Environmental Engineering Reference
In-Depth Information
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Standard length (mm)
Figure 21.1 Differences in size distribution in stocked populations (solid line) and surviving individuals (dashed lines) at six
different release locations of Atlantic salmon ( Salmo salar ) fry in Maine, United States. The size of surviving individuals is
signifi cantly different from that of the stocked population in fi ve of six locations, which is evidence of directional selection on
fry size. A single size was not optimal across sites, as size of surviving individuals was correlated with variation in stream
characteristics. (From Bailey and Kinnison 2010 .)
use local genotypes as a source of restoration prop-
agules, but include a way to introduce potentially
adaptive genes into populations.
tions. Organisms with particular life history traits,
such as long generation times or high incidences of
inbreeding, may be at a disadvantage in rapidly chang-
ing situations (Barton & Partidge 2000 ; Kinnison et al .
2007). Additionally, even within functional groups or
species, some populations will be unable to evolve due
to small population sizes, lack of genetic variation or
constraints of genetic architecture, wherein selection
for optimal phenotypes can be limited by correlated
response to selection of genes with very different
functions (Walsh & Blows 2009). Finally, the ability of
21.2.4
Limits to genetic diversity
Although there are cases where phenotypic plasticity
and adaptive evolution may be able to maintain viable
populations, these processes cannot be expected to
rescue all species or populations in changing condi-
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