       Re: insect population dynamics

• To: mathgroup at smc.vnet.net
• Subject: [mg24617] Re: insect population dynamics
• From: "Seth Chandler" <SChandler at Central.UH.Edu>
• Date: Fri, 28 Jul 2000 17:23:54 -0400 (EDT)
• Organization: University of Houston
• References: <8lj8q0\$8rr@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```How about something like this to obtain a visual solution:

bughistory[ic_List,iters_]:=NestList[{#[]*
Exp[0.63((1 - #[]/50)) - 0.068#[]], #[]*(1 -
Exp[-0.068*#[]])} &, ic, iters];

ListPlot[bughistory[{25,10},200],PlotJoined->True]

"Mark Hunter" <mhunter at ecology.uga.edu> wrote in message
news:8lj8q0\$8rr at smc.vnet.net...
> I'm trying to use mathematica to run insect population models.  I'm new
> to the system, and wolfram support suggested that I post my question
> here.
>
> The models are simple predator-prey models.  They are non-linear
> simultaneous difference equations.  I've tried using RSolve, but it
> doesn't seem to handle the non-linearity.  Is there a way of using a
> Do-Loop for the same kind of thing?  A simple example of the model that
> I tried is:
>
> RSolve[{a[n + 1] == a[n]*Exp[0.63((1 - a[n]/50)) - 0.068b[n]],
>       b[n + 1] = a[n]*(1 - Exp[-0.068*b[n]]), a == 25,
>       b == 10}, {a[n], b[n]}, n]
>
> I want an output for variables a and n at time n, n+1, etc.
>
> I'd be most grateful for any advice that you can offer, and please don't
> underestimate my current level of ignorance.
>
> Many thanks,
>
> Mark Hunter
>

```

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