Mice, owls & peppered moths

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Mice, owls & peppered moths

Postby Chris Sergeant » Fri Feb 25, 2011 5:09 pm

In the deserts of Southwest America, the rock pocket mice are mostly sand coloured, well camouflaged as they scurry across beige coloured outcrops. However in some areas, ancient lava flows have left behind areas of blackened rock. There the same species of rock pocket mouse has only dark coats, having evolved an entirely distinct and, for their surroundings, equally well-disguised pelage. In a study in The Proceedings of the National Academy of Sciences, researchers report identifying the gene responsible for the evolution of dark coat coloration in these mice, pinpointing the DNA sequence changes that underlie this classic story of evolutionary change, the furry counterpart to the famous case of the peppered moth.
In this case the sandy and lava flow substrates are entirely natural phenomena. Thus the genetic changes are underlying an adaptive change where the evolutionary forces are natural.
The researchers found that a certain cluster of mutations at the Mc1r gene could be found in every dark mouse on the Pinacate lava flow. However dark mice on another lava flow in New Mexico did not share those mutations. So the same dark colour has evolved independently in the two different populations through different genetic solutions to the same evolutionary problem.
However while many dark forms are abundant and can be studied at leisure, the black forms of the peppered moth are slowly disappearing due to the clean air.
http://query.nytimes.com/gst/fullpage.h ... A9659C8B63

Brown owls used to form 30% of the tawny owl population in Finland, but now have increased to 50%. The colour of a tawny owl's plumage does not change throughout its lifetime, so the owls can be split into two categories - brown or grey. Colour maps of breeding pairs and their offspring were assembled. This showed that plumage colour was indeed hereditary; pairs with grey plumage had the grey version of the gene that coded for plumage colour, so produced grey offspring. With mixed colour breeding pairs, the grey colour trait was dominant, so the offspring inheriting both grey genes and brown genes were likely to have grey plumage.
Data was gathered from long-term tawny owl studies carried out across Finland over the last 30 years. The team examined tawny owl data, which was compiled by amateur bird ringers from the Finnish Museum of Natural History. This revealed that, in years when winter weather was particularly severe, there was a higher mortality rate in the brown owl population. Perhaps because brown owls were more visible to predators when there was thick snow cover. As the winters have become warmer, and snow cover has reduced, the brown tawny owl populations have greatly increased. So climate-driven selection has led to an evolutionary change in the population.
http://news.bbc.co.uk/earth/hi/earth_ne ... 401733.stm
Chris Sergeant
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