Lec 6 Bild 3 2011 for Ted

Lec 6 Bild 3 2011 for Ted - BILD 3 Lecture 6: Speciation...

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BILD 3 Lecture 6: Speciation Sturnella magna Sturnella neglecta
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Pheidole barbata
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How many species are there? ~1.2 million named (most are insects) ~8.7 million ( ± 1.3 million) suspected species currently alive - many undescribed species - species concepts apply better to some groups of organisms than to others - resources available to quantify biodiversity are diminished Mora et al. 2011, PLOS Biology, 9(8)
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I. What is a species? A. Biological species concept 1. How does reproductive isolation occur? 2. Problems with the biological species concept B. Morphospecies concept C. Phylogenetic species concept II. How do species arise? A. Allopatric speciation 1. vicariance 2. dispersal B. Sympatric speciation 1. habitat differentiation 2. polyploidy in plants III. Is reproductive isolation a byproduct or an adaptation? Speciation
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I. What is a species? Speciation: divergence of a lineage to create new species Speciation bridges microevolution and macroevolution
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A . Biological species concept : group whose members have the potential to interbreed in nature and produce viable, fertile offspring Equus caballus Equus asinus Equus caballus X Equus asinus
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A . Biological species concept : group whose members have the potential to interbreed in nature and produce viable, fertile offspring What unites a biological species? Gene flow What differentiates a biological species? Reproductive isolation
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How does reproductive isolation occur? Prezygotic barriers: individuals never mate (no zygote) - habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation
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Chrysoperla plorabunda Example of prezygotic isolation Two species of green lacewings that are morphologically indistinguishable - were thought to be same species Chrysoperla johnsoni
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Courtship - male and female engage in a duet: male initiates song, female responds Mating does not occur unless female responds, female responds only to male song of her species Male lacewings produce low frequency songs by vibrating abdomen Example of prezygotic isolation: lacewings
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Chrysoperla plorabunda Chrysoperla johnsoni Time (seconds) Oscillograms of lacewing mating songs
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How does reproductive isolation occur? Postzygotic barriers: mating occurs but offspring (zygote) not viable or fertile - due to: reduced hybrid viability, fertility, and/or breakdown Equus caballus Equus asinus Equus caballus X Equus asinus
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Problems with the biological species concept : a. mating or lack of mating hard to observe b. ability to mate versus likelihood of mating c. can not be applied to fossils d. not applicable to asexual populations (e.g. bacteria)
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B. Morphospecies concept : Species are defined by morphological traits alone Used by paleontologists to define fossils Used by others when reproductive biology or phylogeny not available
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Problems Cryptic species - species that are morphologically identical but genetically distinct Species cut offs are arbitrary Chrysoperla plorabunda Chrysoperla johnsoni
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Problems Fossil record Species cut offs are arbitrary
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C. Phylogenetic species concept
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This note was uploaded on 01/16/2012 for the course BILD 3 taught by Professor Wills during the Fall '07 term at UCSD.

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Lec 6 Bild 3 2011 for Ted - BILD 3 Lecture 6: Speciation...

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