Rare and Endemic Trees of Puerto Rico and the Virgin Islands

Little, Jr., Elbert; Woodbury, Roy

ABSTRACT: Puerto Rico and the Virgin Islands together have about 55 I species of native trees, of which 539 are found in Puerto Rico. More than one-fourth, or 142, are known only from these islands (endemic). Only about 13 .rare endemic tree species need additional protection and have been proposed as endangered. Also, 22 are to be watched or monitored and have been proposed as threatened. About 100 others listed as rare are native also beyond (nonend-emic). The economic possibilities of endemic tree species merit special attention. INTODUCTION: Like other oceanic islands, Puerto Rico and the Virgin Islands are rich in rare and local plant species not found elsewhere. Fortunately, most native tree species are protected in natural or near natural forests within public forests and parks. Very few tree species, mostly confined to privately owned lands, need additional protection. This report groups the species of rare and endemic trees into lists; summarizes present occurrence, and may be of use for planning, development, management, and preservation of land. It is one of a series on rare trees of the United States. The British Virgin Islands, which have very few additional species, have been included, as in previous studies. The information summarized here is based largely upon field studies by the authors in Puerto Rico and the Virgin Islands through many years. Nearly all the rare and local trees of this report are present within Puerto Rico. Few of the same or other rare species are native in the smaller islands nearby, such as Mona, Culebra, and Vieques (all belonging to Puerto Rico), the U.S. Virgin Islands, and the British Virgin Islands. The geological history helps to explain present tree distribution. Puerto Rico and adjacent islands began as submarine volcanoes on the ocean floor some 125 million years ago and were built up by the end of the early Cretaceous period about 80 million years ago. The time is sufficient for much accidental migration from the continents. There is some evidence that much higher peaks may have existed, that blocks have been uplifted and subsided, and that sea level may have fluctuated. During glacial periods the climate may have been cooler, vegetation zones as much as 3,000 ft (914 m) lower, and sea level 200 ft (61 m) lower. The Virgin Islands, except St. Croix, apparently were connected with one another and with Puerto Rico as recently as the maximum advance of the last continental glaciation about 11,000 years ago.