Animal communication prelim3

Sexual selection

any selection that arises from fitness differences associated with non-random success in the competition for access to gametes for fertilization

• Can be considered a part of or separate to natural selection

Mechanisms of Sexual Selection

• Can occur before, during or after mating

1. Scramble competition

2. Endurance rivalry

3. contest competition

4. mate choice

5. gamete competition

6. cryptic mate choice

Scramble Competition

• Find mates before competition

• Arrive at breeding locality first

• Sensory and locomotory organs to quickly locate mates

ex spotted salamander: male gather in vernal pools and deposit numerous sperm packets (spermatophores) on the pond bottom, often obscuring others, as they race to fertilize females

Endurance rivalry

• Ability to endure prolonged reproductive activity

• Long breeding season

• Long-lived

ex. elephant seals guard a beach and fast losing 30% of their body weight while fighting for dominance over a harem (breeding group)

Contest competition

Direct combat

• Intrasexual

• Outcompete rivals

• Directly monopolise mates

ex. Ruff males congregate in leks and compete for females

Case study: Satellite male Ruff

Contest competition

• Non-territory holding

• Less frequent displays

• Supports dominant males

• Gains mates by association

Mate choice

• Intersexual

• Ornaments

• Courtship displays

ex. Himalayan Monal displays for females and is highly ornamented

Case study: Bowers

Mate Choice

• Resource-holding ability

• Costly, honest signal

• Females compare multiple bowers

• Enhance ornamentation

ex. MacGregor’s Bowerbird

Gamete competition

• Mate guarding

ex. Dusky dancers: following copulation, the pair often remains connected in a "tandem" position, where the male holds the female with his anal appendages. The male often stays attached to her while she oviposits

• Sperm number

ex. Agile Antechinus males invest heavily in sperm production at the expense of their own survival, die shortly after the breeding season, and females use specialized storage in their oviducts to store sperm.

• Mating plugs

ex. northern Saint Andrew’s Cross Spider during copulation, a male's pedipalp (sex organ) breaks off, clogging the female's genital opening to prevent competitors

Cryptic mate choice

• Post-mating female reproductive control

• Genetic compatibility

ex. Chinook salmon: females use their ovarian fluid to differentially enhance the swimming speed of certain males' sperm, allowing them to favor specific, often more compatible, males

Information in courtship signals: quality and compatibility

ex. hooded warbler: Males that sire EPY have higher song rate and output than cuckolded males

ex. sticklebacks use allele counting to select mates with large number of MHC alleles to avoid inbreeding and confer parasite resistance

• optimize major histocompatability compex (MHC) diversity

• inbreeding avoidance

• parasite resistance

Information in courtship signals: resource holding

ex. satin bowerbird bower is a signal of ectoparasite load and body size

• Extended phenotype

• Honest signal of ability to acquire and retain resources

• Information on other attributes

multimodal signaling in courtship signals

• Ornamented plumage and song in birds

• Wing patterns and pheromones in butterflies

ex. silver-washed fritillary (butterfly) male utilizing a "looping" flight technique to simultaneously showcase his fitness and deliver specialized scents

Dishonest signaling in courtship signals

ex. faeder male Ruff employs a "sneaker" mating strategy by mimicking the appearance of a female

• Deception

• Mimics females to avoid male aggression

• Negative frequency dependent selection

environmental influence of courtship signals

• Firefly flash patterns at dusk for high contrast

• Higher pitched vocalisations of birds and insects to cut through background anthropogenic noise

Recognition systems in sender vs receiver

Sender: production

- Phenotypic variation

- Individual stability

Receiver: Processing and action

- Differentiation among individuals

- Classification of individuals

Recognizing: Class

Distinguishing among members of your species based on a shared attribute

• traits will differ categorically between groups

Common classes that animals signal include:

-sex (male v. female)

-age (juvenile v. adult)

-breeding status (fertile v. not fertile; breeder v. not breeder)

