The plan for the last three lectures of the semester:

1
The plan for the last three lectures of the
semester ? - Monday Dec. 5 - The Red Queen
Hypothesis Microevolution in Pathogenic
Microorganisms ? Wednesday Dec. 7 - Dr.
Berlochers research (Apples, Pests, and
Evolution) ? Friday Dec. 9 - Careers in
Integrative Biology, Dr. Berlochers evaluations
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IB 150 Final Exam 800-1100 AM, Thursday,
December 15 ? The final exam will have about 100
questions. About 50 will come from material
covered since the last hour exam, including
Integrative Topics lectures. The rest will come
from the earlier part of the course. ? We will
take a few questions directly from the two
previous exams. ? Room and other information
later this week.
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A rather amazing fact A tiny fraction of humans
are resistant (not really immune) to HIV due to
a mutation in a human cell membrane protein that
HIV needs to start the process of entering a
T-cell.
4
Thus, humans and our diseases are engaged in a
perpetual, deadly game of molecular warfare.
This game is only understandable in the language
of evolutionary biology. Or maybe Alice...
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Lecture 39 - The Red Queen Hypothesis
Microevolution in Pathogenic Microorganisms
Readings none.
Microorganisms and microevolution. The Red
Queen Hypothesis. Reasons for rapid virus
evolution. high mutation rate fast
generations. Things to remember from early in
course. mutations occur in tree-like patterns
phyogentic tree allele frequency change natural
selection genetic drift.
A little bit about the human immune
system. antigen antibody 2 week antibody
development antibody memory Microevolution in
influenza virus antigen drift antigen shift
1918 pandemic, vaccine development
Microevolution in HIV molecular clock drug
resistance natural immunity
6
Lecture 40 - Apples, pests, and evolutionwhy
are there so many new pests?
Readings none.
Insects constantly adapt to new crop plants or
new condtions. The apple maggot story. host
race timing of life history differences
Hardy-Weinberg violations temperature
adaptations small number of genes
involved? Other host race cases. European Corn
Borer, Brown Planthopper, Pea Aphid
Sympatric speciation. evolution of reproductive
isolation due to adaptation to different plants
or hosts no geographic barriers needed
7
Apples, pests, and evolutionwhy are there so
many new pests?
Research of Stewart H. Berlocher Department of
Entomology University of Illinois
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The problem pest insects are constantly
adapting to new crop plants or new conditions,
formingnew, genetically different populations .
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The beginning of my research story - in the
1860s, farmers in Connecticut observed a new kind
of worm in their apples.
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Benjamin Walsh in Illinois in 1867 realized that
the apple maggot was a true fruit fly, and
named it Rhagoletis pomonella.
pupa in soil
adult fly
larva in fruit
egg in fruit
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Life history of species of apple maggot fly.

• One generation per year
• Adults emerge from pupa in soil to coincide with
  fruit ripening.
• Adults meet and mate on host plant.
• Females oviposit in fruit.
• Larvae develop (2 weeks) in fruit, leave fruit
  when it drops.
• Pupation in soil long overwintering pupal
  diapause.

