This document discusses various topics related to interactions among species and evolution of life history characters. Regarding interactions among species, it covers concepts like coevolution, different types of coevolution (specific, guild, escape-and-radiate, cospeciation), and using phylogenies to study questions like coevolution. It also discusses mimicry and provides examples of different types of mimicry (Mullerian, Batesian, Mertensian). Regarding life history characters, it discusses concepts like reproductive strategies, life history analysis, tradeoffs organisms face, and two theories for why organisms age and die.

1. CHAPTER 18
Interactions Among
Species

2. Coevolution
1.1. Two species that interactTwo species that interact
affecting the genetic structureaffecting the genetic structure
of one another. Each one actsof one another. Each one acts
as a selective force on theas a selective force on the
other (lineages change inother (lineages change in
parallel)parallel)
2.2. Co-speciation – Do 2 lineagesCo-speciation – Do 2 lineages
speciate in the same pattern?speciate in the same pattern?
Perhaps like a lichinous fungiPerhaps like a lichinous fungi
and its algae symbiont.and its algae symbiont.

3. Concepts of Coevolution
• Coevolution as a process of reciprocal adaptive responseCoevolution as a process of reciprocal adaptive response
1.1. Specific coevolution: Coevolution of two (or few) speciesSpecific coevolution: Coevolution of two (or few) species
2.2. Guild Coevolution (diffuse, or multispecific): Coevolution amongGuild Coevolution (diffuse, or multispecific): Coevolution among
sets of ecologically similar speciessets of ecologically similar species
3.3. Escape-and-radiate coevolutionEscape-and-radiate coevolution
4.4. Cospeciation (introduced by interaction)Cospeciation (introduced by interaction)
• Coevolution as a pattern, detected by phylogeneticCoevolution as a pattern, detected by phylogenetic
analysisanalysis
1.1. Cospecieation (coincident speciation)Cospecieation (coincident speciation)
2.2. Parallel cladogenesisParallel cladogenesis

4. Co-evolution VS. Co-adaptation
• Co-evolution is when genetic composition ofCo-evolution is when genetic composition of
both species changes, each affecting theboth species changes, each affecting the
other.other.
• We assume co-evolution leads to co-We assume co-evolution leads to co-
adaptation.adaptation.
• But you can have co-adaptation without co-But you can have co-adaptation without co-
evolution (birds on same island with differentevolution (birds on same island with different
bill shapesbill shapes may have evolved in allopatrymay have evolved in allopatry
before sympatric overlap)before sympatric overlap)
• So, co-evolution should lead to co-adaptationSo, co-evolution should lead to co-adaptation
but co-adaptation is not necessarily thebut co-adaptation is not necessarily the
result of co-evolutionresult of co-evolution

5. Using Phylogenies to Answer
Questions
• CoevolutionCoevolution
– Leaf-cutting ants and fungi they farmLeaf-cutting ants and fungi they farm
• Leaf cutters grow fungus on leaves thatLeaf cutters grow fungus on leaves that
they cut for foodthey cut for food
• 200 ant species of tribe Attini each farm a200 ant species of tribe Attini each farm a
different fungus speciesdifferent fungus species
• Did the two groups cospeciate?Did the two groups cospeciate?
– Phylogenies should be congruentPhylogenies should be congruent
• Hinkle found congruence on all branchesHinkle found congruence on all branches
but onebut one
• Fungi were domesticated more than onceFungi were domesticated more than once

6. Leaf Cutting Ants

8. Evolution of Mimicry
• Complex interaction among multipleComplex interaction among multiple
species believed to arise from co-species believed to arise from co-
evolution, though it has not beenevolution, though it has not been
proven so. For sure, at least, this is co-proven so. For sure, at least, this is co-
adaptation.adaptation.
• Major Types of Mimicry:Major Types of Mimicry:
– Mullerian MimicryMullerian Mimicry
– Batesian MimicryBatesian Mimicry
– Mertensian MimicryMertensian Mimicry

