Lecture 17 - Social Behaviour: Conflict

what are the benefits of focal offspring having more resources than the parents want to give?

they are richer and more fit

what are the costs of the focal offspring having more resources than the parents want to give?

their siblings are poorer (reduced fitness)

B(p)

fitness of focal offspring

C(p)

number of future offspring given up

what maximizes the difference between benefit and cost?

natural selection

offspring demand enhancing gene

it will increase fitness of the focal offspring through itself but will reduce fitness of future offspring/siblings

B(p) - ½ C(p)

what offspring should maximize (benefit to itself - 50% relatedness to future offspring x cost)

parent supply more gene

will potentially increase fitness through focal offspring and reduce by losing out on future offspring + equal chance of focal and future offspring having the gene

½ B(p) - ½ C(p)

parents should maximize this (50% relatedness x benefit of focal - 50% relatedness x cost of future offspring)

stitchbird experiment

examined resource provisioning to a current brood by parents who are likely or unlikely to have a second brood in the season

stitchbird experiment setup

• supplemented adults with carotenoids to enhance reproduction then compared to a control

• supplemented offspring with carotenoids to increase begging signal intensity

stitchbird experiment results

intensity of a begging signal by offspring can increase provisioning by parents but only when the costs are low enough

benefit of deserting for parent

increased quantity of offspring through remating

costs of deserting for parents

reduced quality of each offspring so lower probability of survival and fecundity

kentish plover benefits of deserting experiment set up

both patents caught on nest and one or the other is released and remating time was measured

benefits of deserting experiment results (females)

higher benefit for desertion cause remating time was shorter

benefits of deserting experiment results (males)

lower benefit cause remating time was longer

kentish plover costs of deserting experiment set up

one or the other parent was removed and brood survival was measured

costs of deserting experiment results (female)

cost was lower as brood survival was almost the same as the control group

costs of deserting experiment results (male)

higher cost for males

what is the cost of removing the parent dependent on?

size of the brood

how are benefits likely to change over the course of the breeding season?

decrease over time as the chance of successfully remating decreases as its harder for females to find a mate cause of male care

why do females provide more care later in the breeding season?

cause the benefits of deserting will be lower

why do females provide more care to bigger brood?

because costs of deserting will be higher

what are the implications of the plover population when male care predominates?

level of female care is a function of the brood size so varies with deserting cost but only when the benefits of deserting are high enough