Jared M. Diamond

THE ISLAND DILEMMA: LESSONS OF MODERN BIOGEOGRAPHIC STUDIES FOR THE DESIGN OF NATURAL RESERVES

Abstract A system of natural reserves, each surrounded by altered habitat, resembles a system of islands from the point of view of species restricted to natural habitats. Recent advances in island biogeography may provide a detailed basis for understanding what to expect of such a system of reserves. The main conclusions are as follows: The number of species that a reserve can hold at equilibrium is a function of its area and its isolation. Larger reserves, and reserves located close to other reserves, can hold more species. If most of the area of a habitat is destroyed, and a fraction of the area is saved as a reserve, the reserve will initially contain more species than it can hold at equilibrium. The excess will gradually go extinct. The smaller the reserve, the higher will be the extinction rates. Estimates of these extinction rates for bird and mammal species have recently become available in a few cases. Different species require different minimum areas to have a reasonable chance of survival. Some geometric design principles are suggested in order to optimise the function of reserves in saving species.

China's environment in a globalizing world

How China and the rest of the world affect each other.Chinas place in the worldChinas environmental problems dominate those of the world, not only because China contains a fifth of the worlds people, but also because Chinas economy is so big and developing so rapidly. The expanding links of globalization mean that Chinas problems are the worlds problems too. In a Feature this week, Jianguo Liu and Jared Diamond look at the effects of Chinas sweeping environmental change and socio-economic challenges, synthesizing detailed literature that is scattered even for Chinese readers and largely inaccessible to western readers. On the cover, crowds on Nanjing Lu, Shanghais famous shopping street where global influences are clear to see (Mark Henley/Panos). Elsewhere in the issue, Peter Aldhous reports on how China plans to cope with its exploding need for energy.

ON THE RISK OF EXTINCTION

Well-known theoretical predictions are that the risk of extinction should decrease with maximum population size (K) and should increase with the temporal coefficient of variation in population size (CV). In an unvarying environment, where extinction is caused solely by demographic accidents, the risk of extinction should decrease steeply with K; the greater the contribution of environmental variability to the risk of extinction, the less steep should be the dependence on K. Large-bodied species tend to have long lifetimes but low rates of increase, which have opposite effects on the risk of extinction per year. We show that in comparisons of a large- and small-bodied species at the same average population size (N), the large-bodied species should be at less risk at low N but at greater risk at high N. We test these predictions using a data base of short-term survivals (up to a few decades) of 355 populations belonging to 100 species of British land birds on 16 islands. The mean N and risk of extinction are known for these populations, and we can calculate CVs for 39 of the species. To identify how factors other than N affect the risk of extinction, we devise a means of correcting that risk for much of the effect of N. We make the following observations. (1) Risk of extinction does decrease sharply with N. (2) After correcting for much of the effect of N, we confirm the theoretical prediction that the relative susceptibility to extinction of large- and small-bodied species reverses with increasing population size. Above seven pairs, larger-bodied species are at greater risk than smaller-bodied species; the reverse is true below seven pairs. (3) Migratory species are at greater risk of extinction than resident species. (4) Finally, after accounting for the effects of N, body size, and migratory status, we show that the risk of extinction does increase with the CV.

Evolution, consequences and future of plant and animal domestication

Domestication interests us as the most momentous change in Holocene human history. Why did it operate on so few wild species, in so few geographic areas? Why did people adopt it at all, why did they adopt it when they did, and how did it spread? The answers to these questions determined the remaking of the modern world, as farmers spread at the expense of hunter–gatherers and of other farmers.

Origins of major human infectious diseases

Many of the major human infectious diseases, including some now confined to humans and absent from animals, are ‘new’ ones that arose only after the origins of agriculture. Where did they come from? Why are they overwhelmingly of Old World origins? Here we show that answers to these questions are different for tropical and temperate diseases; for instance, in the relative importance of domestic animals and wild primates as sources. We identify five intermediate stages through which a pathogen exclusively infecting animals may become transformed into a pathogen exclusively infecting humans. We propose an initiative to resolve disputed origins of major diseases, and a global early warning system to monitor pathogens infecting individuals exposed to wild animals.

