Transcript Introduction to communication

Communication
&
The Evolution of Signals
NSF GK12 Workshop: May 9, 2009
Nancy Burley
Professor of Ecology & Evolutionary Biology
University of California, Irvine
Behavioral Ecology
• Animal behavior as “everyone’s” science.
• Behavioral ecology is study of animal behavior from
perspective of evolved functions of behaviors; focus on
social behavior
• Communication illustrates major points about evolutionary
processes.
• Emphasis on “why” questions
Examples of “Why” Questions
• Warning calls in Belding’s ground squirrels
• Interspecific imitation of mating signals by
female fireflies
• (def.) Signal – a trait that has evolved through
natural selection because it has enabled its bearers
to convey information to other organisms.
• Communication involves transmission of signals,
either in intraspecific or interspecific context.
A simple (intraspecific) signaling system
Environment
Sender
Receiver
• Belding’s ground squirrels as example of
intraspecific communication
• Examples of Interspecific communication
• Trumpet creeper hummingbird
• Viceroybutterfly (example of Batesian mimicry, in
which a palatable species possesses an evolved
resemblance to a toxic species)
• Photuris  Photinus communication
Summary of Examples
Interaction
Sender benefit?
Receiver
benefit?
Squirrel - squirrel
Yes
Yes
Flower - hummer
Yes
Yes
Viceroy - bird
Yes
No
Female Photuris –
Male Photinus
Yes
No!
Two kinds of messages
• Signals – messages that serve an evolved
function (which benefits the sender and may
or may not benefit receiver)
• Signs or cues – messages that do not an
evolved function (including intercepted
signals)
• (def.) Communication is a process of information
exchange in which senders influence (the
behavior of) receivers by the use of evolved
signals.
How do signals originate?
In humans,
creation of new signals is
fast and easy.
In other animals, signals
must evolve through
mutation and selection.
Opportunity for new
signals constrained by
ability of receivers to
“get the message.”
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agnolotti
Bollywood
Crunk
Ginormous
Gray literature
IED
Polyamory
Nocebo
Perfect storm
Speed dating
Mouse potato
Routes to evolution of new signals:
1) Ritualization of cue provided by sender.
Ritualization = evolutionary refinement
(reduction of ambiguity) and exaggeration
• (def.) Intention Movement:
incidental movement that “gives
away” what animal is about to do.
• Sky pointing: about to take flight.
• This bird displaying a highly
stylized version of sky pointing
that is exaggerated.
Sequence of signal evolution
1) sends cue
3) selection on
sender to refine
message ritualization
2) selection on
receiver to “get”
message
Routes to evolution of new signals:
1) Ritualization of cue provided by sender.
** 2) Receiver predispositions or biases.
Parent-offspring communication in
herring gulls
Adult herring gulls have
a red spot on beak.
When hatchlings peck it,
parents stimulated to
regurgitate food.
• Tinbergen: chicks
respond to spots of
many colors &
locations.
• Thus, any spot on parent
beak might have triggered
offspring reaction.
Sequence of signal evolution
2)mutation
causes sender to
display stimulus
3)increased RS of sender;
increase in frequency of
signal; evol. refinement
1)Receiver
responds
to certain stimulus
Examples of signal evolution that
capitalize on receiver biases
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Bittern on nest
Frog with “eyes” on back
Lattern bug
Orchid
False coral snake
Cichlid “egg dummies”
Deceit vs honesty of signals
• Obviously-deceptive signals common in
interspecific communication.
• In intraspecific communication, signal
honesty may evolve, because receivers
evaluate reliability of signals and favor
those that are reliable (“honest
advertisement”).
Honest Advertising
• Multiple stages of
assessment
– vigor of ritualized
displays
– multiple stages
of testing, each
one escalated
– e.g., red deer
• Difficulty of
predicting
receiver bias
and meaning of
novel signal.
• Example:
estrildine
finches
Degree of honesty of signal may change over time
• Example: begging call
loudness in nestling
birds
• open circles -- high intra-brood
relatedness
• closed circles --low relatedness.
Summary
• Clear thinking about animal communication enhances understanding of
evolution.
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Unpredictability of evolution
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Constraints on evolutionary response
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Signals evolve to benefit their bearers, not a “species” or group of
species.
•
Communication is the use of evolved signals to manipulate or
influence others of same or different species.
• Signals may be “honest” or “deceitful”.
• Dynamics differ between interspecific and intraspecific systems.
• Response to “receiver bias” is an important route for evolution of
novel signals.