Evolution__3rd_Edition

506 PART 4 / Evolution and Diversity
Figure 17.7
Plate tectonics (or, informally,
continental drift). (a) The
movements of the continents
during the past 200 million
years. (b) The positions of the
main tectonic plates today.
Vicariance biogeography predicts
...
(a)
Triassic 200 Myr BP
P a n t h a l a s s a
G o n d w a n a
Equator
Paleocene 65 Myr BP
(b)
L a u r a s i a
Tethys
Cretaceous 125 Myr BP
Oligocene 30 Myr BP
Mid-ocean ridge
Trench-island arc
Fracture zone
midges. These midges are distributed around the southern hemisphere (Figure 17.9).
Brundin reconstructed their phylogeny by standard morphological techniques
(Chapter 15) and then used the species’ modern biogeographic distributions to draw a
combined picture of their phylogeny and biogeography, called an area cladogram
(Figure 17.10). If the successive splits in the phylogeny were driven by successive breakups
of the land, the phylogeny would imply a definable sequence of tectonic events.
To begin with, the common ancestor of the modern forms would have occupied
a large area made up of all their modern distributional zones a which implies the
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