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Testing hypothesis 2

Testing hypothesis 2. Predict: If high T b harms pregnant females, then 35 o treatment should have lower survivorship lower growth in mass or length Predict: If high T b harms embryos, then 35 o treatment should have more abnormalities smaller size at birth (mass, SVL)

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Testing hypothesis 2

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  1. Testing hypothesis 2 • Predict:If high Tb harms pregnant females, then 35o treatment should have • lower survivorship • lower growth in mass or length • Predict:If high Tb harms embryos, then 35o treatment should have • more abnormalities • smaller size at birth (mass, SVL) • smaller sizes at 9 days

  2. Results: Effects on females • None • Survival = 100% for all • Growth not significantly altered by treatment • High temperature has no effect on females performance

  3. Results: Abnormalities • Of 15 females in each treatment: • at 35oC … 4 females produced 1 or more abnormal or dead offspring • at 32oC … 1 female produced 1 or more abnormal or dead offspring • in Treg … no females produced abnormal or dead offspring • abnormalities rather rare, hard to say much

  4. Results: Effects on embryos

  5. Conclusions • High temperature actually increases development rate of embryos • However, high temperatures reduce mass and SVL at birth • Effects of high temperatures remain for up to 9 days after birth • This size effect is probably sufficient to affect offspring fitness (survival)

  6. Overall conclusions • Pregant females actively regulate at a lower Tb because of negative effects of high temperature on offspring fitness • How might this evolve? • Quantitative trait: Tb when pregnant • Fitness differential (S): females with Tb = 32OC

  7. Physiological EcologySummary • Ecology of individuals • Adaptive value of physiological traits • Homeostasis (e.g., thermoregulation) • “How” vs. “Why” questions • Costs and constraints (e.g., S. merriami) • Benefits related to fitness (e.g., S. jarrovi)

  8. Behavioral Ecology • Another aspect of the ecology of individuals • The relationship between the living and nonliving environment and the actions of animals

  9. Topics within behavioral ecology • Foraging - how environment influences choice of what, how, when, where to eat • Social systems - how environment influences how individuals interact with conspecifics; living in groups • Sex and mating systems - environmental determinants of mating and reproduction

  10. Behavioral ecology focuses on adaptation and evolution • Main focus is on the adaptive value of observed traits in a given environment • There can be questions of both how and why concerning behavior • In both cases, approach is similar to that seen in physiologial ecology (costs, benefits, constraints)

  11. Living in groups • Many animals live in groups with conspecifics • Birds form feeding flocks, migrating flocks • Herds of herbivorous mammals • Schools of fish • Insect aggregations (e.g., monarch butterflies) • What determines group size? • What are benefits and costs?

  12. Major benefits of group living • Improved foraging success • Improved defense against enemies • Improved ability to cope with the physical environment

  13. End 9th Lecture

  14. Improved foraging success of groups • Improved location of food • Individuals observe one another and improve their chances by watching others succeed • e.g., blue herons - prefer to forage in areas where other herons are already foraging • species feeding on large ephemeral clumps of resources (e.g., fish)

  15. Improved foraging success of groups • Improved probability of capture • mammals - most predators fail more often than they succeed • lions • success rate double for 2 lions vs. 1 lion

  16. Improved foraging success of groups • Ability to take larger prey • group hunters - lion, spotted hyena, wolves, wild dog, kill prey >= their own mass • solitary hunters - leopard, coyote, striped hyena, kill prey < their own mass

  17. Improved defense against enemies in groups • Improved detection of predators • More eyes, noses, ears • greater probability of detecting predator • Bird flocks -- large flocks take flight when hawks are farther away • Advantage does not increase with group size indefinitely

  18. Improved defense against enemies in groups • Improved ability to deter a predator • Groups attack predator (e.g., gulls) • Chemical deterrence (e.g., pine sawflies) • Warning coloration - bigger signal

  19. Improved defense against enemies in groups • Confusing a predator • Many targets in a group -- hard to hit one • Shoals of fish attacked by squid • success rate of squid • single fish > small shoal > large shoal

