On the third day of Evolution 2009, things are winding down already. I’ve been up late saying goodbye to folks leaving tomorrow.

A bog turtle
Photo by Wall Tea.

The most entertaining talk of the day was more about physics than evolution as such: specifically, an analysis of turtle shell architecture. C.T. Stayton discussed work he published in the May issue of Evolution, showing that turtle shell shapes are a compromise between streamlining for efficient swimming and ability to resist crushing attacks from predators [$-a]. He referenced Terry Pratchett in his introductory slides, but I didn’t have the presence of mind to ask afterward what the optimal shell shape is to support the weight of four elephants and a Discworld.

Other highlights:

• Simone Des Roches presented more results from experiments that showed how the adaptive divergence of sticklebacks can alter ecosystem dynamics. (I discussed the original publication back in April.)
• The amoeba Dictostelium discoideum responds to stress by forming spore-making fruiting bodies. Some cells “cheat” by taking the beneficial spots in the fruiting body and leaving others to form its non-reproductive stalk — and it seems that the cheaters do this by getting there first.
• Live-bearing guppies are able to compensate for a reduced food supply by restricting the size of their developing babies.
• Although whaling nations argue that Minke whales have become much more abundant due to lack of competition from species hunted to near extinction in the early 20th century, population genetic data suggest that Minke whales are about as numerous as they were prior to that time.
• It’s actually proving pretty tricky to determine the evolutionary relationships of chipmunks in Western North America, both because they hybridize frequently and because they speciated rapidly.
• Boundaries between related species’s geographic distributions may be maintained by locally-adapted pathogens.

And, finally, video of Eugenie Scott’s Gould Award lecture is now online for streaming in Real Video format here.

References

Harmon, L., Matthews, B., Des Roches, S., Chase, J., Shurin, J., & Schluter, D. (2009). Evolutionary diversification in stickleback affects ecosystem functioning Nature, 458 (7242), 1167-70 DOI: 10.1038/nature07974

Stayton, C. (2009). Application of thin-plate spline transformations to finite element models, or, how to turn a bog turtle into a spotted turtle to analyze both. Evolution, 63 (5), 1348-55 DOI: 10.1111/j.1558-5646.2009.00655.x

After a late (early) night yesterday, I started my day at the R.A. Fisher Award talk, a presentation of results from “an outstanding Ph.D. dissertation paper published in the journal Evolution.” This year’s winner turned out to be a paper I remember reading when it was first published, in which Megan Higgie and Mark Blows showed that sexual selection for mate-signaling hydrocarbons in Drosophila serrata is opposed by selection to avoid mating with the closely related D. birchii. Populations of D. serrata that occur with D. birchii have been selected for different hydrocarbon profiles [$-a] than populations that don’t occur with D. birchii — so that adaptive speciation could result from the opposing selective regimes.

Photo by Jo Mur.

On a more natural history-oriented note, today I learned that honeyguides, the African birds known for their habit of guiding badgers (or humans) to bees’ nests, are also particularly vicious brood parasites. Like cuckoos and cowbirds, honeyguides lay their eggs in the nests of other bird species, and let the parasitized parents raise ’em. Apparently the Greater Honeyguide (the chick in the figure provided) has had its eggs selected to more closely match a variety of host species.

Other highlights:

• Flowers of the genus Pedicularis are more different in co-occuring species than would be expected by chance, possibly to minimize the chance that their shared pollinators, bumblebees, transfer pollen between different species.
• When female Hadena bircuris moths pollinate their host plant Silene latifolia, they lay eggs on the flower so that their larvae can eat some of the seeds produced — much like yucca moths — but male moths of the same species also pollinate, and this may help offset the cost of female pollination.
• Host-parasite coevolution may actually drive the evolution of mutation rates in the host and the parasite, much like yesterday’s demonstration that coevolution can alter migration rates.

Finished the day much more quietly than yesterday, with a handful of folks at my place for burgers and beer. And, hey, I’m getting to bed before 4 a.m.!

References

Higgie, M., & Blows, M. (2008). The evolution of reproductive character displacement conflicts with how sexual selection operates within a species. Evolution, 62 (5), 1192-203 DOI: 10.1111/j.1558-5646.2008.00357.x

In this morning’s session on species interactions and coevolution, everyone was talking about these videos of snakes attacking snails. Turns out that snail shell chirality (the direction the shell spirals) can determine how easy it is for a snake to attack. Very, very cool. Detailed discussion by John Dennehy is here. [Edit, 14 June 2009: link to the video originally found by Matt Labrum.]

I presented today, and survived another twelve-minute talk. Immediately after I finished describing my preliminary conclusion that coevolution between species only generates evolutionary diversity if it exerts disruptive selection on one or the other interactor — the best example of which may be competitive exclusion — Jeremy Fox described a model in which competitor species converge on a single set of traits [$-a]. It’s a cool result, and one I’ll need to consider carefully.

I also learned today that

• A bacterial endosymbiont helps fruit flies fight off parasitic worms;
• It might not “cost” anything for some specialist herbivores to sequester the toxins produced by the plants they eat;
• Coevolution can actually change the migration rates of interacting species; and
• Bacteria and phage living inside horse chestnut leaves are locally adapted within individual trees, but not within individual leaves.

Was out way too late, as the timing of this post may indicate. Don’t think I’ll make the morning sessions. Not that the love-in-a-canoe coffee provided by campus catering will help. Ugh.

References

Fox, J., & Vasseur, D. (2008). Character Convergence under Competition for Nutritionally Essential Resources The American Naturalist, 172 (5), 667-80 DOI: 10.1086/591689