DERIVATION OF THE FLORA AND FAUNA 



199 



Table II. 

 Distribution of the endemic genera. 



Centaurodendron 

 Cuminia . . . . 

 Dendroseris . . 

 Hesperoseris . . 



Juania 



Lactoris . . . . 

 Megalachne . . . 

 Nothomyrcia . . 

 Ochagavia . . , 

 Phoenicoseris . . 

 Podophorus . , 



Rea 



Rhetinodendron , 

 Robinsonia . . . 

 Selkirkia . . . . 

 Symphyochaeta , 

 Yunquea . . . . 



I + 



number, for even if we pay due attention to the physiographic difference between 

 them, it tells a story of effective isolation with little possibility for an exchange 

 across the 92 miles of water separating them. 



Of the total number of species (147), loi are endemic = 68.7 %; of the 99 

 species found on Masatierra, 66 (66.'j %) are endemic in Juan Fernandez; the cor- 

 responding figures for Masafuera are 74 and 47 (63.5 %), and for Santa Clara 9 

 and 5 (55.5 %). Thus endemism plays about the same role in all cases, and this 

 is apparent also when local endemism is considered. Of the 68 species restricted 

 to Masatierra 50 (73.5 %) are local endemics, of the 47 species restricted to Masa- 

 fuera, 34 (72.3 %); the single species restricted to Santa Clara is endemic. Of the 

 27 species common to Masafuera and Masatierra 13 (48%) are endemic in Juan 

 Fernandez. If, to the 68 species restricted to Masatierra, 4 also found on Santa 

 Clara are added, the figures are 72 and 73.6%. Of the total number of endemic 

 species (lOi), 50 are, as we have seen, confined to Masatierra (49.5 %), 3 (3 %) 

 to Masatierra + Santa Clara, i (i %) to Santa Clara, 34 (33.7%) to Masafuera, 

 12 (11.9%) common to Masatierra and Masafuera, and i (i %) found on all three 

 islands. The difference between Masatierra and Masafuera stands out even more 

 clearly. It is less pronounced when we come to the 46 non-endemic species: only 

 on Masatierra 18 (39.1 %), on Masatierra and Santa Clara i (2.2 %), only on 



