Lecture 3 (2ab) - Parental Strategies and Ensuring Paternity

Question 1

LRO is about

Answer 1

F1

Question 2

LRS is about

Answer 2

F2

Question 3

What is LRO?

Answer 3

• number of offspring born to a parent in the F1 generation
• product of fecundity (fertility) x fertile lifespan
• fecundity proportional to success in
  
  • locating
  • courting
  • retaining

a mate

• number of offspring you generate in a lifetime
• locating and courting assumes polygamy
• retaining assumes monogamy

Question 4

What determines LRS?

Answer 4

• LRO
• fecundity/fertility of F1
• probability that F1 survive to sexual maturity / achieve fertility
• highly dependent on parenting

Question 5

Difference between LRO and LRS

Answer 5

• LRO about finding mates
• LRS about parenting - surviving to produce children

Question 6

What would influence the probability of offspring surviving to sexual maturity?

Answer 6

• rate of development
• survival
  
  • starvation
  • predation

a parent can influence all of these

(development - ensuring nourished)

Question 7

What maximizes a species’ “reproductive success”?

Answer 7

reproduction

development

PARENTING

Question 8

Species can be

Answer 8

• r-selected
• K-selected

reproductive strategy is r- or K-

Question 9

r-selected

Answer 9

• reproduce and develop rapidly
• highly prolific
• little/no parental investment
• eg most insects

Question 10

K-selected

Answer 10

• reproduce and develop slowly
  
  • eg monotocus
• high level of parental investment
  
  • eg humans and higher mammals
• at carrying capacity

Question 11

How can males maximize LRS?

Answer 11

• maximize LRO output
• maximize number of mates
• strong drive to polygyny (not picky)
• must be incentive for a male to be monogamous
  
  • stay and contribute to parenting rather than finding a new mate

Question 12

How can females maximize LRS?

Answer 12

• maximize survival of offspring to sexual maturity
  
  • PARENTING
• select “fittest” partner - sexual selection
  
  • males visually extravagant
• maximize number of mates
• strong drive to polyandry (picky)
  
  • can be pick after the fact
• SPERM COMPETITION
  
  • impregnate vs inseminate

(invest in egg and yolk/uterine nutrition)

Question 13

What are the parental priorities?

Answer 13

• maximize the number of offspring
• keep offspring alive

Question 14

Parental priority:

maximize the number of offspring

Answer 14

• as dictated by resources - trade off against parental role
• even in K-selected species still want maximum number of offspring
  
  • want more than 2 (the replacement number)

Question 15

Parental priority:

keeping offspring alive

Answer 15

• ensure infants avoid starvation
• ensure infants avoid predation
• ensure infants aren’t born into an overly competitive environment
  
  • ​K-selected - making sure when at carrying capacity that they aren’t born into competition
• ensure infants **don’t **die by misadventure
• ensure infants aren’t killed
  
  • ​different from predation - kill for eg fun, not eating

Question 16

How can parents ensure infants avoid starvation?

Answer 16

• ensure that there is sufficient food in the (immediate) environment
  
  • before laying eggs / giving birth
  • before conceiving
    
    • don’t reproduce if not enough food
    • stressed → won’t reproduce
    • may not have sex if not much food around
• food insufficiency renders animals sub/infertile and can terminate pregnancies

Question 17

How can parents sensure infants avoid predation?

Answer 17

• ensure offspring are cryptic
  
  • ​(hidden)
  • genetically selected to be cryptic
    
    • eg grayscale = can’t see in grass if predator color blind (hidden)
• guard offspring
• put offspring in a “creche”
  
  • leave with other adults when leave so still protected

Question 18

How can parents ensure infants avoid predation?

Answer 18

• don’t produce offspring in the vicinity of predators
• actively guard/protect infants

Question 19

How can parents ensure infants avoid competition?

Answer 19

• don’t produce offspring in an overcrowded/competitive environment
• natural selection against runts
  
  • eg not enough teets for all piglets
  • deliberately produce too many kids so pick (genetically) weakest

Question 20

How can parents ensure infants avoid death by “misadventure”?

Answer 20

• supervised play
• training
  
  • train offspring to be safe
  • looks like play but training for adulthood

Question 21

How can parents ensure infants avoid being killed?

