Evolution__3rd_Edition

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(b) Five other vertebrate groups
Osteoglossine fishes
and chelid turtles
Australia
New Guinea
South America
(a) Marsupials
Recent marsupial groups
Australia
New Guinea
South America
North America
Figure 17.12
(a) Area cladograms of recent and fossil marsupials. (b) Area
cladograms of five other taxa with congruent biogeographic
. . . other taxa illustrate dispersal
and vicariance
CHAPTER 17 / Evolutionary Biogeography 511
Fossil marsupial groups
Australia
New Guinea
South America
North America
Europe
Galliform birds Ratite birds Hylid frogs
Australia
Australia
New Guinea
New Guinea
South America
South America
North America
Europe
Europe
Australia
New Guinea
South America
North America
Europe
distributions. Redrawn, by permission of the publisher, from
Patterson (1981).
would require an unlikely series of coincidences. It is more likely that the common pattern
is simply due to a shared history of range splits by tectonic events.
Dispersal has probably had some influence on the history of the taxa in Patterson’s
study. The osteoglossine fish are found in South East Asia as well as Australia, New
Guinea, and South America (Figure 17.12b). As it happens, none of the other four taxa
are represented in South East Asia. Three explanations for this result are possible. One
is that all six taxa used to live in South East Asia and that five of them have since gone
extinct there. A second is that all six were originally absent from Asia and osteoglossine
fish (in the form of Scleropages) arrived there by dispersal. The fossil record could in
principle be used to show that a taxon once lived in Asia but is now extinct. But in the
absence of any such evidence, Patterson reasoned that it is more likely that only one
group (the osteoglossines) dispersed to Asia than that five groups went extinct there.
Finally, it could be that osteoglossines originally had a broader distribution than the
other five vertebrate groups, and were ancestrally present in South East Asia. The
vicariance of the osteoglossines would then have taken place within a larger range.
Vicariance biogeography has been successful in finding a number of area cladograms that
are mainly consistent between different taxa and also consistent with tectonic history.
Some biogeographic distributions make sense in a history of range splitting (or
vicariance). Others do not. We saw above how Anolis lizards in the Caribbean evolved