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The Genetical Theory of Natural Selection

The Genetical Theory of Natural Selection. Where natural selection occurs. Fundamental patterns of intraspecific natural selection. Disruptive. Rare. Carnivores. Consume nutritionally-rich prey. Problems involve capture Some prey d efensive signals: Aposomatic coloring - Warning colors.

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The Genetical Theory of Natural Selection

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  1. The Genetical Theory of Natural Selection

  2. Where natural selection occurs

  3. Fundamental patterns of intraspecific natural selection Disruptive Rare

  4. Carnivores • Consume nutritionally-rich prey. • Problems involve capture • Some prey defensive signals: • Aposomatic coloring - Warning colors. • Mullerian mimicry: Signal shared among several species of noxious organisms. • Batesian mimicry: Edible species uses same signal as a noxious species. • Crypticity: camouflage

  5. Camouflage and directional selection

  6. Directional selection Biston betularia Pre-pollution control

  7. Original habitat Post pollution control

  8. Directional selection

  9. Disruptive selection Black-bellied seedcracker (an African finch) Multiple-niche polymorphism Bimodal distribution

  10. Black-bellied seedcracker

  11. Balancing selection Polymorphism Maintained because intermediate expression of a continuous character is favored by NS or by hetorozygote advantage Genetic variation at beta-hemoglobin locus Polymorphic in response to malarial organism Two selectors: malaria and sickle-cell anemia

  12. Polymorphic mating strategies Uta stansburiana Side-blotched lizard Polymorphism: males Color and behavior determined by levels of prolactin and testosterone in early development. Fixed for life. 1. Large territories, many females 2. Small territories, one female. 3. Non-territorial, sneak copulations from 1. Morph frequencies shift between generations depending on success of a particular tactic. 1. 2. 3.

  13. Batesian mimicry

  14. Müllerian mimicry Micrurus eryxanthus: Western coral snake Aposematic coloration Problem: how established?

  15. A mimetic system Batesian and Müllerian Mimicry Aposematic coloration Parallel geographic variation Micrurus 6 species. Highly venomous Fixed front fangs Neotropical Elapidae Pliocercus 1 or 2 species. Mildly venomous Fixed rear fangs Colubridae

  16. Does aposematic coloration work? Plasticine models Forest floor: on white paper and on forest floor

  17. Experiment carried out in natural habitat

  18. Resemblance does not have to be perfect to confer protection Significant differences

  19. Is avoidance of aposematic coloration innate? • Naïve motmots (Neotropical birds) • Caged birds presented with: • 1. coral snake models • 2. models of natural prey species.

  20. A famous Müllerian mimicry complex. Each species with subspecies defined by color pattern and geography. What happens at subspecific boundaries?

  21. Phenotypic plasticity: environmentally induced variation operating on common genetic background. Phenology: relationship between climate and the timing of ecological events. Geometrid moth Nemoria arizonaria Water Crowfoot Ranunculus aquatilis

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