UC San Diego biologist Hopi Hoekstra and her co-authors found that the light-colored beach mice of Florida differed from their darker cousin by a single nucleotide in one gene—at least in Western Florida. The Eastern beach mice seem to have evolved their color some other way. She produced a very nice graphic mapping coat color and light/dark allele frequency (her colleague Bill Lynn did the mouse pelts, in Photoshop).

Doesn’t this lay out their argument well? I couldn’t resist making a few changes, of course, because I’m fussy:

• Fading back the coastline and pointers so the data stood out
• Choosing different and related colors for the mouse ranges
• Making the color of the pointers match the ranges
• Changing the circle fills to a dark brown
• Extending the coastline and range into adjacent states, and labelling the states
• Making the state border a little different from the coastline
• And, in a bit of typographic pickiness, raising the baseline of all the “=” by half a point and putting a thin space either side.

(I notice it all looks very Tufte now, with his patented Tufte beige, but that wasn’t the intention.) If one were to do a serious redesign, my first suggestion would be to move the Oldfield mouse up into Georgia, so that it’s physically separated from the beach mice, and on land while they’re in the ocean. Adding a key to the two allele colors would be nice, and would pretty much remove the need for an explanatory caption. But I think the graphic works fine as is.

Reference: There’s a nice popular article on the findings, and the original paper is:
Hopi E. Hoekstra, Rachel J. Hirschmann, Richard A. Bundey, Paul A. Insel, Janet P. Crossland. 2006. A Single Amino Acid Mutation Contributes to Adaptive Beach Mouse Color Pattern. Science, 313(5783): 101–104. 7 July 2006, DOI: 10.1126/science.1126121. (PDF)