Environmental Engineering Reference
In-Depth Information
during the recent, unusually warm, decades and are
not likely to be repaired in the decades to come.
These examples show that the recognition of inter-
actions between populations of species that meet in a
community is crucial in any restoration programme.
Therefore, we conclude this chapter by referring to
' community genetics ' , a new fi eld of science focused on
the evolutionary genetic processes that occur among
interacting populations in biotic communities. Herita-
ble genetic variation within species, especially domi-
nant or
keystone species
, can have effects beyond the
population level, a phenomenon referred to as the
extended phenotype effect
(Whitham
et al
. 2003 ). For
example, distinct genotypes of narrowleaf cottonwood
(
Populus angustifolia
) support unique arthropod com-
munities that remain consistent over many years. This
is an example of so-called
community heritability
(Keith
et al
. 2010). There is increasing evidence that the
extended phenotype effect can affect ecosystem proc-
esses ranging from nitrogen mineralization and litter
decomposition to community structure of the insect
species associated with a particular species of plant.
For instance, differences in resistance among Pinyon
pines to a keystone herbivore have community-level
consequences for bird, mammal and rhizosphere
microbe communities (Whitham
et al
. 2003 ). Geno-
typic diversity in a dominant old-fi eld plant species, late
goldenrod (
Solidago altissima
), affects arthropod diver-
sity and community structure as well as net annual
primary productivity. The magnitude of this effect can
be as large as the effects generally observed for between-
species diversity (Crutsinger
et al
. 2006 ).
One of the consequences of the extended phenotype
effect of genes is that we have to reconsider how we
should estimate minimum viable population (MVP)
size. Whitham
et al
. (2003) defi ned MVIP as the
minimum viable interacting population size, the size of
a population needed to maintain genetic diversity at
levels required for other interacting species in the com-
munity as well. No empirical estimates have been made
to date, but clearly these will be larger than MVP. These
observations emphasize the cascading effects of the
impact of human activities on the evolution of species
and communities.
In Chapter 21, the authors address how restoration
ecologists and practitioners can apply theories on evo-
lutionary and community dynamics to anticipate and
incorporate future - and largely uncertain - environ-
mental changes. In the present chapter, we have
explored the foundations of the mechanisms of selec-
tion and evolution, knowledge that is indispensable for
estimating whether the current
evolutionary potential
of species is a suffi ciently sound ecological basis to
'restore to the future'. A bit more than 40 years after
the pivotal work of Heslop-Harrison (1964), entitled
'Forty years of genecology', we can now state that the
interface between population ecology and populations
genetics has come of age.
