Lecture 22. Misleading signals of crypsis Warning signals of aposematism S ignals as isolating mechanisms Sexual selection Parental social selection Membracid bizzare may be sensory crypsis Neuron stereotypy and the omega neuron. Male stalked eye fly Papua New Guinea (PNG)
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Misleading signals of crypsis
Warning signals of aposematism
Signals as isolating mechanisms
Parental social selection
Membracid bizzare may be sensory crypsis
Neuron stereotypy and the omega neuron
Male stalked eye fly
Papua New Guinea (PNG)
Exhibit sexual dimorphism
Males gain access to mates
by defending resources
Stalked eye lengths are important in rivalry
Some morphology just seems bizarre.
is part of a bizarre
display. Why does it seem bizarre? Because natural selection should improve flight, not detract from it. How could natural selection favour survival and reproduction in individuals that fly badly?
bird of paradise
Beautiful but bizarre
Signals are transmitted information. The bodies of animals are used to communicate with others of their species. And body form is selected as the basis of a signal or display; stereotyped movements of specially modified body parts become a display: a signal between a sender and receiver. Sometimes an animal's body is selected to NOT send signals or more precisely, to 'misinform': cryptic patterning and coloration is really the absence of signals. Many animal bodies involve crypsis combined with an absence of movement.
Both eggs and hatchlings blend into the substratum and are difficult to detect visually.
Smaller majority website
The body may also be selected to signal a warning: an honest warning in a coral snake that this creature is truly dangerous and should be left alone; a dishonest warning in a mimic of the venomous (noxious) model.
Red and yellow kill a fellow
Red and black venom lack
An oedipodine crackling locust on an abandoned asphalt road surface, near Lake Superior. This coloration is certainly not bizarre, it is expected, i.e., is produced by natural selection favouring beneficial markings.
Cryptic and aposematic body forms are reasonably seen as the product of natural, not sexual or social selection. Long tails are bizarre and seem unlikely to contribute aerodynamically to flight.
Why do these birds have long tails?
And surely this tail is bizarre for a flying animal.
Gouldian finch chick begging: gape marks are
signals selected to achieve parental attention as chicks compete for food. They are produced by the choices being made by the parents.
Parental choice can impose selection too and create signals that may seem bizarre though perhaps carrying less cost than display plumage.
Lyon B.E., Eadie J.M., Hamilton L.D. 1994. Parental choice selects for ornamental plumage in Amercian coot chicks. Nature 371: 240-243.
The bizarre Membracidae
A bizarre pronotum
Morphological diversity in treehopper pronota
Crypsis and sensory
diversity. There is no sexual dimorphism
involved in these bizarre pronotal differences. So they seem not to be the product of sexual selection.
Could they actually be cryptic but it is not apparent to us because we have different sensory capacities than the predators whose eyes were the basis of this selection?
B Prud’homme et al. Nature473, 83-86 (2011) doi:10.1038/nature09977