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9. Similar major disjunctions involving oceanic islands and many transoceanic ranges, 
on the other hand, generally involve long-range, overseas dispersal including 
transport by aboriginal or modem man. 
The fragmentary, disharmonic nature of the biota and the high proportion of 
endemism on oceanic islands are indicative of this waif origin of highly vagile 
organisms from many directions, often over long periods of time (Balgooy 1971, 
Barlow & Schodde 1993, Fosberg 1948, Thorne 1963, Zimmerman 1948). Many 
transoceanic range disjunctions, as those involving Africa and South America (Thorne 
1972, 1973, 1978) seem to require long-distance dispersal as the most reasonable 
explanation. Similarly, the rather common western North American-temperate South 
American transtropical disjunction is best explained by long-distance dispersal, 
probably by shore- or water-birds (Raven 1963, Thorne 1970, 1978, 1986). 
10. Coincidence in biogeographic patterns, tracks, or range disjunctions, though often 
suggestive, does not guarantee that two or more taxa have similar dispersal histories. 
Often taxa with similar ranges or disjunction patterns have achieved those ranges 
from different source areas, at different times, by different vectors, and by different 
routes. Thus each taxon should be studied on its own merits. The primary goal of 
vicariantists to identify similar patterns is commendable, but to attempt to explain 
all similar patterns by the same vicariant event is overly simplistic. The bipolar 
disjunct distributions of Empctrum L., Hippuris L., Littorella P. Bergius, and other 
genera probably indicate long-distance dispersal from northern North America in 
Pleistocene or later time. However, Euphrasia L. is, at least, an exception to this 
probable route and explanation. According to Du Rietz (1960) and Barker (1986), the 
South American species of the genus are more closely related to the western and 
southern Pacific species than they are to the boreal North American species (Thorne 
1972). A similar Gondwanic distribution pattern to that of Euphrasia is discussed by 
Wilson (1986) for various alpine species of Cyperaceae and Juncaceae. 
11. Interpretation of range disjunctions must involve careful reference to a time frame, 
probable time of origin of the group under study as well as the time when the 
suspected catastrophic event, continental displacement, mountain building, inundation 
by epicontinental seaway, glaciation, desertification, etc. might have occurred. 
It is naive to argue that separation of conrinents explains a major continental disjunction 
when the group concerned had apparently not evolved until after the continental 
disjunction. This has been done regularly for tropical African - tropical American 
disjuncts, even for Rhipsalis baccifera (J.S.Miller) Steam, so obviously specialized for 
bird dispersal in its succulent, white berries with viscous pulp (Thorne 1973). 
12. Degree of differentiation between vicariant groups of two disjunct areas reflects 
the amount of evolution that has occurred since the origin of the sister groups from 
a common ancestor and veiy roughly the time that has been available for that evolution. 
Understood, of course, is the truism that evolutionary rates do vary greatly among 
different organisms and different organs of different taxa. Nonetheless, subspeciation 
and speciation surely take place much more rapidly than the evolution of genera, 
tribes, subfamilies, families, or even higher categories. The separation of South 
America from Africa, suggested from 100 to 90 million years ago, is not necessarily 
a valid explanation for those species and genera, and even perhaps most families, 
that are transatlantic in their ranges. It may well be the explanation for those 
caryophyllalean families that are endemic or largely so to Madagascar, Africa, and 
America. The protocaryophyllalean ancestors were probably isolated on the resulting 