Answer 21

• ensure infant is cryptic/guarded
• social bonding with group members that might pose a threat
  
  • mother might engratiate self with male
  • complex societies
  • eg baboons - biggest danger is other baboons

Question 22

How long are parents “useful” to their offspring?

Answer 22

• until offspring achieve sexual maturity and can give rise to F2 generation
  
  • then become redundant
• until parents achieve “reproductive senescence”
  
  • ​should basically die when can’t reproduce
  • not contributing to gene pool, becomes competitor
• concept of extended family in matriarchal species - “aunt behavior”
  
  • tolerate elders who don’t reproduce because form creche while F1 parents feed (babysit F2)
  • grandparents in elephants

Question 23

Which parental roles CAN’T be assumed by males?

Answer 23

males can’t

• nourish the embryo
  
  • yolk or female tract secretions
• lactate (mammals)
  
  • pathology, not normal physiology

Question 24

Which roles CAN be assumed by males?

Answer 24

males CAN

• carry the embryo
  
  • “pregnant males”
• guard the embryo (egg)
• carry and guard the neonates (infants)

dad is normally (biologically) finding another mate

Question 25

"Pregnant males" | (Sygnathidae)

Answer 25

* eg pipe fish * white underbelly = pregnancy belt * male sea horse giving birth * female deposits egg * female still nourishes with egg yolk * no placenta * homones involved in giving birth

Question 26

Incubating males

Answer 26

* male guarding embryo * embryo nourished by egg sac * mom goes off to feed * hungry because invested all her energy in producing the egg * eg penguins, flightless bird in new zealand

Question 27

Carrying neonates | (Callithricidae)

Answer 27

* 2 babies on dad's back * twins to trap males into parenting

Question 28

Strategies for ensuring paternity

Answer 28

* sperm competition

Question 29

Sperm competition

Answer 29

* if a female is inseminated by 2 or more males, creates the opportunity for **sperm competition** within the female * compete to fertilize the egg * certain he'll win (see another slide) * guard female (before mating) * more gametes/volume * more volume * volume several times

Question 30

How can a male win the "sperm competition"?

Answer 30

* fast sperm (long sperm) * doesn't always hold up - longest doesn't always win * Drosophila sperm 10x longer than fly * high sperm number * ejaculate volume or sperm density * repeated insemination of same female * drives toward monogamy * amphibians release at righ time (time eggs come out) and when just about to ovulate * exclude other sperm * break penis off * biochemical plug in female

Question 31

Highest sperm competition →

Answer 31

largest amount of ejaculate or sperm density

Question 32

Harem

Answer 32

* **single** reproductively active male * **all** offspring sired by **harem-holder** * only males tolerated are **"followers"** * usually offspring of the harem-holder, inherit harem * followers tolerated as long as subordinate * 2 choices - wait your turn for harem to die, take on harem-holder * extreme case of **mate guarding** * example - Hamadryas baboon

Question 33

Types of harem

Answer 33

* patriarchal harem - male holds it together * another male comes along → fight * canine teeth lethal in hamadryas baboons * mate-guarding, sexual selection * matriarchal harem - females choose harem lions - take on harem with fight, espically if against harem with brother

Question 34

Infanticide

Answer 34

* eg lions * ensure that a male isn't **wasting resources** on offspring that he didn't sire * female then mates with new harem * new harem better/more fit → better offspring

Question 35

Mate guarding

Answer 35

* pre-copulatory mate guarding * has she already been inseminated? * post-copulatory mate guarding * has she been fertilized yet? * could she still be fertilized by another male? * block female tract

Question 36

Mate guarding ## Footnote *Gerris gracilicornis*

Answer 36

* paint pair, but back * don't match = guarding male replaced * high turnover

Question 37

Mating (copulatory) plugs

Answer 37

* widespread - invertebrates, reptines, metatheria, eutheria * keep semen inside and other semen out * plug may remain until impregnated, then sometimes comes out

Question 38

Mating (copulatory) plugs complex composition

Answer 38

* **​fatty acids** * seminal **proteins** * **anti-reproductive **molecules * eg cycloprolylproline in invertebrates * suppress her mating drive * kil any other sperm before new male deposits * can also be produced by **females** (polyandrous) * when mated by desirable male

Question 39

*Argiope bruennichi*

Answer 39

* male leaves reproductive structure inside female * can only do this twice (only 2 reproductive structures) * male then dies