The traditional view: whales as the

1
Artiodactyla
Perissodactyls (horses, rhinos)
The traditional view whales as the sister
group of the artiodactyls.
2
Synapomorphy of all artiodactyls, a
spindle-shaped ankle bone.
3
Modified ankle bone a synapomorphy defining a
monophyletic group without whales.
4
Note synapo- morphies in sequence data
Part of the whippo data set
5
Genetic distance analysis supports a close
relationship between whales and hippos.
Important note distance analyses like the one
above are phenetic rather than phylogenetic.
They are based on differences between or among
several species, generally as measured by
allozyme surveys, and not on shared
derived characters.
6
The presence of a SINE in several gene loci
defines a unique synapo -morphy for hippos and
whales, lending considerable additional support
to this view of their relationship.
7
SINE short interspersed elements, a large
family of mobile repeat sequences found in many
genomes.
Why might SINES and LINES be perfect characters
for constructing phylogenetic trees?
Bottom line little or no convergence, little or
no character reversal minimal homoplasy
8
The Biological Species Concept (Ernst
Mayr) Species are groups of actually or
potentially interbreeding natural populations
which are reproductively isolated from other
such groups
9
Phylogenetic species concept Species are the
smallest diagnosable monophyletic groups.
10
Morphospecies concept Species are groups of
organisms which share a common morphology and can
be distinguished by some aspect of
this morphology from other natural
groups. Ecological species
concept Species are groups of organisms (or
populations) which sharea common ecological
niche in the same community.
11
This is the red wolf, called Canis rufus. This
form is a valid species by the morphospecies and
ecological species concepts, but not by the BSC
or PSC.
12
males
females
Both the PSC and the morphospecies concept can be
grossly inaccurate when there is extreme sexual
dimorphism (as shown here - , the males and
females of these Cynolebias spp were actually
described as different species). Similar
problems occur when developmental stages of the
same organism differ in appearance.
13
Sometimes it is even difficult to tell which
females go with which males, if there are
several closely related species in the same area.
14
Pseudotropheus zebra from Lake Malawi.
Sometimes INTRAspecific variation in appearance
is as great as INTERspecific variation. This can
be compounded by sexual dimorphism and
developmental variation.
15
The BSC is not based on absolute interfertility,
but on interfertility in nature. There are
two key elements to the BSC Gene flow (in
nature) Reproductive isolation The BSC is
usually easily applied to sympatric organisms
but it is more difficult to allopatric
populations. It is also very difficult to
apply it to asexual organisms.
Sympatric living within breeding range of
eachother Allopatric NOT living within
breeding range of eachother
16
No heterozygotes!
This is an allozyme survey of a single collection
of fish made in a small stream in Mexico. The
analysis was done by an undergraduate working in
my laboratory in 1982. How many separate gene
pools are present?
17

• There are 16 individuals on the gel.
• Their presumptive genotypes are as
• follows
• A2 A2 B1 B1 9. A2 A2 B1 B1
• A1 A1 B2 B2 10. A1 A1 B2 B2
• A2 A2 B1 B1 11. A2 A2 B1 B1
• 4. A1 A1 B2 B2 12. A2 A2 B1 B1
• 5. A1 A1 B2 B2 13. A1 A1 B2 B2
• 6. A2 A2 B1 B1 14. A1 A1 B2 B2
• 7. A1 A1 B2 B2 15. A1 A1 B2 B2
• 8. A2 A2 B1 B1 16. A2 A2 B1 B1
• Follow the color coding. Notice that
• there are only two genotypes and
• that their allelic compositions are
• mutually exclusive. There are no

fast
slow
fast
slow
1 2 3 4 5 6 7 8 9 10 1112 13 14
1516
There are two gene pools on these gels,
indicating the presence of two sibling species
in the sample. To see this, lets concentrate on
the two middle gel slices that are stained
for different enzymes. We will call the gene for
the upper enzyme A and the fast and slow
alleles are A1 and A2 respectively. Likewise, we
will call the gene for the lower enzyme B and
the alleles are (fast) and B2 (slow).
18
Platyfish Xiphophorus maculatus
Swordtail, X. helleri
X. maculatus and X. helleri occur in the same
streams in Mexico and Central America they do
NOT hybridize in nature.
19
Yet many (mostly) fertile hybrids of these two
species are for sale in almost any petshop, and
they are the backbone of the Florida tropical
fish industry.
20
The swordtail and the platyfish are examples of
forms which do not exchange genes in nature,
yet can be intercrossed in forced matings to
yield viable and usually fertile hybrids. What
keeps these species like these genetically
distinct in nature? In other words, what limits
gene flow between them? Ans. Isolating
mechanisms of various types