... time.¹

Ordovician - 25 million years; Devonian - 30 million years; Permian/Triassic - 100 million years; Cretaceous - 20 million years

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...Roman-Palumbi2003.²

This estimate is very sensitive to estimates of the rate of nucleotide substitution in mitochondria. Roman and Palumbi use estimates of 1.5-2.0 $\times 10^{-8}$ per base pair per year. If the rate were higher, say, 1.5-2.0 $\times 10^{-7}$ per base pair per year, the pre-exploration population sizes would be estimated at 0.6-2 times greater than current estimates.

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... endangerment.³

The numbers add to more than 100% because each species may face threats in more than one category.

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...Master-etal2000.⁴

We should probably change the vertebrate extinction number to 44, given the apparent rediscovery of the ivory-billed woodpecker [3].

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... extinct⁵

And maybe only 3, if the ivory-billed woodpecker is still extant.

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... examples:⁶

And don't forget the example of Pacific northwest salmon populations cited earlier [4].

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... dominant.⁷

We'll return to this topic again when we talk about landscape change in a couple of months. There is substantial evidence that human occupation of the Americas and of Australia led to many extinctions among large mammals.

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... ago.⁸

Candidate species - Plants and animals that have been studied and the Service has concluded that they should be proposed for addition to the Federal endangered and threatened species list. These species have formerly been referred to as category 1 candidate species. From the February 28, 1996 Federal Register, page http://endangered.fws.gov/96cnorwt.html: ``those species for which the Service has on file sufficient information on biological vulnerability and threat(s) to support issuance of a proposed rule to list but issuance of the proposed rule is precluded.''

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