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POPULATION CYCLES

POPULATION CYCLES. I. WHAT IS A CYCLE?. A. The Concept of Cycles multiannual fluctuations that occur with some regularity (periodicity). CYCLE CHARACTERISTICS. MORE CHARACTERISTICS OF CYCLES. Regional synchrony in fluctuations of coexisting species, Summer crashes in abundance

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POPULATION CYCLES

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  1. POPULATION CYCLES

  2. I. WHAT IS A CYCLE? A. The Concept of Cycles • multiannual fluctuations that occur with some regularity (periodicity)

  3. CYCLE CHARACTERISTICS

  4. MORE CHARACTERISTICS OF CYCLES • Regional synchrony in fluctuations of coexisting species, • Summer crashes in abundance • A gradual disappearance of cycles southward

  5. I. WHAT IS A CYCLE? B. Cycles and Body Size • Biological times scale as : • nerve conduction time • cardiac cycle time • respiratory cycle time • generation time • lifespan

  6. I. WHAT IS A CYCLE? B. Cycles and Body Size

  7. I. WHAT IS A CYCLE? D. Longer-Period Cycles: Hares • period of 9-10 years • amplitude of 15-200 fold

  8. I. WHAT IS A CYCLE? D. Longer-Period Cycles: Hares • period of 9-10 years • amplitude of 15-200 fold

  9. I. WHAT IS A CYCLE? D. Longer-Period Cycles: Hares • Coincident cyclic species animaldiversity.ummz.umich.edu www.arttoday.com www.aquatic.uoguelph.ca

  10. II. A GENERAL THEORY OF POPULATION CYCLES • Archbishop Olaus Magnus and Lemmings

  11. II. A GENERAL THEORY OF POPULATION CYCLES • Archbishop Olaus Magnus and Lemmings • Intrinsic Versus Extrinsic factors

  12. Some Theories 1) Chitty’s Hypothesis - NS 2) Social Fence Hypothesis - Social behavior

  13. Competition increases: tolerants stay but low fertility Pop size decreasing = emmigration & fertility Pop Size increases Animals spaced out & competition reduced

  14. Some Theories 3) Climate - indirect/direct

  15. Some Theories 4) Nodal Lunar Cycles & Sun Spots - 9.3 yr phase of moon = full moon during spring breeding - 11 yr periodicity on sun spots

  16. Some Theories

  17. Some Theories 5) Trophic-Level Interactions * plant-herbivore * predator-prey * parasite-host * seasonality * predator switching

  18. II. A GENERAL THEORY OF POPULATION CYCLES A. Increase Phase • high fertility rate • low mortality rate • young age structure • large litters • early age at first reproduction • few predators

  19. II. A GENERAL THEORY OF POPULATION CYCLES B. Peak Phase • fertility rate declines • hares: decline in quality and quantity of food

  20. II. A GENERAL THEORY OF POPULATION CYCLES B. Peak Phase • fertility rate declines • voles and lemmings: social factors

  21. II. A GENERAL THEORY OF POPULATION CYCLES C. Decline Phase • low fertility rates • high mortality rates • old age structure

  22. II. A GENERAL THEORY OF POPULATION CYCLES C. Decline Phase • Role of food quality • Proteinase inhibitors • common plant toxin • pancreatic enlargement • build up during peak and year 1 decline phase

  23. II. A GENERAL THEORY OF POPULATION CYCLES • Proteinase inhibitors could cause: • drastic declines in herbivore density • changes in body size and organ mass • the high degree of synchrony in fluctuations

  24. II. A GENERAL THEORY OF POPULATION CYCLES C. Decline Phase • Role of food quality • Reversion to juvenility • woody plants and winter browsing by hares • juvenile defenses • time lags of 2-3 years

  25. Winter Dormant Twigs of Alaska Paper Birch (B. neoalaskana) Mature Stage Juvenile Stage Note Catkin And The Lack Of Resin Glands Note Resin Glands

  26. Resin Gland on Current Year Twig Internode

  27. Results of B. neoalaskana Mature Vs. Juvenile Feeding Trial Juvenile Stage Twigs Note That These Twigs Do Not Have Catkins At Their Tip. Mature Stage Twigs

  28. II. A GENERAL THEORY OF POPULATION CYCLES C. Decline Phase • Role of predators • Direct effects on vital rates

  29. II. A GENERAL THEORY OF POPULATION CYCLES C. Decline Phase: Role of Predators • Direct effects on vital rates • voles and buffer prey • buffer prey promote stability www.abdn.ac.uk

  30. II. A GENERAL THEORY OF POPULATION CYCLES • Indirect effects of predators • Example: Bank Vole

  31. II. A GENERAL THEORY OF POPULATION CYCLES • Indirect effects of predators www.abdn.ac.uk

  32. II. A GENERAL THEORY OF POPULATION CYCLES • Indirect effects of predators • diurnal raptors and indoor plumbing by lemmings • birds of prey detect UV light • tundra = vulnerable lemmings • underground latrines in summer European kestrel Collared lemming www.goals.com

  33. II. A GENERAL THEORY OF POPULATION CYCLES C. Decline and Low Phase • Interaction of Food and Predators • >2-3x when food added or predators removed • >11x when food added and predators removed

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