Natural Selection on a Major Armor Gene in Threespine Stickleback
Rowan D. H. Barrett*,Sean M. Rogers,
Science 10 Oct 2008:
Vol. 322, Issue 5899, pp. 255-257
Abstract
Experimental estimates of the effects of selection on genes determining adaptive traits add to our understanding of the mechanisms of evolution. We measured selection on genotypes of the Ectodysplasin locus, which underlie differences in lateral plates in threespine stickleback fish. A derived allele (low) causing reduced plate number has been fixed repeatedly after marine stickleback colonized freshwater from the sea, where the ancestral allele (complete) predominates. We transplanted marine sticklebacks carrying both alleles to freshwater ponds and tracked genotype frequencies over a generation. The low allele increased in frequency once lateral plates developed, most likely via a growth advantage. Opposing selection at the larval stage and changing dominance for fitness throughout life suggest either that the gene affects additional traits undergoing selection or that linked loci also are affecting fitness.
Barbarian chuckles:
Ham is well aware of the evidence showing evolution. He responded years ago, by redefining"evolution" to mean "change so drastic that no one could live long enough to see it happen."
As in the above case, it is the cause of most evolution. As you just learned, observed natural selection resulted in a change in alleles frequencies that made the sticklebacks more fit in their new environment. Which is, as you just learned, what evolution is.
Any other questions?