Centrifugal community organization.

If the primary preference of all species is shared, but their secondary preferences are distinct, they are said to be organized centrifugally. The biological basis for centrifugal structure may be that habitats represent combinations of different environmental variables and, although the ideal combination is the same for many species in a guild, each species is adapted to tolerate relative deprivation of a different component of the mixture. The isolegs of centrifugal organization (lines of equal optimal behavior drawn in a state space) are modelled. Their principal distinguishing feature is their negative slope. Because of this, niche shifts in such communities should occur backwards; removing a competitor produces narrower niches in those left. Another feature which distinguishes it is its inability to generate a 'ghost of competition past': competition should always be a strong dynamical influence. Two species of gerbils in the Negev Desert, Israel, both exhibit negative isolegs. Other aspects of their habitat selection are consonant with a picture of centrifugal organization. -from Authors