Behavioral Ecology. Animal behavior as
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1. Communication & The Evolution of Signals
NSF GK12 Workshop: May 9, 2009
Professor of Ecology & Evolutionary Biology
University of California, Irvine
3. Examples of “Why” Questions Warning calls in Belding’s ground squirrels
Interspecific imitation of mating signals by female fireflies
4. (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.
6. Belding’s ground squirrels as example of intraspecific communication
7. 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
9. 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)
11. How do signals originate? agnolotti
(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.
14. Sequence of signal evolution
16. Parent-offspring communication in herring gulls Adult herring gulls have a red spot on beak.
When hatchlings peck it, parents stimulated to regurgitate food.
17. Tinbergen: chicks respond to spots of many colors & locations.
Thus, any spot on parent beak might have triggered offspring reaction.
18. Sequence of signal evolution
19. Examples of signal evolution that capitalize on receiver biases Bittern on nest
Frog with “eyes” on back
False coral snake
Cichlid “egg dummies”
20. 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”).
21. Honest Advertising Multiple stages of assessment
vigor of ritualized displays
multiple stages of testing, each one escalated
e.g., red deer
22. Difficulty of predicting receiver bias and meaning of novel signal.
Example: estrildine finches
23. Degree of honesty of signal may change over time Example: begging call loudness in nestling birds
24. Summary Clear thinking about animal communication enhances understanding of evolution.
Unpredictability of evolution
Constraints on evolutionary response
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.