Niche specialization and species diversity along a California transect.

The structure of the food-web at the flower-herbivore interface was examined along a transect of fourteen communities across central California. All results are commensurate with the hypothesis that in most environments there is selective pressure towards specialization. However, it is only in the most predictable or stable environments that the resultant diminishment of behavioral and genetic flexibility is in a sense "permitted" by subsequent natural selection. In the most extreme environments, behavioral specialization may be a necessary prerequiste permitting briefly thriving ephemeral populations which must recolonize frequently. The data results indicate: 1) Total species number increases with stability and predictability of the climate; 2) As the climate ameliorates, niche-specialization is a progressively more successful strategy; 3) The percentage of niche-specialized species of both plants and flower-feeding herbivores increases in the most severe environments at the expense of the more moderately specialized species; 4) Energetic flow chart redundancy increases in extreme environments; 5) Especially important to an understanding of pollination interactions is the fact that similar physiognomic communities at very different altitudes are in all cases much more similar than different community types within a research site.