0198566123.pdf

will have gained significant proportions of their
species from more than one land mass and more
than one biogeographical province. For instance,
Fosberg (1948) calculated that the flowering plants
of Hawaii could have descended from some 272
original colonists, of which 40% were believed to be
of Indo-Pacific origin; 16–17% were from the south
(Austral affinity); 18% were from the American con-

tinent; less than 3% were from the north; 12–13%

were cosmopolitan or pantropical; and the remain-

der could not be assigned with confidence. Can the

Hawaiian islands logically be put into an Oriental

province when appreciable portions of their flora

and fauna are American in origin? Most phytogeo-

graphers, in fact, assign the flora to its own floristic

region (Davis et al. 1995).

54 THE BIOGEOGRAPHY OF ISLAND LIFE

Damma

Kei Is.

Tanimbar

Wetar

Bali Sumbawa Flores Alor

Java

Western (Oriental) species

Eastern (Australian–

New Guinean) species

Birds (%)

100

50

0

Reptiles (%)

100

50

0

Lom-

bok

Aru

Is.

Figure 3.4The two-way filter effect, showing trends in the proportion of Oriental and Australian species of birds and reptiles across the Sunda
islands, South-East Asia. In contrast to the gradual changes shown here, mammals ‘obey’ Wallace’s line, a sharp line of demarcation between Bali
and Lombok (see Fig. 3.5). (Modified with permission, from Carlquist, S. (1965).Island life: a natural history of the islands of the world. Natural
History Press, New York, Fig. 3.7.)

Palaearctic

60 °

30 °

0 °

60 °

30 °

African

Neotropical

Nearctic

Oriental

Australian

Figure 3.5Based on the distribution

of extant mammals, A. R. Wallace in

1876 divided the world into zoogeographical

regions. (The map shown here has been

redrawn from Cox and Moore 1993,

Fig. 8.1.)