Adaptive Coloration
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adaptive coloration concealment, advertisement, and disguise crypsis, etc. Much of the results of Natural Selection can be seen in the color, pattern, and form of organisms. Explaining the adaptive significance of how organisms look is helpful in understanding how natural selection operates. Understanding the adaptive significance of traits involves a speculation of what type was selected for in the evolutionary past and what the selection pressures were. Having words to describe these things enhances one’s enjoyment and understanding of the world of nature. What follows is a list of vocabulary used to describe various categories of adaptive coloration, especially in animals. Study these terms for test 3. We will have a brief review before the test. Crypsis – achieving concealment Eucrypsis - concealment through color and/or pattern. homochromy – body color matches the background homochromy “transparency” glasswinged butterfly Sometimes crypsis is as simple as being invisible, or almost. disruptive coloration – when a color pattern breaks up the body outline countershading lighter color below and darker above – Counters the effect of sunlight and shade on a 3-dimensional object. Functions for crypsis in aquatic or terrestrial environments. protective resemblance – cryptic resemblance or mimesis when an organism looks like something else in its environment sargassum fish in Sargassum protective resemblance protective resemblance Lithops, stone plant protective resemblance (mimesis) Behavior may play an important part in crypsis. dead-leaf butterfly broken-twig moth katydid Bizarre patterns, shapes: Some organisms benefit from an appearance that just doesn’t look like what it is. This spider, for instance, may not be noticed by birds in search of spider prey because it doesn’t really look like a spider. rubber boa Pseudocephalism A predator may not recognize prey, may be frightened by what appears to be a larger organism, or may be confused by what direction they will move in escape. Pseudocephalism The Io moth has more than one “trick up its sleeve.” shock patterns False eyes or other patterns may produce a startle effect when revealed suddenly. Non-cryptic coloration: Aposematism = advertisement of noxiousness Individuals benefit from bright, easy to see and easy to remember coloration (or sound) when learned predators avoid them because of association with a bad experience. It is sometimes said that a rattlesnake is a “gentleman” because he warns before he bites. Does he really do this for your benefit? Its best not to call this “warning coloration.” What noxiousness does aposematism each of these have to advertise? Let’s review what we’ve covered so far: Adaptive Coloration crypsis eucrypsis homochromy transparency disruptive coloration countershading protective resemblance bizarre pattern/shape pseudocephalism shock pattern aposematism Next…. mimicry – mimicry is involved when one organism looks specifically like another organism, in a non-cryptic way, and gains advantage over predators or prey. There are several types. Mimicry Noncryptic resemblance between two or more species giving one or both a selective advantage in relation to predators or prey. Batesian Mimicry Also known as Pseudaposematism .a non-noxious mimic looks like a noxious model and is avoided by experienced, would-be predators. Model = noxious/aposematic Mimic = non-noxious Dupe - receives signalal bee fly Other examples of Batesian Mimicry mimic spider model lady beetle AR Wallace frequency criterion – The proposed idea that the presence of the mimic reduces the effectiveness of aposematism of the model; that models should be more abundant than mimics. • Not necessarily so. Data show otherwise. (One bad experience produces a powerful learning experience.) Other examples of Batesian mimicry Heliobolus lugubris lizards mimic oogpister beetle Oogpister beetles produce a noxious secretion that protects them from predators. They advertise this with bold patterns and a slow distinctive walk. Young lizards of this species mimic the pattern and behavior of the beetles. Their success is evidenced by a lower rate of tail breakage than in other species. more Batesian mimicry Behavioral Batesian Mimicry – eg. woodboring beetle and circus beetle The circus beetle produces a noxious spray to defend itself against predators and advertises this with a head stand. The harmless woodboring beetle mimics the behavior. olfactory Batesian mimicry has been proposed for stink bugs, some of which taste bad and others that do not. Other interesting observations of Batesian mimicry: Geographical separation of model and mimic has been observed in cases of migrating bird predators. Data have shown that in insects, models may have tougher exoskeleton than mimics – can you explain why? Batesian con’t. Monarch and viceroy butterflies are often considered the classic example of Batesian mimicry – Monarchs feed on milkweed as caterpillars and accumulate toxic cardiac glycosides – they are the model. Viceroys are usually non-noxious and are the