Environmental Engineering Reference
In-Depth Information
lines, with some showing a strong increase while in
others a strong decrease in resistance with inbreeding
coeffi cient is observed. The inbreeding lines of
S. latifolia
also show varying levels of inbreeding depression in
traits involved in the attraction of vectors of the disease,
that is transmitted by pollinating insects, such as fl ower
size and nectar production. Inbreeding depression in
resistance and attraction traits even appear to be
uncorrelated (Ouborg & Biere 2003 ), further hamper-
ing predictions of the overall effect of inbreeding on the
probability of becoming diseased.
populations. Genetic aspects of restoration are chal-
lenging because in the case of both population rein-
forcement and species reintroductions the question has
to be answered: from which external sources will prov-
enances be taken? The knowledge that plant popula-
tions are often adapted to local site conditions implies
that external seed sources may not match the condi-
tions of the target site (McKay
et al
. 2005 ). Indeed,
research-based 'seed transfer zones' have to be deline-
ated, defi ned as the geographical regions within which
individuals (seeds, seedlings, or adults) of native species
can be transferred with no detrimental effects on popu-
lation mean fi tness (Hufford & Mazer 2003). Ecological
similarity (matching habitat conditions) between
source and introduction site may be at least as impor-
tant as small geographic distance (Vander Mijnsbrugge
et al
. 2010 ; No ë l
et al
. 2011 ).
Another important challenge for restoration ecolo-
gists is that conservation efforts may no longer be suf-
fi cient to ensure that populations can stand impending
future unfavourable change due to the rapidly increas-
ing habitat degradation and fragmentation, globaliza-
tion of pests and diseases and climate change. Indeed,
understanding the response of populations and com-
munities to climate change, and their genetic conse-
quences, is one of the most pressing research questions
for the near future (Kramer & Havens 2009). As climate
change is far beyond the control of organizations in
charge of nature management, this is a most challeng-
ing argument to move from conservation to restora-
tion, indeed (see also Chapter 21). Seed sourcing for
restoration may therefore shift from a purely local prov-
enancing strategy to a strategy based on careful admix-
ture with seeds from more distant sources to maximize
evolutionary potential (Broadhurst
et al
. 2008 ) or even
from sources that better match the future local climate
predicted by climate models (Crowe & Parker 2008).
There is an increasing body of literature about mis-
matches between interacting populations of different
species as a result of changing temperature regimes.
For example, reduced spatial variability in plant phe-
nology as a result of experimental and observed
warming in the growing season resulted in a decline in
the offspring production by female caribou,
Rangifer
tarandus
, in Greenland (Post
et al
. 2008 ). Similarly,
Visser
et al
. (2006) show from their analysis of a 20-
year data set in a Natural Park in the Netherlands that
the synchrony between offspring needs of the insectivo-
rous great tit (
Parus major
), and the caterpillar biomass
of this bird's main food species, have been disrupted
7.4.3
Corollaries and consequences
Habitat fragmentation has ecological consequences
(changes in encounter rates among species) and
genetic consequences (changes in the outcome of
interactions) for species interactions that cannot be
viewed in separation. Dynamics of host and pathogen
population sizes feed back on the dynamics of frequen-
cies of resistance and avirulence alleles and vice versa.
For instance, changes in encounter rates with mutual-
ists or antagonists can induce changes in selection
pressures on resistance, avoidance and life-history
traits (Hochberg & Moller 2001). Moreover, rapid evo-
lution can take place if species interactions are
changed, as in climate change-induced shifts and
species invasions (Chapters 20 and 21). For instance,
habitat fragmentation can select for traits related to
dispersal (Olivieri
et al
. 1995). Likewise, loss of interac-
tions with pollinators may select for traits related to
reproductive assurance. These examples make it clear
that to be effective, restoration efforts must incorporate
considerations of the likely, multiple effects of inter-
ventions, manipulations and management on species
interactions. This suggests the need to preserve or
enhance pollinator interactions, genetic variation for
defense-related traits, and minimize risks of connectiv-
ity on disease transmission, as many restoration pro-
grammes indeed already do.
7.5 FROM CONSERVATION TO
RESTORATION: PERSPECTIVES
Conservation science and restoration ecology are com-
plementary disciplines. Restoration may become essen-
tial if conservation efforts have failed to preserve local
