No abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. We compiled studies that report data on the relationship between animal population density and patch or island area for 287 individual species and 21 faunas. We tested the assumption of the equilibrium theory of island biogeography that population densities are independent of area by performing a meta-analysis using the linear correlation coefficient, r, as a measure of the effect of area on population density. We fit meta-analyses that used a random-effects model to these data to test for the effects of taxa, habitat, latitude, spatial scale, and overall population density. We also fit meta-analyses that used a fixedeffect model to the same data to estimate the repeatability of measurements of the correlation between population density and area within species.Contrary to the equilibrium theory of island biogeography, our results indicate that, on average, animal population densities are positively correlated with area, which suggests that density compensation may be uncommon. This result was found for individual species, but not for faunas. We found taxonomic differences in the correlation between population density and area, with insects and birds having on average large or moderately large positive correlations, respectively, and mammals having correlations near zero. Observations within individual species showed considerable repeatability. The observed overall positive correlation between the population density of individual animal species and area is best explained in the context of the resource concentration hypothesis.Our results imply that the regional abundance and persistence of animal populations may depend strongly on the presence and,continued persistence of a few large patches of suitable habitat, rather than on a regional network of small and large habitat patches.

MINI-REVIEW Minireviews provides an opportunity to summarize existing knowledge of selected ecological areas, with special emphasis on current topics where rapid and significant advances are occurring. Reviews should be concise and not too wide-ranging. All key references should be cited. A summary is required.

Although spatial patterns of seed distribution are thought to vary greatly among plant species dispersed by different vectors, few studies have directly examined this assumption. We compared patterns of seed rain of nine species of trees disseminated by large birds, monkeys, and wind in a closed canopy forest in Cameroon. We used maximum‐likelihood methods to fit seed rain data to four dispersal functions: inverse power, negative exponential, Gaussian, and Student t. We then tested for differences in dispersal characteristics (1) among individuals within species, and (2) among species dispersed by the same vector. In general, an inverse power function best described animal‐dispersed species and the Gaussian and Student t functions best described wind‐dispersed species. Animal‐dispersed species had longer mean dispersal distances than wind‐dispersed species, but lower fecundities. In addition to these distinct differences in average dispersal distance and functional form of the seed shadow between animal‐ and wind‐dispersed species, seed shadows varied markedly within species and vector, with conspecifics and species within vector varying in their dispersal scale, fecundity, and clumping parameters. Dispersal vectors determine a significant amount of variation in seed distribution, but much variation remains to be explained. Finally, we demonstrate that most seeds, regardless of vector, fall directly under the parent canopy. Long‐distance dispersal events (>60 m) account for a small proportion of the seed crop but may still be important in terms of the absolute numbers of dispersed seeds and effects on population and community dynamics.