| Natural selection occurs in the context of functional biomechanics, life cycles, and resource ecology, along with other aspects of the biology of organisms. The generalities of biology naturally come to constitute habits in the way selection works within restricted universes, such as selection on floral characters for pollination by animals. In this universe, I provide three examples of how selection might be habitually biased. (1) For flowers of Impatiens being visited by Bombus, there seems to be almost no detectable selection for the way the flowers fit around the bees, suggesting that selection for mechanical fit in flowers might be much less stringent than selection for encouraging animal visitation. (2) In principle, selection on features of floral attractiveness can act through the success of pollen grains (male function) or the success of ovules (female function), and I propose alternative models by which selection through male and female function might often be strongly unequal. (3) Using Drosera tracyi flowers, a phytometer study found evidence for the view that selection on floral traits can be strongest when there are intermediate numbers of pollinators, meaning that flowers might well be adapted to times of modest pollinator abundance even if the plants experience such circumstances only occasionally. These three examples show how functional mechanics, life cycles, and resource ecology might cause adaptive regularities in the features of organisms. This approach of studying selection in action does not, however, attempt to explain the special adaptations of specific organisms. |
