Selection and community interaction

Selection: composite of the forces that limit the reproductive success of the genotype

Fitness: comparative ability of a genotype to withstand selection

Frequency dependent selection: selection against a gene depends on its frequency within the population

Batesian mimicry: a palatable species mimics an unpalatable species and gains protection from predation

Batesian mimicry

Monarch butterfly(distasteful)

Viceroy butterfly(tasty)

Muellerian mimicry

Muellerian mimicry: 2+ unpalatable species share similar aposematic coloration

both species distasteful

Selection & industrial melanism

Peppered moth

http://web.nmsu.edu/~wboeckle/biston.html

Departure from highest fitness

it is quite as dangerous to be conspicuously above a certain standard of organic excellence as it is to be conspicuously below the standard

Bumpus 1899

Departure from highest fitness

Human birth weight

Selection modes - stabilizing

Selection modes - directional

Selection modes - disruptive

If some of these many species become modified and improved, others will have to be improved in a corresponding degree or they will be exterminated

Darwin 1859

Community interactions

Through the looking glassLewis Carroll"Now, here, you see, it takes all the running you can do, to keep in the same place."

Community interactions

Red Queen hypothesis - organisms have to evolve as fast as they can just to stay in the same place

Community interactions

predation commensalism mutualism

amensalism neutralism

competition

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spec

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A

species B

Community interactions

Competition - two groups depend on same limited resource so each group leads to a demonstrable reduction in numbers of the other

Community interactions

Resource partitioning - species minimize harmful effects of direct competition by using different aspects of their common environment

Character displacement - measurable phenotypic differences accompany resource partitioning

Community interactions

Competitive exclusion - two groups cannot coexist in the same ecological niche

Owing to the high geometrical rate of increase of all organic beings, each area is already fully stocked with inhabitants; and it follows from this, that as the favored forms increase in number, so generally will the less favored decrease and become rare

Darwin, 1859

Community interactions

Coevolution: evolutionary changes in 1+ species in response to changes in other species in the same community

-can lead to an evolutionary ‘arms race’

Coevolution

Coevolution

Cospeciation: speciation process that occurs in 2 interacting species simultaneously

Coevolution