Evolution__3rd_Edition

..
Time
Biogeographic
distribution
Species
C B A
3 2 1
(a) Dispersal (b) Vicariance
3 2
C B
A
1
Dispersal Common
ancestor
C 2–3 B
1 A
Common
ancestor Dispersal
B
C
A
1–3
. . . the tectonic history of the Earth
will match the phylogeny of species
3
2
C B
A
1
C
Common
ancestor
2–3 B
1
A
Common
ancestor
1–3 A
C B
CHAPTER 17 / Evolutionary Biogeography 507
Figure 17.8
Dispersal and range splitting can be alternative hypotheses to
explain the biogeography of a group. (a) An ancestral species
with its center of dispersal in area A dispersed first to area B and a
descendant from there then dispersed to area C. (b) An ancestor
occupying area A + B + C had its range split first into A and B + C
and then the descendant in B + C had its range split.
existence, sometime in the past, of a southern supercontinent, Gondwanaland.
Gondwanaland would then, Brundin’s analysis predicts, have split in the following
order. First, South Africa split from a combination of Australia, New Zealand, and
South America; then New Zealand split from South America and Australia; and finally
Australia split from South America. This prediction can be tested against the geological
evidence, which was only accumulating during and after Brundin’s work. The geology
turned out to fit Brundin’s prediction (see Figure 17.7a, but more detailed maps are
needed for a strong test). It could also be tested by the molecular clock, but this is yet to
be done.
Brundin’s test concerns a single taxon. A second test is to compare the relation
between phylogeny and biogeography in many taxa. As continents a or, in general, the
habitats occupied by species a move in a particular pattern through time, all the groups
of living things living in an area will be affected in a similar manner. If members of each
group tend to speciate when their ranges are fragmented, they should all show similar