The Currency and Tempo of Extinction

Regan, Helen M.; Lupia, Richard; Drinnan, Andrew N.; Burgman, Mark A.

doi:10.1086/317005

Cited by 100 publications

(39 citation statements)

References 22 publications

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“…Estimates for the loss of biodiversity use a variety of methods to compare current rates of species extinction against background rates (33,34). All of these methods suggest that we are entering a period of mass extinction that is directly comparable to the mass extinctions recorded in the fossil record.…”

Section: How Rapidly Are We Losing Hosts and Parasites?mentioning

confidence: 99%

Homage to Linnaeus: How many parasites? How many hosts?

Dobson

Lafferty

Kuris

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

581

511

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Estimates of the total number of species that inhabit the Earth have increased significantly since Linnaeus's initial catalog of 20,000 species. The best recent estimates suggest that there are Ϸ6 million species. More emphasis has been placed on counts of free-living species than on parasitic species. We rectify this by quantifying the numbers and proportion of parasitic species. We estimate that there are between 75,000 and 300,000 helminth species parasitizing the vertebrates. We have no credible way of estimating how many parasitic protozoa, fungi, bacteria, and viruses exist. We estimate that between 3% and 5% of parasitic helminths are threatened with extinction in the next 50 to 100 years. Because patterns of parasite diversity do not clearly map onto patterns of host diversity, we can make very little prediction about geographical patterns of threat to parasites. If the threats reflect those experienced by avian hosts, then we expect climate change to be a major threat to the relatively small proportion of parasite diversity that lives in the polar and temperate regions, whereas habitat destruction will be the major threat to tropical parasite diversity. Recent studies of food webs suggest that Ϸ75% of the links in food webs involve a parasitic species; these links are vital for regulation of host abundance and potentially for reducing the impact of toxic pollutants. This implies that parasite extinctions may have unforeseen costs that impact the health and abundance of a large number of free-living species.climate change ͉ habitat loss ͉ parasite biodiversity T he year 2008 marks the tercentenary of the birth of Linnaeus, the scientist who first provided a formal classification for biological diversity. In the initial edition of Systema Naturae (1), Linnaeus included a group of species-the Paradoxa-that confounded his classification or whose actual existence he questioned. Pelicans, for example, were placed in Paradoxa because Linnaeus thought they might reflect the over-fervent imaginations of New World explorers. Parasitic worms were also placed in Paradoxa because Linnaeus initially thought that they might be confused, or misplaced, earthworms. In later editions of Systema Naturae, Linnaeus revised his opinions about both pelicans and parasitic worms. We now know much about parasites but still rarely think of them as major components of biodiversity. One primary goal of this article is to revise this misconception and quantify the ubiquity of parasitism as a lifestyle. We then attempt to quantify how many parasite species are threatened with extinction.To quantify the abundance and potential loss rates of parasite biodiversity, we initially need to quantify these measures for their host species. For this we have briefly synthesized the work of May (2, 3), Stork (4), Purvis and Hector (5), and Erwin (6). We then restrict our tally of parasite diversity to parasitic helminths of the vertebrates: trematodes, cestodes, acanthocephalans, and the parasitic nematodes. This tally will synthesize and update a...

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Section: How Rapidly Are We Losing Hosts and Parasites?mentioning

confidence: 99%

Homage to Linnaeus: How many parasites? How many hosts?

Dobson

Lafferty

Kuris

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

581

511

View full text Add to dashboard Cite

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“…However, the high extinction rate is not consistent throughout North America as a detailed study of a CretaceousPalaeogene boundary section in Saskatchewan, Canada, demonstrated a mass-kill of standing vegetation but lacked evidence of mass-extinction (McIver, 1999). Regan et al (2001) extensively discussed the problems associated with calculation of background extinction rates in relation to various groups of animals and plants. Background extinction rates are generally quoted to vary from < 1% to 25% per million years.…”

Section: Permian-triassic Eventmentioning

confidence: 99%

Extinction and recovery patterns of the vegetation across the Cretaceous–Palaeogene boundary — a tool for unravelling the causes of the end-Permian mass-extinction

Vajda

McLoughlin

2007

Review of Palaeobotany and Palynology

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High-resolution palynofloral signatures through the Cretaceous-Palaeogene boundary succession show several features in common with the Permian-Triassic transition but there are also important differences. Southern Hemisphere CretaceousPalaeogene successions, to date studied at high resolution only in New Zealand, reveal a diverse palynoflora abruptly replaced by fungi-dominated assemblages that are in turn succeeded by low diversity suites dominated by fern spores, then gymnosperm-and angiosperm-dominated palynofloras of equivalent diversity to those of the Late Cretaceous. This palynofloral signature is interpreted to represent instantaneous (days to months) destruction of diverse forest communities associated with the Chicxulub impact event. The pattern of palynofloral change suggests wholesale collapse of vascular plant communities and short-term proliferation of saprotrophs followed by relatively rapid successional recovery of pteridophyte and seed-plant communities. The Permian-Triassic transition records global devastation of gymnosperm-dominated forests in a short zone synchronous with one or more peaks of the fungal/algal palynomorph Reduviasporonites. This zone is typically succeeded by assemblages rich in lycophyte spores and/or acritarchs. Higher in the succession, these assemblages give way to diverse palynofloras dominated by new groups of gymnosperms. Although different plant families were involved in the mass-extinctions, the general pattern of extinction and recovery is consistent between both events. The major difference is the longer duration for each phase of the Triassic recovery vegetation compared to that of the Paleocene. The protracted extinction-recovery succession at the Permian-Triassic boundary is incompatible with an instantaneous causal mechanism such as an impact of a celestial body but is consistent with hypotheses invoking extended environmental perturbations through flood-basalt volcanism and release of methane from continental shelf sediments.

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“…However, extrapolating from one group, such as mammals relies upon these rates being representative of completely different taxa [21]. Hence with the paucity of reliable data few global estimates of species loss based upon methodologically sound research are available.…”

Section: Forestry and Biodiversity Projectionsmentioning

confidence: 99%

“…Estimates of both background (natural) extinction rates and current extinction rates remain highly uncertain [21]. Estimates also vary due to uncertainty about the total number of species present on Earth, together with uncertainty about the precise distribution of those species.…”

Section: Forestry and Biodiversity Projectionsmentioning

confidence: 99%

“…Regardless of the exact rate of extinctions there is little doubt that the world is in the midst of a major extinction interval that is not sustainable since it is well above background extinction rates [21] although probably not unprecedented in the Earth's history [23]. On a different note, Nee and May [25] argue that even when 95 percent of species are lost, approximately 80 percent of evolutionary history is preserved, with the proportion of evolutionary history surviving being relatively insensitive to whether the saved species are chosen randomly or optimally.…”

Section: Forestry and Biodiversity Projectionsmentioning

confidence: 99%

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