Ecology of Marcus Island — SAKAGAMI 
101 
low coral islands: "Atolls and other low coral 
islands have a small fauna — similar in widely 
separated groups of islands— -which is limited 
by the lack of ecological diversity, the limited 
haplophytic strand flora, the presence of brack- 
ish ground-water, the scarcity of soil, and ex- 
posure to salt-spray.” 
The land biota of Marcus, with its extreme 
poverty in both taxonomic and ecological com- 
ponents, offers nothing other than a very typical 
example of Gressitt’s generalization. He also 
wrote: "The extent of speciation is directly re- 
lated to the island’s age, size, isolation and 
diversity of environment.” This proposition can 
be applied to biocoenology if the word "specia- 
tion” is replaced by the phrase "differentiation 
of ecological components.” On Marcus Island 
the isolation is fairly great, but its size and its 
diversity of environment are incomparably small 
to be able to promote any ecological differentia- 
tion. Moreover, this isolation may modify a 
given biota only when human interference is 
absent or at least negligible, because this factor 
acts, however locally, with an incomparably 
more rapid tempo and more violent means than 
do other natural agents. It would be rather 
surprising if Marcus Island had maintained any 
ecological peculiarities — even if such had existed 
in this most simple environment — despite the 
accumulation of various human interference dur- 
ing 50 years, including intensive skinning, co- 
conut collecting, public works which modified 
the appearance of the island, a high human pop- 
ulation during wartime (when 4,000 persons 
were living on this mere heap of coral sand 
and pebbles), and, finally, violent bombing. 
However, although Marcus Island may be 
little more than a disappointment to biologists 
who approach the island to study its flora or its 
biogeography, investigation of such an undif- 
ferentiated biota does reveal some important 
problems, as follows: 
1. Our knowledge of the ecology of Pacific 
islands, as mentioned by Gressitt ( 1954) , is still 
very far from complete. In this account, the 
study of a relatively simple biota as that of 
Marcus may serve as a useful guide either to 
study more complex biotas or to find general 
principles underlying their diversities. 
2. Considering the fact that any given eco- 
logical assemblages, either simple or complex, 
consist of interactions among numerous parts 
and processes, it is obvious that the analysis of 
such entities is far easier to do in simpler biota 
than in more complicated ones. It should be 
remembered that, while we may be interested 
in discovering any specificities and comparing 
them with each other, we must always seek gen- 
eral rules governing such specificities. 
3. Because of their extreme isolation, eco- 
logical simplicity, and lack of industrial im- 
portance, the remote low islands such as Marcus 
may serve as the best laboratories in field eco- 
logy for the study of the intra- and inter- 
specific ecology of given species, both native 
and purposely introduced, as living isotopes. 
The clarification of land biota should be a pre- 
requisite for such experimental studies. 
ACKNOWLEDGMENTS 
The present survey was made in close col- 
laboration with Dr. N. Kuroda of Yamashina 
Ornithological Institute, and Mr. M. Yamada of 
the Zoological Institute, Hokkaido University, 
under a plan prepared by Professor Tohru 
Uchida of Hokkaido University. 
The survey was made with the permission of 
Dr. S. Wadachi, Head of Central Meteorological 
Observatory in Tokyo, aided by numerous staff 
members of the Observatory, especially Mr. N. 
Yamada, Chief Secretary, Mr. Y. Nakada, Head 
of the Remote Islands Section, Mr. T. Doi, 
Head of the Supply Section, Mr. H. Hasegawa 
of the Entomological Laboratory, the National 
Institute of Agricultural Sciences, Tokyo, and 
Mr. H. Okuyama, Botanical Laboratory of the 
National Science Museum, Tokyo. 
The specimens collected by me were identi- 
fied by the following gentlemen, who also gave 
me valuable information on the distribution 
and habits of the species collected: Mr. T. Aoto 
( Reptilia ) , Dr. S. Asahina (Odonata), Mr. S. 
Ehara (Acari), the late Dr. T. Esaki (Embiop- 
tera ) , Mr. H. Hasegawa ( Heteroptera ) , Mr. K. 
Hori (Muscidae and Sarcophagidae ) , Dr. A. 
Kawada ( moths ) , Mr. S. Kato ( Anthomyidae ) , 
Mr. M. Konishi (Cossoninae) , Mr. K. Kosugi 
( Coleoptera ) , Mr. Y. Miyoshi (Myriapoda), 
