Re: New Zealand Flora

Island biotas, like NZ, are about the first things to come to mind when I
hear the complaint that evolution isn't "scientific", because it's telling
stories about things that are just history, rather than doing experiments.
In fact, each island, and its island group, is a separate experiment is
evolution, and the results we see usually make sense, given the original
colonists in each story.

NZ flowers are mostly white [but there are plnety of yellows]:  we
shouldn't be surprised that flower color is related to the available
pollinators.  And by history, there are few bees and butterflies in NZ.
It may actually be simpler than that -- the fact that blue is fairly
common in the northern latitudes may relate to one very important group of
bees, the bumblebees.  Again, there's an important feedback: groups like
composites and umbellifers have radiated in NZ, and these don't support
specialized pollinators elsewhere.  Most spp, most places, are open,
pollen-rich, and white or blue.

It's interesting that there are probably more, wilder hybrids in NZ
composites than about anywhere else in nature.  Many are intergeneric.
The NZ daisies seem to "specialize" in dumb pollinators and all-comers
pollen, and this may have actually fueled their evolution.

It's interesting, conversely, to look at a particular stock of plants that
has a
fairly complex flower, and see how it behaves in different evolutionary
experiments. Gentians are a wonderful
case: there are a number of NZ species in alpine and shorelone habitats
[ie,
the only non-forested sites in pre-human NZ], and they're all while, and
they have open bowls, easy-to-get-at.

In the northern continents, most gentians are blue, and most have deep
floral tubes that are hard to get into.  Some ["bottle" gentians] never
open: the muscular and smart bumblebees have to wrestle into them.

In South America, many gentians go to bright yellows and reds: they're
still tubular, but they've become hummingbird flowers...


Evergreen habit:  this is interesting too, but remember that evergreen is
the original, primitive, trait in woody plants.  The deciduous habit
becomes usual both in cold-winter, nice summer, and in really-nasty dry
season subtropical environments.  So continental vs. oceanic climates
correlate.  But Gondwanaland WAS an ideal place for deciduousness to
evolve.  It was huge, and so predominately continental in climate, and it
spent a lot of time in polar-to-temperate array.  NZ did start with
Gondwana elements, but to the degree that its flora is PRIMITIVELY
evergreen, this is due to the early date of separation, not the climatic
conditions in the southern continents.  

In the cold-adapted groups, like the beeches, it's hard to think that
anything is involved beyond the oceanic climate [and, importantly the 
opportunity to photosynthesize through the winter].  I would expect
deciduousness to evolve pretty quickly if the balance of
energy-expenditure rewarded it.  But most of the NZ flora is really
warm-temperate forest.  It's instructive that even in North America until
very recently, evergreen woodies predominated [eg, late-Miocene floras in
Oregon].  

Relative lack of herbs, no bulbs.  It's the damned forest! Most geographic
areas that are mostly closed forest, especially evergreen forest, would
show this "imbalance", if one
excludes epiphytes [which are mostly ferns and mosses in NZ, but
certainly rich there].  In the Cascade Mts of Oregon, there are many more
native plants species, mostly herbs, in open habitats [originally less
than 5% of the area], than in the forest flora.     


"Barbed-wire" seedlings:  Moas, and no predators, before the Maori.  There
are a few similar seedlings around the world, but most rain-forest trees
simply try either to put everything into vertical growth, to break into
the light, or they perk along on the least possible expenditure, waiting
for an opening into the light.  The barbed-wire might be useful against
browsers, but it would lake energy.  It's possible to guess that in the
absence of significant predators in the forest, moas would have raised
browsing pressure to the level of suburban deer in North America.  At some
point, unprotected tree seedlings would have no chance at all.

Another puzzle: Why all the brown?  I don't think there's any place else
on earth where kelp-brown foliage is common.  It occurs [among species
I've seen in cultivation] in alpine hebes, sedges, grasses, Arthropodium
[a lily], a few raoulias, corokia.... I'd guess that NZers could fill in
others.  Most of the ones I mention are alpine [because I grow alpine
plants], so could it relate to something about the "quality of light". Or
is it the moas again: browser/grazer types with color vision???

loren russell, corvallis, oregon
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