Selection by interactive competition explains the Damuth allometry and a green world
The fact that the densities of animals are limited to the degree that the world is green is evidence for a natural selection limitation that is driven primarily by interference competition instead of exploitation. Exploitative competition is usually generating constant relative fitnesses with
A second piece of evidence is the Damuth allometry on abundance (Damuth, 1981, 1987). Although this allometry tends to vary somewhat with the scale of observation (Nee et al., 1991), the exponent is usually around -0.75 across terrestrial species (Damuth, 1981, 1987; Peters, 1983; Nee et al., 1991) on scales where effects from inter-specific interactions are negligible (as assumed in the allometric deduction). And the exponent has been found to declined from -0.79 to -0.86 across species with two and three dimensional behaviour (Pawar et al.,2012); in close agreement with a predicted change from -0.75 to -0.83 (Witting, 1995, 2016).
A third piece of evidence comes from life history studies across gradients of differential survival. Here it is usually found that populations with increased mortality evolve smaller body masses and an increased rate of reproduction (e.g., Reznick et al., 1996; Haugen and Vøllestad, 2001; Sinclair et al., 2002; Coltman et al., 2003; Carlson et al., 2007; Herczeg et al., 2009; Rossetto et al., 2012). When the mortality rate is increased and the abundance is initially declining, there is counter-balancing selection in action, where energy is reallocated from mass to replication with a compensatory increase in the abundance and level of interactive competition.
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