Puerto Rico and Hawaii Compared 



The importance of the rare and endemic trees of Puer- 

 to Rico and the Virgin Islands can be understood and 

 evaluated by a comparison with those of the Hawaiian 

 Islands in table 1. The Commonwealth of Puerto Rico 

 and the State of Hawaii have several characteristics in 

 common. Both are located in the northern tropics at 

 about the same latitude, and both became territories of 

 the United States 1898. 



The "Big Island" of Hawaii (area 4,038 mi 2 , 10,458 

 km 2 ) is slightly larger than Puerto Rico (area 3,435 mi 2 , 

 8,897 km 2 ). The Hawaiian archipelago also embraces 7 

 smaller islands with a total area of 2,411 square miles 

 (6,244 km 2 ), and scattered isles. In contrast, the U.S. 

 Virgin Islands, purchased from Denmark in 1917, and 

 the British Virgin Islands have a combined area of only 

 about 200 square miles (518 km 2 ). 



The Hawaiian Islands are the most isolated in the 

 world, near the center of the largest ocean and farthest 

 from the continents. North America, the nearest conti- 

 nent, is 2,400 miles (3,862 km) to the northeast at 

 California and slightly more at southern Alaska. These 

 oceanic islands originated, like Puerto Rico and the 

 Virgin Islands, as submarine volcanoes from the ocean 

 floor but much later, about 5 to 10 million years ago. The 

 "Big Island" perhaps only a million years old, is the 

 largest and youngest. Its highest peaks are Mauna Kea 

 (altitude 13,796 ft, 4,205 m), the State's loftiest, and 

 Mauna Loa (altitude 13,677 ft, 4,169 m), which has ac- 



tive craters and occasional lava flows. Thus, the 

 Hawaiian Islands have very diverse geography, climate, 

 and vegetation. 



The native trees of the Hawaiian Islands are unique, 

 different from those everywhere else in the world. Seeds 

 of the ancestral trees were transported accidentally across 

 long expanses of ocean. Some floated or came on drift- 

 wood, and others were carried by birds or the wind. 

 Long-distance dispersal was a very rare occurrence, an 

 accidental migration. After arrival and establishment, an 

 immigrant species isolated from the distant parent prob- 

 ably changed and became a new species. 



The latest compilation of the flora of Hawaii by St. 

 John (20) accepted approximately 370 species of native 

 trees. However, 60 years earlier, Rock (18, 19) described 

 only about 230 species in his book "The Indigenous Trees 

 of the Hawaiian Islands." The number could be revised 

 and reduced perhaps to fewer than 300 through union of 

 minor variations. 



The native trees of Hawaii, 300-370 species, are 

 grouped into 70 genera and 40 plant families. More than 

 one-half belong to the 5 largest families: rue (Rutaceae), 

 ginseng (Araliaceae), madder (Rubiaceae), palm 

 (Palmae), and pittosporum (Pittosporaceae). Some 

 familiar families of tropical trees are absent, for example, 

 mahogany (Meliaceae), bombax (Bombacaceae), mela- 

 stome (Melastomataceae), and bignonia (Bignoniaceae). 

 There are no native conifers, figs (Ficus), or mangroves. 



Table 1. — Comparison of rare native trees of Hawaii and Puerto Rico and the Virgin Islands 



Native trees 



Hawaii 



Puerto Rico and 

 the Virgin Islands 



Plant families with trees 









40 



Families with endemic species 









39 



Tree genera 









70 



Genera with endemic species 









66 



Endemic tree genera 









17 



Tree species 









300-370 



Named varieties 









Many 



Island totals' 











Genera on 1 island 









52-66 



Species on 1 island 









84-165 



Nonendemic species 









11 



Rare nonendemic species 









1 



Endemic species 









289-359 



Percent of endemic species 









96-97% 



Average number of endemic s 



pecies per genus 



with endemic species 



4.4-5.4 



Species endemic to 1 island 









236(?) 



Extinct species 









21 



Rare endemic species 









7 



Rare endemic species needing 



additional 



protection 



About 50 



Rare endemic species to be watched 







About 20 



85 



50 



273 



94 



1 



551 



Very few 



271 



539 



409 



100 



142 



25.8% 



1.5 



106 2 



0(?) 



83 



13 



22 



Approximate totals by islands: Kauai, 65 genera and 134 species; Oahu, 66 and 165; Molokai, 55 and 90; Maui, 61 and 127; Lanai, 52 and 84; 



Hawaii, 61 and 119; and Puerto Rico, 271 and 539. Totals in Virgin Islands not available. 

 "Puerto Rico, species not found also on any smaller island. 



20 



