Jay--

I'm not sure how one would combine SEM / graphical models with
compositional dissimilarity as a response.  You might be able to fit a
series of models in adonis() or capscale(), comparing just direct factors
to direct + intermediate, etc..  I don't have any good ideas on how you
might test more complex causal structures.

Given that you are dealing with diatoms across space (with environmental
measurements) and down time (in cores, often without environmental
measures), there may be an alternate approach possible based on calibration
approaches to inferred environments (e.g., WACAL) or modern analogs.  I
would look at packages bio.infer, paltran, fossil, and analogue, and search
to see if anyone has pushed them in the direction you want to go.

Tom



On Thu, Mar 7, 2013 at 6:50 AM, Jay Kerns <gjkernsysu@gmail.com> wrote:

> Dear Sarah,
>
> On Thu, Mar 7, 2013 at 9:32 AM, Sarah Goslee <sarah.goslee@gmail.com>
> wrote:
> > That sounds like a job for path analysis or for structural equation
> > modeling, depending on the level of sophistication desired and the
> > hypotheses to be tested.
> >
>
> *Yes!*  I said almost the exact same thing (I didn't say anything
> about Path Analysis because I don't know much about it), but I had it
> in my mind that SEM was targeted more to sociological things and
> didn't know if/that it was common in ecological contexts.  Anyway,
> it's nice to hear that word coming from somebody else.
>
> > There are plenty of good resources for both, in and out of R.
>
> Indeed.  I have some work to do.  Thank you.
>
> --
> Jay
>
>
>
> > Sarah
> >
> >
> > On Wednesday, March 6, 2013, Jay Kerns wrote:
> >>
> >> Hello,
> >>
>
> _______________________________________________
> R-sig-ecology mailing list
> R-sig-ecology@r-project.org
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>



-- 
-------------------------------------------
Tom Philippi, Ph.D.
Quantitative Ecologist & Data Therapist
Inventory and Monitoring Program
National Park Service
(619) 523-4576
Tom_Philippi@nps.gov
http://science.nature.nps.gov/im/monitor

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