NANFA-- Devil's Advocate:Exotics-The Florida Connection

Jeffrey Fullerton (
Fri, 13 Dec 2002 22:00:18 -0500

> Places with already high diversity support exotics with
> little impact to existing biomass, while places with low diversity caused by
> habitat alterations ( be it pollution or physical changes) are showing signs
> of higher impact from exotic species."
South Florida definitely fits into that pattern. It's sort of a
biogeographical no-man's land between the life zone typical of the
southeastern US and the neotropical realm. Climate is just warm enough
for species from places like Mexico and the West Indies to gain a
tenuous toehold in the years between freezes and at the same time warm
enough to stress temperate species that dwell there. It's noteworthy
that the ranges of many fishes that are typical of northern Florida do
not go south of Lake Okeechobee. Likewise for the plant life.

Gone are all the interesting shiners and killies leaving a few of the
latter and the rest are the livebearers like Gambusia and Mollies.
sunfishes, bass and gar. The low diversity is likely a contributing
factor to the ease at which exotic fishes can establish themselves in
these waters.

Water is actually the key to the survival of many things that are
marginally hardy in that subtropical climate. Water is the best storage
medium for heat which can get even tropical fishes thru the occassional
freeze when arctic fronts push all the way down to the Everglades. Also
Florida has quite a few warm springs where the water upwells at a
constant 72 degrees- perfect for tropical fishes.

It's also great for the natural immigrants like the Manatees and a
variety of marine species that will ascend rivers to the springheads.

Above the water life is a little harder for tropical plants and
critters- even though some notorious examples get along too well. Alot
of exotic reptiles and amphibians are confined to the warm microclimates
of urban areas- you can catch Iguanas on the beaches near Miami. Many of
the natural plant migrants- bromeliads and orchids take advantage of the
slightly warm microclimates to be found near the base of cypress trunks
or on branches hanging within a few feet of the water surface. In a
freak cold snap it can make a difference between life and death. You can
pretty much tell which epiphytic orchids in the Everglades are more cold
tollerant by how high they grow in the trees and how far north they
range in the state!

There is little doubt that South Florida is a no-man's land when it
comes to temperate vs tropical flora and fauna. Such a place is bound to
have an abundance of vacant niches just like places where life is
scoured away by glaciers. There the equivalent are hurricanes which not
only scour the land but also bring in new migrants in the form of seeds
and things riding on the winds. Plus the wild fires all making for an
unstable environment that is a golden opportunity for the opportunistic
colonizer- be it natural or brought in by humans.

Many of the exotics living in Florida are pretty much there to stay for
better or worst and humans have claimed alot of the real estate. At
least one bright ray of hope in it all is the bourgeoning interest in
using native plants in landscaping which helps reduce the use of
invasive exotics and also conserves rare native plants by including them
in the human habitat- also beneficial to wildlife and it conserves
resources and reduces pollution of groundwater because native landscapes
don't require intensive watering and fertilization that pampered
cultivated plant life does.

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