Please, can anyone explain to me disjunctive plant life?

Question

Why is it that the Joshua Tree exists in Israel and in Joshua Tree, California...ONLY. (Joshua Tree, CA. is approx. a 45 min. drive from Palm Springs, CA. in case your curious.) Definitely, a rather unique life form, on opposite sides of the planet! Please help! If your not really sure, please spend your time answering someone elses question.

Answer 1

Although the Joshua Tree has a very restricted environment, it does grow in other regions of the United States such as Mojave Desert of extreme southwest California, Nevada, Utah and Arizona, at elevations from 2,000 to 6,000 feet.

To be able to reproduce it has evolved a symbiotic relationship with another species, in this case the Pronuba Moth and even then it is narrowed to the female. Joshua trees (and most other yuccas) rely on the female Pronuba Moth (Tegeticula) for pollination. No other animal visiting the blooms transfers the pollen from one flower to another. In fact, the female Yucca Moth has evolved special organs to collect and distribute the pollen onto the surface of the flower. She then lays her eggs in the flowers' ovaries, and when the larvae hatch, they feed on the yucca seeds.

Without the moth's pollination, the Joshua Tree could not reproduce, nor could the moth, whose larvae would have no seeds to eat. Although an old Joshua Trees can sprout new plants from its roots, only the seeds produced in pollinated flowers can scatter far enough to establish a new stand.

Answer 2

Two possibilities:

1) the plant somehow dispersed (on a bird's foot, etc.) all the way from California to Israel, or was brought there by people.

or 2) All of the continents used to part of one supercontinent, Pangea, and have been connected at various times since then. If the Joshua Tree used to be more widespread, then what you have are two remnant populations. The Lost Maples of Texas and the Lost Pines of Texas are two examples.

Answer 3

There may be a particular need for technical assistance to developing countries in adopting coordinated approaches to biosecurity, and the strengthening of relevant national and regional institutions, both in the implementation of controls in their own countries and the negotiation of relevant instruments at the international level, in the light of the pressures on them of an incomplete and disjunctive international framework.