[Ipmpack-users] modelling a gender-switching iteroparous herb

[Eelke Jongejans]

Dear Christopher,

there are probably multiple ways to do what you're describing, but I 
guess your modelling choices also depend on what you want to achieve. Is 
it the population trends you are interested in, and/or the population 
structure of non-flowering, male and female flowering individuals? If 
you are just interested in seed production and assume that pollen is not 
limiting, a size-dependent female-flowering probability in the F matrix 
might be enough. You would then have a size-structured model and no need 
for additional states. I guess you could even translate the stable size 
distribution to proportions males and females. However, if you do need 
males as a state, the options you describe should work: either model a 
series of conditional probabilities as functions of the previous state 
and size of individuals, or use multinomial models. The number of needed 
parameters will increase rapidly if you want both size and state 
transitions to depend on both previous size and previous stage. Or are 
you interested to include 'marriage functions' as well? Not sure if you 
could include those with just size as a continuous state variable and 
size-dependent male and female flowering probabilities. Anyone?

As for IPMpack: we now do accomodate simple age x size IPMs, but I don't 
think you can make such a complicated size x flowering stage IPM with 
IPMpack functions only. Probably (as often when you want to include very 
complex life histories) you will have to develop code to construct your 
own IPM. However, it is often very useful to use bits and pieces of 
IPMpack to achieve this (e.g. by using IPMpack functions to create 
survival, growth and fecundity objects for subsets of individuals).

best wishes,
Eelke


On 09-Jun-14 8:03 PM, Christopher Heckel wrote:
>
> Hello all,
>
>
> I would like to use IPMs to model the population dynamics of a plant 
> that is not only an iteroparous perennial, but also exhibits 
> size-dependent gender switching. Generally for this species (/Arisaema 
> triphyllum/) plants progress from non-flowering to male-flowering to 
> female-flowering over the course of several years depending mainly on 
> biomass accumulation.  However, plants also can retrogress to previous 
> states; for example, a plant that was female in year t could return as 
> male in year t+1.
>
>
> My questions:
>
>
> 1. I think I need to set this up as a stage-size-dependent IPM but I 
> am unsure how to allow individuals to move back and forth between stages.
>
>
> 2. I can use polytomous logistic regression to find size-based 
> transition probabilities among the three stages with greater power 
> compared to a series of binomial logistic regressions.
>
>     a. Is polytomous log-reg appropriate for this?
>
>     b. Could IPMpack tools handle this?
>
>
> Thanks to all for any suggestions to help get me moving forward.
>
>
> Christopher Heckel
>
>
> PhD candidate
>
> University of Pittsburgh
>
>
>
>
>
> _______________________________________________
> IPMpack-users mailing list
> IPMpack-users at lists.r-forge.r-project.org
> http://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/ipmpack-users

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.r-forge.r-project.org/pipermail/ipmpack-users/attachments/20140609/388df3ac/attachment.html>