lpetrich

Over at <a href="http://www.pnas.org" target="_blank">http://www.pnas.org</a> (subscription may be necessary for full articles), there are some interesting evolution articles:

* Waddington's canalization revisited: Developmental stability and evolution

is about how the wild-type varieties of many organisms show remarkably little variability compared to what is conceivably possible; consider wild vs. domestic of several species, like wolves vs. dogs.

This could be due to such low variability being directly adaptive, but the paper's authors explored another hypothesis: that it is a side effect of features having been produced by a big network of development-control genes. They simulated such a network and found such low variability, which was a byproduct of the gene networking -- genes were selected to be compatible with each other, limiting how much they could reasonably vary.

* A hemocyanin from the Onychophora and the emergence of respiratory proteins

Hemocyanins are copper-containing, oxygen-carrying proteins found in arthropods and mollusks; these are separate co-optations of other enzymes. Onychophorans look much like caterpillars, and have long been thought to be closely related to arthropods.

An onychophoran was discovered to have hemocyanin, and it was sequenced and compared with those of several arthropods. The resulting family tree was largely consistent with other work, with this branching order:

Onychophoran
(short branch)
Chelicerates (spiders, scorpions, mites, horseshoe crab)
(very short branch)
Myriapods (centipedes, millipedes)
(medium-length branch)
Insects and crustaceans (shrimp, lobsters, crabs)

This means that oxygen-carrying proteins have evolved at least three times: in arthropods/onychophorans, in mollusks, and in vertebrates.

* Tracing the LINEs of human evolution

Long Interspersed Nuclear Elements are snippets of DNA that induce copying of themselves; much of the human genome is composed of the &gt;500,000 LINE's in it. Though many of them in are older than the late-Cretaceous mammalian radiation, the paper presents evidence that some of them have appeared relatively recently, after the divergence of our species and the chimpanzees.

* The metapopulation genetic algorithm: An efficient solution for the problem of large phylogeny estimation

Another application of simulated Darwinian evolution: finding family trees from molecule sequences. And a successful one at that.


(Not in PNAS) Here's a myriapod/metric joke:

1 centipede = 1/100 pede
1 millipede = 1/1000 pede
Therefore,
1 centipede = 10 millipedes