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G M Mace

Publications and source records attributed to G M Mace.

8 recordsLinked to original sources
PubMed2000

Predicting extinction risk in declining species.

What biological attributes predispose species to the risk of extinction? There are many hypotheses but so far there has been no systematic analysis for discriminating between them. Using complete phylogenies of contemporary carnivores and primates, we present, to our knowledge, the first comparative test showing that high trophic level, low population density slow life history and, in particular, small geographical range size are all significantly and independently associated with a high extinction risk in declining species. These traits together explain nearly 50% of the total between-species variation in extinction risk. Much of the remaining variation can be accounted for by external anthropogenic factors that affect species irrespective of their biology.

Animals↗
PubMed2000

Nonrandom extinction and the loss of evolutionary history.

The hierarchical nature of phylogenies means that random extinction of species affects a smaller fraction of higher taxa, and so the total amount of evolutionary history lost may be comparatively slight. However, current extinction risk is not phylogenetically random. We show the potentially severe implications of the clumped nature of threat for the loss of biodiversity. An additional 120 avian and mammalian genera are at risk compared with the number predicted under random extinction. We estimate that the prospective extra loss of mammalian evolutionary history alone would be equivalent to losing a monotypic phylum.

Animals↗
PubMed2000

Extinction.

In the life of any species, extinction is the final evolutionary process. It is a common one at present, as the world is entering a major extinction crisis. The pattern of extinction and threat is very non-random, with some taxa being more vulnerable than others. Explaining why some taxa are affected and some escape is a major goal of conservation biology. More ambitiously, a predictive model could, in principle, be built by integrating comparable studies of past and present extinctions. We review progress towards both explanatory and predictive frameworks, comparing correlates of extinction in different groups at different times. Progress towards explanatory models for the current crisis is promising, at least in some well-studied taxa, but the development of a truly predictive model is hampered by the formidable difficulties of integrating studies of present and past extinctions.

Animals↗
PubMed1999

Energetic constraints on the diet of terrestrial carnivores.

Species in the mammalian order Carnivora exhibit a huge diversity of life histories with body sizes spanning more than three orders of magnitude. Despite this diversity, most terrestrial carnivores can be classified as either feeding on invertebrates and small vertebrates or on large vertebrates. Small carnivores feed predominantly on invertebrates probably because they are a superabundant resource (sometimes 90% of animal biomass); however, intake rates of invertebrate feeders are low, about one tenth of those of vertebrate feeders. Although small carnivores can subsist on this diet because of low absolute energy requirements, invertebrate feeding appears to be unsustainable for larger carnivores. Here we show, by reviewing the most common live prey in carnivore diets, that there is a striking transition from feeding on small prey (less than half of predator mass) to large prey (near predator mass), occurring at predator masses of 21.5-25 kg. We test the hypothesis that this dichotomy is the consequence of mass-related energetic requirements and we determine the predicted maximum mass that an invertebrate diet can sustain. Using a simple energetic model and known invertebrate intake rates, we predict a maximum sustainable mass of 21.5 kg, which matches the point where predators shift from small to large prey.

Animals↗
PubMed1995

Local extinction in a small and declining population: wild dogs in the Serengeti.

Altered assumptions about how different ecological factors limit population numbers may lead to different conclusions about the causes of decline and ultimate extinction of a small population. Here, alternative hypotheses for the local disappearance of the Serengeti plains study population of African wild dogs (Lycaon pictus) are examined in light of observations of density dependence, deterministic decline and frequent rapid fluctuations in population number. After a population crash from 60 individuals in 1975 to 30 individuals in 1976, the Serengeti plains population fluctuated around a mean value of 22 individuals for 16 years before local extinction occurred. Variation in population numbers was extreme, with inter-annual reductions in population size of at least 40% occurring three times. Several explanations are consistent with the observed trends in population size including outbreaks of various epizootics and competition with other predators. Monte Carlo simulation, with parameters set to reflect observed fluctuations, demonstrate that population extinction was likely from chance factors alone. In small and declining populations, for which precise data and controls are unavailable, determining the cause(s) of extinction usually will be impossible.

Africa↗
PubMed1980

Brain size and ecology in small mammals and primates.

Comparisons of brain-body size relationships within small mammal and primate families reveal intergeneric differences related to diet and foraging strategy. These same associations between relative brain size and ecology are also evident among interfamily comparisons.

Animals↗