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whichbelongtothegenealogicalhierarchy(Morrone2004c).Thisshowsthe
fuzzy limits between evolutionary and ecological biogeography and allows
one to speculate on the possibilities of integration.
In order to build a unified biogeography, it would be possible to limit the
scopes of ecological and historical biogeography based on scales: ecolo-
gical explanations for local, short-term spatiotemporal scales and historic-
al or evolutionary explanations for larger, long-term spatiotemporal scales.
However, it has been noted that there is no obvious point at which to divide
the domain of ecology from that of history and that some ecological factors
may have wide geographic effects, whereas some historical factors may
be responsible for local distributional patterns (Gray 1989). In fact, ecology
and history are not independent variables acting on different spatiotemporal
scales. They act together at all times. Historical changes are mediated eco-
logically, and ecological changes are historically contingent because organ-
isms experience historical factors such as a tectonic change not directly but
indirectly through changes in altitude, climate, and so on. After analyzing the
possibility of isolating ecological and historical determinants of Andean bird
distributions, Vuilleumier and Simberloff (1980) concluded that ecology and
history have played significant roles together and at all times. Gray (1989)
suggested that a new biogeographic vision should emerge in which differ-
ent ecological and historical factors are integrated in a network of interacting
processes.
Figure 2.3
Balanced biogeography, as envisioned by Haydon et al. (1994), based
on the complementary roles of ecology, history, and chance.
