[R-sig-eco] Probabilistic maturation reaction norms

[Marc Taylor]

I'm having some difficulty getting my head around the concept of
'Probabilistic maturation reaction norms' (PMRN) () - as are often used to
describe maturation schedules. These models generally describe when a
certain species becomes mature (e.g. as a function of size and age).

My issue is not in fitting such a model in R to data (e.g. fit <- glm(mat ~
size + age, family = binomial(link = "logit")) ). Rather, I wonder how such
a model can be used in simulating a maturity event in an iterative growth
model (say for a given individual). The above model can predict the
"probability of *being *mature" at a given size and age, but what I am more
interested for my simulation model is the "probability of *becoming *mature"
at a given size and age, and during a given period of time. These two
points of view do not mean the same thing in my opinion, but it looks as if
they may be used interchangeably in the literature. It would seem that the
latter perspective involves use of the model's derivative in some way.

I would be interested if anyone has any thoughts on how such a model could
be correctly applied in a model that simulates a change in maturity for a
given individual.

If this seems like a question more appropriate to r-sig-dynamic-models, I
could also ask there.

Cheers, Marc

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