Phenotypic Plasticity Midterm Examples

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Entrenchment

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gizzard, mitochondria, symbiotic gut microorganisms ... all obligatory symbioses or mutualisms .... silicon in plants .... essential vitamins & minerals (& amino acids) Calcium in seawater.

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indirect evidence for adaptive plasticity

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Pocket gopher size & associated traits. Dwarf island elephants. Neotenic salamanders. Seasonal polyphenisms in butterflies. Sticklebacks?CAM plants – 30 families, hot, arid, low CO2 envts, fix CO2 at night. Facultative CAM changes expression of hundreds of genes – genes also needed for C3 photosynthesis. P. 513
Oxygen & atmospheric density pulse involved in origin of flight? insect gigantism?Calcium levels in sea water & the appearance of calcareous skeletons?

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"entrenchment" of historically available cues in regulation of development

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2-headed fish

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early development effects later in life

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Rat LG anxiety

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neutral point

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In Araschnia, Ecdysterone injections at different times or rearing in intermediate environments reveal continuous variation

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Gene of major effect

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Necessary under artificial selection to “jump” to new pheno in strong selective enviro, e.g. toxic soil

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artificial selection for plasticity

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Fly study, selecting largest avg delta(cold fly - warm fly) for family (see pic)

Chlamydomonas auto/heterotrophy, asexual Imposed spatial or temporal variation on some Spatial caused persistence of light specialists, w/ some intermediates due to dark pop Temporal caused all to become generalists (here, plastic maintenance of homeostasis)

Mole salamander paedomorphosis in sometimes drying carolina bays 6 wild pops grown in tanks w/w/out water stress Decrease in paedos in water stress but more in some pops than others RN of paedomorphosis to drying regime differ among populations RN can evolve rapidly in response to selection on trait Populations differ in their response to selection

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observation of threshold shift in nature

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Dung beetle in w australia vs. n carolina sees opposite shifts in large horn threshold relative to ancestral pop Maybe bc food availability, drift/found effect Proved not drift bc exotic pops outside range of ancestral pop variation Therefore, selection

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evolution of toad plasticity

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Toads Pelobates cultripes = v plastic (ancestral state) Spea multiplicata = intermediate bc ponds larger Saphiopus couchii = less plastic Measured time to dif development points Couchii does not accumulate fat even when metamorphosis blocked due to increased TH, increased tissue sensitivity, and increased corticosteroid

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stress

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Tomato hornworms Black when colder Mutants always black (lower jh) Heat shock of blacks revealed gen variation Selection for 2 colors, polyphenic green line becomes greener after heat shock, monophenic blakc line always black Involves DDC melanin synthesis pathway enzyme, lowering of JH lowers threshold

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not indicative of adaptive plasticity, just dif selection

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snake jaw differences