Dear All - I find it quite interesting that the majority (if not all) of
the responses to David's question about why Salix predominate at high
latitudes and altitudes are dominated by population ecologists,
discussing mostly pollination syndromes, whereas contributions by
ecophysiologists are entirely absent. One can not fully understand the
distribution of a species without also considering it's physiological
tolerances to biotic and abiotic stresses.
This could especially involve aspects of hydraulic architecture
(avoiding freezing-induced embolisms), phenology (leafing out only when
the probability of xylem freezing is mostly past), achieving high rates
of photosynthesis due to a short growing season, producing a high ratio
of leaves to biomass to maximize whole plant carbon uptake,
biochemical/anatomical/physiological tolerances or avoidance of flooding
stress, and so on. These suites of ecophysiological/biomechanical
adaptations might also have a major influence on reproductive
strategies, yet there is little in the literature relating
ecophysiological adaptations to reproductive adaptations; rather, the
two are most often viewed as separate magisteria (to badly paraphrase
Stephen J. Gould).
To give but one example - if Salix do indeed have high rates of
photosynthesis either on a leaf or whole plant basis, it would suggest
they also have high hydraulic conductivities, which in turn would
support high stomatal conductivities. This would mean they might have
relatively weak wood (large lumens, thin walls). That in turn means a
lowered mechanical advantage, or in other words, the tree can not
support a lot of weight (think hanging, pendulous willow branches on
some species). That in turn might mean producing small seeds which are
highly dispersable, rather than 5 lb coconuts. Just a thought exercise
- I'm sure someone smarter than me (I?) can find logical flaws in this
argument. The point is that we should be considering all aspects of a
species ecology, not just how it has sex.
Howie Neufeld
--
Dr. Howard S. Neufeld, Professor
Department of Biology
572 Rivers Street
Appalachian State University
Boone, NC 28608
email: [EMAIL PROTECTED]
departmental webpage: http://www.biology.appstate.edu/faculty/neufeldhs.htm
personal webpage: http://www.appstate.edu/~neufeldhs/index.html
Tel: 828-262-2683
Fax: 828-262-2127
