Think Bomb

Tuesday, August 29, 2006

Traveling the Salmon River in Search of Evolution

For this week’s Blue Monday I interviewed Mathew Burns from Scott Nuismer’s lab. Like last week’s interviewee, Matt has been looking at a very specific case of coevolution (only a little closer to home).

As one travels up the Salmon River, one can find moths from the genus Greya and their host, the flowering Heuchera grossulariifolia plant. Like the Yucca moths and Joshua tree, these two species are in a constant evolutionary arms race. Unlike the previously mentioned species though, there is not a distinct group of plant to go with their distinct moth population. Instead, there is a convenient gradient of coevolution that can be seen as one travels up the Salmon.

Imagine yourself on hike along the beautiful Salmon River. As you travel, you will begin to see plants with thicker stems and hairs along with corresponding moths with longer ovipositors.

Why does this occur and what genetic mechanisms are at play here? That is what Matt and the Nuismer lab is trying to discover. One interest is how polyploidy (multiple chromosome sets) shapes the host range of their predatory insects. Unlike us, plants can pass on multiple chromosome sets to their offspring. Even the most minor chromosomal duplication in humans produces disastrous effects (for example, three copies of chromosome 21 produces Down Syndrome). Additional chromosome sets are not always a problem in plants though, so long as they are inherited in even numbers so they may be separated evenly during gamete formation. Polyploidy, along with other types of gene flow and selection, shape the population of Greyas and their flowers along the river.

The Nuismer team hopes to develop and test mathematical models of the gene flow occurring in this Salmon River area, including models that helps explain the geological structure that shapes and is shaped by these host-parasite interactions. These models could hopefully be applied to more widespread populations and useful in predicting possible evolutionary outcomes in the future.

Source: the Nuismer lab web site,


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