Gerald Fisher wrote: > If experience/observation leads us to believe "... it seems clear that most > orchid pollinators do not coevolve with the orchids they pollinate.." then > what is going on? > > It seems 'reasonable' to me that the more (attractive, stronger, 'you pick > it') the blossom AND the pollinator the more likely the plant would survive. > Not necessarly the pollinator because many of the blossoms are 'sex' objects > and really doesn't do the next generation of pollinator a lot of good.
Coevolution is a reciprocal relationship where changes that occur in one species influence changes in another species, and vice versa. It implies a fairly important relationship between the two species. In the Angraecum-moth example, mutations that increase the length of the Angraecum spur would select for a longer proboscis on the Xanthophan morgani moths, if and only if the Angraecum is a major source of nectar for the moth. Conversely, the longer proboscis on the moth drives the evolution of longer nectar spurs only if the moth is the main pollinator of the Angraecum. If the moths get most of their nectar from another plant and the orchids are an occasional, relatively unimportant source of nectar, then changes in the orchid are unlikely to make much difference in the pollinator. In most cases, it is probably more likely that orchids compete with each other. For example, in deceptive insect-mimic species, the flowers that are better mimics will be pollinated more efficiently than those that look less like an insect. Over time, selection would drive the evolution of flowers that look more and more like an insect without any effect on the insect species that is doing the pollination. Nick -- Nicholas Plummer [EMAIL PROTECTED] _______________________________________________ the OrchidGuide Digest (OGD) [EMAIL PROTECTED] http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
