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improved knowledge of mainland source areas
and as a result of taxonomic revisions. Although
the proportion of endemics appears to have
declined (Fig. 3.10b), this is mostly the result of
increases in numbers of introduced species. If
these species are excluded, the proportion of
endemics in the flora has remained reasonably
constant. The basic pattern established by Hooker
and Darwin (Ridley 1994) has thus proved to be
robust. As a proportion of the indigenous flora of
the Galápagos today, the endemics represent 43%
of the indigenous taxa (species, subspecies, or
varieties); allowing for recent extinctions and
uncertainties in taxonomy, the figure could fall to
37% (Porter 1979). Recently published estimates
for Hawaii are that the following proportions of

native taxa are endemic: birds, 81%; angiosperms,

91%; molluscs, 99%; and insects, 99% (Sohmer and

Gustafson 1993).

The following sections provide a few estimates

that set such figures in the broader context of

regional or global diversity.

Endemic plants

Groombridge (1992) provides the following ‘best

estimates’ for the number of higher plant species

in the world: 12 000 pteridophytes (ferns and their

allies); 766 gymnosperms (conifers, cycads, and

their allies); and 250 000 angiosperms (flowering

plants). This makes for a grand total of

about 263 000 species. It will be recalled that if

ENDEMISM 65

200

400

600

300

500

700

800

100

1840 1860 1880 1900 1920 1940 1960 1980 2000

Number of species

Year

(a)

1840 1860 1880 1900 1920 1940 1960 1980 2000

20

25

30

35

40

45

50

55

Per cent endemic

Year

(b)

Flora including introduced species

Flora excluding introduced species

Number of endemics

Flora including introduced species

Flora excluding introduced species

Figure 3.10Changing estimates of the Galápagos flora through time: (a) the size of the flora; and (b) the proportion of endemics. (Data from
Porter 1979 and Davis et al. 1995.)