Individuals organise in interaction units as predicted by density dependent competitive interactions
There is no doubt that the individuals of many natural populations organise themselves into groups or units, and that some of these are used in the defence of natural resources against other such units. It is also evident that the deduced structuring exists; with individual interactors being widespread in self-replicating cells, with pair-wise and co-operative units being widespread in multicellular animals, and eusocial units existing only in relatively few taxa.
Whether these units have evolved by density dependent interactive competition, or by other mechanisms, is a more open question that is difficult to prove. We do however note that the organisation of individuals into co-operative kin-groups is a function of population density in some species (Stacey and Koenig, 1990; Watson et al., 1994; Piertney et al., 2008). And eusocial insects, although few in number of species, may comprise as much as 75 percent of the total insect biomass (Beck, 1971; Fitthau and Klinge, 1973), in agreement with the extreme population densities that are predicted by the upward constrained competitive interaction fix-point.
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