9. Mullerian Mimicry
• When a group of species that are distasteful,When a group of species that are distasteful,
poisonous, or otherwise noxious, resemblepoisonous, or otherwise noxious, resemble
each other in morphology or behavioreach other in morphology or behavior
• Often brightly colored and have some kind ofOften brightly colored and have some kind of
warning systemwarning system  Aposematic TraitAposematic Trait
• They call attention to themselves and warn ofThey call attention to themselves and warn of
danger. This warning is assumed to ward offdanger. This warning is assumed to ward off
potential predators or increase fitness inpotential predators or increase fitness in
some way.some way.
• The more these species look alike, the easierThe more these species look alike, the easier
it is for a predator to remember that oneit is for a predator to remember that one
warning pattern (eg. coral snakes bands)warning pattern (eg. coral snakes bands)

10. • Coral snakesCoral snakes all coral snakesall coral snakes
are venomous. There are aroundare venomous. There are around
70 species in the new world. Over70 species in the new world. Over
90% of them look extremely90% of them look extremely
similar, especially with respectsimilar, especially with respect
to color and patternto color and pattern
• We assume that their similarity inWe assume that their similarity in
appearance allows predators to evolve theappearance allows predators to evolve the
ability to identify them as poisonous andability to identify them as poisonous and
leave them alongleave them along
• Thus, there is an advantage that all shareThus, there is an advantage that all share
from looking similarfrom looking similar
Examples of Mullerian Mimicry

11. Batesian Mimicry
• A non-noxious or non-poisonous mimicA non-noxious or non-poisonous mimic
looks like a noxious modellooks like a noxious model
• For our coral snake example, theFor our coral snake example, the
venomous coral snakes would be thevenomous coral snakes would be the
model and non-venomous snakesmodel and non-venomous snakes
looking like coral snakes are thelooking like coral snakes are the
mimicsmimics

12. Examples of Batesian Mimicry
In each picture, the snake to
the right is the Venomous Coral
Snake, while those to the
left are the mimics (harmless)

13. Mertensian Mimicry
• We have seen some examples of deadlyWe have seen some examples of deadly
poisonous snakes such aspoisonous snakes such as MicrurusMicrurus
(Elapidae) and non-poisonous snakes such(Elapidae) and non-poisonous snakes such
asas LampropeltusLampropeltus andand PliocercusPliocercus
(Colubridae).(Colubridae).
• But there are other snakes that areBut there are other snakes that are
moderately poisonous, such as members ofmoderately poisonous, such as members of
the generathe genera RhinobothryumRhinobothryum,, ErthrolammprusErthrolammprus
andand PseudoboaPseudoboa..
• Mertens suggests that the moderatelyMertens suggests that the moderately
poisonous snakes could be the model, notpoisonous snakes could be the model, not
the poisonous snakes.the poisonous snakes.

14. Mertensian Mimicry
• If the moderately poisonous snakes bite aIf the moderately poisonous snakes bite a
predator, it would get sick and therefore wouldpredator, it would get sick and therefore would
learn to avoid those and similar snakes in thelearn to avoid those and similar snakes in the
future.future.
• But, if a deadly poisonous snake bites a predator,But, if a deadly poisonous snake bites a predator,
it would die and never have a chance to learn.it would die and never have a chance to learn.
• So, Mertens proposes that theSo, Mertens proposes that the moderatelymoderately
poisonous snakes are the model and both thepoisonous snakes are the model and both the
poisonous and non-poisonous snakes are thepoisonous and non-poisonous snakes are the
mimicsmimics. This situation is termed Mertensian. This situation is termed Mertensian
mimicrymimicry

15. Ecomorphs
• What is an ecomorph?What is an ecomorph?
• We can loosely define an ‘ecomorph’We can loosely define an ‘ecomorph’
as a particular set or characters thatas a particular set or characters that
define a body plan commonlydefine a body plan commonly
associated with living in a particularassociated with living in a particular
habitathabitat
• Eg. snakes that live in trees areEg. snakes that live in trees are
typically Green, slender, elongate...typically Green, slender, elongate...

16. Parallel Evolution of Anolis lizard
ecomorphs on Caribbean islands
# species per island shown# species per island shown
There are 138 species in the Caribbean andThere are 138 species in the Caribbean and
about 340 species of anoline lizards overall.about 340 species of anoline lizards overall.