• leads to divergence in class-typical traits between groups but conformity within a group

ex. clear sexual dimorphism in ducks but not eagles; juvenile vs adult plumage strongly differs in both ducks and eagle

• eagles need to differentiate juvenile because not sexually mature

• ducklings use countershading to avoid being eaten by big fish

Recognizing: Individual

Requires distinctive (i.e., variable) traits among individuals within

a group/population

Those traits need to be stable within an individual over time

(not necessarily permanent, but stable-ish at least)

• multiple traits need to vary

• low to no correlation among traits

Identity Signaling in Humans

MORPHOLOGY

1.Facial features are more variable than other aspects of body morphology (relative nose width has more variability then relative finger length)

2.Facial features are less correlated than other aspects of body morphology (nose width is much less correlated with nose length than hand length is to hand width)

Signal Design and recognition: class vs individual

Which graph best illustrates traits that might mediate individual recognition?

D

Information and Signal Design

Signal efficacy depends on

1. detectability (how well does it transmit through environment/picked up by receiver)

2. discriminability (how easily are different possible values of the signal differentiated from one another)

3. memorability (how easily can the signal be remembered by receiver)

Recognition requires phenotypes that have…

1. variation (ie information)

2. stereotypy

we want to know whether we can reliably discriminate among individuals on the basis of their features (is an individual consistently like itself and different from others?)

information theory

Information or entropy is the unpredictability or uncertainty contained in a signaling system

More possibilities = more information

e.g. six-sided die has more information than a two-sided coin

How do we measure information content?

1. discrete signal (H’=-SUM(p*lnp)

2. continuous signal (H’=-int p(x)* log(p(x))dx)

which trait has the highest degree of information content

Blue

H’ can be readily compared across traits if:

1. There is an ideal receiver that can detect differences as finely as you have measured them

2. Completely sampled all relevant traits

3. The weighting of trait values is in accordance to their perceptual salience

Information content of wasp color patterns

Measured wasp color patterning in queens and daughters on wild nests: Scored facial patterns on a scale of 0-4, counted number of abdominal segments with yellow stripes or brown markings.

Largest nests have higher proportions of doppelgangers, likely because there is a limit to the number of combinations possible among closely related wasps

identity cue

Traits that allow for individual recognition but have not evolved for that purpose.

e.g. Fingerprints

Identity Signal

Traits that have been selected to facilitate efficient recognition

Why would signals of identity need to evolve? (costs of mistaken identity)

-Receive a punishment meant for another

-A benefit meant for you goes to someone else

Costs/benefits of individuality could arise for

many different reasons: social hierarchies,

mate choice, parent/offspring recognition,

Identity Signaling Hypothesis predictions

Predictions:

1. unique phenotypes provide benefits to individuals

2. species/traits with history of selection for recognition should have more variable phenotypes

3. Traits selected as identity signals will show evidence of increased genetic diversity.

Frequency-dependent benefits of rare phenotypes?

When being confused with others is costly, selection should favor rare phenotypes that signal identity.

• Individuality is expected to be under negative frequency-dependent selection (rarer is more fitness benefit)

ex. In wasps, Individuals with rare phenotypes receive the less aggression on average than those with common phenotypes

benefits of individual recognition

wasp populations with individual recognition (north) had

1. Different social organizations

2. Improved cooperative nesting outcomes

Facial diversity increases with latitude and so does cooperation

• Northern groups show more biased interactions with a subset of individuals.

