Lecture 06

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Biological Sciences
Kamini Persaud

Lecture 6: Parental Care & Kinship - Costs vs. Benefits  Sexual Conflict over PARENTAL CARE [Parental Care in the Magnificent Frigatebird]  Parental care = a cooperative venture between a male and a female in many socially monogamous birds.  Care = costly; so sexual conflict arises between the parents about how much effort they should invest into rearing their young.  The sexual conflict over care is most apparent when one parent abandons the brood before the offspring are independent.  The deserted parent has three options: (1) desert the brood because a single parent is unable to raise the young on its own; (2) continue care provision at the same level as during biparental care, and thus do not compensate for the absence of mate; (3) increase care and compensate partially or totally.  During biparental care, females fed the chick more often than the males. After their mate deserted, the females nearly doubled their feeding rate and thus, fully compensated for the lost care.  Growth rates of chicks provided with biparental and female-only care did not differ.  Females may withhold care during biparental care to manoeuvre their mates into prolonged care provision. A female only provides at her full capacity once her mate has deserted.  What IS “Parental Care”?  Behaviour by parent which increases OFFSPRING’S fitness (and would not occur in absence of offspring).  MODES of Parental Care  Feeding  Protection  Transportation  Maintenance (grooming, heat, gas exchange, defense against disease etc)  Teaching  WHY Care? (at all …)  It all comes down to benefits/costs  PRECOCIAL young: species in which the young are relatively mature and mobile from the moment of birth or hatching; e.g. fish, insects, spiders  ALTRICIAL young: where the young are born or hatched helpless; e.g. birds, canines, felines, primates  Expect parental care to EVOLVE when …there is a high benefit/low cost to it!  ENVIRONMENT  Selection pressure from the environment  K-selection (stable environments):  Constant, predictable environment  Individuals are larger, longer lifespan… population at capacity  Selection Pressure: Intense INTRAspecific competition  Strategy: QUALITY (few, but well-prepared offspring –strength, knowledge, etc.)  Parental care has HIGH BENEFIT  r-selection (unstable environments):  Uncertain, variable environment  Low survivorship, short lifespan  Selection Pressure: unpredictable environment, predation  Strategy: QUANTITY (many cheap offspring – some will survive by chance alone)  Parental care has LOW BENEFIT; therefore, little parental care!  TYPES of Care (Systems) 1. NO Parental Care; e.g. many invertebrates, some fish, reptiles & amphibians 2. UNIparental Care aka ONE PARENT; e.g. (usually female) e.g. many mammals, some invertebrates, fish, reptiles, amphibians & birds 3. BIparental Care aka BOTH PARENTS; e.g. many birds, some mammals, few fish  WHO Cares?  WILLIAM’S PRINCIPAL: Investment in the present comes at the COST of investment in the FUTURE  LIFETIME REPRODUCTIVE SUCCESS (LRS) depends on: 1. Present Success (P); P is a function of what you are giving to your present offspring:“Reproductive Effort” (RE) 2. Future Success (F); F is a function of what you have to give your future offspring (your own growth and survival): “Somatic Effort” (SE) 3. LRS = P(RE) + F(SE); you want to MAXIMIZE your LRS! As RE = SE  HOW MUCH Care?  Differential Alloc
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