17. Parallel Evolution of Anolis lizard
ecomorphs on Caribbean islands
Anolis lizards occupy many
different ecological niches
on Caribbean Islands

18. Ecomorphs are not closely related!!
Each Island has independently
evolved ecomorphs!!!
Common Ancestor
Island 1 Island 2
tree-top
tree-top
Trunk-
dweller
Trunk-
dweller Twig-
dweller
Twig-
dweller

19. CHAPTER 19
Evolution of Life
History Characters

20. Reproduction Strategies
• Mice mature early and reproduceMice mature early and reproduce
quickly whereas bears mature late andquickly whereas bears mature late and
reproduce latereproduce late
• Some plants live and flower for onlySome plants live and flower for only
one season, others live and flower forone season, others live and flower for
centuriescenturies
• Some bivalves produce millions of tinySome bivalves produce millions of tiny
eggs at once, others less than 100eggs at once, others less than 100
large eggs at a timelarge eggs at a time

21. Life History Analysis
• The branch of evolutionary biology thatThe branch of evolutionary biology that
tries to sort our reproductive strategiestries to sort our reproductive strategies
• A “perfect” organism would mature atA “perfect” organism would mature at
birth and produce many high qualitybirth and produce many high quality
offspring throughout lifeoffspring throughout life
• No organism can do this because thereNo organism can do this because there
are tradeoffs in time, size of offspring,are tradeoffs in time, size of offspring,
and parental investmentand parental investment

22. Life History Analysis
• Life history extremesLife history extremes
– Thrip egg mites are born already inseminated byThrip egg mites are born already inseminated by
mating with brothers inside mother’s bodymating with brothers inside mother’s body
• Adults have short livesAdults have short lives
• The offspring eat there way out of their motherThe offspring eat there way out of their mother
when she is four days oldwhen she is four days old
– Brown kiwis lay eggs 1/6 of their body weightBrown kiwis lay eggs 1/6 of their body weight
• Chicks are self-reliant within a weekChicks are self-reliant within a week
• Takes one month for female to produce each eggTakes one month for female to produce each egg

24. Life History Analysis
• Organisms may grow to a large size toOrganisms may grow to a large size to
make large offspring or reproducemake large offspring or reproduce
earlier at a smaller size to make smallerearlier at a smaller size to make smaller
offspringoffspring
• For organisms that wait, chance ofFor organisms that wait, chance of
dying before reproducing is highdying before reproducing is high
• Environmental variation creates lifeEnvironmental variation creates life
history variationhistory variation

25. Life History Analysis
• Questions to ConsiderQuestions to Consider
– Why do organisms age and die?Why do organisms age and die?
– How many offspring should an individualHow many offspring should an individual
produce in a year?produce in a year?
– How big should each offspring be?How big should each offspring be?
• Must balance among fitness aspectsMust balance among fitness aspects
• Conflicts arise between male andConflicts arise between male and
female parentsfemale parents

26. Life History Analysis
• Female Virginia opossumFemale Virginia opossum
– Nursed for three months and then weanedNursed for three months and then weaned
– Continued to grow for several months untilContinued to grow for several months until
reaching sexual maturityreaching sexual maturity
– Had first litter of 8 offspringHad first litter of 8 offspring
– Months later had second litter of 7Months later had second litter of 7
offspringoffspring
– At 20 months was killed by a predatorAt 20 months was killed by a predator
– Energy allocation changed through lifeEnergy allocation changed through life

28. Life History Analysis
• Differences among life history concernDifferences among life history concern
differences in energy allocationdifferences in energy allocation
• Other female opossums could matureOther female opossums could mature
earlier and reproduce earlierearlier and reproduce earlier
– Or devote less energy to reproduction andOr devote less energy to reproduction and
more to maintenancemore to maintenance
• Natural selection optimizes energyNatural selection optimizes energy
allocation in a way that maximizes totalallocation in a way that maximizes total
lifetime reproductionlifetime reproduction

29. Why Do Organisms
Age and Die?
• Senescence = late life decline of fertilitySenescence = late life decline of fertility
and probability of survivaland probability of survival
• Aging reduces an individual’s fitnessAging reduces an individual’s fitness
and should be opposed by naturaland should be opposed by natural
selectionselection
• Two theories on why aging persistsTwo theories on why aging persists

