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

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 glass Lewis 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 predationcommensalismmutualism amensalismneutralism competition species 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

Cospeciation: speciation process that occurs in 2 interacting species simultaneously Coevolution