Island Isolation

Torrey pine

Tim Hauf, timhaufphotography.com

Island Plant Adaptations Guide Stop 5

Approximately 137 (22 percent) of the 621 native plants found on the Channel Islands are endemic; that is, these plants are found only on the Channel Islands. When a localized plant population is isolated for a very long time, environmental and genetic factors can result in the development of a new species. If the new species remains isolated, it is said to be endemic.

Some endemic plants are relict species. Relict species are plants that evolved under a different climate and were once widespread, but which are now restricted to locations where conditions resemble the earlier environment.

A prime example of a relict species is the Torrey pine, which graces the eastern shore of Santa Rosa Island. Ten thousand years ago, when the climate was cooler and moister, Torrey pines were probably widespread throughout coastal California. As the climate grew warmer (and drier) these trees became restricted to cool, foggy sites near the ocean. Today Torrey pines are found in only two locations; approximately 4,000 trees grow on Santa Rosa Island, and a closely related subspecies is found in Torrey Pine State Reserve near Del Mar in San Diego County.