PowerPoint Presentation - Parental Care by ewghwehws


									      Parental Care
• Patterns
• How much care to provide?
• Who should provide care?
• When should care be
• Who should receive care?
Insect parental care
Distribution of parental care in vertebrates

 • Teleost fishes = 21% of families show PC
   – 61% have male parental care
 • Amphibians = 71% show PC
   – 50:50 maternal:paternal
 • Birds = 100% show PC
   – Usually biparental, sometimes one sex
 • Mammals = 100% show PC
   – Usually maternal, sometimes biparental
    How much care to provide?
• Parental investment: “any investment by the
  parent in an individual offspring that
  increases the offspring’s chance of
  surviving at the cost of the parent’s ability
  to invest in other offspring (Trivers 1972)
• Costs of parental care include
  – Reduced future survival
  – Reduced mating opportunities
Parental investment changes
Parental care decreases survival in
            willow tits
Parental care decreases mating opportunities

A female-biased sex ratio increases the cost of brood care for males
           because parental care detracts from mating
    Alternative hypotheses for
          providing care
• Confidence of paternity
  – Expect parent with highest certainty to be
• Order of gamete release
  – First to deposit gametes can desert
• Association
  – Sex nearest to offspring when care is needed
Parental care
in fishes and
Alternative hypotheses for providing
           care: evidence
• Confidence of paternity (fish and herps)
   – Internal fertilization - 86% maternal care
   – External fertilization - 70% paternal care
• Order of gamete release
   – Simultaneous fertilization (most species) - 78%
   – Other species - male deposits first, but doesn’t leave
• Association
   – Territorial males have external fertilization
              Why male
                         Randall’s jawfish

Mallee fowl
fecundity and
 paternal care
                             Parental care can
                            cost females more
                                than males

Mouthbrooding results in weight loss due to reduction in feeding,
and the cost of brood care is higher in females than males
Parent-offspring conflict
            Parent-offspring conflict
                                       Wallaby conflict
• Assume fixed total resource that
  can be used to feed offspring
• Parents want to distribute
  resource equitably to all n
• Offspring want more than 1/n
  but not all since they are related
  to siblings
• Difference between parent and
  offspring optimum increases as
  relatedness decreases
            Parent-offspring conflict:
            how much care to provide
Parent is equally related           B - measured in +units of RS of current offspring
to all offspring, but               C - measured in - units of RS of future offspring

offspring are less related
to sibs than themselves.                                                   B
Assuming full siblings,
i.e. r = 1/2
                       Benefit or                                          C
                       cost to
   Max. inclusive fitness
   for parent

   Max. inclusive fitness
   for offspring
                                    Level of parental investment
 Begging loudness increases as
relatedness within nest decreases

                      Brown-headed cowbird
Parent-offspring conflict:
    time of weaning


     Parental investment and maternal age

If reproductive value declines
with maternal age, then older
females should be willing to
expend more on parental care
     Who should receive care?
• Concorde fallacy: past investment should
  not determine future investment - only
  prospects for future success
• Expect parents to use honest indicators of
  offspring quality to allocate care
Sibling competition
Sibling conflict
        Chick color affects parental feeding in
               mixed broods of coots

Control broods were unaltered
(orange) or had orange feathers
trimmed (black)
Experimental broods had
1/2 orange, 1/2 black chicks

Chick color likely indicates
offspring health

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