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Lecture 17

BIO152H5 Lecture Notes - Lecture 17: Directional Selection, Genetic Variation, Stabilizing Selection

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Fiona Rawle

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Speciation Part C
Hybrid zone (regions where different species mate and produce hybrids)
Fire-bellied toad vs. Yellow-bellied toad
Same genus, but very different
Hybrid Zone
Hybrids have less fitness
More complex
Hybrid Zone
Species come together
Weakening of reproductive barriers if hybrids are fit
If gene flow strong, fuse into one species
Pundamilia species (same genus) but different species
Hybrid is turbid water (environment)
Check on Lec
Gene flow from outside
Drives species apart (when hybrids come close)
If hybrids are less fit
Rate of hybridization decreases
Morphological data (structure)
Fossil record
Punctuated equilibria
Apparent stasis by sudden changes
Punctuated models
Stability, stability, and change
Sunflower Helianthus anomalus (from hybridization)
Interval between speciation events (4000 to 40 million years)
Average is 6.5 million
Speciation might require change of only a single allele or many alleles
Allele affects reproductive isolation → fewer alleles to change
In Monkey flower, two loci affect flower color
Affects pollinator → reproductive barrier
Cumulative effect of speciation and extinction events
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