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Biological warfare and the coevolutionary arms race :

The end?

Edmund D. Brodie, Jr.
The discovery of trait matching within different snake and newt populations strongly supported the Brodies' hypothesis that garter snakes and newts had coevolved. After showing that the newts' toxicity level could evolve by natural selection and that the snakes' resistance level could evolve by natural selection, they had finally shown that the snakes and newts actually seem to be evolving in response to each other.

Butch's original quest to figure out what killed the hunters in their campsite started him on a serious journey into evolutionary biology. After discovering that the newts were indeed toxic, he began investigations into why they had evolved such extreme toxicity, and, in the process, uncovered a raging battle — an evolutionary arms race. The unfortunate hunters were simply caught in the crossfire.

The Brodies have answered many questions since Butch began investigating newt toxicity more than 40 years ago. What killed the unlucky hunters? How did newts evolve toxicity? Why are some newts so extremely toxic? What predator evolved resistance to the newt toxin? What are the tradeoffs involved in this arms race? The Brodies' studies have shed light on those questions and many more. With so many questions answered, could this be the end of the Brodies' investigation?

Dr. Edmund D. Brodie, III
Edmund D. Brodie, III
In fact, the Brodies have even more questions to answer now! For example, in their studies of trait matching, the Brodies discovered that in some populations, the arms race seems to be more heated than in others. In those populations engaged in the most intense evolutionary battles, toxicity and resistance have hit incredibly high levels; but in other populations, the battle seems to have either petered out at intermediate levels of toxicity and resistance or is just getting started. And in a few cases the Brodies even encountered mismatched traits within a population — highly toxic newts paired with low resistance snakes or mild newts paired with super-resistant snakes...What heats up the battle in some populations and cools it down in others — and what it is going on in those mismatched populations? Other factors must be at play, but what are they? The investigation (and the battle) continues...

Photos provided by Edmund D. Brodie, III and Edmund D. Brodie, Jr.

Biological warfare
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To learn more about what the Brodies are investigating now, check out these advanced side trips: