What is the Wallace Line?

Why is there a huge difference in diversity? What causes it?

Is the wallace line applicable to flora biodiversity?

I find it interesting how ecological isolation creates such functional diversity within species. I used to live in Hawaii, and many of the plant and animal species are endemic to those islands. Because the islands are geologically young, many of the plant and insect species display relatively prehistoric features.

There are touch sensitive plants that will close their fronds as you move your hand across them. The islands also have ferns that can grow to twenty feet tall, spiders that glow in the dark, and white flowers with glass like thorns in the pistils, among other things. When I was a kid, I used to walk through the bushes on the island pretending I was a prehistoric hunter searching for long extinct animals.

@ Istria- I find what you say to be very interesting. I wonder if the evolution of Russian and North American brown bears is an example of parallel evolution.

I once read about the parallel evolution of marsupial and placental animals in South America, The Old World, and Australia. When these continents split 100 million years ago, the species on each landmass evolved into similar species that had completely different reproductive systems. In Australia, the marsupials became the dominant species, while the rest of the old world saw the rise of placental species. In South America, the proliferation of both types of animals was present. An example of a specific species is the saber tooth tiger of Europe and the marsupial saber tooth of South America. These species were very similar, yet they evolved with completely different reproductive systems. Could this be the same for North American and Russian species?

I had never heard of the Wallace line before reading this article. I find it interesting that there is such a marked difference between the species that lie on opposite sides of the Wallace line. It makes sense though. It also explains why some of the animals that inhabit parts of Russia are so similar to the some of the animals that inhabit North America. Grizzly bears, wolves, rabbits, deer, and so many other animals are similar even though they are on other sides of the world.

I imagine that their similarities are due to the fact that the two continents were connected by ice bridges at various times in history. This must have enabled many of these animals to migrate across continents. It seems like unless there is some type of impassable land barrier, or species have small habitat ranges than few species are endemic to only one continent or region. This is just an idea. Does anyone else have any thoughts?