Origins_Sep23Lecture

Origins_Sep23Lecture - Evolutionary Origins of Signals...

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Evolutionary Origins of Signals
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2 Sender Receiver Communication Channel Signal Modalities: acoustic chemical vibrational visual tactile (Key: signals provide “information”) signal Where do they come from?
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3 signals = selected for information content as opposed to cues = attributes simply correlated with information communication is distinct from ‘eavesdropping’ receiver uses sensory cues to detect information about sender (= illegitimate receiver) information transmitted by sender is side-effect of some activity e.g., cues NOT signals: drunk man lurching down sidewalk field mouse rummaging in dry leaves for food Evolutionary origins of signals
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Cues produced by sender 1 contain information Selection on receivers to pay attention (sensory systems) Selection on sender 2 to elicit response in receiver Evolutionary origins of signals 1 = SENSORY EXPLOITATION
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Sensory Exploitation e.g., moths and bats Bats (sender 1) hunt using ultrasound moth ears selection on moths (receiver) to hear ultrasound selection on male moths (sender 2) to produce acoustic signals to attract females e.g., p. 294-295, 299 whistling moths
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Sensory Exploitation e.g., predatory mites and copepods Copepod prey (sender 1) produce water vibrations net stance selection on mites (receiver) to grasp sources of vibration selection on male mites (sender 2) to tremble & attract female attention e.g., p. 300-301 Water Mites
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Sensory Exploitation e.g., guppies and fruit Female guppies generally prefer males with larger, more orange spots Orange may be an honest signal of male quality (carotenoid pigments) BUT In nature, females are attracted to rare, valuable orange fruit
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Hypothesis: Male orange signal evolved to exploit preexisting sensory bias of females for orange PREDICTION 1: Males & females should be attracted to orange (outside of mating context) METHODS: Field (Trinidad) Colored discs placed in pools •Rate of attraction of males & females noted
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Hypothesis: Male orange signal evolved to exploit preexisting sensory bias of females for orange PREDICTION 1: Males & females should be attracted to orange (outside of mating context) RESULTS: Field (Trinidad) •Guppies of all ages and both sexes show a strong attraction to orange discs •Female preference for orange disc more than any other (except red) at 7/8 field sites (p < 0.0001) •Males also preferred orange to other colors (p. < 0.0001)
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Hypothesis: Male orange signal evolved to exploit preexisting sensory bias of females for orange PREDICTION 2: ACROSS populations, female mate preference for orange males should be correlated with attraction to orange objects by males & females METHODS: Lab •Pecking behavior to discs in aquaria •Choice trials with females exposed to males of different orange intensity
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Strength of female preference for orange related to FEMALE attraction to orange across populations
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Cues produced by sender contain information Selection on receivers to pay attention (sensory systems) Selection on sender to optimize information transfer Evolutionary origins of signals 2 = Sender- receiver co- evolution
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Origins_Sep23Lecture - Evolutionary Origins of Signals...

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