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The ecology of extinction

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Simberloff D.

Acta Palaeontologica Polonica

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1993

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tom 38

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nr 3-4

159-174

Studies of species-area curves and of the spatial correlation of biogeographic ranges with climatic variables may allow some crude prediction of amount of extinction over large regions in the face of major environmental change. However, these approaches tell little about the proximate causes of species loss. The contention that failure of metapopulation dynamics is at the root of many species extinctions is so far not borne out by observed rates of inter-population movement. Rather, most species that have a metapopulation structure seem to have central source populations and peripheral sink populations. Much of the extinction recorded in the ecological literature is probably of such peripheral populations and their loss has little to do with species extinctions. The disappearance of central, source populations is more important but its causes are not well documented. Habitat loss is the single greatest ultimate cause of current extinction. However, disappearance of the very last individuals of the last population of a species may not be obviously related to habitat loss. Rather, it may seem mysterious, because the last individuals will look healthy, or it may seem attributable to one of the stochastic forces widely assumed to set minimum viable population sizes.

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A morphometric trend linked to male sociality in the small Indian mongoose Herpestes javanicus in Hawaii

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Hays W. S. T., Simberloff D.

Acta Theriologica

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2006

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tom 51

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nr 3

303-310

Introduced populations of the small Indian mongooseHerpestes javanicus (Geoffroy St. Hilaire, 1818), in Hawaii have been shown to include male breeding coalitions. Young individuals of this species stay with their mothers until they reach adult size, suggesting that young males are not exposed to the full pressure of intrasexual competition until they have completed skeletal development. It was hypothesized that variance of male skeletal characteristics should therefore be similar to the variance seen in females. It has been observed that adult males with small body mass are not typically members of breeding coalitions, suggesting that body mass is a key factor in male intraspecific competition. It was thus hypothesized that variance in male mass should exceed that in female mass. These hypotheses were tested by direct measurement of live animals in the field and by measurement of museum specimens. Both hypotheses were strongly supported. A significant correlation was also found between male body length and variance in male mass, but no correlation was found among females. It is suggested that males with low body length, like females, maintain only as much mass as is physiologically required, whereas long males maximize their mass with varying degrees of success, to facilitate intrasexual competition.

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Habitat use and potential interactions between the house mouse and lesser white-toothed shrew on an island undergoing habitat restoration

45%

Pascal M., Lorvelec O., Bioret F., Yesou P., Simberloff D.

Acta Theriologica

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2009

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tom 54

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nr 1

39-49

To forecast the potential impact of plant community and dry-stone wall restoration on an insular population of the lesser white-toothed shrewCrocidura suaveolens Pallas, 1811, shrew and house mouseMus musculus Linnaeus, 1758 abundances were assessed in 3 anthropogenic habitats on Béniguet Island, Brittany, France, by a standardised annual trapping system checked yearly for 9 years and in 6 “natural” habitats by trap-lines. The standardised trapping system showed that abundances of both species fluctuated synchronously for nine years, suggesting that interactions between the species had little impact if any on abundances. Mice were trapped in all habitats, but shrews only in “stone” habitats except for rare occurrences in one damp depression. Ruderal habitat was rarely used by either species. Data suggest that on Béniguet Island: (1)M. musculus is associated with anthropogenic habitats but is not as strictly tied to them as at nearby continental sites; (2)C. suaveolens is synanthropic, as has been reported in continental northern France; (3) shingle beaches and seashore food resources are particularly important forC. suaveolens; (4) the relationship betweenC. suaveolens andM. musculus could not be determined by the experiments and, if it exists at all, appears to be more competitive than predatory. Grassland restoration is unlikely to affect shrew populations. Dry-stone wall restoration may temporarily affect shrews but should ultimately benefit them

Ograniczanie wyników

2 Acta Theriologica

1 Acta Palaeontologica Polonica

3 Simberloff D.

1 Bioret F.

1 Hays W. S. T.

1 Lorvelec O.

1 Pascal M.

1 Yesou P.

1 2009

1 2006

1 1993

The ecology of extinction

A morphometric trend linked to male sociality in the small Indian mongoose Herpestes javanicus in Hawaii

Habitat use and potential interactions between the house mouse and lesser white-toothed shrew on an island undergoing habitat restoration