The Floristics of the California Islands

The Southern California Islands, with their many endemic species of plants and animals, have long attracted the attention of biologists. This archipelago consists of two groups of islands: the Northern Channel Islands and the Southern Channel Islands. The first group is composed of San Miguel, Santa Rosa, Santa Cruz, and Anacapa islands; the greatest water gap between these four is about 6 miles, and the distance of the nearest, Anacapa, from the mainland only about 13 miles. In the southern group there are also four islands: San Clemente, Santa Catalina, Santa Barbara, and San Nicolas. These are much more widely scattered than the islands of the northern group; the shortest distance between them is the 21 miles separating the islands of San Clemente and Santa Catalina, and the nearest island to the mainland is Santa Catalina, some 20 miles off shore. The purpose of this paper is to analyze the complex floristics of the vascular plants found on this group of islands, and this will be done from three points of view. First will be considered the numbers of species of vascular plants found on each island, then the endemics of these islands, and finally the relationship between the island and mainland localities for these plants. By critically evaluating the accounts of Southern California island plants found in the published works of Eastwood (1941), Millspaugh and Nuttall (1923), Munz (1959), and Raven (1963), one can derive a reasonably accurate account of the plants of the area. Using this as a basis, it is possible to outline the major features of the floristics of the region.