• Southern nest associations are less stable (All multi-foundress southern nests failed to rear offspring because oophagy: egg eating)

Marmots

Comparative evidence for ID signal evolution

• species with higher social group sizes had higher individuality

Evolution of facial variation in humans WITHIN populations

Possible hypotheses:

1. Facial differences are the result of neutral processes and are cues of identity.

• variation: same as rest of body

• correlations: same as rest of body

• genetic variation: same as background genetic diversity

2. Facial differences are the result of adaptive processes, with faces evolved to signal individual identity.

• variation: higher than rest of body

• correlations: lower than rest of body

• genetic variation: higher than background genetic diversity

3. Facial differences are the result of adaptive processes, with faces under selection for attractiveness

• variation: higher than rest of body

• correlations: higher than rest of body

• genetic variation: lower genetic diversity

Reality: probably 3 but social interactions maintain slightly elevated genetic diversity

• variation: higher than rest of body

• correlations: higher than rest of body

• genetic variation: slightly higher

Sexual dimorphism

• Males ornamented, females are not

• Ornaments appear at sexual maturity

• Male ornaments during breeding season

Ornamentation in immatures

ex. victoria’s riflebird

• Acquires ornamentation through successive moults

• Five years to reach maturity

• Practices display as immature

Year-round ornamentation

ex. Northern Cardinal

• Ornamentation is an honest signal

• Associated with non-breeding season dominance but not causal

Why are females ornamented

1. Consequence of selection on male ornaments

2. Sex role reversal and sexual selection

3. Resource competition

4. Incitation of male competition

Consequence of selection on male ornaments

• Shared genetic architecture

• Additive genetic variation

ex. cyrtodioposis dalamanni: longer eye stalks selected for in males is also causing offspring (including females) to have longer eyes stalks

• female eye stalk length is not advantageous but just a byproduct of SS on males

ex. Dark eyed junco: amount of white on tail feathers

• but could be a result of selection for foraging behaviors

Sex role reversal

• Females compete for males

• Polyandrous

ex. red neck phalarope

Evolutionary steps to classic polyandry

mainly male parental care of eggs —> female ability to lay more eggs than a male can care for —> female competition to obtain several mates

Resource competition

• Natural selection

• Evolution of weaponry

ex. reindeer: both sexes have antlers, males compete for females and females also compete for resources and territories

white necked Jacobin

resource competition: females selected for male plumage reduces harassment at feeders and thus have better access to resources

• ornamented immature plumage for both sexes when resources are more important than mating opportunities

• 20% females remain ornamented

• ornamentation reduces male harassment

• multimodal signaling to show sex despite plumage

Incitation of male competition

ex. Striped plateau lizard: orange throat patch is a direct signal of quality, more males want to compete for higher quality females

What is the function of coordinated signalling?

1. Synchronise breeding effort

2. Mate guarding

3. Pair bond maintenance

4. Collective territory defense

Synchronise breeding effort

• Breeding timing critical

• Signals physiological readiness to breed

• Seasonal triggers (ex signs of spring)

ex. great crested grebe: dance together, male gifts female seaweed to incorporate into the nest —> synchronized breeding/nest building

Mate guarding

ex. eastern whipbirds: duets allows females to defend their exclusive position in the relation

• vocal duetting

• simulated intrusion of other birds (experiment): females sings with males (duet) most frequently when the intruder is another female

  • defend their mate saying he’s taken

Pair bond maintenance

• Long-term monogamy

• Divorce rare

• Recognition following reunion

ex. waved albatross: live for decades and really low divorce rate

Collective territory defense

ex. purple crowned fairywren: when threat of intrusion males and females got together to address the threat despite being initially apart

• playback experiments

• males and females equally aggressive

• spatial coordination

Mechanism for ornamentation in white shouldered fairywren

one population with sexually dimorphic brown female and one with black and white female

• female plumage developed in response to testosterone

• benefits: different selective pressures

  • if resource limited males need to know female is high quality

  • certain environments might favor crypsis

• tradeoffs:

  • physiological costs (test reduces immune function)

  • less parental care (also associated with test)