31. Why Do Organisms
Age and Die?
• Rate-of-Living TheoryRate-of-Living Theory
– Senescence is caused by accumulation ofSenescence is caused by accumulation of
irreparable damage to cells and tissuesirreparable damage to cells and tissues
– Damage caused by errors duringDamage caused by errors during
replication, transcription, and translation,replication, transcription, and translation,
and by accumulation of poisonousand by accumulation of poisonous
metabolic by productsmetabolic by products
– All organisms have been selected to resistAll organisms have been selected to resist
and repair damage as much asand repair damage as much as
physiologically possiblephysiologically possible
– Have reached limit of possible repairHave reached limit of possible repair

32. Why Do Organisms
Age and Die?
• Rate-of-Living TheoryRate-of-Living Theory
– Populations lack genetic variation needed toPopulations lack genetic variation needed to
enable more effective repair mechanismsenable more effective repair mechanisms
– Two predictions of theory:Two predictions of theory:
• Because damage is partially caused by metabolicBecause damage is partially caused by metabolic
by products, aging rate should be correlated toby products, aging rate should be correlated to
metabolic ratemetabolic rate
• Because organisms have been selected to repairBecause organisms have been selected to repair
the maximum possible, species should not be ablethe maximum possible, species should not be able
to evolve longer life spansto evolve longer life spans

33. Why Do Organisms
Age and Die?
• Rate-of-Living TheoryRate-of-Living Theory
– Austad and Fischer tested first predictionAustad and Fischer tested first prediction
• Calculated amount of energy expended perCalculated amount of energy expended per
gram of tissue per lifetime for 164 mammalgram of tissue per lifetime for 164 mammal
speciesspecies
• Should expend same amount regardless ofShould expend same amount regardless of
length of lifelength of life
• Found great variation in energyFound great variation in energy
expenditureexpenditure
• Found that bats expend three times theFound that bats expend three times the
energy of other mammals their sizeenergy of other mammals their size

35. Why Do Organisms
Age and Die?
• Rate-of-Living TheoryRate-of-Living Theory
– Luckinbill tested second predictionLuckinbill tested second prediction
– Artificially selected for longevity in fruitArtificially selected for longevity in fruit
fliesflies
– Increased life span from 35 days to 60Increased life span from 35 days to 60
daysdays
– These long-lived fruit flies had lowerThese long-lived fruit flies had lower
metabolic rates during first 15 days of lifemetabolic rates during first 15 days of life

37. Why Do Organisms
Age and Die?
• Rate-of-Living TheoryRate-of-Living Theory
– Both of the predictions of the theory haveBoth of the predictions of the theory have
been falsifiedbeen falsified
– Examine energy expenditure on cells andExamine energy expenditure on cells and
chromosomes, not whole organismchromosomes, not whole organism
• Normal animal cells are capable of a finiteNormal animal cells are capable of a finite
number of divisions before deathnumber of divisions before death
• All cells except cancer cells, germ lineAll cells except cancer cells, germ line
cells, and stem cellscells, and stem cells
• Senescence may result from chromosomeSenescence may result from chromosome
damagedamage

38. Why Do Organisms
Age and Die?
• Rate-of-Living TheoryRate-of-Living Theory
– Telomeres of chromosomes consist ofTelomeres of chromosomes consist of
tandem repeatstandem repeats
– Added by enzyme telomeraseAdded by enzyme telomerase
• Overactive in cancer cellsOveractive in cancer cells
– During each replication pieces are lostDuring each replication pieces are lost
– Progressive telomere loss is associatedProgressive telomere loss is associated
with senescence and deathwith senescence and death
– Cells die because chromosomes are tooCells die because chromosomes are too
damaged to functiondamaged to function

39. Why Do Organisms
Age and Die?
• Rate-of-Living TheoryRate-of-Living Theory
– Life spans of mammals are correlated withLife spans of mammals are correlated with
life spans of skin and blood cellslife spans of skin and blood cells
– These results consistent with rate-of-livingThese results consistent with rate-of-living
– Why doesn’t natural selection activateWhy doesn’t natural selection activate
telomerase to add more telomeres?telomerase to add more telomeres?
– Could be tradeoff between extending cellCould be tradeoff between extending cell
life and proliferating cancerlife and proliferating cancer

