Why Ecology Matters by Charles J. Krebs

Author:Charles J. Krebs [Krebs, Charles J.]
Language: eng
Format: azw3
ISBN: 9780226318295
Publisher: University of Chicago Press
Published: 2016-05-24T16:00:00+00:00

Figure 8.1 Natural selection for birth weight in humans. Data from United States for infants for 1990 and 2008. The optimal birth weight (arrow) is 4.25 kilograms, with a broad range of minimal mortality between 3.2 kilograms and 4.8 kilograms. Because of medical advances, infant mortality has been falling steadily, so the 1990 curve is higher than the 2008 curve. (Data from Mathews and MacDorman 2012.)

Evolution of Resistance to Poisons in Rodents

Evolution can work to our disadvantage if we are not careful, and this is the history of rodent control with anticoagulants. The main poisons used to control rats in cities and on farms are anticoagulants. The first-generation anticoagulant was warfarin (patented in 1948 by the Wisconsin Alumni Research Foundation, or WARF). Warfarin prevents mammalian blood from coagulating and in minute doses it was discovered to have a great medical benefit by preventing blood clots in people susceptible to strokes. In larger doses it is toxic to mammals and birds. Warfarin in its various trade names was considered to be the solution to the problem of rats in cities and farms, but already in 1958 Norway rats (Rattus norvegicus) were found in Wales that were resistant to warfarin (Buckle 2013). Five mutations have been discovered that confer resistance to anticoagulants in Norway rats in the United Kingdom, but in continental Europe only one or two genetic mutations seem to be involved. The development of resistance to first-generation anticoagulants has occurred independently in different localities in Europe (Figure 8.2).

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