Reintroductions are a common approach for
preserving intraspecific biodiversity in fragmented landscapes.
However, they may exacerbate the reduction in
genetic diversity initially caused by population fragmentation
because the effective population size of reintroduced
populations is often smaller and reintroduced populations
also tend to be more geographically isolated than native
populations. Mixing genetically divergent sources for
reintroduction purposes is a practice intended to increase
genetic diversity. We documented the outcome of reintroductions
from three mixed sources on the ancestral composition
and genetic variation of a North American fish, the
slimy sculpin (Cottus cognatus). We used microsatellite
markers to evaluate allelic richness and heterozygosity in
the reintroduced populations relative to computer simulated
expectations. Sculpins in reintroduced populations
exhibited higher levels of heterozygosity and allelic richness
than any single source, but only slightly higher than
the single most genetically diverse source population.
Simulations intended to mimic an ideal scenario for maximizing
genetic variation in the reintroduced populations
also predicted increases, but they were only moderately
greater than the most variable source population. We found
that a single source contributed more than the other two
sources at most reintroduction sites. We urge caution when
choosing whether to mix source populations in reintroduction
programs. Genetic characteristics of candidate
source populations should be evaluated prior to reintroduction
if feasible. When combined with knowledge of the
degree of genetic distinction among sources, simulations
may allow the genetic diversity benefits of mixing populations
to be weighed against the risks of outbreeding
depression in reintroduced and nearby populations.
Huff, David, D.; Miller, Loren, M.; Vondracek, Bruce.
Patterns of ancestry and genetic diversity in reintroduced populations of the slimy sculpin: implications for conservation.
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