41. Why Do Organisms
Age and Die?
• Evolutionary Theory of AgingEvolutionary Theory of Aging
– If genetic variation for extending life spansIf genetic variation for extending life spans
does exist, why hasn’t natural selectiondoes exist, why hasn’t natural selection
produced this result in all species?produced this result in all species?
– Aging is not caused by damage itself butAging is not caused by damage itself but
the failure to repair the damagethe failure to repair the damage
– Damage is not repaired because ofDamage is not repaired because of
deleterious mutations or tradeoffs betweendeleterious mutations or tradeoffs between
repair and reproductionrepair and reproduction

42. Why Do Organisms
Age and Die?
• Evolutionary Theory of AgingEvolutionary Theory of Aging
– Hypothetical life history of individual withHypothetical life history of individual with
wild-type genotypewild-type genotype
• Mature at age 3Mature at age 3
• Die at age 16Die at age 16
• Probability of survival from one year to theProbability of survival from one year to the
next is 0.8next is 0.8
• Expected lifetime reproductive success =Expected lifetime reproductive success =
2.4192.419
– Will consider two mutations that alter lifeWill consider two mutations that alter life
history strategyhistory strategy

44. Why Do Organisms
Age and Die?
• Evolutionary Theory of AgingEvolutionary Theory of Aging
– Mutation Accumulation HypothesisMutation Accumulation Hypothesis
– Mutation cause death at age 14Mutation cause death at age 14
– Deleterious mutation, but howDeleterious mutation, but how
deleterious?deleterious?
– Expected lifetime reproductive successExpected lifetime reproductive success
reduced to 2.340reduced to 2.340
• Still 96% of originalStill 96% of original
– Weakly selected againstWeakly selected against
• May persist in mutation-selection balanceMay persist in mutation-selection balance

46. Why Do Organisms
Age and Die?
• Evolutionary Theory of AgingEvolutionary Theory of Aging
– Deleterious mutations that affectDeleterious mutations that affect
individuals late in life can accumulate inindividuals late in life can accumulate in
populations and be the cause of agingpopulations and be the cause of aging
– Cancers that usually occur late in life onlyCancers that usually occur late in life only
slightly affect fitness of the individualslightly affect fitness of the individual
– Not strongly selected against and canNot strongly selected against and can
accumulate rapidlyaccumulate rapidly
– Can cause senescence and death with fewCan cause senescence and death with few
fitness consequencesfitness consequences

47. Why Do Organisms
Age and Die?
• Evolutionary Theory of AgingEvolutionary Theory of Aging
– Mutation of two different life history charactersMutation of two different life history characters
with pleiotropic actionwith pleiotropic action
– Matures at 2 yearsMatures at 2 years
– Dies at 10 yearsDies at 10 years
– Tradeoff between early reproduction and survivalTradeoff between early reproduction and survival
late in lifelate in life
• Antagonistic pleiotropic effectsAntagonistic pleiotropic effects
– Expected lifetime reproductive success is 2.66Expected lifetime reproductive success is 2.66
• Mutation is beneficialMutation is beneficial

49. Why Do Organisms
Age and Die?
• Evolutionary Theory of AgingEvolutionary Theory of Aging
– Reproduce so much early that early death is notReproduce so much early that early death is not
selected againstselected against
– Mutation devotes less to repair and more toMutation devotes less to repair and more to
reproductionreproduction
– Heat-shock protein hsp70Heat-shock protein hsp70
– Prevents damage due to denaturationPrevents damage due to denaturation
– Heat-shock binding interferes with normal cellularHeat-shock binding interferes with normal cellular
functionsfunctions
– Heat-shock genes only expressed duringHeat-shock genes only expressed during
environmental stressenvironmental stress
• Proteins removed after stress passesProteins removed after stress passes

50. Why Do Organisms
Age and Die?
• Evolutionary Theory of AgingEvolutionary Theory of Aging
– Expression of hsp70 inExpression of hsp70 in DrosophilaDrosophila causescauses
longer life span but lower reproductionlonger life span but lower reproduction
early in lifeearly in life
– Tradeoff between early fecundity and lateTradeoff between early fecundity and late
survival is mediated by hsp70survival is mediated by hsp70
– Heat-shock proteins may mediate thisHeat-shock proteins may mediate this
tradeoff in many organismstradeoff in many organisms