Biogeography of the Puerto Rican Bank: Flotsam Transport of Terrestrial Animals

Of 59 pieces of flotsam picked up at sea 0.5—16 km from its nearest probable origin, 25% contained at least one live terrestrial animal and 6% had three or more species; one green plant contained 12 species. In many cases a number of conspecific individuals occurred in the same drift item. The animals represented included 19 families of insects, as well as psuedoscorpions, snails, spiders, mites, millipedes, isopods, and worms. Some families were represented by several (up to five) species. Eight drift items recovered approximately 120 km from the nearest land lacked terrestrial animals. A piece of bamboo which washed up on the beach of Cayo Ahogado contained a dipteran and a beetle. Flotsam transport is clearly a significant biogeographic factor among the islands of the Puerto Rican Bank.