Jason and all:
Answering questions like this one should be a cornerstone of the discipline
of ecology, but all that has been done (based on my limited knowledge) thus
far is to conjecture on the basis of thin evidence, most of it lacking
integration and characterized by looking backwards.
I have advanced the proposition (again based on my limited knowledge and
understanding--my own conjecture) that the first law of ecology is the
simple fact that ORGANISMS DO WHAT THEY CAN, WHEN THEY CAN, WHERE THEY CAN.
I have drawn criticism for this (including, but not limited to, stony
silence, cries of outrage, and sniffy dismissal), but I have yet to receive
a point-by-point denial of this proposed axiom. I suspect that no
prestigious journal would publish my musings upon this theme, but I consider
Ecolog to be even more prestigious (and a helluva lot cheaper).
While physiological ecologists, geneticists, and their allies have laid
considerable groundwork upon which a deep understanding of what is involved,
I suggest that nothing short of a scientific inquiry on the scale of a
"biological Manhattan Project" or genome-mapping project-type effort as a
launching pad and model will be necessary to go much beyond conjectures in
answer to the principles involved or to questions such as Hernandez has
proposed.
A centralized repository and a framework for data entry would be necessary,
and a worldwide data-collection effort would be required. I suspect that
such could be done, relatively speaking, "on the cheap," largely by
volunteers. Some of the work could be done by children in the primary and
secondary grades, and by serious amateurs. Errors would eventually be
ferreted out, and the project would likely never be finished, but would be
under continuous extension and refinement. Much of the data already exists;
it is simply not organized in relation to other similar data embedded in
countless studies around the world. Conjectural values could even be
inserted temporarily until the real data comes along.
This would be a giant "employment act" for ecologists and others, and the
payoff would be huge. It would have huge economic implications, so once
understood by bean-counters (yeah, I know--that's asking a lot) it should
receive support from industry, commerce, and government.
As to Jason's excellent question, he could start by comparing some of the
more obvious suspects like temperature ranges/seasons/changes, pH, and
light/radiation, adding other factors that are uniquely present or absent as
well as scale differences of those factors and combinations thereof and the
physiological/genetic characteristics which are governed by and govern them,
and perhaps come up with some seductive guesses.
My own conjectural guess (noting my almost total lack of specific knowledge
about the taxon under consideration) is that the disjunct populations he has
observed may be relict stands that have defied past climate shifts, which
have influenced both their survival and the displacement of their
less-well-adapted cousins over time. Lots more guesses come to mind, but
that would lead to the need for a more expensive platform. It would be
interesting, for example, to compare any early aerial photography with
current remote-sensing data to get a feel for stand expansion contraction
and some on-site studies of age classes, increment core studies, and other
old-fashioned stuff.
Yr. Ob't. Sv't.,
WT
----- Original Message -----
From: "Jason Hernandez" <[email protected]>
To: <[email protected]>
Sent: Wednesday, January 25, 2012 9:08 AM
Subject: [ECOLOG-L] Isolated populations of Sitka spruce
Sitka spruce (Picea sitchensis) is a characteristic tree of the coastal "fog
belt" of the Pacific Northwest. Arthur Kruckeberg, in _Natural History of
the Puget Sound Country_, shows a nice map of the "Sitka spruce" zone's
extent relative to the "western hemlock/Douglas-fir" zone in Washington
State. Essentially, the Sitka spruce zone extends in a belt approximately 20
miles wide along the coast and the Strait of Juan de Fuca, but ends at the
Olympic rain shadow at the San Juan archipelago; it does not extend south
through the inland waterways of Puget Sound. The explanation given is that
this species lacks the ability to regulate transpiration, and so requires
the high humidity of the fog belt.
However, in my years of observations, I have found at least three
populations of Sitka spruce in central and southern Puget Sound, far outside
the regular "Sitka spruce zone." These populations are small in extent, with
the species absent from the rest of the central and southern Puget Sound
basin. I have been curious about what factors have allowed these populations
to establish and persist outside the fog belt, but I struggle to formulate
any workable hypotheses. Has anyone else worked with any similar phenomena?
Jason Hernandez
