70 
THE CORAL TRIANGLE: HEARST BIODIVERSITY EXPEDITION 
During his travels in the Malay Archipelago and based largely on his careful observations of 
bird and mammal distributions, Alfred Russel Wallace (1860) first postulated a biogeographic line 
defining a faunal discontinuity that “abmptly separates two of the great Zoological regions of the 
globe.” Subsequently, Wallace (1880) perceptively deduced that varying degrees of isolation result¬ 
ed from profound geological changes in the past. Subsequent biogeographers showed that the 
nature of ocean depths in the region and former deviations from the present sea levels, were respon¬ 
sible for Wallace’s striking demarcation (Quammen 1996). The line which separates Bali from 
adjacent Lombok in Indonesia, and Sulawesi (The Celebes) from Borneo to its west, was later 
called “Wallace’s Line” by Thomas Henry Huxley (Raby 2001). In the same paragraph Huxley 
(1868:313) not only names the line after Wallace, but also modifies Wallace’s boundary to include 
the Philippines, “...the boundary in question would comcide with what may be called ‘Wallace’s 
line,’ between the Indian and the Papuan divisions of the Malay archipelago. But it would run 
northward as far as the Philippines, and passing between them and Formosa, would trend south¬ 
ward and eastward to the Samoan archipelago” Huxley (1868:294) provides a map to illustrate his 
alteration. 
Our modem concept of the biogeographic region known as “Wallacea” (Conservation Interna¬ 
tional 2010; Beccaloni 2012) does not recognize Huxley’s modification, but rather agrees with 
Wallace’s original boundary delineation. Wallacea encompasses a group of islands in “the heart of 
Indonesia” that are separated by areas of deep water from the Asian and Australian continental 
shelves (Beccaloni 2012). These islands were thus never connected to either of these continental 
regions, and are entirely included within the boundary of the coral triangle (Fig. 2A). In 1860, Wal¬ 
lace viewed the zoogeography of the Philippines as somewhat problematic since the archipelago at 
the same time resembled and differed from either the Asian or Australian regions, but nevertheless, 
he aligned them as a whole with the Asian region. By 1880, significant additions to the Philippine’s 
fauna had been recorded by various researchers. 
Wallace (1880) then reasoned that the peculiarities of isolation of the islands can be explained 
by the deep seas surrounding the archipelago, but that the archipelago was connected with Borneo 
by shallow arms of the Asian continental shelf, referred to by him as Wo narrow submarine banks. 
These represent southwestern extensions of Palawan and the Zamboanga Peninsula of Mindanao. 
He ftirther deduced that as a consequence, the Philippines were once part of what he called “the 
great Malayan extension of Asia.” He maintained that the Philippines have experienced prolonged 
isolation in the past and were later fragmented by extensive volcanic activity, which produced his 
observed faunal peculiarities. Although his observations and conclusions were for the most part 
based on terrestrial vertebrate distributions, our contemporary tectonic knowledge of ocean floor 
bathymetry and topography largely verifies his writings of the latter half of the nineteenth century. 
Coral Biodiversity. — An additional consideration to be noted when studying aspects of the 
world’s coral faunas, is the widely varying perception of comparative coral diversity. Contraiy to 
a popular belief assumed by many individuals that all corals are inliabitants and builders of coral 
reefs, it is currently estimated that hermatypic corals (reef-building corals) represent only about 
15% of total coral species diversity, as tlie majority of corals are non-hennatypic (Fig. 2B). This 
small percentage is comprised of approximately 14% by hard corals (scleractinians) and perhaps 
1% by others including several species of the hydrocoral genus Millepora, and two monotypic 
octocoral genera — Heliopora and Tubipora (Williams and Cairns 2013). 
OcTOCORAL Biology. — Gorgonians and pennatulaceans are octocorals that have a central 
axis in the interior of the colony — composed of consolidated sclerites, or hard proteinaceous 
and/or calcareous material. In addition, unconsolidated skeletal components composed of calcium 
carbonate in the form of numerous minute sclerites are present in the thin tissues surrounding the 
