845 
Some guiding principles of biogeography 
Robert F. Thorne 
Abstract 
Thorne, Robert F. (Rancho Santa Ana Botanic Garden, 1500 North College Avenue, Claremont, 
California 91711, United States of America) 1996. Some guiding principles of biogeography. Telopea 
6(4): 845-850. Some years ago, as a response to the proponents of the currently popular 
vicariance biogeography and in defence of classical biogeography, 1 drew up a set of guiding 
principles of biogeography. Until now this set has remained unpublished. These statements of 
the obvious are guidelines that good biogeographers have been using through the centuries. 
They are here reorganized and elucidated by some pertinent examples, and submitted in 
honor of Dr. Lawrie Johnson who has exemplified many of them in his botanical publications 
(as Johnson & Briggs 1984, HiU & Johnson 1995). 
Introduction 
Some years ago in a Southern California Botanists symposium on biogeography at 
Fullerton, California, I was asked to defend classical biogeography against the then 
current onslaught of the 'vicariantists.' A few years earlier a group of museum 
zoologists, mostly ichthyologists, having discovered the prolix works of the botanist 
Croizat and the cladistic writings of the German zoologist Willi Hennig, had decided 
that all the biogeographers that had gone before were 'Darwinian dispersalists 
(Rosen in Nelson & Rosen 1981) and essentially obsolete (Nelson in Nelson & Rosen 
1981), and that now Biogeography based on the suggestions of Hennig and Croizat 
could become a True Science. This development was not a new phenomenon. Every 
ten years or so new procedural bandwagons, crowded with young zealots, appear 
on the biological scene to put the discipline on a Solid Scientific Basis. Their new 
techniques, often quite useful, new buzzwords, and new pantheon of biological 
gods, reign supreme at the U. S. National Science Foundation and in many university 
departments until the next bandwagon comes along to displace them. 
To present classical biogeography fairly and to show that vicariance biogeography 
was not entirely new, 1 presented in the symposium as many of the guiding principles 
of biogeography as 1 could assemble. I made no claim for the originiality nor the 
completeness of these principles, which are, of course, only statements of the obvious. 
They are guidelines that good biogeographers have been using through the centuries 
in their efforts to understand the distribution of plants and animals through time 
and space on our planet. 1 have since then reorganized these principles and assembled 
more pertinent examples to elucidate them. Any suggestions for their improvement 
or the addition of further principles will be gratefully received. 
Guiding principles 
1. Biogeographic inferences and conclusions should be based upon the study of 
the known past and present geographic distribution of all biotic groups, both 
plant and animal. 
This would seem to be the most important dictum of all (Thorne 1963). Unfortunately, 
a couple of the vicariance biogeography books (Nelson & Platnick, 1981; and some 
