Considerations Regarding the Evolution of Hawaiian Animals 
William A. Gosline 1 
Interest in the biotas of oceanic islands is 
of long standing. There are several reasons for 
the continuing interest. One is the possibility 
that insular evolution may in some respects 
represent a small-scale model of what has oc- 
curred on continents. Another is that, despite 
all the work on the subject, the "hows” and 
the "whys” of insular evolution remain inade- 
quately answered. Finally, there is the realiza- 
tion that, with the rapid decimation of native 
insular habitats, it will soon be impossible to 
study many aspects of the subject (Hubbell, 
1967 ). 
The general held of evolution in oceanic ani- 
mals has been reviewed many times, most re- 
cently by Miller (1966) and Carlquist (1965). 
Zimmerman’s summary ( 1948 ) for the Ha- 
waiian terrestrial forms is classic. Here, I shall 
deal with only certain facets of the subject, and 
I shall cite only those references from the tre- 
mendous literature most pertinent to the matter 
at hand. This selective method of presentation 
has serious faults, but any attempt to be compre- 
hensive would seem only to obscure the threads 
of thought that it is the purpose of the paper 
to present. 
Recently, in writing of land plants, Carl- 
quist (1966:433) has spoken of an "insular 
syndrome of interrelated evolutionary phe- 
nomena.” Insofar as Hawaiian animals are con- 
cerned, what is more striking to me is the di- 
versity of evolutionary results. Such variations 
occur not only between groups but within some 
groups as well. For example the evolution of 
the Hawaiian drepaniid finches has been very 
different from that of the sea birds. 
This diversity of evolutionary results could 
be exemplified from various animals groups, 
most notably insects. However, I shall not deal 
with Hawaiian insects at any length, primarily 
because of unfamiliarity with them but also 
1 Department of Zoology, University of Hawaii, 
Honolulu, Hawaii 96822. Manuscript received June 
13, 1967. 
because at the present time they are the subject 
of an intensive continuing investigation (Zim- 
merman, et al., 1948 — ; Spieth, 1966 : 246 ). 
Rather, I shall emphasize the evolutionary prob- 
lems of three Hawaiian animal groups: the in- 
shore fishes, the achatinellid land snails, and 
the drepaniid finches. As an introduction to the 
problems involved the evolutionary status of 
these three groups in Hawaii is summarized 
briefly. 
The Hawaiian inshore fishes (Gosline, 1958; 
Gosline and Brock, I960) form part of a 
marine biota that is essentially similar to, but 
somewhat impoverished, as compared with that 
of the Central Pacific islands to the south and 
west. There are few conspicuous gaps in the 
Hawaiian marine biota, and, of those that do 
occur, at least one — the coral genus Acropora — 
was present in Hawaiian waters in the past 
(Menard, Allison and Durham, 1962). There 
seems to be a more or less constant infiltration 
of non-resident species into the Hawaiian 
marine biota today, some of which have be- 
come established (Doty, 1961), while some 
have not (Brock, 1948 ). Intentional introduc- 
tions of purely marine forms into Hawaiian 
waters have been mostly unsuccessful. (By con- 
trast, a number of introductions into areas of 
reduced salinity, e.g., Kaneohe Bay on Oahu, 
have done quite well.) One of the few that has 
succeeded, the "Marquesan sardine,” has spread 
throughout the waters of the high Hawaiian 
Islands in a matter of a few years (Murphy, 
I960). Endemism above the species level 
among Hawaiian fishes is dubious. However, 
about one third of the inshore species are rep- 
resented by endemic forms. These can usually 
be distinguished from Central Pacific counter- 
parts in 100% of the individuals (for some 
exceptions, see Gosline, 1955 ). Aside from a 
few expected correlations between morphologi- 
cal traits and the relatively cool Hawaiian water 
temperatures (see, for example, Strasburg, 
1955), the morphological characters by which 
the Hawaiian endemics differ from their Cen- 
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