Lists of Trees of Puerto Rico and the Virgin Islands 



Puerto Rico and the Virgin Islands have about 551 

 species of native trees. The 2-volume reference (12, 13, 

 15) accepted 547. Five additions of shrub species ob- 

 served by Woodbury to reach tree size are mentioned 

 below and numbered to indicate place of insertion in the 

 second volume. They were listed as rare and endangered 

 trees in the committee report. Two are additional 

 endemic tree species. Also, Malpighia shaferi Britton & 

 Wils., an endemic, has been united recently as a synonym 

 of 421, M. fucata Ker, palobronco. 



368.1. Caesalpinia monensis Britton, mato negro, 

 Leguminosae, legume family. Rare shrub or small tree to 

 20 ft (6.1 m) high and 5 in (13 cm) in trunk diameter. The 

 only endemic tree species of Mona Island. 



446.1. Phyllanthus cuneifolius (Britton) Croizat (An- 

 drachne cuneifolia Britton), Euphorbiaceae, spurge fam- 

 ily. Shrub or small tree to 15-20 ft (4.6-6.1 m) high and 3 

 in (7.5 cm) in trunk diameter, rare and very local on 

 southern coast. Also Hispaniola and Cuba. 



495.1 Hibiscus clypeatus L., Malvaceae, mallow fam- 

 ily. Very rare tree to 20 ft (6.1 m) high and 4 in (10 cm) in 

 trunk diameter, near Guanica. Public forest — Guanica. 

 Greater Antilles, Cayman Islands, and Mexico. Reported 

 long ago from St. Croix. 



538.1. Leptocereus quadricostatus (Bello) Britton & 

 Rose (Cereus quadricostatus Bello), sebucan, Cactaceae, 

 cactus family. Rare cactus sometimes forming a trunk to 

 1 ft (30 cm) in diameter, mostly shrubby and vinelike. 

 Endemic to southwestern Puerto Rico and Icacos. Public 

 forest — Guanica. 



676.1. Rochefortia cuneata Sw., espino, Bor- 

 aginaceae, borage family. Shrub or small tree to 25 ft (7.6 

 m) high and 5 in (13 cm) in trunk diameter, near 

 Quebradillas. Very rare, cited by Britton and Wilson (2) 

 earlier from La Plata near Guanica and from Sardinera 

 near Dorado. Recorded also from Jamaica, Hispaniola, 

 Antigua, Guadeloupe, Dominica, and Martinique. 



About 539 of the 551 tree species are found in Puerto 

 Rico. Thus, the Virgin Islands have about 12 additional 

 tree species that are not present on the larger island. 



This total is much greater than that of any of the 50 

 States. The State of Hawaii, for example, has about 370 

 named trees on 8 islands, though the number could be 

 reduced perhaps to fewer than 300 through union of 

 minor variations. Florida has about 272 species of native 

 trees including nearly 100 tropical species in the southern 

 part not native elsewhere in continental United States 



(11). 



More than one-fourth, or 142 of the 551 species, of 

 native trees in Puerto Rico and the Virgin Islands are 

 known only from these islands (endemic), including 

 about 83 classed as rare. About 100 others listed as rare 

 are native also beyond (nonendemic). Thus, endemic and 

 rare species together as listed in this report total about 

 242, more than two-fifths. 



These rare and endemic trees can be grouped here into 

 six lists, as follows: (1) Extinct species, (2) endemic 

 species needing protection, (3) endemic species to be 

 watched, (4) other rare endemic species, (5) common 

 endemic species, and (6) rare nonendemic species. As 

 used here, rare species are those in lists (1), (2), (3), (4), 

 and (6) combined. In the following six lists, the plant 

 families and species are arranged alphabetically for com- 

 parison with similar lists. 



1. Extinct Species 



No endemic tree species of Puerto Rico and the Virgin 

 Islands is known to have become extinct. However, a few 

 border or peripheral species may have disappeared there. 



These islands were discovered in 1493 by Christopher 

 Columbus on his second voyage and were among the first 

 to be occupied by colonists from Europe. For many 

 years, Puerto Rico has had a high population density, 

 both rural and urban. As a result, undisturbed vegetation 

 is very restricted in area, and habitat destruction has been 

 widespread. 



The native vegetation developed in the absence of large 

 mammals, such as herbivores, and may have been suscep- 

 tible to introduced goats and cattle. However, trees 

 would be less affected than smaller plants. Dry forests, 

 which can be damaged severely by grazing animals, are 

 restricted in Puerto Rico, though common in nearby 

 islands including the Virgin Islands. The lowland coastal 

 areas, where the first settlements were made, have few 

 endemics. The mountain forests, centers of endemism, 

 remained nearly undisturbed for centuries. 



There is no indication that any rare plants, and trees in 

 particular, may have been eliminated by human activities 

 before the arrival of plant collectors. As early as 1793, a 

 363-page flora of St. Croix and others of the Virgin 

 Islands was published by West (29), head of the school in 

 St. Croix. However, three centuries had lapsed since the 

 discovery by Columbus. 



Almost all the endemic tree species named long ago 

 from Puerto Rico or the Virgin Islands have been found 

 by later collectors including the present authors. Like- 

 wise, nearly all rare border or peripheral species of older 

 lists have been located. Several tree species not observed 

 by Nathaniel L. Britton and associates during the 

 preparation of the flora have been rediscovered in recent 

 years. Besides, a few range extensions from other islands 

 and undescribed species have been detected. Botanical ex- 

 ploration of remote areas increased with accessibility 

 after construction of a network of highways. For many 

 years, every part of Puerto Rico has been within 5 miles 

 of a paved road. 



Four species of the large myrtle family, Myrtaceae, 

 were published long ago from incomplete specimens and 