  • conflicts with other hormonal pathways

  • higher predation

Flower mimicry: bee orchid

ex. bee orchid looks like female bee

• cost of false acceptance: loss of sperm and energy

• cost of false rejection: loss of potential mating opportunity

unlikely to discriminate because cost of acceptance is low

Sexual predation: firefly

ex. firefly deception: predator mimics flashes to draw sexual attention

• cost of false acceptance: get eaten

• cost of false rejection: lose potential mating opportunity

discrimination very high because cost of mistaking is very high

Batesian mimicry: coral snake

ex. coral snakes mimicked by king snake (non-venomous)

• cost of false acceptance: loss of meal

• cost of false rejection: dying by venom

high discrimination because cost of false reject is high (dont do it unless very sure)

Brood parasitism across classes

• birds: cuckoos lay eggs in bird nest

• fish: cuckoo catfish eat some eggs and replace

• insects: cuckoo bees lay eggs in nests of solitary bees

  • rove beetle eggs laid with army ant

• rare/absent in mammals becauseinternal fertilization and incubation; it is harder to parasitize internally

Why are host parents so bad at recognizing parasites?

1. Evolutionary lag

2. Costs of accepting parasite (non-kin) are low

3. Costs of rejecting own kin are high

brood parasitism evolutionary lag

(takes a while for the host to evolve to discriminate)

ex. cowbirds expanded range allows to parasitize new hosts who havent evolved recognition

Mechanisms of kin recognition

1. spatial location: simple but easy to cheat

2. familiarity (associative learning)

3. phenotype matching: hard but hard to cheat

kin recognition in beldings ground squirrel

• mixed paternity broods

• full sisters are less aggressive than half siblings

• more aggressive to sisters if introduced after weeing

• explanation: early in life learn who they grew up with as well as phenotype matching to decide like me or not (maybe pheromones)

Associative learning

associate stimuli or events: did we grow up together?

phenotype matching

compare traits of unknown individuals to traits of individuals of know relation

brood parasitsm: honey guides

parasitize burrow nesting birds

• chicks are born with a big tooth/hook on bill to kill other kin and puncture eggs, tooth reabsorbed after first few days

• high costs of parasitism —>expect higher level of discrimination and signals of identity

brood parasitism: great spotted cuckoos

parasitize larger birds like carrion crows

• low costs of parasitism

• cuckoo chick exude toxins that deter predators

• since they dont kill other nestlings, it can be beneficial (mutualism) to have cuckoo chicks in high predators

Evolution of acceptance thresholds

phenotypes of desirable and undesirable (ex own kin and parasites)

• threshold of acceptance evolves based on costs of mistaken acceptance/rejection

acceptance threshold: low cost of mistaken acceptance

if low cots, accept things that dont looks right

• occurs when parasitism is rare or costs of being parasitized are low

acceptance threshold: high cost of mistaken acceptance

high cost means reject more things that dont look right (event things that do look right)

• occurs when parasitism is common and costs of being parasitized are high

When will there be selection to recognize young

• few nests parasitized —> no need to recognize young

• eggs recognized —> no need to recognize young

• eggs NOT recognized —> selection to recognize young

Host parasite coevolution

egg mimetics

eggs are very similar in hosts that have evolved to recognized eggs and different in hosts that have not yet evolved to recognize eggs

ex. dunnocks are a relatively new host for cuckoos

young mimetics

sometimes cuckoo chicks mimic the host chicks

Why to call others for food?

1. nepotism

2. reciprocity

3. overwhelm competitors

4. overwhelm defenses of prey

Nepotism

help out relatives

ex. honey bee waggle dance

reciprocity

help me out next time

ex. vampire bats feeding each other

overwhelming competitors

safety in numbers or defend against other scavengers

ex. ravens call others to the food when they find it

• young birds without territory call in others to help overwhelm territory owners

