334 ^- SKOTTSBERG 



but each new species would mean competition, and the entry of an additional 

 species would be very difhcult and consequently of rare occurrence. This may 

 be so, but tiiere are nian\- communities of a more open character than the forest, 

 and even a closed forest is not like a tin packed with cigarettes; young secondary 

 forest associations, steppes and savannas ought to offer good housing grounds 

 to an intruder, suj)posing that he likes climate and soil. Experience shows that 

 numerous aggressive plants brought by man, not only herbs but also trees and 

 shrubs, tind suitable living conditions even in undisturbed natural communities. 

 In Juan Fernandez I have had occasion to follow the invasion by Aristotelia maqui 

 (chilensis) and to witness the fabulous ease with which it crowds out the native 

 vegetation, and to observe I'i^Jii Moliiiac springing up on the ridges where the 

 j)lant cover was o|)en and, from there, to enter the dense native brushwood. 

 And they are only two of the many successful weeds, a third one, equally dan- 

 gerous but of quite recent introduction, is Rubus nluiifolius. All three have fleshy 

 fruits and are eaten by man and birds and propagate themselves rapidly. They 

 are conunon on the opposite mainland (where, of course, the brambleberry was 

 introduced from luirope), but man, no bird, carried them across to the islands. 

 Similar examples are, I presume, oftered by almost all oceanic islands. I just hap- 

 j)ene(l to read a book on Cape Verde Islands, where a naturalist tells us about 

 La)ita)ia caniara sj^reading like wildfire and menacing the little there is left of 

 natural savanna and steppe [326). 



Most zoologists favour the theory of long-distance dispersal. Mammals are, 

 as a rule also bats, flying foxes and the like, excluded, but of birds some are able 

 to cover very large distances, winged insects are carried ofl" to distant places 

 where they never wanted to go, and so forth. I shall quote some zoogeographers 

 who, with reference to the Pacific, have expressed their opinion on overseas transport. 



Pl-.KKINS, in his introduction to Fauna Haw-aiiensis (j^j. XLVl), wrote: 



All the islands being volcanic and having been built up from a great depth of ocean 

 at various j)eriods, their entire fauna naturally originated from immigrants derived from 

 other lands. These immigrants must have arrived either by flight, like the birds, or in 

 drift Hke the flightless insects and jirobably the land Mollusca. 



Dritting logs were often regarded as an important kind of conveyance, but they 

 come from North America and what they bring of animals, PERKINS says, would 

 ser\e no |)urpose because it is unlikely that the passengers would become acclim- 

 atized in ilawaii. The fauna must have come from the warmer parts of America, 

 from Australia, Polynesia etc. "at rare intervals from the F^ocene until now". If 

 we have to belie\e the geologists, no Ilawaii existed in the F^ocene — and how 

 did those, who arrive "now", manage to become endemic genera and species? — 

 non-endemic (lowering plants not brought by man are few. 



In some instances (ii LICK [Tig] admits the possibility of land connections, 

 but Ilawaii, Juan hernandez, (ialaj)agos, St. Helena, etc. etc., have always been 

 isolated. 'I he (juestion whether their fauna shows that "the ancestors possessed 

 an almost inconceivable capacity for passing uninjured over vast stretches of ocean" 

 is answered in the affirmative. It is significant that the Galapagos archipelago 



