Frequently Asked Questions
FAQs will periodically be added to the pages for each software package below. Answers to the FAQs may or may not be provided (!) and users are encouraged to submit both proposed FAQs and answers via the forms on the pages. Submitted FAQs may or may not be included, at the sole discretion of the website manager. Please ask questions about the use of the software tools only, not about modeling in general or conservation issues.
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Q:> The Vortex Manual states (p23) that "In a population-based simulation, all genetic options and modeling
(e.g., of inbreeding depression) are disabled, as is individual variation (demographic stochasticity)."
Below this it states that "if N typically stays above about 1000, it might be more efficient to run as a population-based simulation."
My question is, for clarification, if I have no inbreeding or genetic data input, will I get the same results using a population-based versus an individual based model if my sample size is high (Ninit 175,000)? I don't want to lose any important information from using population-based, but my population size is so large, the program is taking a very long time to run as individual based. I supposed the demographic stochasticity would be very small and therefore insignificant?
Thank you for your time! A:> If population size stays above a few 1000, the results from a population based model should be almost identical to the individual-based model, except that the population based model will run a LOT faster. The exception to this would be if you are using individual state variables to create a complex model of individual variation in some trait -- but that would be an uncommon thing to do. A disadvantage to the population based model will be that you won't get genetic statistics, but for a population as large as 10,000 or more, genetic drift and loss of variation will be undetectably small anyway.
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