Evolutionary arms race

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An evolutionary arms race is when two species (or populations) are so linked that a change in one indirectly causes a change in the other.[1] It is a metaphor drawn from the so-called arms race between the West and the Soviet Union, after the second world war. Evolutonary arms races are a kind of co-evolution.

Examples[change | change source]

  • Predatorprey evolution is the classic example. A new twist by the predator must be answered with a new defence by the prey.
    • Conifers grew tall, to some extent out of the reach of sauropod dinosaurs. Dinosaurs grew taller and continued eating the conifers.[2]
    • Gazelles run fast and so do cheetahs; both have been under a continual series of similar changes which increase their running speed.
    • The Rough-skinned newt, the Garter snake and toxin resistance is a well-researched case study. Where the two species live together, the newt produces more toxin, and the snake has evolved to resist it; where they live separately the newt toxin is milder, and the snake has little resistance. The snakes pay a price for their resistance: their digestion and body metabolism is slower than related species. "Really resistant snakes have slower crawl speeds than snakes with little or no resistance".[3][4]
  • Parasitehost evolution is another classic.[5] As a host species splits into two, so do its parasites. And when the host immune system defends against the parasites, so they adapt and survive.
  • Sexual selection can be a kind of evolutionary arms race.
    • Female mating preferences are known to be responsible for the evolution of male secondary sex characteristics.[6] Selection is between males in species where female choice is the pairing method.
    • Sexual conflict between breeding partners is quite common.[7] The basic interests of the male and female can be quite different, and each develops adaptations to get the best 'deal' in terms of offspring. Males: their interest is to mate with a large number of completely faithful females, thus spreading their genes widely in the population. Females: Their interest is to mate with a large number of fit males, thus producing a large number of fit and varied offspring.[8][9]

References[change | change source]

  1. In the sense that, the selection pressure on the second partner changes, and counters the change in the first partner.
  2. Bakker, Robert T. 1986. The dinosaur heresies: new theories unlocking the mystery of the dinosaurs and their extinction. Morrow, New York. Chapter 9 When dinosaurs invented flowers. p181 "The warfare between plants and herbivores...".
  3. Science Daily
  4. Garter snake info
  5. Price, Peter W. 1980. Parasites. Princeton University Press, Princeton N.J. p34: "The stepwise coevolutionary process results in extreme specialization and complex defense mechanisms".
  6. Andersson M 1994. Sexual selection. Princeton Univ Press, Princeton, NJ.
  7. Arnqvist G. and Rowe L. 2005. Sexual conflict. Princeton University Press, Princeton New Jersey
  8. Schilthuizen, Menno 2001. Frogs, flies and dandelions: the making of species. Oxford University Press, p92. ISBN 019850392X
  9. Crudgington H. & Siva-Jothy M.T. 2000. Genital damage, kicking and early death. Nature. 407: 855-856.