January American Naturalist highlights( Experimental evidence that selecti...),Health

"Experimental evidence that selection favors character displacement in the ivyleaf morning glory"
Robin Ann Smith and Mark D. Rausher (Duke University)

How do we know that interactions between plant species affect their evolution" While there is abundant evidence to suggest that plant-pollinator interactions influence the evolution of floral traits, there is little direct evidence that interactions between plant species shape the evolution of such characteristics. Evolutionary biologists Robin Smith and Mark Rausher of Duke University recently examined this question in a study of two morning glory species that commonly co-occur in the southeastern United States. By measuring patterns of selection on floral traits of the focal species (the ivyleaf morning glory) in the presence and absence of flowers of a second species (the tall morning glory), they found direct experimental evidence that reproductive interference between closely related plant species can alter patterns of selection on floral traits that influence the mating system and contribute to reproductive isolation.

In the summer of 2004, Robin Smith and Mark Rausher conducted a field experiment in which they planted over 1,350 morning glories (~650 individuals of each species) checkerboard fashion in an abandoned agricultural field in central North Carolina. Using hand-sewn bags made of bridal veil mesh to cover the plants and control whether pollinators could transfer pollen between the two species, their aim was to determine whether reproductive interference from the tall morning glory alters the pattern of selection on floral traits of the ivyleaf morning glory. The advantage of this experimental design is that it allowed us to manipulate only one variablethe presence vs. absence of flowers of the second specieswhile keeping all other environmental conditions constant, says Robin Smith, the studys lead author. They found that selection acts to increase clustering of anthe
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