ABSTRACT
This chapter explains the value of investigating the adaptive syndrome for hummingbird pollination as a means of understanding better major adaptive shifts that give rise to evolutionary novelty. Many flowers are visited by vectors other than the predominant one, but their occasional visits have little or no effect on selection for the adaptive syndromes. These partial and intermediate situations illustrate two important points. First the shift from insect to hummingbird pollination is not necessarily saltational, although, given strong enough selection pressures, it could be rapid in terms of the geological time scale. Second, the completion of the three parallel trends of selection, giving rise to fully developed differential syndromes, is unlikely to occur in sympatry. Nearly all hummingbird-pollinated species as perennials. A few are shrubby, but the majority are herbaceous. Annuals are exceptional as hummingbird flowers, the only example of the shift from insects to hummingbirds in the western flora being Gilia splendens.
