Lecture 3: Stable biparental care Flashcards
biparental distribution among taxa
unevenly
- birds common, rare in mammals
- some beetles & fish
parental care is __
e.g. matrophagy
costly
matrophagy spider where young eats mothers
why is parental care costly and what could it then lead to
costs are borne individually and the benefits of biparental care are shared —> may lead to “tragedy of the commons” (Hardin 1968)
study biparental care using
game theory
Houston & Davies 1985
‘sealed bid’ model –> parents efforts evolves through time
(effort can only change through generations)
- each parent has an optimal response to partners effort
- -> more parent 1 invests, less parent 2 must
- > until ESS is reached (evolutionarily stable strategy)
sealed bid model:
outcome when females best response if always greater than the male
= pure female only care
sealed bid model:
outcome when males best response if always greater than the females
= pure male only care
sealed bid model:
male line is steeper than the females
either male only care or female only care as optimum is unstable e.g. penduline tit
sealed bid model: female line is steeper than the males
over evolutionary time come to optimum responses in care
penduline tit: sexual conflict over care
- males build a nest and advertise it to female
- near clutch completion 1/both parents desert nest
- 50-70% female only care
- 5-20% male only care
- 30-40% both parents desert
house sparrows and fixed effort
males parental effort is repeatable within and between years
hard working m always hard working, low working m always low
-females moderately repeatable
long tailed tits and individuals parental effort
parental effort is heritable, so to some extent is genetically determined
commonly is parental effort fixed?
no, varies due to number of factors
- -nestling age
- brood size
- food supply
- numbers of carers
McNamara et al (1999, 2003)
‘negotiation’ model – parents to respond to each other in real time
which model (negotiation or sealed bid) is more likely
negotiation
both the sealed bid and negotiation models predict:
Stable biparental care evolves only when one parent compensates INCOMPLETELY for reduced effort by partner
types of experiments to test for biparental care compensation
- removal experiments (remove one parent, does other compensate incompletely)
- handicapping experiments (reduce effort of one parent)
e.g. of removal experiment
Markman et al 1996
orange-tufted sunbirds
- ‘widowed’ female increases effort
- compensation incomplete so supports negotiation model
- ->chicks when M removed = less body mass
meta-analysis from removal experiments Harrison et al 2009
- left F/M increased effort
- total effort falls below so incomplete total effort
issues with removal experiments
- no negotiation can be made if M/F is removed
handicapping experiments methods
- add fishing weights to tail of birds
- tie some feathers together restricting of efficiency of flying
meta-analysis of 54 handicapping experiments
Harrison et al 2009
- handicapped reduce their effort, partners increase their efforts but again incompletely but results of experiments are extremely variable
handicapping experiment, variable results Starling
Wright & Cuthill 1990
- partner of handicapped bird increases effort BUT compensate complete
handicapping experiment, variable results Blue tit
Slagsvold & Lifjeld 1990
- partner of handicapped bird did not increase effort
NO compensation
handicapping experiment, variable results Dark-eyed junco
- Ketterson et al 1992
- testosterone experiments (increase T Males just sing)
- females compensate completely for reduced male effort
cause of inconsistent responses when looking at reproductive effort from mates
- METHODOLOGY
- -removal -> no negotiation
- -handicap -> partner perceived as poor quality
- -testosterone -> partner perceived as high quality
- INFORMATION
- -models assume parents have knowledge of partner effort and offspring need
information model (johnstone & Hinde 2006)
a parent may use partners effort as a cue to the needs of a brood, or may integrate information from partner & brood –> variable response to manipulation
experiment looking at information model
nestling playback experiments
- increase one partners effort, what does partner do
e. g. great tits (hide 2006) - parent MATCHES increased effort of partner
negotiation via conditional cooperation
Johnstone et al 2014 -negotiation via 'tit-for-tat' -great tits & long-tailed tits -parents should alternate their visits to the nest more than expected by chance -F then M etc ==there form of negotiation
stable biparental care evolves via a process of ____ in ___ & __ time
negotiation
in evolutionary and behavioural times
models predcit __ compensation for changes in partner effort
incomplete
