Biology Reference
In-Depth Information
locally evolved ecotypes of white clover (
Tr ifolium repens
), for example,
occur throughout the world (e.g., Gustine et al. 2002).
Rapid evolution of ecotypes adapted to new conditions also occurs in
aquatic plants. In 1984, a strain of a tropical marine green alga,
Caulerpa
taxifolia
, is believed to have been released accidentally into the Mediter-
ranean Sea from the Oceanographic Museum of Monaco (Meinesz
1999).This strain apparently arose through selection in European aquaria
and is characterized by vigorous clonal growth, resistance to cold water,
and lack of sexual reproduction.This strain has not only spread over thou-
sands of hectares of shallow coastal waters along the northern coast of the
Mediterranean Sea, but has appeared in coastal waters of southern Cali-
fornia and coastal waters far south of its native range in eastern Australia.
Caulerpa
contains a series of toxins that provide defense against grazing
animals and organisms that might attach to its surfaces (Ribera Siguan
1996).Thus, evolutionary change under human selection may create alien
forms that are highly invasive in new environments.
Adaptation of Animals to New Habitats
Evolutionary changes in life history features also occur in animals intro-
duced to new regions. Adler and Levins (1994) have described an “island
syndrome” of adjustments in morphology, behavior, and demography
made by rodents on islands in the ocean or large freshwater lakes. These
include increased body mass, delayed sexual maturity, altered territorial
behavior, increased population density, increased survival, and greater
population stability. In most cases, the species examined are not recent
invaders, so these changes may be the result of long-term ecological and
evolutionary adjustment. Populations of the house mouse (
Mus musculus
)
on Corsica, for example, show several of these demographic responses,
together with more sedentary behavior (Navajas y Navarro et al. 1989).
Birds also exhibit a distinct “island syndrome” (Blondel 2000) involving
many features of ecology, reproductive biology, and behavior.Again, many
of these changes are long-term evolutionary responses, which we will
examine in more detail in chapter 18.
Rapid evolutionary change in life history characteristics can be seen
in many recently introduced alien animals, however.Among invertebrates,
very rapid changes are apparently occurring in several alien species in
North America. Zebra mussels (
Dreissena polymorpha
), for example, were
introduced to North America in 1986 (Elderkin et al. 2001). First appear-
ing in Lake St. Clair, between Lakes Erie and Huron, this species has now
