lecture 19 Flashcards
Distribution of males and females when food is sparse, patchy, and slowly renewed
territorial females that are uniformly distributed, non-territorial males
Distribution of males and females when food is abundant, evenly distributed, rapidly renewed
non-territorial females, territorial males
When females are asynchronous and clumped or dispersed in space
males are non-territorial and promiscuous
when females are synchronous and clumped in space
males are territorial and polygamous
when females are synchronous and dispersed
males are territorial and monogamous
Study: How much to invest in offspring based on lifespan
If you have a shorter lifespan, you should invest more in your current offspring; Starlings have short lifespan and invest more; storm petrel have longer life and invest less
3 factors to determine how much care to give current brood
Brood size, genetic relatedness, future mating opportunities
Sunfish example: effect of brood size on parental care
If brood size (# of eggs guarded) is experimentally reduced, defense of brood is reduced accordingly; smaller the brood, the less males defend it
Bluegill sunfish: importance of genetic relatedness
males defend offspring based on degree of parental certainty; in the experimental condition where additional males were placed in the tank, male defended eggs less than when male was only male in tank; however, defend fry more than eggs even when there is another male around because he can tell whether the hatched fry are related to him
Rainbow cichlids: importance of future mating opportunities
the more female-biased the population, the more likely that the male will abandon the brood
Bluethroat birds: effect of sibling size on allocated resources
when offspring differed in size, parents invested more (provided more food) in larger sibling, because larger offspring would have greater chance of being reproductively successful in future
Spotted hyenas- sibling rivalry
when alpha female has female offspring, they fight for dominance as soon as they are born over who will become the direct subordinate to mom (beta); the weaker female sibling often dies from lack of nursing since more dominant sister takes all the resources
Why would parents condone siblicide?
efficient brood reduction when food is scarce since only strongest sibling survives; maybe you produce too many offspring just in case due to high prevalence of disease
2 primary questions of parental care
- Who cares?
2. How much care?
Mode of fertilization and role on who provides care
Internal fertilization: female parental care; external fertilization: male parental care (male wants to guard his fertilized eggs)
Back brooding
males take care of the young; females produce the eggs and then males guard them
Hamilton’s Inequality (Kin selection)
rB>C
r: coefficient of relatedness; B: benefit to recipient for help provided; C: cost to self for providing help
Parent-offspring conflict curve
Looks at time of dependency of offspring on parent vs the B/C ratio for parent; predicts that the parent prefers an earlier end to dependency and offspring prefers a later end, resulting in some conflict over when the parent will stop providing resources
Costs vs benefits of parental help
Benefit= benefit to current offspring; cost= reduction in future offspring
Weaning
period of conflict during which the offspring tries to acquire resources and parent attempts to withhold them; this conflict ends when both parents and offspring agree that future investment of parent is better directed at future rather than current offspring
