www.chicagowildernessmag.org/issues/fall2007/sexandprai -
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Published on: 1/1/2007
Last Visited: 11/14/2007
Even if you had a little botany in school long ago, and vaguely remember terms like pistil and stamen, it can come as a jolt to be reminded that plants breed , that almost all plants inherit their genetic make-up from a mother and a father, and that, in the words of University of Illinois at Chicago biology professor Mary Ashley, some plants, seemingly so rooted, could still be described as "getting around."
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To learn the genetic ramifications of our now fragmented landscape, Ashley and a cohort of rising biologists are using techniques familiar from TV's CSI series to trace the parentage of plants.They find that some species continue to hook up over surprising distances.Others only pair with nearby neighbors.For these species, biologists are measuring the risk of outbreeding depression so we can decide which inbred populations might survive being outcrossed, and which would do better if left alone.
The common oak of the prairie is the bur oak, a wind-pollinated tree with thick bark adapted to survive searing prairie fire, living in open groves known as savannas.When Mary Ashley began studying bur oak relationships in Illinois savannas, little was known about the distance at which these trees could pollinate."The savanna landscape is naturally fragmented," she said."Bur oaks grew on less than 5 percent of the land, in groves separated by grassland.We assumed that most pollination was from trees right next door, but how would you know how far pollen is moving?"
Ashley, along with then graduate students Beverly Dow and Kathleen Craft, set out to map the exact relationship between every bur oak in a savanna and the acorns produced by pollinated oak flowers.
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"At one study, the local sheriff took out a gun and shot off branches for us," Ashley said.
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"For these acorns, the father wasn't even in our sample, so the pollen had to be coming from somewhere outside the grove," Ashley said.
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Hummingbirds, however, bear pollen far enough that the cardinal flowers developed as a single population over long distances, much like Mary Ashley's bur oaks.
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