#Evol2012: Competitive flowers, bleached lizards, burrowing mice, and robust invaders

Iochroma fuchsioides. Photo via Wikimedia Commons.

It’s already the third day of concurrent sessions a Evolution 2012, and I’m starting to get science overload. And I still have to present my own science tomorrow! But here are some more cool results I saw Sunday and Monday:

Vera Domingues presented a study of beach mice, which have evolved lighter fur after colonizing the sandy dunes of barrier islands off the Gulf Coast. As in many other animal species, a mutation at the pigment-related locus MC1R explains a lot of the color change; Domingues showed that in the population of barrier island mice, every copy of the mutant, “light color” form of MC1R is descended from the same ancestor, and that DNA sequence near the mutation resembles sequence from the ancestral population on the mainland—which suggests that the original mutant predates the move to the barrier islands.

Richard Lankau showed how garlic mustard, an invasive weed in the United States, uses chemical warfare to out-compete native plants. Garlic mustard secretes chemicals into the soil that suppress the growth of other plants, and alters the environment for beneficial mycorrhizal fungi—and plants grown with competitors produce more chemicals. But native plants can adapt; samples of a native competitor collected from sites invaded by garlic mustard were better able to survive near the invader than plants from non-invaded sites, and were less able to benefit from mycorrhizal fungi in soil that hadn’t been exposed to garlic mustard chemistry.

Nathan Muchhala examined floral divergence within communities of Iochroma, a relatively small genus of flowering shrubs from the Andes. Muchhala hypothesized that competition for pollinators would explain the diversity of flower color and shape in different Iochroma species—if nearby flowers of different species attract the same polliantor, they risk recieving pollen from the wrong donor. He found that Iochroma species growing together were no more distantly related than expected by chance, but they did differ in color more than expected, which suggests exactly tthe kind of selection he expected.

Friend of the blog Simone Des Roches presented results from ongoing field work—she arrived in Ottawa almost directly from New Mexico, where she studies several species of lizards that have evolved lighter coloration after colonizing an expanse of white gypsum sand dunes. Simone’s currently using mark-recapture methods to watch selection for lighter color in real time, seeing whether lizards caught at the beginning of the sumer field season are more likely to be recaptured at the end of the season if their color blends into the sandy background better—and her preliminary data seem to show that trend.

Two different color morphs of Holbrookia maculata. Photo by Simone Des Roches, via Denim and Tweed

Hillery Metz showed that the shape of deer mouse burrows may be determined by just a few genes. She’s bred hybrids between Peromyscus maniculatus, which digs simple, shallow burrows, and Peromyscus polionotus, which digs deep burrows with carefully-dug escape tunnels. First-generation hybrids dig burrows like P. polionotus, which suggests that the differences in burrow architecture are due to dominant genes; later hybrids which have been back-crossed to P. maniculatus dig burrows with a continuous range of lengths, and with or without escape tunnels.

Gina Quiram demonstrated that beetles introduced as biocontrol agents for the invasive weed Lythrum salicaria have had the opposite effect intended, thanks to the plant’s evolutionary response: populations of L. salicaria with historically higher concentrations of the bio-control beetles have evolved to tolerate the beetles and to be more competitive against native cattails. Oops.