Density Compensation in Island Faunas

This paper analyzes factors determining the extent of density compensation on islands: i.e., is the summed population density of individuals of all species on islands equal to the summed mainland density as a result of niche expansions and higher abundances of island species compensating for the absence of many mainland species? In addition, a method is described for estimating bird population densities based on analysis of the time dependence or mist—netting yields. Puercos Island in the Pearl Archipelago off Panama has less than one—third as many resident birds species as comparable mainland habitats. Analysis of the Pearl avifauna suggests that about one—quarter of the island species may be relicts of the Pleistocene land bridge and that the remainder are subsequent over—water colonists. The successful colonists are a highly nonrandom sample of the mainland avifauna in such respects as family composition, social structure, and second—growth habitat origin. Song—based censuses and analysis of mist—netting show that Puercos has a slightly density of individuals than the mainland. Niche shifts between islands and mainland, or among different islands, include habitat expansions, wider ranges of vertical foraging strata, abundance increases checkerboard distribution patterns, and decreased morphological variability. Comparison of the present study with other studies shows that summed population densities on islands may be higher than, comparable to, or less than mainland levels, depending upon the particular island, habitat, and group of animals studied. Among factors affecting the extent of density colonists less appropriate to the vacated habitat, tending to lower island densities; and underrepresentation of large species on islands, tending to increase island population densities for a given biomass.

The double puzzle of diabetes.

Why is the prevalence of type 2 diabetes mellitus now exploding in most populations, but not in Europeans? The genetic and evolutionary consequences of geographical differences in food history may provide the answer.

Interpretation of nonelectrolyte partition coefficients between dimyristoyl lecithin and water.

SummaryNonelectrolyte partition coefficients (Ks) and free energies of solution (ΔFls) in dimyristoyl lecithin liposomes and in bulk nonpolar solvents were compared. Individual substituent groups tend to have consistent effects onK, permitting the extraction of incremental free energies (δΔF), enthalpies (δΔH), and entropies (δΔS) of partition and of solution. Values of the selectivity constants and of δΔFl for the −CH2−and −OH groups in lecithin suggest that partitioned solutes are mainly located in a region slightly less hydrophobic than octanol and similar to C5H11OH in its solvent properties. Lecithin discriminates against branched solutes more than does a bulk solvent with the sames value. Below the endothermic phase-transition temperature (i.e., when the hydrocarbon tails “freeze”), ΔS and ΔH of partition increase 10-fold,K jumps down slightly, ΔS and ΔH of solution reverse in sign from negative to positive, and the Barclay-Butler constants become more positive. Partition in lecithin and in erythrocytes is similar, except for the absence of surface charge effects in lecithin. Resistance to nonelectrolyte permeation is inhomogeneously distributed through the bilayer, and the region of maximum partition does not provide the rate-limiting barrier. An appendix derives a simple general expression for the nonelectrolyte permeability of a membrane that may be asymmetrical, may have position-dependent partition coefficients and diffusion coefficients, and may have significant interfacial resistances.

An Experimental Test for a Ceiling on Sustained Metabolic Rate in Lactating Mice

Time-averaged sustained metabolic rates (SusMRs) of humans and wild animals have been observed not to exceed about seven times basal metabolic rate (BMR), which suggests a possible ceiling on sustained metabolic scope. We tested experimentally for such a ceiling by subtracting or adding pups to vary the litter size of lactating mother mice between five and 26 pups. Mothers could regularly wean 14pups but not more (natural litter size is 8-10). Although food intake at peak lactation increased to as much as 3.4 times virgin values and increased with litter size, digestive efficiency remained constant The mass of the small intestine and of other gut compartments increased up to severalfold at peak lactation, and as a consequence so did the intestines brush-border uptake capacities for glucose and for proline. Time-averaged sustained metabolic rate at peak lactation reached 7.2 times BMR; this ratio is evidently close to a ceiling on sustained metabolic scope. Estimates of intestinal nutrient uptake capacities exceeded nutrient intakes by only a modest safety margin of reserve capacity. Intestinal hypertrophy during lactation tended to preserve those safety margins and thus to maintain digestive effciency. Conversely, postlactational intestinal atrophy and the modest size of the safety margins tended to avoid waste of biosynthetic energy.

A vertebrate model of extreme physiological regulation.

Investigation of vertebrate regulatory biology is restricted by the modest response amplitudes in mammalian model species that derive from a lifestyle of frequent small meals. By contrast, ambush-hunting snakes eat huge meals after long intervals. In juvenile pythons during feeding, there are large and rapid increases in metabolism and secretion, in the activation of enzymes and transporter proteins, and in tissue growth. These responses enable an economic hypothesis concerning the evolution of regulation to be tested. Combined with other experimental advantages, these features recommend juvenile pythons as the equivalent of a squid axon in vertebrate regulatory biology.