Weird result of overdominance
Prothama Manna
I am simulating an invasion scenario where a fraction of the native population is separated to form a new population. This new group remains in a bottleneck for several generations before expanding under a Wright–Fisher (WF) model. I log heterozygosity and Fst every 10 generations.
When I plot these metrics, I observe a sudden bump at the 13th generation, particularly for overdominance. My expectation was that as the founding population begins to interbreed, homozygosity would increase and heterozygosity would decrease—trends that are evident in later generations. While this bump could represent an interesting biological phenomenon, I want to ensure that the code is functioning as intended. In the plot, Scenario 8 is overdominance, 2 is no selection and 9 is additive dominance.
Do you think there might be an issue with the code?
Have a great rest of your day,
Best,
Prothama
Ben Haller
This is really a population genetics question, not a SLiM question, so it's outside of my area of expertise (and the domain of this mailing list, too). There has been some discussion of overdominance on the list before, and it can certainly behave strangely; you might search the list for the term "logjam". However, I don't know whether that's relevant to your situation. If you wonder whether your code is correct, I'd suggest standard debugging tactics – insert print()/catn() statements to check relevant values, use debug points in SLiMgui to trace the execution, validate the model by implementing the same concept in an alternative modeling framework like fwdpy, examine the behavior of the model in SLiMgui, etc. Good luck!
Cheers,
-B.
Benjamin C. Haller
Messer Lab
Cornell University
Prothama Manna wrote on 3/27/25 9:44 AM:
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SLiM forward genetic simulation: http://messerlab.org/slim/
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