Rare and Endemic Trees of Puerto Rico and the Virgin Islands 



By Elbert L| Little, Jr., and Roy OJWoodbury 1 



Introduction 



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 pro- 

 tected 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. 2 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 con- 

 tinents. There is some evidence that much higher peaks 

 may have existed, that blocks have been uplifted and sub- 

 sided, and that sea level may have fluctuated. During 

 glacial periods the climate may have been cooler, vegeta- 

 tion 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. 



Endangered Species Act 



The Endangered Species Act of 1973 (public law 

 93-205) has directed attention to rare animal and plant 

 species that may be classed as endangered and in need of 

 protection against extinction. It provided legal defini- 

 tions of two groups not previously separated, endangered 

 and threatened species. 



As authorized by this act, lists of proposed endangered 

 and threatened plant species have been prepared by the 

 Smithsonian Institution. The preliminary published lists 

 (21, 24, 25) contain more than 2,000 species and varieties 

 in continental United States and many others in Hawaii. 



Respectively, chief dendrologist (retired), Timber Management 

 Research, U.S. Department of Agriculture, Forest Service, Box 2417, 

 Washington, D.C. 20013; and plant taxonomist, University of Puerto 

 Rico, Rio Piedras, Puerto Rico 00928. 



""Three others have been published (8, 9, 10). Italic numbers in paren- 

 theses refer to Literature Cited, p. 25. 



Separate lists of proposed endangered, threatened, and 

 extinct species of Puerto Rico and the Virgin Islands have 

 been included in a revision (7). 



The act also provides that the Secretary of the U.S. 

 Department of the Interior must study the Smithsonian 

 Institution's preliminary list and determine which species 

 are truly threatened and endangered. The first official 

 list, with additions through 1978, contains 17 plant 

 species (only 1 a tree), with none from Puerto Rico and 

 the Virgin Islands (26). 



