Chapter 12

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Biological Sciences
Maydianne Andrade

Chapter 12 • Parental care balance – predators can ambush parent or nest o Sea turtles: hatch in sand, off to sea on own o Differ on duration, amount, timing, and who o Tree hoppers –guards eggs and repel predators o Egrets: brood young until independence (fledging) o Primates: feed and protect young until independence • Classical view – parents unselfish provider, child recipient • Evolutionary: benefits – increased offspring survival, cost of future reproduction o Trade off of current and future production o Birds with low adult mortality – minimize self risk , high mortality rate – more sensitive to nest • Why care? Physiological costs – sustained energy cost o Future reproduction and survival o Opportunity costs – foraging and matings  Parental care evolves if there is a net fitness increase Factors which affect cost and benefit of environment • Environmental o K selected: stable environment, large body size, slower development, longer lifespan. (quality)  intraspecific competition  Iteroparity: offspring in successive bouts  Small # of young that receive care  Low mortality of young  Parental strategy: Intelligent, autonomous – expensive offspring • Learning and physical abilities – benefit of parental investment – increase in success of young  Altrical young: relatively helpless and immature  Example: monkeys – flexible behaviour, behaiour repertoire, social system, develop brain • African dogs – social system, group hunting o R selected: fluctuating environment, smaller body size, rapid development, shorter lifespan (quantity)  Environmental, fluctuation, predation selecton factor  Semelparity: production of offspring once/few in a lifetime  Large # of young that receive little to no care  High mortality rate of young  Parental strategy: large # of cheap offspring – some survive • Low benefit of parental involvement  Prococial young: relatively advanced stage  Example: Coho salmon: ocean environment, single explosive breeding event, parents die and no care • Clutchlings may die 100% to predation, water problems • Redback spiders: disperse as spiderlings to unpredictable habitats – thousands of offspring for a mother – tiny and no parental care – high mortality rates, catch prey autonomous • Gross simplication, biotic and abiotic factors affect selection on favoured traits of offspring, and some require care to develop o Gull – start off K selected, as parents age become R selected o Likelihood of survival at old age decreases, so does parental investment • Residual reproductive value o Function of age and expected reproductive lifespan opportunities • How many surviving offspring are you likely to have o Lower RRV = lower cost of parental investment • Factors affecting RRV = age, health, timing, finding future mates • Eg. Eresid spiders o 100 of offspring and high offspring mortality – r selected o spider adult longevity – 1 summer – low RRV o suicidal maternal care – offspring feed on mother – low RRV Who provides Care • exclusive mom/dad, male or female, biparent • Female biased parental care o Females invested so much energy in making eggs – incentive to make sure gametic investment is not wasted  However, idea fails when we observe female leaving eggs  Concorde Fallacy (sunk costs) o Larger benefit-cost difference  A) lower cost: opportunity for additional mating • Cost Male > female, so female care o B) highest benefit: Females always derive max since offspring are hers  Sperm competition • Benefit female > male, so female care  More common in external than internal fertilization • Male can see which eggs are fertilized that are his • Mouth broodingfish (St Peter) o Gamete production constrains female but not male reproduction  But caring males fertilize same # of eggs o Females take longer to spawn than males  Both lose weight from caring • Overall more costly for females • Exceptions to the rule o Male sticklebacks can care for more eggs clutches o Female can forage more freely – more growth – more eggs • Why unilateral care female – increased cost for male leads to desertion How much care • Eventually parents benefit more by abandoning young o Increasing cost and diminishing retuns
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