This week the topic of
predator-prey coevolution is continued. The relationship that I will be talking
about has resulted in an evolutionary arms race where the predator has
developed incredible tolerance to its highly toxic prey!
The rough-skinned newt has
over time concentrated an extremely potent neurotoxin within its skin; and
through a series of genetic mutations and natural selection for increased
resistance, the common garter snake has developed a resistance to the newts
neurotoxin (Williams et al., 2003).
The relationship is an evolutionary arms race because as the garter snakes’
resistance is continuing to increase, so is the levels of toxin that the
rough-skinned newt can produce.
The studies show that the
garter snake assesses the newt toxicity and its own resistance, rejecting newts
that are too toxic to devour. The really interesting thing is that all of the
newts that were rejected by the snakes survived attempted ingestion and attack,
even if they had already been ingested for over 50 minutes!!
If the predator doesn’t survive the encounter with the
toxic prey, natural selection for increased resistance cannot occur.
References:
Williams, B. L., Brodie Jr, E. D. & Brodie III, E. D. 2003. Coevolution
of Deadly Toxins and Predator Resistance: Self-Assessment of Resistance by Garter
Snakes Leads to Behavioral Rejection of Toxic Newt Prey. Herpetologica, 59(2), 155-163.
Credits for image located bottom right of image.
That is very interesting. Do they know how the snake assesses the toxicity? Is it just a case of "I feel sick and I'm going to regurgitate this" or is there something more complex going on? What kind of effect does this neurotoxin have on an animal without resistance?
ReplyDeleteThat’s very cool! Have other animals in the environment where newts occur shown a resistance to the toxin, or just the garter snake? Do you think that an evolutionary stand-point will be reached, whereby newts can no longer produce stronger neurotoxin and snakes can no longer develop stronger resistance?
ReplyDeleteDo they know how long it takes to develop their resistance (both animals)? Does it happen over a couple or many generations or perhaps, however unlikely, over a single generation? very interesting!
ReplyDelete