Rhagoletis pomonella
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Since apple was not native, and the insect seemed
to be, What did it feed on originally?
Not native crabapples! (which are in the genus
Malus like the domestic apple)
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Hawthorns are related to apples (rose family) but
not in the same genus. North American is very
rich in hawthorn species.
But on hawthorns, Crataegus species!
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Walsh did more than just name the species - he
observed that there appeared to be differences
between the apple and haw forms. In fact, he
called them called host races - biologically
different populations that do not mate randomly.
15
We can now confirm a lot of Walshs differences,
as well as add some. The first difference is that
the apple and hawthorn populations occur at
slightly different times of the year.
16
Emergence curves differ between apple and
hawthorn at a site in Grant Michigan that has the
two plants growing in a completely interspersed
manner. We know this is a genetic difference.
17
Second, we know that adaptation to the different
fruiting times of apples and hawthorns produces
reproductive isolation - the populations together
are not in Hardy-Weinberg equilibrium.
18
Acon 95 data
Haw
Proof that the two forms, all mixed together
spatially at the Grant site, do not make a
Hardy-Weinberg population - because there are
different allele frequency differences!
Apple
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Why different allele frequencies? Pupae of
early emerging apple flies endure a longer period
of warm weather in the soil than haw
pupae. Natural selection favors genotypes that
have a lower pupal metabolic rate (use of stored
energy reserves) in the apple flies. Flies with a
high metabolic rate run out of energy reserves
and die. Acon-295 proteins use energy reserves
faster than other Acon-2 proteins. In a lab
experiment, keeping hawthorn pupae at summer-like
temperatures for extended periods of time
actually did select against the Acon-295 allele,
so that the experimental hawthorn population
eventually had the lower Acon-295 allele
frequency characteristic of an apple population.
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Third, apples and haws are unequally attractive
to the two races! Volatile blends for apple and
hawthorn fruit Apple blend Hawthorn
blend Butyl hexanoate (0.37) Butyl hexanoate
(0.01) Pentyl hexanoate (0.05)
3-Methylbutan-1-ol (1.0) Propyl hexanoate
(0.04) Isoamyl acetate (0.4) Butyl butanoate
(0.10) 4,8-Dimethyl-1,3(E),7-nonatriene
(0.02) Hexyl butanoate (0.44) Ethyl acetate
(20.0) Dihydro--ionone (0.02)
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Test flies in wind tunnel
22
Open symbols are apple flies, filled dark symbols
are hawthorn flies.
23
Beyond Walsh What we know of genetics so far F1s
are odor-impaired - they dont respond to plant
odor very well at all. F2s indicate that there
may be a relatively few genes involved - we
recover some flies that respond strongly to apple
blend, some that respond strongly to hawthorn
blend, and many that act like F1s - no response.
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So, what can we say thus far? 1. The apple race
evolved from the hawthorn race about 150
years/generations ago. 2. Each race is adapted to
its host plant with respect to timing of life
history, soil temperature conditions, and odor
recognition. 3. A small number of genes may be
involved in odor response. 4. Even when occurring
together in areas where the host plants are
intermixed, the two races do not interbreed
randomly - they are displaying partial
reproductive isolation - acting like species to
some extent. About 6 gene flow from direct
observation.
25
Insect host races are seen in many insects, such
as the European Corn Borer, the Brown Planthopper
of rice (both of these involve a shift from a
non-crop plant to a crop) and the pea aphid
(shift from alfalfa to peas or vice versa - not
yet clear)
26
This all raises the question, has this process of
host race formation been going on with native
fruiting plants in the more distant past - in
evolutionary time?
27
Some native fruits in eastern North America...
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All of these plants have their own species of
flies similar to the apple maggot - such as the
Blueberry Maggot Rhagoletis mendax.
29
Most of these species occur in sympatry...
The plum fly and the like here are species that
have not yet been given a formal taxonomic
(Latin) name.
30
Thus, the formation of host races may be the
first stage in sympatric speciation - the
formation of species by ecological
specialization, instead of geographic isolation.
But is sympatric speciation restricted to just a
few species groups? At a minimum it may occur in
the many other species of true fruit flies (some
examples on the next slides).
31
Drosophila - not a true fruit fly!
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So, my research occurs in the intersection of
three worlds - I have been integrative all my
professional life!
Evolution
Agriculture
Genetics
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Lecture 40 - Apples, pests, and evolutionwhy
are there so many new pests?
Readings none.
Insects constantly adapt to new crop plants or
new condtions. The apple maggot story. host
race timing of life history differences
Hardy-Weinberg violations temperature
adaptations small number of genes
involved? Other host race cases. European Corn
Borer, Brown Planthopper, Pea Aphid
Sympatric speciation. evolution of reproductive
isolation due to adaptation to different plants
or hosts no geographic barriers needed