EVOLUTIONARY TRANSITION FROM AMMONITE SUBPRIONOCYCLUS TO REESIDITES-PUNCTUATED OR GRADUAL?

Abstract

indicate that the foraging pattern of bees and consequently the neighborhood size in plant populations may be density related. The number of individuals comprising a neighborhood at high density would be greater than at very low densities. Neighborhood area would be greater at the low densities. (This is a direct consequence of the greater frequency of near neighbor moves at low densities.) This result must, however, be modified somewhat since at very low densities pollinator foraging trip length is quite short in relation to the high density population. At extremely low plant densities one may expect neighborhood size to again increase. The proportion of long distance flights is increased. The results of this study indicate that genetic structure in an entomophilous plant may be density related. A final aspect of this study is related to the attractiveness of a population to pollinators. Populations of high density are presumably more attractive to pollinators since they offer more reward per unit area than populations of low densities. The data from the average number of plants visited per bee foraging trip are consistent with this hypothesis. The denser the population the greater is the proportion of the flower population visited per bee. At very low densities the experimental population attracted few bees and only few plants were visited while at high densities many bees were attracted and each plant was repeatedly visited. ACKNOWLEDGMENTS