• not relayed to others called in

• if territory owner find it, it wont call

overwhelm prey

need help tearing in or catching

ex. lions join together to catch prey

ex. bark beetles call in others using pheromones to overwhelm the trees defense

signals to help other find food

1. leading to food resource

2. broadcasting

3. leave a trail

4. give directions

leading to food resource

ex. ants

+ no attracting unwanted attention, get them right where the food is

- takes energy and time, only a few individuals at a time

broadcasting

ex. Ravens, bark beetles

+ more efficient

- easy to eavesdrop

leave a trail

flagging or pheromone trail

ex. ants tap butt on the ground

+ could be species specific, more efficient than leading, leads right to food

- costly of resources, eavesdroppers

give directions

map

ex. honey bee waggle dance

+ very efficient

- sophisticated/difficult, requires flexible communication, risk not finding food

Mutualism signals

1. pollination: one gets pollinated, one gets nectar

2. cleaners and clients: one gets cleaned and one gets food (signal ahead of time)

3. cooperative hunting: both get food

ex. grouper cant get little fish in cracks but eels can

• grouper signals by shaking head

Honeyguides

honeyguides work with humans and honeybadgers to show them where a bee nest is so the other animal can open the nest

• communicate using calls

The predation process

1. detection of the prey

2. evaluation of prey

3. approach and attack

4. dinner

Reducing probability of detection/evaluation of prey

1. crypsis

2. masquerading and mimicry

3. decoys

There are not signals because predators dont benefit

• can only persist if rare

crypsis

blend in with background

• aggressive crypsis: hide from prey

ex. crab spider sits on flower and catches pollinators

Masquerade

not matching background but looking like something you are not

ex. looking like a leaf

• aggressive masquerading: hide from prey

ex. orchid mantis hides from prey by looking like a flower

decoys

startle predator or get to attack another spot

ex. lizard loses its tail which wiggles to distract the predator while lizard flees

reduce probability of being attacked/eaten

1. predator detecting signals

2. aposematic signals

3. prey condition signals

these are signals because predators benefit by not wasting time or eating something toxic

predator detection signals

ex. white tailed deer flashing tail

predator inspection: starting at predator (ex. herding animals)

prey condition signals

prey signals condition to make predators rethink

stotting: weird jumping thing deer do

• costly display of condition

• ex. spring buck to avoid cheetahs

  • costly because reduces speed getting away from predator

  • saying I can jump higher than other guy, go after him

aposematism

brightly colored as warning of toxicity

• predators learn or innately know to avoid toxic prey

ex. monarch get toxins from eating milkweed

Batesian mimicry

model is unpalatable/toxic and mimic is palatable

• only works if rare

ex. viceroy mimics monarch

ex. king snake mimics coral snake

• king snake only looks like coral snake in regions where they coexist

Mullerian mimicry

both species are unpalatable/toxic

• makes it easier for predators to learn to avoid

ex. heliconius butterflied mimic melinea in own regions

ex. poison dart frogs

Aggressive mimicry

mimics for predatory purposes

• only works if rare

ex. firefly that mimics differen species to eat

ex. bolar spider waves around sticky blob smelling like moth pheromones and catches moths out of the air

ex. false cleanerfish mimic cleaner wrasse cleaning signals then attacks fish

ex. mirror orchids (bee orchids)

why give alarm calls?

1. warn others

2. call for help

3. startle predators

what kind of information might an alarm call contain

1. type of predator

2. how big the risk is

ex. Chickadee alarm call alerts to perched raptor versus seet call of aerial predator, number of dees indicates threat

Whining call

calls produced when dangerous (local) brood parasite is nearby to call

• learned, not innate

• increase speed of finding parasite

• invokes con and heterospecific mobbing (fairywren and scrubwren)

• similar across species and respond to calls from geographically isolated species (global convergence of alarm call all likely derived from a distress call)

• high acoustic roughness (high freq spread with little modulation)

Mobbing calls by plants

Oviposition and herbivory cause plant to produce Herbivore-induced Plant Volatiles (HPIV’s)

• attract natural enemies of the herbivore

• can cause neighboring plants to increase induced defenses