Biology Reference
In-Depth Information
ing into new regions may show very high migration rates. The range of
the coyote (
Canis latrans
) spread eastward in North America at a rate in
excess of 20 km per year between 1900 and 1990 (Malcolm et al. 2002).
Analyses of the abilities of plants and animals to shift their ranges to
keep pace with changing climates have given little consideration to
intraspecific genetic adaptation (Davis and Shaw 2001). Most widely dis-
tributed plants and animals show some degree of genetic adaptation to
local environmental conditions. In particular, plant species that have
undergone altitudinal or latitudinal migrations following retreat of the last
continental glaciers show various patterns of genetic variability and eco-
typic adaptation (see, e.g., Cwynar and MacDonald 1987). Some species,
for example, show a decline in variability from southern areas close to
their interglacial refugia to northern areas, where sequential founder
effects have caused progressive loss of alleles. Others, such as Scotch pine
(
Pinus sylvestris
), which followed retreating glaciers northward in Europe,
now show ecotypic adaptation to local temperature and photoperiod
conditions.The same is true of several North American trees and shrubs.
Inouye et al. (2000) documented an example of the origin of new cli-
matic and phenological conditions to which existing species do not
appear to be well adapted.At the Rocky Mountain Biological Laboratory
in Gothic, Colorado, warmer spring temperatures appear to be coupled
with increased winter snowfall in a manner that has kept the time of dis-
appearance of the winter snowpack essentially constant. In response to
warmer temperatures, however, American robins (
Tu r dus migratorius
) are
appearing about 2 wk earlier than in the early 1980s, and yellow-bellied
marmots (
Marmota flaviventris
) are emerging from hibernation about 38
days earlier than in the mid-1970s. These species, and presumably other
migrants and hibernators, are thus experiencing a much longer period of
spring snowpack at the beginning of their summer breeding season.This
represents a new combination of environmental conditions to which they
may not be fully adapted.
Although attention has been concentrated on the abilities of native
species to respond to climatic change, invasive alien species possess the
same opportunities. As we have seen, many of these species possess high
evolutionary adaptability and respond to resources made available by
environmental disruption. The spread of invasive tree species into high
mountain zones made favorable by climatic warming in Sweden demon-
strates that alien plants are taking advantage of such opportunities (Kull-
man 2002). Several alien trees that are widespread in the Mediterranean
