1. Outline Introduction to Ecology Evolution and Natural Selection
Physiological Ecology
Behavioural Ecology

2. Behavioural Ecology

3. Behavioural Ecology
The study of ecological and evolutionary processes that explain the occurrence and adaptive function of behaviour
Examples of potential questions:
Why do birds migrate?
Why do grazing animals condense into herds?

4. Behaviour
Affects an individual’s ability to survive and reproduce in a particular environment
Develops under the influence of both genetic inheritance and environmental experience (learning)
the genetic component of behaviour is subject to natural selection

5. Behaviour to maintain internal conditions

6. Behaviour to get food or prevent becoming food

7. Behaviour to reproduce

8. Plants manipulate behaviour

9. Outline Reproduction: Why have sex? Life histories and mate choice
Predation:
Optimal foraging
Applications to fisheries management

10. Outline Reproduction: Why have sex? Life histories and mate choice
Predation:
Optimal foraging
Applications to fisheries management

11. Why have sex?
Ch , Bush

12. Outline The basics of sex The evolution of sex
Variations in sexual systems

13. Outline The basics of sex The evolution of sex
Variations in sexual systems

14. Reproduction
The goal of reproduction, for any organism, is to ensure the survival of its genetic lineage
Two ways to do this:
ASEXUAL: offspring are exact (almost) genetic copies of a single parent
SEXUAL: chromosomes of two parents are segregated and recombined so that no two offspring are identical to each other or to either parent

15. Most organisms are sexual
Of the 1.8 million known species only 2000 of them are totally asexual

16. Asexuality is concentrated among the basal organisms

17. Asexual reproduction The cell divides to produce two daughter cells
This type of reproduction can be very rapid; several generations can be produced each hour

18. Sex = meiosis
Meiosis is the process whereby gametes are made with half the number of chromosomes
The original number of chromosome is reformed when two gametes come together

19. Meiosis versus mitosis

20. Outline The basics of sex The evolution of sex
Variations in sexual systems

21. Why did sex evolve?
Life originated without sex (as best we can tell) so sexual reproduction is something that had to evolve
There are a large number of disadvantages to sexual reproduction which makes the evolution of sex a conundrum

22. Sex is not necessary for all life
Some plants and animals have entirely abandoned sex
Others have sex only when its convenient and are asexual most of the time (facultatively sexual)

23. Sex in the news…

24. Ancient asexuals: Bdelloid rotifers
bdelloid rotifers date back ~100 million years
Despite bdelloids' asexuality, they've diversified into 380 species

25. Facultative sexuality in animals
In some animals, such as Hydra, asexual reproduction can occur through budding
These animals are still capable of reproducing sexually as well
Sexual and asexual processes are governed by environmental conditions

26. Parthenogenesis – offspring from unfertilized eggs
Cnemidophorus velox, a parthenogenic lizard

27. Aphids – asexual and sexual
Females give birth to live females during the summer months
As winter approaches, both males and females are produced, which mate to produce eggs

28. The Cost of Sex The cost of males The cost of recombination
The cost of mating

29. The Cost of Males

30. Passing on genes is like tossing coins
Two copies exist for each gene
Whether you pass on a certain copy of a gene is an independent event for each child
If you have two children, sometimes you will pass on the same copy to both children (leaving the second copy passed on to neither child)

31. Fitness
FITNESS:
the number of offspring an individual produces that survive to reproduce themselves
Fitness = 1.0 means that individuals of this phenotype are successfully passing on 100% of their genes, on average

32. How is fitness calculated
Fitness = the number of genes passed on to the next generation
Because diploid organisms (I.e., most organisms) only pass on half of their genes to each child, they must have two offspring living to reproductive age to have Fitness = 1
Fitness = 1 does not exactly mean that you have passed on 100% of your genes to the next generation (Remember: sometimes you send two copies of the same gene and zero copies of the other)

33. Cost of recombination Asexual Sexual F F F F F F M M Fitness 2 1
of females

34. The Cost of Mating Cost of sexual mechanisms Cost of mating behaviour
Chemical attractants
Sexual organs
Flowers
Cost of mating behaviour
Courtship is costly
Potential exposure to predators
Injury
Disease Transmission

