Of Mice and Moths and Lizards Too

Earlier today I published an interesting picture. Here it is again for reference:


Candidates for adaptation from standing variation. (a) Peromycus polionotus subspecies. The mouse in (i) is a typical mainland mouse (P.p. subgriseue) and the mouse in (ii) is a typical Santa Rosa Island beach mouse (P.p. leucocephalus). Two candidate genes, the melanocortin-1 receptor (Mc1r) and its antagonist, the Agouti signaling protein (Agouti), control most of the difference in pigmentation between subspecies. (b) Threespine stickleback Gasterosteus aculeatus, cleared and stained with alazarin red to highlight bone structure. The fish in (i) has many bony lateral plates, a phenotype typically found in the ocean. The fish in (ii) has many fewer plates and is typically found in freshwater lakes. (c) Apple maggot fly Rhagoletis pomonella. The flies in (i) are from a host race specialized to feed on hawthorn. The fly in (ii) is from a host race specialized to feed on apple. Standing variation originating in Mexico is implicated in the evolution of overwintering pupal diapause in the apple race.

Candidates for adaptation from standing variation. (a) Peromycus polionotus subspecies. The mouse in (i) is a typical mainland mouse (P.p. subgriseue) and the mouse in (ii) is a typical Santa Rosa Island beach mouse (P.p. leucocephalus). Two candidate genes, the melanocortin-1 receptor (Mc1r) and its antagonist, the Agouti signaling protein (Agouti), control most of the difference in pigmentation between subspecies. (b) Threespine stickleback Gasterosteus aculeatus, cleared and stained with alazarin red to highlight bone structure. The fish in (i) has many bony lateral plates, a phenotype typically found in the ocean. The fish in (ii) has many fewer plates and is typically found in freshwater lakes. (c) Apple maggot fly Rhagoletis pomonella. The flies in (i) are from a host race specialized to feed on hawthorn. The fly in (ii) is from a host race specialized to feed on apple. Standing variation originating in Mexico is implicated in the evolution of overwintering pupal diapause in the apple race.

Sticklebacks are amazing creatures and have been the subject of quite a few studies looking at the effects of natural selection on the reduction of spines and pelvic reduction. Below that we see Rhagoletis which has also been the subject of a few studies looking at the effects of natural selection on speciation. By themselves both of these two species are interesting, but the really interesting critter in the above picture is the mouse, or I should say mice. As the caption explains one of these (the darker colored one) is a mainland form and the other (the lighter colored) is a island form that lives on beaches. The color of the coat is controlled by a complex interaction between the melanocortin-1 receptor (Mc1r) and the agouti signaling protein. Mc1r has been implicated in the color variation in reptiles, wild and domestic pigs, and rabbits, to name a few species.
In wild pigs mutations occur in the Mc1r gene but they are silent mutations that don’t affect coat color. In domestic pigs the mutations do affect coat color. In each case selection is present (natural in the former and artificial in the later). At any rate, the idea that selection affects coloration and that different colors have survival value or can be selected against has been around for awhile. One of the earlier studies looked at color variation among mammals in the Tularosa Basin of New Mexico. Substrate color in the Tularosa Basin undergoes some quite dramatic changes and the coat color of the vertebrates matches it.
I mention all this because Michael Majerus has an interesting article on Biston
betularia
in Evolution: Education and Outreach
Industrial Melanism.jpgNonmelanic (left) and industrial melanic (right) forms of some British moths. From top to bottom: peppered moth–Biston betularia, lobster moth–Stauropus fagi, figure of eighty–Tethea octogesima, scalloped hazel–Gonodontis bidentata, brindled beauty–Lycia hirtaria, pale brindled beauty–Apocheima pilosaria, green brindled crescent– Allophyes oxyacanthae, dark arches–Apamea monoglypha
As Majerus points out, Biston betularia isn’t the only species of moth affected by melanism, nor is England the only country the phenomena occurred in, rather it occurred in parts of America also. Majerus quite convincingly answers all of the criticisms leveled against the Biston betularia experiments, but even had he not the central premise, that variation in coloration can be acted upon by selection, is well established by countless examples – some of which have been mentioned above. Majerus cites a number of studies that have occurred since Kettlewell did his studies – none of which get mentioned by creationists or their cheaper tuxedoed cousins in the ID movement. For the creationists and the ID movement Kettlewell’s research apparently exists in a vacuum with no antecedents and nothing following from it. The same lack of concern with context – whether it be what came before or what came after – can be seen in creationist’s discussion of Barrett et al’s paper on threespine sticklebacks. Even though there are quite a few papers relevant to the issue raised by Barrett et al none of them get mentioned. The result of which is that creationists tend to adopt conflicting positions each time a new paper comes out and they end up arguing at cross purposes. I guess they agree with Emerson that:

A foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines.

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