10. Terrestrial Vertebrate Diversity in New World Temperate Rainforests
217
all Chilean amphibians are anurans (N = 28 species) , and 82% of these
are in one family, the Leptodactylidae. For South America as a whole,
leptodactylids make up only 38% of the amphibians (Duellman, 1979a).
Similar to salamanders, leptodactylids have exploited the moist terrestrial
environments in the southern temperate forests. Some 14/28 (50%) species
of amphibians have highly localized distributions within the southern
temperate forest region (defined as occuring in only one latitudinal region,
as identified in Table 10.1) compared to 9/26 (35%) in the Pacific Northwest . These species may be considered to be essentially endemic. Lizards
make up a majority of southern temperate forest reptiles (8/10 species, or
80%) and all but one are in the genus Liolaemus, whereas snakes comprise
a majority of Pacific Northwest reptiles (12/19 species, or 63%) regionally.
Finally, 15/38 (40%) reptile species have highly localized distributions
within the southern temperate forest region versus 9/45 (20%) species in
the Pacific Northwest. Also of interest is the general decline in numbers
of herptiles proceeding toward the pole in both regions (see Table 10.1).
Bury, Corn, & Aubry (1991) note the decline in numbers of reptiles
northward to the southern Washington Cascades; this pattern continues
into British Columbia and southeastern Alaska. Whereas amphibians also
decline in number, a greater proportion of this decline is due to the
salamanders.
Clearly, continental drift and isolation have contributed to these intercontinental differences. For example, leptodactylids are considered to be
an ancient Gondwanaland element (Cracraft, 1974), and available evidence suggests that they dispersed northward from South America into
Central America via island hopping (Duellman, 1979a) . Cei (1979) has
suggested an austral origin for primitive members of this family , and
pockets of diversity in the Argentine Patagonian steppes may represent
remnants from periods of forest expansion eastward. Similarly, different
species complexes of the lizard genus Liolaemus may have originated
from northern and southern Argentina (Cei, 1979).
The impoverishment of the southern temperate forest mammal fauna is
evident in Table 10.2. The Chilean (and Argentine) forests include a
maximum of 29 native species in contrast to 69 in the Pacific Northwest.
Most of these differences are due to the lack of insectivores in South
America (a total of 11 species) , a poorer chiropteran fauna (6 versus 13
species), and the absence of sciurid and microtine rodents (a total of 17
species) . Subtracting this difference of 34 species from the 69 species in
the Pacific Northwest yields 35 species, more similar to the total for the
southern temperate forests . Some 7/29 (24%) species are endemic to the
southern temperate forests (versus 10/69 species, or 14% , for the Pacific
Northwest). Specific forests and sites in the Pacific Northwest also have
more small-mammal and chiropteran species than those in southern Chile.
There appears to be a less dramatic decrease in numbers of mammal
species polarward as compared to herptiles.
217
all Chilean amphibians are anurans (N = 28 species) , and 82% of these
are in one family, the Leptodactylidae. For South America as a whole,
leptodactylids make up only 38% of the amphibians (Duellman, 1979a).
Similar to salamanders, leptodactylids have exploited the moist terrestrial
environments in the southern temperate forests. Some 14/28 (50%) species
of amphibians have highly localized distributions within the southern
temperate forest region (defined as occuring in only one latitudinal region,
as identified in Table 10.1) compared to 9/26 (35%) in the Pacific Northwest . These species may be considered to be essentially endemic. Lizards
make up a majority of southern temperate forest reptiles (8/10 species, or
80%) and all but one are in the genus Liolaemus, whereas snakes comprise
a majority of Pacific Northwest reptiles (12/19 species, or 63%) regionally.
Finally, 15/38 (40%) reptile species have highly localized distributions
within the southern temperate forest region versus 9/45 (20%) species in
the Pacific Northwest. Also of interest is the general decline in numbers
of herptiles proceeding toward the pole in both regions (see Table 10.1).
Bury, Corn, & Aubry (1991) note the decline in numbers of reptiles
northward to the southern Washington Cascades; this pattern continues
into British Columbia and southeastern Alaska. Whereas amphibians also
decline in number, a greater proportion of this decline is due to the
salamanders.
Clearly, continental drift and isolation have contributed to these intercontinental differences. For example, leptodactylids are considered to be
an ancient Gondwanaland element (Cracraft, 1974), and available evidence suggests that they dispersed northward from South America into
Central America via island hopping (Duellman, 1979a) . Cei (1979) has
suggested an austral origin for primitive members of this family , and
pockets of diversity in the Argentine Patagonian steppes may represent
remnants from periods of forest expansion eastward. Similarly, different
species complexes of the lizard genus Liolaemus may have originated
from northern and southern Argentina (Cei, 1979).
The impoverishment of the southern temperate forest mammal fauna is
evident in Table 10.2. The Chilean (and Argentine) forests include a
maximum of 29 native species in contrast to 69 in the Pacific Northwest.
Most of these differences are due to the lack of insectivores in South
America (a total of 11 species) , a poorer chiropteran fauna (6 versus 13
species), and the absence of sciurid and microtine rodents (a total of 17
species) . Subtracting this difference of 34 species from the 69 species in
the Pacific Northwest yields 35 species, more similar to the total for the
southern temperate forests . Some 7/29 (24%) species are endemic to the
southern temperate forests (versus 10/69 species, or 14% , for the Pacific
Northwest). Specific forests and sites in the Pacific Northwest also have
more small-mammal and chiropteran species than those in southern Chile.
There appears to be a less dramatic decrease in numbers of mammal
species polarward as compared to herptiles.