EVOLUTION SELECTION –1 SMOUSE –SPRING 2011 1SELECTION AND ADAPTATIONAdaptive Complexes:One of the first things you notice about adaptations is that they are usually complex. Futuyma spends a bit of time describing particular adaptations, just to give you the idea. The orchid story is so beautiful that it can stand a bit of elaboration here, but read Futuyma. Recall that orchids, like other monocots, have a basic floral morphology in 3’s. Orchids- The orchid has 3 petals. One of the petals, the labellum, is greatly modified. The sexual organs are fused into a single structure, the column, usually involving a single anther with two pollen masses (pollinia), with the stigmatic surface just below the anther. The labellum is quite pretty and highly aromatic, basically luring the insects into the flower. In some cases, the insects are after nectar, in some cases pollen. In other cases, male insects are confused by the aromas, and attempt to copulate with the labellum (pseudocopulation). The insects are physically challenged to move in a particular route through the flower. They are so constrained that they first leave pollen on the stigmatic surface, and then are forced to pass by the anther, where their movements trigger the application of a pollinium, on a body part that is the point of contact with the stigmatic surface of the next flower visited. The Orchidaceae is the largest family of plants, with between 18,000 – 25,000 species, and they have several thousand variations on this theme. For most species, the insect gets what it came for (food), but in some cases (sexual deception), it just gets faked out. If we didn’t know better, we could read Divine Intentinto the system. Futuyma – Figure 12.3
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