Traffic in plants and plant seeds

[Paul Cherubini]

In reponse to John Grehan:

My intention was to point out that yes,  the monarch butterfly would
have had alot less choice in available overwintering habitat if it were
not for the introduction of eucalyptus trees from Australia to
California in the late 1800's.  This example points out that sometimes
even native insects can be opportunists and benefit from the
introduction of exotic plants.

In the late 1800's the North American monarch also became established in
Australia. This coincided with the inadvertent introduction of an Africa
species of milkweed (Asclepias fruticosa) which became abundant in
Australia. 

Here is a practical example of the impact of plant bigotry:  In Pacific
Grove, California where monarch butterflies have always had native
Monterey Pines on which to roost, the pines are dying of an
uncontrollable pitch canker disease.  Even new plantings succumb to the
disease within 5-10 years.  Thus to maintain suitable monarch habitat in
Pacific Grove a monarch conservation group wants to plant eucalyptus
trees.  But the California Native Plant Society and similar groups don't
want a foreign exotic growing in their native pine forests. So the
monarch habitat is in decline due to a clash of philosophies in a city
the prides itself on being known as the "Monarch Capital of the World".

Paul Cherubini, El Dorado, California
paulcher at concentric.net