35. Sexual Mechanisms

36. Mating Behaviour

37. Injury to females - unintentional
When males are much bigger than females, the females can be injured by intercourse

38. Injury to females - intentional!
Callosobruchus maculatus
Male genitalia

39. Why hurt the female?
Reducing the fitness of your mate ought to reduce the fitness of yourself as well
Copulation is not always a cooperative venture between the sexes.
In C. maculatus, females mate repeatedly
genital wounding could increase the fitness of male C. maculatus if:
it causes females to postpone remating (less sperm competition)
increase immediate oviposition (egg-laying) rates because females perceive damage as a threat to survival and invest more in current reproduction

40. Costs of mating are widespread
Female Drosophila melanogaster that mate more often die more often
seminal fluid increases female death rate
Fluid is also responsible:
in elevating the rate of female egg in elevating the rate of female egg-laying,
in reducing female receptivity to further matings
in removing or destroying sperm of previous mates

41. Birds, bees, and STD’s
Most organisms are plagued by a few sexually-transmitted diseases
E.g., earwigs, frogs, koalas, or humans
Ustilago violacea (smut fungus) infects flowers of Silene alba and is transferred via pollinators

42. Sexuality must have its advantages
Hardly any asexual lineages seem old, and fossil evidence has suggested that asexuality is a dead end
The prevalence of sexuality amongst species is caused not because asexual species don't evolve, but because they don't last

43. Sex increases variation

44. Sex increases variation
Genes from maternal and paternal parent get “shuffled up” when gametes are made
Causes some gametes to have “superfit” genotypes and others to have “superunfit” genotypes

45. Sex leads to more variation in offspring

46. Sex and speed of evolution
More variation leads to natural selection operating faster
Most selection, however, is stabilizing selection, as individuals are well-adapted for a given environment and try to stay that way

47. Sex and speed of evolution
What aspect of the environment is so variable that the production of variable offspring could offset the cost of sex? - Parasites and pathogens
Hosts are constantly evolving to protect themselves from parasites and parasites are constantly evolving to overcome their host’s defenses
Parasites and hosts are locked in a host-parasite arms race

48. Red Queen Hypothesis
"Well in our country," said Alice, still panting a little. "you'd generally get to somewhere else-if you ran very fast for a longtime as we’ve been doing.”
"A slow sort of county!" said the Queen. "Now, here, you see, it takes all the running you can do to keep in the same place."

49. Evidence for Red Queen Hypothesis
In top minnows, sexual and asexual lineages coexist
Sexual lineages are the least susceptible to parasites
Genetic variation needed to keep up with evolution of parasites

50. Muller’s Ratchet Vast majority of mutations are detrimental
Mutation acquisition is a one-way process in the genomes of asexuals
In Salmonella typhimurium 444 lineages started from a single colony
After 1700 generations, 1% of lineages showed decrease in fitness (growth rate) but no lineages showed increased fitness

52. Outline The basics of sex The evolution of sex
Variations in sexual systems

53. Variations in the sexual theme
Are there always two separate sexes?
Do females always have the offspring?
Do females control who fathers their offspring?

54. Sexual systems Depends on the sexual system of the organism:
Hermaphroditic
Dioecious (Latin for “two houses”)

55. Flowering plants
Wide diversity of sexual systems ranging from strict hermaphroditism to dioecy
Hermaphroditism is the most common (~90% of all flowering plants)

56. Hermaphroditic animals

57. Snail copulation
Copulation involves a two- to six-hour marathon that is actually an exchange of sperm between two individuals, combined with plenty of rubbing, biting and "eye-stalk" waving
shoot centimetre-long darts out of their bodies and into the genital area of the other (which happens to be just behind the head on the right side).

58. Helix aspersa

59. Why only two sexes at most?
If we describe the individuals that have the offspring as females, then the other sex is male
If we introduce another sex that also does not have offspring (i.e., males) then we increase the cost of males
a higher cost of males would be maladaptive

60. Seahorse anatomy

61. Mating and Males Giving Birth

62. Sperm storage in female insects
Many female insects have the ability to store sperm from
many males, only choosing the best to fertilize her eggs
when the reproductive season is over

63. Male Drosophila bifurca
Male Drosophila flies
Drosophila flies have sperm cells that are up to 6 centimetres long!
Their testes take up 11% of their body mass
Male Drosophila bifurca

64. Summary
Considering the short-term advantages of asexuality, it is not entirely clear why so many organisms are sexual
Although the exact reason why sex is advantageous has not been determined, the increase in variation that sex brings is thought to play a large part
A wide variety of variations in sexuality have evolved in terms of the separation of sexes, the placement of parental care, and the timing of sexuality