ASCDC
E-NEWSLETTER

On Taiwan‚ an island separated from the rest of the world‚ there are many species that do not live anywhere else in the world; these species are called endemic species; endemism occurs when a species’ range is limited to a certain area because of historical‚ ecological or physiological factors.

How‚ then do endemism species appear. Imagine for a second‚ a colony of deer live on an unnamed mainland. One day‚ a big earthquake separates this colony on the east and west sides of mountains that appear as a result of orogeny‚ colony A on the east side and colony B on the west side; the two colonies then live their lives totally separately‚ of course having no opportunity to interbreed. These two colonies will evolve separately; for example‚ the east side is grassland terrain‚ with bushes so the deer just need to keep their short necks and they can eat the leaves and grass. On the west side there is only a small amount of grassland and trees that are taller than they are. Over time‚ colony B’s deer’s short necked deer are gradually superseded and the ones that are left have longer necks. Gradually‚ A and B colonies look and behave more and more differently‚ and eventually separate species are evolved. This example is‚ of course‚ just a hypothetical separation of a species‚ there are other reasons and other evolutionary results.

Formosan Blue Magpie
( Source of photo credit : Digital Taiwan )


To understand Taiwan’s situation‚ we have to go back 18‚000 years ago: at that time the world was hit by the coldest period for almost 150‚000 years‚ known as the last glacial maximum. The ice caps of the north and south poles expanded and a large amount of the earth’s water became ice and snow‚ stored in glacier‚ depriving the seas and oceans of water and causing their water level to fall substantially.

The continental shelf of the Taiwan Straits‚ just 80 meters deep‚ was exposed and Taiwan and Mainland China were joined. After the appearance of this “land bridge‚” many animals moved south to avoid the extreme cold; Taiwan’s high mountains also allowed vertical distribution and meant the island had hot‚ warm‚ temperate and frigid climatic zones. At that time Taiwan had both mainland and island species. Around 14000 years ago the earth gradually began to warm up and sea levels slowly rose‚ leaving Taiwan once again an island; the species on the island were separated from the colonies on the mainland and evolved separately‚ becoming the endemic species of Taiwan of today.