Environmental Engineering Reference
In-Depth Information
low fitness). Finally, there are extreme temperatures and radiation regimes
that these species cannot cope with and so exhibit zero fitness.This is be-
cause extreme temperatures or solar radiation levels could cause species to
overheat or freeze to death depending on their physical (e.g., presence of
fur or feathers) and physiological (e.g., ability to adjust metabolism) traits.
Note that figure 3.3 also depicts an important characteristic of species,
namely a trade-off in coping abilities. Species 2 is able to tolerate higher
temperatures than species 1 but it is less able to tolerate higher solar radia-
tion regimes than species 1.These trade-offs are noteworthy because they
indicate that species cannot be good at coping with everything.
The species-specific information
provided in the upper graphs in fig-
ure 3.3 can be combined to create a
“contour map” depicting different
levels of fitness over the entire range
of temperature and solar radiation
that each species has been deter-
mined to tolerate. The value of this
information is that it can help us un-
derstand how individuals of a species
might play the game of life. For ex-
ample, individuals of species 2 will
have the highest fitness in regions with high temperatures but modest solar
radiation.These conditions are considered optimal for that species. Individ-
uals of that species are then expected to seek out habitats on a landscape
that provide such optimal conditions for living. Environmental conditions
could change such that the optima shift to a new location. For example,
species 2 might be associated with meadow habitats.As plant succession fills
in the meadows with trees, and it thus becomes cooler with less solar radi-
ation hitting the ground, the location is no longer optimal for this species.
Individuals will either have lower fitness or even die if they remain at this
location. Or they can move and seek out new meadow habitats on the land-
scape that offer optimal conditions.The ability to move and seek optimal
conditions obviously varies with the kind of species. Individual trees that
are firmly rooted in a location have no recourse to move. Animal species
have considerable flexibility to move and seek better conditions.
The net result is that we tend to find
that individuals of a species have a
temperature or solar radiation level
where they exhibit peak perform-
ance (high fitness) and there are
neighboring temperatures or
radiation regimes where they can
perhaps do all right (medium to
low fitness).
