Hi, cody,
Yes, the fact that the height of the stalk is a function of number of altruists in the aggregation is what drives the model. We made the reproductive rate a linear function of height. We could have biased the model more toward altruism if we had made it a geometric function of height. This would actually be reasonable. We considered two models for how the spores in the reproductive part are distributed, the dandelion model and the burr model. In the dandelion model, they are carried away on the wind and disseminated into the world; in the burr model, they are picked up by some perambulating insect and deposited in one spot. We did some heavy thinking and came to the conclusion that the dandelion model was implausible; apparently the air in the layer that close to the ground is about as “windy” as molten led. The burr model, however, seemed much more promising. We did little experiments “brushing up against” the fruiting bodies with a forceps and indeed the do stick and can restick to something else as a whole
The two types, altruist and cheats, are assigned to the fruiting body and to the stalk at random, so that if ¾ of the members of the aggregate are cheats, then ¾ of the cells in the reproductive bit are cheats, as well as ¾ of the cells that WOULD go to the stalk. Those cheats that WOULD go to the stalk if they weren’t cheats, instead roll themselves up into resistant particles and remain in the soil as individuals. I think I give them one chance in 3 to survive, since the reason that fruiting bodies are formed seems to have something about the deterioration of local conditions for slime mold amoeba survival. This is the reason that only cheats end up as dropouts. Only altruists end up in the stalk because that’s what it is to be an altruist.
Does this help?
I yield to no other man in the depth of my newbieity.
Nick
Nick Thompson
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https://wordpress.clarku.edu/nthompson/
From: Friam <[hidden email]> On Behalf Of cody dooderson
Sent: Monday, April 19, 2021 9:24 PM
To: The Friday Morning Applied Complexity Coffee Group <[hidden email]>
Subject: Re: [FRIAM] OOOOPS! RE: Evolution of fruiting bodies in slime molds
Can you explain this a little bit to a newby. I may have this all wrong. Is this diagram saying that the more altruists in a group the taller the fruiting body? Why do cheats always end up at the top of the fruiting body?
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slime mold diagram 210418.1501pdf.pdf (130K)