Curious ranges for a species (poison ivy), why??.?

Question

The "New YorkTimes" today (July 17) has an article about poison ivy. The article says that poison ivy ranges in eastern North America from Canada to Guatemala, and also in eastern Asia, including Japan..

How could it evolve that way, with two populations so distant from each other, separated by the Pacific and by the western

North American land mass and the Rockies and Mexican Sierra? This cannot be explained by continental drift, as North America was attached to Europe, not Asia.

Are there other examples of land species naturally occuring (not spread or interrupted by human action) in ranges separated by thousands of kilometers?

Answer 1

The kudzu analogy is one explanation; it might have somehow traveled between continents via humans or other animals. As "poison ivy" was coined by Capt. John Smith (of Jamestown) in 1609, and it was present in 7th-century China, it could not have spread recently. It doesn't do well in cold climates, so crossing over via the Alaska-Siberia land-bridge seems unlikely. A second explanation could be that if it is a species old enough to predate the continental drift, it could have been present in both Asia, North America, and other locales before somehow dying out in many places. If the American and Asian plants are genetically different (even different species or subspecies?), that would suggest they have been there long enough to adapt and diverge, backing up the second hypothesis. The toxin affects only the higher apes (deer love it!); I assume this is by random chance, but if it did evolve specifically to deter us, that would suggest it originally evolved in East Africa (where we did) and that our very distant ancestors liked eating it.

Answer 2

Didn't foreigners bring it over here? Like kudzu I guess.