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Colautti et al.
2005 Molecular Ecology
When an invasive species first colonizes a new area, we
typically imagine that genetic diversity will be reduced due to the founding
event followed by drift in small populations.
What evidence did the authors find that supports this hypothesis? What evidence contracts this hypothesis?
Supporting evidence:
- Overall
levels of heterozygosity (Ho) were
lower in the introduced North American populations than in the native
European populations.
- The
one inland lake in Canada
showed the lowest heterozygosity (Ho),
lowest allelic diversity (k), and the lowest index of repeated
bottlenecking (M) suggesting strong genetic drift during sequential
founder events.
Contradictory
evidence:
- There
are a large number of rare alleles in the Superior
and Erie
populations leading to high measures of allelic diversity (k) and a high measures of (M) suggesting that drift is not strongly
shaping genetic structure.
Resolution
of this contradictory evidence?
- The
initial invasion was followed by multiple subsequent invasions and high
gene flow between Lakes Erie and Superior
as evidenced by low Fst (divergence)
between North American populations.
- Assignment
test showed that the invasion bottleneck has been offset by gene flow from
at least two and maybe more European populations.