  20. Improved defense against enemies in groups • Dilution effect • One predator takes one victim •  group size,  individual’s prob.(death) • Have conspecifics nearby so they can be the victim • Effect reduced if : • >1 individual taken • prob.(attack) increases with group size

  21. Forming selfish herds • Group = cooperation? • Animals may move to position conspecifics between themselves and predators • If predators take nearest animal, moving to center benefits individual • Result: form tight groups because each individual selfishly seeks middle

  22. Forming a selfish herd

  23. Forming a selfish herd

  24. Forming a selfish herd

  25. Forming a selfish herd

  26. Forming a selfish herd

  27. Forming a selfish herd

  28. Forming a selfish herd

  29. Forming a selfish herd • Point: Forming groups does NOT imply cooperation • Each individual may be acting selfishly for its own benefit • Effects on the group as a whole secondary

  30. Improved ability to cope with the physical environment in groups • Improved ability to thermoregulate • e.g., musk ox, roosting bats • groups minimize cost of thermoregulation by clustering • clustering reduces heat loss

  31. Benefits of group living weighed against costs • Aggressive interactions between conspecifics • Sharing resources that may be scarce • Nonexclusive access to mates • Disease transmission

  32. End 10thLecture

  33. Mating systems • Who mates with whom • Environment influences the mating system

  34. Sexual Selection • Selection that arises when individuals of one sex (usually ) gain advantages over other members of that sex in acquiring mates. • Darwin originated the concept • Now viewed as a subclass of natural selection

  35. Two kinds of sexual selection • Intrasexual selection: typically - competition •  compete for access to  • Darwin “power to conquer males in battle…” • Weapons; large, strong, aggressive 

  36. Characters for combat

  37. Two kinds of sexual selection • Intersexual selection: typically  choice of mates •  prefer  with particular characters • Darwin “power to charm females…” • showy structures, behaviors

  38. Characters to charm 

  39. Mating systems • Description of who mates with whom? • Differential investment of  and  •  - high cost gametes • produce few gametes • choosy • low variation in reproductive success •  - many, low cost gametes • produce many gametes • indiscriminant • high variation in reproductive success

  40. Mating systems • Promiscuous • all individuals mate with a number of mates • marine invertebrates, many insects, some fish, nearly all plants • Polygynous •  mate with >1;  mate with 1 at a time • many mammals, some birds, many insects, many amphibians

  41. Mating systems • Polyandrous • mate with >1;  mate with 1 at a time • a few birds, a few insects, a few fish • Monogamy • 1 with 1 • many birds, some mammals, a few insects, some fish

  42. Mating systems depend on ecological conditions • Territories for mating, breeding (e.g., birds) • Resources (e.g., food, nest sites) • Defense against enemies •  gets material benefits from choosing certain 

  43. Mating systems depend on ecological conditions • Resources uniformly spread •  gain most by seeking unmated  • no sharing resources • Monogamy • Resources patchy (best males--best patches) •  may gain most by seeking best  (best patch) even if he has a mate • Polygyny

  44. End 11thLecture

  45. monogamous 2nd  FEMALE FITNESS 5 4 3 2 1 Males TERRITORY QUALITY Polygyny threshold

  46. Ecology and mate choice • Distribution of resources influences mate choice • all territories good, resources uniform - monogamy • territories vary a lot in resources - polygyny

  47. Ecology and mate choice • What about cases where there is no material benefit? • Why should females prefer showy males? • Male quality • colors, ornaments, songs, displays etc. are costly • “good” males can pay that cost • handicap principle • Presumes “quality” is heritable

  48. Parasite-mediated sexual selection (Hamilton-Zuk Hypothesis) • Why should females prefer showy males? • Enemies (specifically parasites) • parasitized males have reduced showiness • showy colors  males resistant to local parasites • resistance to parasites heritable • benefit of choosing those males  resistant offspring • ectoparasites of birds - gnaw feathers • endoparasites - general reduction in vigor

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