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BIOLOGY 3FF3 Lecture Notes - Allopatric Speciation, Zygote, Hybrid Zone

Course Code
Kim Dej

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Figure 16-1. Quickthink: Consider
the situation wherein you
conducted a phylogenetic
systematic analysis on 14
populations amount 6 species,
ABCDEF. Try to explain possible
events as to what happened at
B4. Possibly the species is just
Mechanisms of Speciation
things that look alike are classified in the same taxa
Phylogenetic Species
We can build phylogenetic trees and
expect all species fall out into a clade
If we found one of the members to fall
out in a sister group, then we'd have to
reconsider the species (i.e. like B4)
phylogenetic species - elephants
They separated African savannah
species and African forest into
two different species. Some
morphological differences,
however, cladogram was
constructed by genetic data.
Important for conservation work
b/c it matters whether one
collection of organisms are two
species or one species.
3:26 PM
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--stop gene flow
-- no longer can interbreed, b/c they've
diverged too much in their traits
Allopatric = ancestral population, and then
something breaks them apart, like the
changing direction of a river and so species
cannot mix anymore. They are separated by
Sympatric = the two groups are still in
contact, in overlapping geography, and they
interact with each other, however, they are
still able to differentiate, and after a
significant time they become two separate
Everything else in between is just a
shade of these two
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physical - dispersal, vicariance
A mainland and an island, and
some organisms can be
transported to the island. The
net result is that one population
is separated to the other.
Enough to disrupt gene flow
provided they don't go back
and forth.
Vicariance: Same result, but
due to a breaking up for a land
mass, or changing direction of a
river, etc
geographical - dispersal and colonisation
Hawaiian fruitflies -- huge variety
of shapes, colours, size, etc. They
all live in the Hawaiian islands,
and they are volcanic and very
young. The oldest island is shown
on the left, newer ones on the
Each fly species live on a separate
island, and so it's found that
dispersal and colonization of
islands are shown by the
phylogenetic tree.
geographical - vicariance
Snapping shrimp: Different sized
claws -- snap their claws to create
soundwave that confuses prey.
Populations are on the pacific and
Caribbean side -- separated.
The ones on the Pacific side look
like those on the Caribbean side,
and so morphologically we may
try to classify them as the same
taxa, but b/c they are separated
by land mass we don't. We may
not know that though.
So we have genetic data. Pacific and
Caribbean populations are sister
groups. Meaning they are more closely
related to those on the other side of
the landmass (even though they are
further away)
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