We consider a mathematical model for the spatio-temporal evolution of two biological species in a competitive situation. Besides diffusing, both species move toward higher concentrations of a chemical substance which is produced by themselves. The resulting system consists of two parabolic equations with Lotka-Volterra-type kinetic terms and chemotactic cross-diffusion, along with an elliptic e...

Community ecology has traditionally relied on the competitive exclusion principle, a piece of common wisdom in conceptual frameworks developed to describe species assemblages. Key concepts in community ecology, such as limiting similarity and niche partitioning, are based on competitive exclusion. However, this classical paradigm in ecology relies on implications derived from simple, determinis...

The population dynamics of two cladocerans, Ceriodaphnia pulchella and Diaphanosoma brachyurum competing under laboratory conditions in lake water was analysed using crosscorrelations. Both mixed and isolated populations of the two cladocerans showed delayed densitydependence in the death rates of juveniles and adults as well as in fecundity rate. The regressions for each of the three rates on ...

Density-dependence is a term used in ecology to describe processes such as birth and death rates that are regulated by the number of individuals in a population. Evolutionary biologists have borrowed the term to describe decreasing rates of species accumulation, suggesting that speciation and extinction rates depend on the total number of species in a clade. If this analogy with ecological dens...

In this work we introduce a general class of spatially heterogeneous competing species models where the species are assumed to disperse in a random way through the inhabiting region in the presence of some refuge patches where they are free from the aggressions of the antagonist species. Our model shows that the competitive exclusion principle fails to be true under these circumstances, as the ...

A: It is possible, but unlikely in most circumstances, that the antitrust laws will provide an effective remedy for exclusion from hospital privileges. Determining whether an antitrust violation exists in any particular case will be very fact-specific and depend on a number of circumstances, including who ultimately controls the privilege decisions, the purpose of the exclusion, and the resulti...