BIOL 329 Lecture Notes - Lecture 45: Panmixia, Common Starling, Interspecific Competition

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Lect 45
Reef island: 120 deer. No young red cedar because deer browsed on all the seedlings. Fst: 0 = panmixis,
1 = no gene flow. Unless you continually maintain low populations levels, it will not be productive as a
few migrants swim over every year.
FINAL: Raptors to the end! After the midterm
Red squirrel: widespread in BC, historically absent most islands other than VI. Non-hibernating. Eat
conifer seeds, mushrooms, flowers, occasional nestling birds. Introduced by Govt to Haida Gwaii ~1950
to drop Sitka Spruce cones from canopy.
Exponential increase in population size and now are everywhere on the islands. Source of revenue for
locals.
Potential two-way interaction with positive effects on Haida Gwaii marten but negative effects on the
much rarer weasel.
Potentially high predation rate on the nests when squirrels were present. Low predation without
squirrels (raccoons, etc.).
Increased crow predation on nests from increased visibility decreased numbers of songbirds. Low
ground vegetation: squirrels prey on cones in the fall but on small bird eggs in the spring.
Population trends on islands with deer and squirrels: species that nest in shrubs and on the ground are
more likely to be affected by browsing and squirrel predation.
Gulf islands: get rid of the top carnivores and deer populations will increase exponentially. The large
number of herbivores will deplete the ground vegetation, impacting birds which nest on the ground or
below the browse line.
Large expansion of Pacific Treefrog on Haida Gwaii. As a result, Northern Saw-whet Owl populations are
declining, possibly due to the noise pollution of the treefrogs.
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