mimic. Birds are the dupes. BUT - Some monarchs are non-noxious, yet benefit from looking like the noxious members of their own species – this is called Automimicry. ALSO – Viceroys are sometimes noxious themselves and benefit by sharing aposematic coloration with monarchs. This is called Mullerian Mimicry. monarch viceroy Mullerian Mimicry Also called synaposematism. Shared aposematism. All species are co-models. This is often seen in tropical butterflies, all of which are toxic and protected by aposematism. By their similarity they share the cost (learning experience of predators). Each individual benefits from the likelihood that they will be avoided by predators. Lycorea sp. Helioconus spp. Mertensian Mimicry This type of mimicry has been proposed to explain cases of snakes, or other prey, so deadly that learning by predators is not possible. The idea is that deadly snakes mimic a less dangerous species for which aposematism is plausible. The classic example is the deadly coral snake (highly toxic), suggested to mimic the moderately toxic false coral snake, which is also mimicked by the non-toxic milk snake. MertensianX Mimicry This type of mimicry has been proposed to explain cases of snakes, or other prey, so deadly that learning by predators is not possible. The idea is that deadly snakes mimic a less dangerous species for which aposematism is plausible. The classic example is the deadly coral snake (highly toxic), suggested to mimic the moderately toxic false coral snake, which is also mimicked by the non-toxic milk snake. It is no longer considered to be a valid idea as data have shown that coral snake bites are not always fatal and their aposematism is functional. MertensianX Mimicry This type of mimicry has been proposed to explain cases of snakes, or other prey, so deadly that learning by predators is not possible. The idea is that deadly snakes mimic a less dangerous species for which aposematism is plausible. The classic example is the deadly coral snake (highly toxic), suggested to mimic the moderately toxic false coral snake, which is also mimicked by the non-toxic milk snake. It is no longer considered to be a valid idea as data have shown that coral snake bites are not always fatal and their aposematism is functional. Back to the original idea…..If coral snakes are the model for mimicry by milk snakes, what should we call it? If coral snakes and false coral snakes share similar aposematism, what should we call it? MertensianX Mimicry This type of mimicry has been proposed to explain cases of snakes, or other prey, so deadly that learning by predators is not possible. The idea is that deadly snakes mimic a less dangerous species for which aposematism is plausible. The classic example is the deadly coral snake (highly toxic), suggested to mimic the moderately toxic false coral snake, which is also mimicked by the non-toxic milk snake. It is no longer considered to be a valid idea as data have shown that coral snake bites are not always fatal and their aposematism is functional. Back to the original idea…..If coral snakes are the model for mimicry by milk snakes, what should we call it? Batesian mimicry If coral snakes and false coral snakes share similar aposematism, what should we call it? Mullerian mimicry Aggressive Mimicry Also called Peckhamian mimicry This is mimicry by an “exploiter,” usually a predator, to gain advantage over their prey, or “exploited.” Sometimes the predator resembles the prey and it is likened to “a wolf in sheep’s clothing” ex. European cuckoo – a nest parasite. They lay eggs in the nests of other species. Their eggs vary but always resemble the eggs of the host species. Can you spot which is the cuckoo egg in the pictures below? Aggressive Mimicry Sometimes the exploiter resembles a helpful species ex. Sabre-tooth blenny and cleaner wrass Cleaner wrasses set up stations and experienced fish stop by to be cleaned of parasites, etc……but they may get a surprisie as a blenny takes a bite out of them! more Aggressive mimicry Exploiter resembles harmless species ex. Zone Tailed Hawk resembles a vulture Many small mammals flee from the sight of a hawk, but are not alarmed by harmless vultures. This species has wing tips and flight pattern that fool them. Aggressive mimicry con’t. Here are several good examples of the exploiter resembling an edible species. angler fish’s lure young cottonmouth – colorful wiggling tail alligator snapping turtle’s tongue appendage Asian flower mantid Aggressive mimicry con’t Freshwater mussels of the family Unionidae have glochidia larvae that are parasitic on fish. Several species have amazing lures that attract fish and increase the likelihood that their larvae will find a host. glochidium superconglutinate – a packet of glochidia dangle downstream at the end of a cord of mucus. Aggressive mimicry con’t Auditory Aggressive Mimicry African crowned eagles mimic the call of their monkey prey. Olfactory Aggressive Mimicry Bolas spiders swing a sticky web that smells like female moth pheromone. Several species of carrion flowers look and smell like carrion, attracting carrion flies as pollinators.