Mountain Wildlife - Mountain Geography: Physical and Human Dimensions - page 412

The lowland species is poorly insulated, has different food preferences, and lives en-
tirely in trees, while the hyrax of the alpine zone has a heavy fur coat, burrows under
the ground, and makes its home in rocky areas. The species living at different altitudes
have become so differentiated that they no longer interbreed (Coe 1967).
In general, however, the alpine areas of the tropics have been colonized primarily
through direct immigration from other alpine areas, not from the surrounding lowlands
(Fig. 8.5b). This is because the lowland organisms evolved from very ancient stock in
a specific and relatively stable environment. Very few apparently have the ability to
pioneer new habitat, especially one that requires the ability to withstand freezing, a
phenomenon unknown in the tropical lowlands. Consequently, most high-altitude spe-
cies in the tropics have been derived from species in the middle latitudes and are fun-
damentally different from anything found in tropical lowlands. Research in the Andes,
however, indicates that climatic change in the tropics may have been considerable, pos-
sibly lowering the vegetation zones by as much as 1,500 m (5,000 ft) in some locations
(F. Vuilleumier 1969, 1970; B. S. Vuilleumier 1971). Under these circumstances, the is-
lands of alpine vegetation would have been greatly expanded, and in some areas they
may have overlapped, allowing free interchange of species.
FIGURE 8.5 Schematic representation of different methods of colonizing mountains. (Figure by L. W.
Price.)