Geography Reference
In-Depth Information
German ornithologist Jürgen Haffer (1969, 1974, 1978, 1981) analyzed the
biogeography of birds inhabiting the Amazon forest. He found six areas of
higher endemism, which contained about 25% of the bird forest species of
the area, and between them areas where related species hybridized (Cox
and Moore 1998). Haffer hypothesized that during the glacial periods of the
NorthernHemisphere,thesecentersofendemismwereislandsofrainforest
surrounded by a sea of grasslands (Lomolino et al. 2006). These refugia al-
lowed many forest species to survive therein and eventually evolve in isol-
ation as separate species. When the conditions allowed the forests to ex-
pand, these species could spread over them. As a result, these species
could meet with their related species and hybridize, whereas others that had
developed reproductive isolation mechanisms did not.
Refuge theory initially provided an interesting explanation for the high di-
versity and endemism of tropical rain forests. In recent decades, however,
many authors have questioned its general validity (Lomolino et al. 2006).
Colinvaux (1997, 1998) argued that ice age climate was not sufficiently arid
to fragment the Amazonian forest and that vicariance occurred because cli-
matic change created islands in the elevated areas. Thus, on one hand, the
refuge hypothesis would have the facts reversed: Ice age climatic change
raised an archipelago of islands while the forest sea remained intact (Colin-
vaux 1997). On the other hand, molecular and morphological data indicate
that many endemic species are much older than the hypothesized refugia
(Cracraft and Prum 1988; Marshall and Lundberg 1996). Finally, Haffer's hy-
pothesis is not the most parsimonious explanation for the diversity of the
tropical forests, which may derive, at least in part, from the fact that they
are much more spatially heterogeneous than once assumed (Lomolino et al.
2006).
At the moment of the formulation of panbiogeography, most of the scientific
community reacted negatively or ignored it. Nevertheless, U.S. ichthyolo-
gists Gareth Nelson and Donn Eric Rosen and U.S. arachnologist Norman
Platnick, from the American Museum of Natural History of New York, knew
and appreciated it. In 1973, when Nelson was the editor of
Systematic Zoo-
logy,
he invited Croizat to send a manuscript on panbiogeography. Sever-
al of the experts whom Nelson contacted as reviewers of the manuscript
refused to comment on it, and of those who accepted, only one recom-
