The two population groups represent different

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The two population groups represent different ecotypes , i.e. genotypes adapted to particular environments Arabis fecunda: Common Garden experiment
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19 Clines Yarrow, Achillea millefolium = gradual changes in genotype or phenotype over an environmental gradient
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20 Ayre, 1985: Reciprocal transplant experiment Anemonies transplanted between 3 sites 3 plots/site After 11 months, determined proportion of adults reproducing Actinia tenebrosa
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21 Ayres, 1985: Results Anemones from two of the three sites reproduced poorly in “foreign” colonies “specialized” for own environment
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22 Note: natural selection increases susceptibility to future environmental change As populations become more specialized for one environment, they may become less fit for other environments
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23 Colour variation in guppies Trinidad In mountain rivers consisting of pools separated by waterfalls Guppies present in most pools Colour variation : at high elevations, male guppies are more brightly coloured than at low elev. Bright males preferred as mates by females
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24 Guppy predators: Killifish, Rivulus hartii Feeds on juvenile guppies only Pike-cichlid, Crenicichla Feeds on guppies of all sizes Occur only in low-elevation pools Do brighter males suffer higher risk of predation?
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25 Guppy experiments 1. Lab experiment: artificial ponds 1. No predators (K) 2. Killifish (R) 3. Pike-cichlid (C) # spots per fish increased --> # spots per fish decreased
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26 Guppy experiments 2. Field experiment Selected 3 ponds: 1. Pike-cichlid & guppies (c) 2. Killifish only (x) 3. Killifish & guppies (r) Transfer guppies Results: In transferred guppies the size and number of spots increased Female choice affects male colouration (sexual selection) Presence of a strong predator counteracts effect of female preference (natural selection)
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27 What is a species?
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