not appear to be linked to human disturbance. Because only 30–40 Puerto Rican parrots survive in the wild, with as few as three pairs nesting in 2002, we concluded that the abundance and pervasiveness of exotic mammalian predators poses a greater threat to the parrots than has been generally acknowledged. This is evidenced by mammalian predation during recent parrot breeding seasons, including six fledglings taken by mongooses and one nest failure from rats during 2000–2003.

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Population Size and Extinction: A Note on Determining Critical Population Sizes

Cited by 147 publications

References 0 publications

Persistence of Different‐sized Populations: An Empirical Assessment of Rapid Extinctions in Bighorn Sheep

Persistence of Different‐sized Populations: An Empirical Assessment of Rapid Extinctions in Bighorn Sheep

Experimental separation of genetic and demographic factors on extinction risk in wild populations

Monitoring invasive mammalian predator populations sharing habitat with the Critically Endangered Puerto Rican parrot Amazona vittata

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