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Evolution Notes

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Biology 3466B
Yolanda Morbey

Evolution NotesOct 2011 A species shouldreflect morphological distinctiveness reflect evolutionary independence be objective classify organism to species be testable be applicable to sexual and asexual forms cryptic species fossils make identification easyThree species concepts morphological species biological species phylogenetic speciesMSC BSC PSC Primary criteria Morphological traits Reproductive isolation Unique diagnostic traits Testable No Yes Yes Fossils Difficult Difficult Yes ObjectiveNo Yes Yes Easy to apply Yes No NoSpeciation requires reproductive isolation evolution does not Example of species concepts using an insect MSC found 1 species BSC found 38 species and PSC found 9 species There is no single answer to how many species there are It depends on the concept youre using In PSC some of the populations clustered together forming fewer species Phases of speciation traditional view 1 Genetic isolation allopatric geographically separatedsympatricbehaviour same area but have differences in behaviour so that they never interact or matesympatricgenetic incompatibility 2Divergencemutation genetic drift selection 3 Secondary contact doesnt have to happenreinforcement come back togetherno longer separated reinforces differencesbetween speciesGenetic isolation and divergence can happen simultaneously or not Genetic isolation in allopatrydispersal Happens when a small group leave the larger population to colonize another area This could be from one island to another and results in two reproductively isolated populations An example is insects on the Hawaiian Islands The oldest species are from the oldest island The most recently evolved species are on the youngest islandGenetic isolation in allopatryvicariance Happens when the land splits due to a river forming or other geological event This results in two populations that are reproductively isolated However for some species this doesnt affect them if they can fly between the land masses The effect of vicariance depends on their dispersal movement An example is the formation of the Panama isthmus The isthmus separated the Pacific and Caribbean regions and allowed them to evolve separately For every species in the Pacific theres a closely related species in the Caribbean Genetic isolation in sympatrygenetic incompatibility This happens when improper segregation causes the production of diploid gametes Nonviable offspring are produced if diploids mate with haploids Only pairings between diploid gametes will be successful This happens in only 1 generation
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