Biology Reference
In-Depth Information
fish (
Lepomis macrochirus
), and green sunfish (
Lepomis cyanellus
), are likely
to spread into higher latitudes and altitudes (Eaton and Scheller 1996). At
the same time, at high latitudes, many cold-adapted aquatic species may
disappear as freshwater ecosystems warm and are invaded by such species
(Lodge 2001).
Global Change, Shifting Ranges,
and Accelerated Evolution
Alien invasions have led to evolutionary responses of both aliens and the
native species with which they interact, as we have seen in detail. Global
climatic change is now modifying the ecological theater in which these
evolutionary processes are playing out. Both native and alien species are
now influenced by the selective pressures of global change. The increas-
ing husbandry of transgenic plants and animals is a wild card that will cer-
tainly have increasing evolutionary consequences.
Most analyses of the possible response of biotas to climatic change
have considered either the need or the potential for species to track the
climatic zones to which they are adapted by dispersal and colonization of
areas that become suitable. Typically, such analyses have assumed genetic
uniformity of species in question and landscape conditions permissive to
dispersal mechanisms. Malcolm et al. (2002) modeled the migration rates
required by member species of various biomes to keep pace with the
shifts of climatic zones resulting from a doubling of carbon dioxide over
the next 100 yr. This analysis showed that required rates were much
higher than those calculated for species that moved northward rapidly
during the last glacial retreat in the northern hemisphere. Required rates
were highest for arctic and temperate biomes, where global warming is
predicted to be greatest. Not surprisingly, incorporation of migration bar-
riers, such as water areas for terrestrial communities, increased the migra-
tion rates required to keep pace with climate change. Other modeling
efforts suggest that the effect of reducing the latitudinal gradient of tem-
perature will be to increase the rapidity of northward invasions (García-
Ramos and Rodríguez 2002).
Few studies have been attempted of the capability of plant species for
dispersal into new areas of favorable habitat such as those created by cli-
mate change. Many of the available studies deal with invasive plant
species, which show migration rates of several to many kilometers per
year (Malcolm et al. 2002). Among animals, birds and mammals expand-
