Lect4-26March_v2 - Todays Lecture Finish what are species...

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Today’s Lecture Finish: what are species • Speciation
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Quick Review What is a species, according to the biological species concept? What are the different types of isolating mechanisms between species?
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What are species Biological Species Concept Major Advantages Many biologists would agree that interbreeding among populations is an important attribute of species (probably the most important) Interbreeding separates “species” from other taxonomic units (conspecific individuals interbreed, heterospecific individuals do not)
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What are species Biological Species Concept First Major Problem Hard to tell if putative species are reproductively isolated unless sympatric (living in same place)
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Basic Terms for Geographic Distribution of Species Allopatric (separate) Parapatric (adjacent) Sympatric (same place) species 1 species 2 species 1 species 2 species 1 species 2
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What are species Biological Species Concept Major Problems-1 Hard to tell if putative species are reproductively isolated unless sympatric (living in same place) Can bring species into lab to see if they will interbreed (or transplant them), but may be hard to get species to behave “naturally”
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What are species Biological Species Concept Related Problem Biologists who follow BSC generally cannot tell whether allopatric populations are distinct species Huge problem, because most closely-related species are allopatric! Instead most utilize “diagnostic” differences between populations to recognize different species
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Species Concepts Biological Species Concept Second Major Problem Species that are not closely related can interbreed (“hybridize”) in many cases Hybridization = mating between individuals of different species Introgression = hybridization leading to gene flow
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Speciation • Speciation is the general process by which new species arise How speciation works depends (in part) on the geographic mode of speciation Geographic mode depends on how new species are geographically situated
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Overview of Geographic Modes of Speciation Allopatric Parapatric Sympatric Ancestral species new species 1 new species 2 new species 1 new species 2 new species 1 new species 2 Ancestral species Ancestral species
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Allopatric Speciation Generally considered very straightforward, with two parts Populations become geographically isolated Reproductive isolating mechanisms evolve (i.e., prezygotic, postzygotic)
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How does allopatry happen?
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